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Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

Vestibular function testingFloris L. Wuytsa, Joseph Furmanb, Robby Vanspauwena

and Paul Van de Heyninga

Purpose of review

This review provides an overview of vestibular function

testing and highlights the new techniques that have

emerged during the past 5 years.

Recent findings

Since the introduction of video-oculography as an

alternative to electro-oculography for the assessment of

vestibular-induced eye movements, the investigation of the

utricle has become a part of vestibular function testing,

using unilateral centrifugation. Vestibular evoked myogenic

potentials have become an important test for assessing

saccular function, although further standardization and

methodological issues remain to be clarified. Galvanic

stimulation of the labyrinth also is an evolving test that may

become useful diagnostically.

Summary

A basic vestibular function testing battery that includes

ocular motor tests, caloric testing, positional testing, and

earth-vertical axis rotational testing focuses on the

horizontal semicircular canal. Newer methods to investigate

the otolith organs are being developed. These new tests,

when combined with standard testing, will provide a more

comprehensive assessment of the complex vestibular

organ.

Keywords

saccule, SVV, unilateral centrifugation, utricle, VEMP

Curr Opin Neurol 20:19–24. � 2007 Lippincott Williams & Wilkins.

aAntwerp University Research Center for Equilibrium and Aerospace, Departmentof ENT, University of Antwerp, Antwerp, Belgium and bUniversity of PittsburghSchool of Medicine, Departments of Otolaryngology and Neurology, Pittsburgh,USA

Correspondence to Floris Wuyts, PhD, Antwerp University Research Center forEquilibrium and Aerospace, UA, Groenenborgerlaan 171, 2020 Antwerp, BelgiumTel: +32 3 821 47 10/þ32 3 265 34 29; e-mail: [email protected]

Current Opinion in Neurology 2007, 20:19–24

Abbreviations

ENG electronystagmographyEVAR earth-vertical axis rotationGVS galvanic vestibular stimulationHORT head only rotational testingOCR ocular counter-rollingOVAR off-vertical axis rotationSCM sternocleidomastoid muscleSVH subjective visual horizontalSVV subjective visual verticalVEMP vestibular evoked myogenic potentialVOG video-oculographyVOR vestibulo-ocular reflex

� 2007 Lippincott Williams & Wilkins1350-7540

IntroductionThe purpose of vestibular function testing is to objectively

and quantitatively assess the status of the vestibular sys-

tem. Some techniques provide information regarding peri-

pheral vestibular function while others focus on central

processing. This review will primarily address tests of

peripheral vestibular function. Since there are five vestib-

ular end organs in each inner ear – three semicircular

canals that transduce angular acceleration and two otolith

organs (utricle and saccule) that transduce linear accelera-

tion – no single vestibular test can assess the entire

labyrinth. Until recently, only the horizontal semicircular

canals could be reliably assessed, using caloric testing and

earth-vertical axis rotation. During the last decade, ves-

tibular testing has evolved such that the vertical semicir-

cular canals and the otolith organs also can be investigated.

Thus, vestibular testing not only can be used to lateralize a

lesion but also to deduce which part of the vestibular organ

appears to be affected. Although sophisticated equipment

is needed to assess the entire vestibular apparatus, clinics

specialized in assessing patients with dizziness and dis-

equilibrium are gradually implementing these new tests.

After a general description of some techniques that are

common for testing the different parts of the peripheral

vestibular system, this review will discuss specialized tests

of the five anatomical subsystems that comprise the

vestibular labyrinth.

Methods of eye movement recordingThis section presents the three methods for eye move-

ment recording with emphasis on the more recently

evolved video-based technique.

Electronystagmography/electro-oculography

Electronystagmography (ENG), also known as electro-

oculography (EOG), was for many decades the primary

technique for recording eye movements in patients of all

ages. Although proven to be clinically very useful several

factors influence the robustness of this method: correct

placing of the electrodes, appropriate skin preparation for

optimal skin–electrode impedance, increased signal to

noise ratio by using two electrodes per eye, and most

importantly, repeated calibration, to account for the fluctu-

ation in the corneo-retinal dipole potential. Very little

evolution of ENG is expected, especially as other

techniques emerge.

Videonystagmography/video-oculography

Videonystagmography (VNG) also known as video-ocu-

lography (VOG) recently became the preferred method

19

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for recording eye movement during vestibular testing.

VOG offers a particular advantage over conventional

EOG in that it enables an accurate measurement of

vertical eye movements. The main component of a

VOG system is a small infra-red sensitive video camera

connected to a PC system for determination of eye

position based on image processing algorithms [1,2].

Two-dimensional VOG uses pupil-tracking to extract

horizontal and vertical eye position. To assure accuracy,

VOG systems must account for the shape of the pupil

when the eyelids are partially closed or when eye position

is not straight ahead. Three-dimensional VOG addition-

ally extracts the torsional component of eye position,

generally based on polar cross-correlation techniques

using iris pigmentation patterns. For 3D VOG, geometri-

cal correction for eccentric gaze is very important as well

as correction for artifacts due to partial eyelid closure [3].

Some VOG systems use goggles that resemble ski glasses

with which the camera is placed in front of the eye. Other

systems allow unobstructed vision and the camera can

image the eye via a specialized mirror. Most commercial

VOG systems have a standard frame rate of 50 or 60 Hz,

which may limit the use of VOG for some ocular motor

tests such as saccades, for which a typical eye movement

has a speed of about 2008/s and a duration of about 50 ms

for a 108 gaze shift [4]. With a sample rate of only 50 Hz,

only two points of the saccade are recorded. Video

cameras are rapidly improving in dimensions and per-

formance, including higher resolution and frame rates

(>200 Hz). In the next years these new cameras will

gradually replace the currently used slower cameras.

It is essential that VOG goggles are firmly attached to the

patient’s head, since any relative movement of the cam-

era with respect to the head will result in an artifactual

eye movement recording. Thus, some VOG systems are

attached to the patient’s skull by means of a bite board

but this technique reduces clinical applicability [5]. VOG

can also be used for bedside testing especially for the

qualitative assessment of eye movements. Such VOG

goggles have been called ‘video frenzels’. Most likely, 2D

VOG will coexist with ENG for several years since each

technique has its strengths and weaknesses. Three-

dimensional VOG systems are currently mainly limited

to research facilities due to the greater complexity of this

technique. Because VOG is new, standardization is an

important issue that has not yet been adequately

addressed.

Scleral search coil

The scleral search coil method, developed by Robinson

[6], is based on the measurement of electric current

induced in a small coil of wire placed on the eye. The

search coil method has emerged as the gold standard for

the accurate recording of eye movements. It is, however,

an invasive technique which requires that a wired contact

lens be placed on the patient’s eye. It causes discomfort

for the patient and recording time is limited to approxi-

mately 30 min. Also, torsional slippage can lead to arti-

facts. Still, Halmagyi advocates this method as the most

preferable for all semicircular canal testing [7]. Very

few laboratories use this technique routinely despite

its capabilities [8,9].

Assessment of the horizontal semicircularcanalIn most clinical vestibular laboratories the following test

battery is performed: ocular motor screening; positional

testing; caloric testing; and rotational testing. A detailed

description of these tests can be found in Wuyts et al. [10].

Ocular motor screening consists of the assessment of

spontaneous nystagmus, gaze-evoked nystagmus, saccadic

eye movements, pursuit eye movements, and optokinetic

nystagmus. The purpose of ocular motor screening is to

uncover eye movement abnormalities that may interfere

with the interpretation of the positional, caloric, or

rotational tests. Furthermore, it can provide some infor-

mation in and of itself concerning central nervous system

abnormalities. Ocular motor screening can be performed

using either ENG or VOG with the restrictions described

in the previous section.

Caloric testing

The caloric test has been unchanged for decades. It

remains a mainstay of vestibular function testing. Each

laboratory should establish its own normal values. A less

desirable practice is to use normative values derived from

a meta-analysis by which the means are weighted based

on the number of subjects in the different studies [10].

Reasonable upper limits for normality are 22% for

reduced vestibular response (labyrinth asymmetry) and

26% for directional preponderance.

The caloric test assesses only the horizontal semicircular

canal. Thus, caloric abnormalities do not necessarily

imply that the labyrinth is totally dysfunctional and

should be interpreted in light of other tests. Fetter and

Dichgans [11] investigated 3D eye movements in 16

patients with acute unilateral vestibular lesions and found

that none of them had spontaneous nystagmus whose

direction indicated a complete unilateral vestibular

lesion.

Earth-vertical axis rotational testing

Rotational testing using whole body rotation is usually

performed with the patient seated upright during earth-

vertical axis rotation (EVAR). This stimulus evaluates

primarily the horizontal semicircular canals by assess-

ing the horizontal vestibulo-ocular reflex (VOR). Well

known measures obtained from EVAR include gain,

phase and asymmetry for sinusoidal rotation at a range

20 Neuro-ophthalmology and neuro-otology


of frequencies from about 0.01 Hz to 1.0 Hz and gain and

time constant for trapezoidal (constant velocity) rotation.

Although in several clinics the head is tilted forward 308during rotation, Van der Stappen et al. [12] showed that

better results were obtained with the head upright.

Recently, Peterka [13] introduced a novel method to

identify the side-of-lesion in subjects with well com-

pensated unilateral vestibular loss. The cyclic ‘pulse-

step-sine’ stimulus has a bias component and a probe

component. The testing uses a higher frequency, more

physiologically relevant, stimulus than the low fre-

quency caloric test or standard EVAR.

A drawback of rotational testing is the dependence of the

measures on the patient’s mental alertness. Patients

should be systematically asked to perform mental tasks.

Despite some methodological drawbacks of EVAR, the

technique provides complementary information to the

caloric test. Arriaga et al. [14] demonstrated that EVAR

has a greater sensitivity whereas caloric testing has a

greater specificity for peripheral vestibulopathy.

Head-only rotational testing

Head only rotational testing (HORT) relies on head

movement alone to stimulate the vestibular system

[15]. This technique is convenient and has relatively

low cost. Testing is limited in terms of magnitude and

frequency because of physical constraints. HORT is

generally performed at higher frequencies than EVAR

but at considerably lower velocity than head thrust test-

ing. HORT is used by many laboratories but has not

become a standard method because it does not consist-

ently identify labyrinthine dysfunction.

Another evolving technique for assessing the functional

status of the VOR is dynamic visual acuity (DVA) [16]

and the gaze stability test (GST). Both DVA testing and

the GST use a computer-displayed optotype that the

subject needs to identify while rotating their head. These

tests may be a valuable adjunct to vestibular testing when

it is important to assess functional ability. Problems arise

however when using these tests for diagnosis when the

head movements are active and made by the subject

themselves because results can be influenced by non-

vestibular factors. For example, active head movements

toward the lesioned side can generate both compensatory

and anticipatory saccades [17].

The Halmagyi–Curthoys head impulse test [18], when

performed at the bedside, does not necessarily require

any equipment. The test is of particular value when first

investigating a patient with vertigo at the bedside.

Although the head impulse test can be especially useful

for identifying a loss of function of the horizontal semi-

circular canal, it should not replace the caloric test [19].

Recently, Ulmer and Chays [20] proved that with a

dedicated video camera, the sensitivity of the head

impulse test can be improved.

Assessment of vertical semicircular canalsThe most reliable yet cumbersome method to test the

anterior and posterior semicircular canals consists of a

combination of the head impulse test [18] and the scleral

search coil technique. This method has been used by

Minor and colleagues as well as Halmagyi et al. [8,9]. The

test is based on brisk movements of the subject’s head

in the left anterior–right posterior canal or the right

anterior–left posterior semicircular canal planes. These

planes are approximately 458 from the sagittal plane.

Moving the subject in these planes either forward or

backward will generate eye movements that result from

exciting the posterior or anterior canal on one side and

silencing the complementary canal on the other side.

Analysis of the eye movements can provide a quantitative

assessment of the vertical semicircular canals.

Assessment of the utricleThe utricles can be assessed by observation of the ocular

counter rolling during simple head or body lateroflexion,

but this method does not prove to be particularly robust

because even in cases of unilateral deafferentiation the

responses are similar to those obtained in healthy subjects

[21]. Other methods therefore emerged.

Unilateral centrifugation

The most current technique for assessing unilateral utri-

cular function uses eccentric rotation as proposed by

Wetzig et al. [22] and further employed by Clarke et al.[5,23] and Wuyts et al. [24]. Utricular sensitivity and

preponderance of the right or left utricle can be assessed

by this so-called ‘unilateral centrifugation test’. In this

test, subjects are rotated about an earth-vertical axis at a

velocity of 300–4008/s. During the ongoing rotation, the

subject is gradually translated 3.5–4 cm [25] first to the

right, and then to the left, along an interaural axis, to a

position at which one utricle becomes aligned with the

axis of rotation, and at this point is subjected only to

gravitational forces. At 4008/s the contralateral utricle is

exposed to the combination of gravity and a centrifugal

acceleration of 0.4 g, corresponding to an apparent roll-tilt

of 21.78. This stimulus induces ocular counter-rolling

(OCR), which reflects the otolith ocular reflex (OOR).

OCR is measured using 3D VOG. Some laboratories do

not have the equipment to automatically translate

the chair to left or right during ongoing rotation but

instead before rotation position the chair manually at

the eccentric points and then measure either OCR or

subjective visual vertical. Unilateral centrifugation is

becoming more common since it provides complemen-

tary information to the traditional ENG. Signs of any

dominance of one or the other utricle should emerge from

Vestibular function testing Wuyts et al. 21


high speed rotation since an imbalance in the afferent

firing rate due to the symmetric loading of both utricles

should give rise to OCR. The amount of OCR, however,

is small and difficult to measure. Nevertheless, Clarke

and coworkers have shown OCR during centered EVAR

to be a valuable screening method for otolith organ

asymmetry [26]. Any indication of OCR response asym-

metry during EVAR with the patient centered should be

pursued with unilateral centrifugation [26].

Off-vertical axis rotation

Off-vertical axis rotation (OVAR), when performed at

constant velocity, stimulates the otolith organs and not

the semicircular canals [27]. The test is easily adminis-

tered but requires specialized equipment and can pro-

duce unpleasant nausea. Both the right and left otolith

organs are stimulated. Thus, OVAR does not provide

lateralizing information. Moreover, in studies of patients

with confirmed unilateral peripheral vestibular loss,

OVAR responses are essentially normal, further reducing

its clinical utility. OVAR continues to be used in some

laboratories as a convenient means of activating the

otolith organs and assessing the otolith–ocular reflex [28].

Assessment of the sacculeThe sole method that currently is readily available for

assessment of the saccule consists of the vestibular

evoked myogenic potential (VEMP) test.

Vestibular evoked myogenic potentials

VEMPs, which serve as a tool for investigating saccular

function, are inhibitory myogenic potentials measured

from the tonically contracted sternocleidomastoid mus-

cle (SCM) in response to loud sound stimuli [29]. The

VEMP waveform is biphasic, containing a positive (p13)

and a negative (n23) peak occurring after a latency of

approximately 13 and 23 ms, respectively, generated by

activation of saccular afferents. The VEMP response

amplitude is dependent on the magnitude of the stimulus

intensity and on the magnitude of the SCM contraction

[29]. For left–right amplitude differences to be con-

sidered reliable, it is important to provide feedback to

the subject regarding the amount of SCM contraction. A

simultaneous electromyography and VEMP recording is

the most appropriate method. If not possible, a feedback

method, based on the use of a blood pressure manometer

with an inflatable cuff, has been recommended to control

the SCM contraction [30,31]. Another option for activat-

ing the SCM is to ask the subject to elevate the head

when in a supine position. In this way the SCM muscles

on both sides are activated simultaneously. Both clicks

(0.1 ms, 105 dBnHL) and tone bursts (95 dB nHL,

500 Hz, ramp, 1 ms, plateau, 2 ms) can be used to evoke

VEMPs [32,33]. The stimulus intensity threshold for

tone bursts is lower than for clicks. When applying tone

bursts, there is a frequency tuning with lowest thresholds

at 500–1000 Hz and best responses at 500 Hz. [34��].

Patients with endolymphatic hydrops appear to have

an altered frequency tuning and elevated thresholds

[34��,35]. Thus, performing VEMPs at multiple frequen-

cies and with threshold determination may enable the

discovery of preclinical Meniere’s disease [36]. In sub-

jects with conductive hearing loss with air-bone gaps

20 dB or higher [37], bone conducted tone burst stimu-

lation at the mastoid (70 dB nHL, 500 Hz, ramp, 1 ms,

plateau, 2 ms) is preferred [33]. It is known that in these

conditions the bone conducted acoustic stimulation con-

ducts across the skull and stimulates the contralateral side

as well [38]. Animal experiments demonstrate that air-

conducted sound selectively activates the saccule [39].

There is less information on the site of action of bone

conducted sound. Curthoys et al. [40�] described that in

guinea pigs bone conducted sound preferentially acti-

vated irregularly firing utricular as well as saccular affer-

ents. Recently, Rosengren et al. [41�] and Curthoys and

coworkers [42] described vestibular evoked extraocular

potentials in response to bone conducted sounds, so

called o-VEMPs (o for ocular) in contrast to c-VEMPs

(c for colic). These extraocular excitatory potentials were

produced by synchronous activity in extraocular muscles

and were dependent upon contralateral otoliths acti-

vation. This method of recording vestibular evoked

potentials may prove to be an additional and robust test

for vestibular function and provides an alternative for

measuring VEMPs at the SCM in patients who, for

example, are unable to contract their neck muscles.

Vestibular tests with uncertain focusMore global oriented tests are the subjective visual

vertical or horizontal test and the galvanic stimulation

test.

Subjective visual vertical/subjective visual horizontal

The subjective visual vertical (SVV) and subjective visual

horizontal (SVH) have been employed for several years as

relatively simple tests for evaluating the otolith system

[43]. SVV and SVH can be measured while the subject is

in the upright position or with body inclined in the roll

plane. A normal subject sitting upright can accurately

align in total darkness a dimly illuminated bar with high

accuracy to the true gravitational vertical or horizontal

[44]. Misalignment of more than 2.58 is considered patho-

logical [44] with the tilt deviation toward the affected

side. Tribukait states that the SVV or SVH as measured in

the upright position is influenced by the utricles, saccules

and horizontal semicircular canals. This has been gener-

alized to all semicircular canals by Pavlou et al. [45].

Others state that measuring SVV with body inclination

increases its sensitivity [46]. When using a roll tilt of the

body to assess SVV, however, the initial position of the

light bar influences the outcome [47]. Healthy subjects

were able to set the SVV correctly when the light bar had



an initial inclination relatively parallel to the body axis.

The subject could not, however, properly estimate the

true vertical when the light bar was initially inclined in

the opposite direction. Also, SVV is subject to variation

over time, due to central compensation [48]. Given these

methodological as well as physiological reasons, SVV is a

less reliable technique for vestibular assessment.

Galvanic stimulation

Galvanic vestibular stimulation (GVS) of the labyrinth,

delivered by electrodes placed on the mastoids, modu-

lates the spontaneous discharge rate of the vestibular

afferents of all vestibular end organs and produces various

behavioural responses such as postural changes, eye

movements and perception of movement [49]. Like

unilateral centrifugation, caloric testing and VEMPs,

GVS is applied unilaterally, which enables the identifi-

cation of vestibular asymmetries. In contrast to the other

methods, however, GVS is a ‘broad spectrum’ stimulus

since it affects both the semicircular canals as well as the

otolith organs.

Anthropometric differences among individuals may

account for the large between-subject variability as

described by MacDougall et al. [50]. Galvanic stimulation

was shown to serve as a valid model for the walking

disturbances as experienced by astronauts upon return

from space [51]. Clarke and colleagues used GVS as an

alternative to ice water calorics to investigate the degree

of remaining brain function in comatose patients [52]. In a

recent study, MacDougall et al. [53] showed the growing

applicability of GVS in the clinic to help identify the

location of lesions.

ConclusionIn addition to the basic methods available for assessing

the vestibular apparatus, several newer methods have

emerged during the past decade, mainly due to the

increased use of fast computers in the clinical setting.

For tests requiring the measurement of eye movement,

video-oculography has the major advantage of allowing

the investigation of all eye movements and, therefore,

different components of the vestibular system when used

in combination with the appropriate stimulus. Unilateral

centrifugation is evolving as a utricular test. The saccule

can be evaluated with the VEMP method. Subjective

visual vertical or horizontal can be regarded as a quasi-

otolith test although not a direct measure of otolith organ

function, and therefore more prone to other influences,

such as compensation. Galvanic stimulation is mainly

used for posture and gait studies, but recently also has

been used as a complementary vestibular function test.

A basic vestibular function testing battery, including

ocular motor tests, caloric testing, positional testing,

and earth-vertical axis rotational testing, are a solid basis

onto which other tests can and should be added to

provide a comprehensive assessment of the complex

vestibular organ.

References and recommended readingPapers of particular interest, published within the annual period of review, havebeen highlighted as:� of special interest�� of outstanding interest

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��Rauch SD. Vestibular evoked myogenic potentials. Curr Opin OtolaryngolHead Neck Surg 2006; 14:299–304.

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40

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The authors prove that bone-conducted sound stimulates in particular the utricle,which indicates that the ocular VEMPs that are generated by bone conduction arealso assessing the utricle, as an alternative to the air-conducted colic VEMPs thatare mainly stimulating the saccule.

41

�Rosengren SM, Angus Todd NP, Colebatch JG. Vestibular-evoked extra-ocular potentials produced by stimulation with bone-conducted sound. ClinNeurophysiol 2005; 116:1938–1948.

The authors offer a novel test to investigate the otolith system based on anexcitatory reflex at the level of the extra-ocular muscles, generated by bone-conducted sound. This yields an alternative to the c-VEMPs.

42 Iwasaki S, McGarvie LA, Halmagyi GM, et al. Head taps evoke a crossedvestibulo-ocular reflex. Neurology (in press).

43 Kingma H. Function tests of the otolith or statolith system. Curr Opin Neurol2006; 19:21–25.

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46 Aranda-Moreno C, Jauregui-Renaud K. The subjective visual vertical investibular disease. Rev Invest Clin 2005; 57:22–27.

47 Hoppenbrouwers M, Wuyts FL, Van de Heyning PH. Suppression of theE-effect during the subjective visual vertical test. Neuroreport 2004; 15:325–327.

48 Takai Y, Murofushi T, Ushio M, Iwasaki S. Recovery of subjective visualhorizontal after unilateral vestibular deafferentation by intratympanic instilla-tion of gentamicin. J Vestib Res 2006; 16:69–73.

49 Fitzpatrick RC, Day BL. Probing the human vestibular system with galvanicstimulation. J Appl Physiol 2004; 96:2301–2316.

50 MacDougall HG, Brizuela AE, Burgess AM, Curthoys IS. Between-subjectvariability and within-subject reliability of the human eye-movement responseto bilateral galvanic (DC) vestibular stimulation. Exp Brain Res 2002; 144:69–78.

51 Moore ST, MacDougall HG, Peters BT, et al. Modeling locomotor dysfunctionfollowing spaceflight with galvanic vestibular stimulation. Exp Brain Res 2006;174:647–659.

52 Schlosser HG, Unterberg A, Clarke A. Using video-oculography for galvanicevoked vestibulo-ocular monitoring in comatose patients. J Neurosci Methods2005; 145:127–131.

53 MacDougall HG, Brizuela AE, Burgess AM, et al. Patient and normal three-dimensional eye-movement responses to maintained (DC) surface galvanicvestibular stimulation. Otol Neurotol 2005; 26:500–511.


General vestibular testing

Thomas Brandt*, Michael Strupp

Department of Neurology, Ludwig Maximilians University, Marchioninistr. 15, 81377 Munich, Germany

Accepted 19 August 2004

Available online 30 September 2004

Abstract

A dysfunction of the vestibular system is commonly characterized by a combination of phenomena involving perceptual, ocular motor,

postural, and autonomic manifestations: vertigo/dizziness, nystagmus, ataxia, and nausea. These 4 manifestations correlate with different

aspects of vestibular function and emanate from different sites within the central nervous system. The diagnosis of vestibular syndromes

always requires interdisciplinary thinking. A detailed history allows early differentiation into 9 categories that serve as a practical guide for

differential diagnosis: (1) dizziness and lightheadedness; (2) single or recurrent attacks of vertigo; (3) sustained vertigo; (4)

positional/positioning vertigo; (5) oscillopsia; (6) vertigo associated with auditory dysfunction; (7) vertigo associated with brainstem or

cerebellar symptoms; (8) vertigo associated with headache; and (9) dizziness or to-and-fro vertigo with postural imbalance. A careful and

systematic neuro-ophthalmological and neuro-otological examination is also mandatory, especially to differentiate between central and

peripheral vestibular disorders. Important signs are nystagmus, ocular tilt reaction, other central or peripheral ocular motor dysfunctions, or a

unilateral or bilateral peripheral vestibular deficit. This deficit can be easily detected by the head-impulse test, the most relevant bedside test

for the vestibulo-ocular reflex. Laboratory examinations are used to measure eye movements, to test semicircular canal, otolith, and spatial

perceptional function and to determine postural control. It must, however, be kept in mind that all signs and ocular motor and vestibular

findings have to be interpreted within the context of the patient’s history and a complete neurological examination.

q 2004 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Keywords: Vestibular function; Vestibular disorders; Vertigo; Dizziness; Vestibulo-ocular reflex; Neuro-otological examination; Neuro-ophthalmological

examination; Electronystagmography; Posturography

1. Introduction

Vertigo and dizziness are among the most frequent

presenting symptoms, not only in neurology. According to a

survey of over 30,000 persons, the prevalence of vertigo and

dizziness over all ages lies around 17%; it rises to 39% in

those over 80 (Davis and Moorjani, 2003). Vertigo and

dizziness are not unique disease entities. Sometimes vertigo

is attributed to vestibular disorders, while dizziness is not

(Neuhauser and Lempert, 2004). There is no general

agreement, and visual stimuli can cause vertigo (e.g. height

vertigo or optokinetic vection) just as otolith disorders can

cause dizziness. Furthermore, central vestibular disorders

such as lateropulsion in Wallenberg’s syndrome may occur

without subjective vertigo or dizziness (Dieterich and

Brandt, 1992). Vertigo and dizziness are considered either

an unpleasant disturbance of spatial orientation or the

illusory perception of a movement of the body (spinning,

wobbling, or tilting) and/or of the surroundings. Both terms

refer to a number of multisensory and sensorimotor

syndromes of various etiologies and pathogeneses (Baloh

and Halmagyi, 1996; Brandt, 1999; Brandt et al., 2004;

Bronstein et al., 2004).

A dysfunction of the vestibular system is commonly

characterized by a combination of phenomena involving

perceptual, ocular motor, postural, and autonomic manifes-

tations: vertigo/dizziness, nystagmus, ataxia, and nausea

(Fig. 1, Brandt and Daroff, 1980). These 4 manifestations

correlate with different aspects of vestibular function and

emanate from different sites within the central nervous

system. Vertigo/dizziness itself results from a disturbance of

Clinical Neurophysiology 116 (2005) 406–426

www.elsevier.com/locate/clinph

1388-2457/$30.00 q 2004 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

doi:10.1016/j.clinph.2004.08.009

* Corresponding author. Address: Department of Neurology, University

of Munich, Klinikum Grosshadern, Marchioninistrasse 15, D-81377,

Munich, Germany. Tel.: C49 89 7095 2570; fax: C49 89 7095 8883.

E-mail address: [email protected] (T. Brandt).

http://www.elsevier.com/locate/clinph

cortical spatial orientation. Nystagmus is secondary to a

direction-specific imbalance of the VOR, which activates

brainstem neuronal circuitry. Vestibular ataxia and postural

imbalance are caused by inappropriate or abnormal

activation of monosynaptic and polysynaptic vestibular–

spinal pathways. Finally, the unpleasant autonomic

responses of nausea, vomiting, and anxiety traverse

ascending and descending vestibulo-autonomic pathways

and activate the medullary vomiting center.

This review on general vestibular testing is organized in

4 parts: first, background concepts about the malfunctioning

of the vestibular system; second, approaching the dizzy

patient; third, different clinical neuro-ophthalmological and

neuro-otological bedside tests, which are clearly illustrated

in the figures; and fourth, the laboratory examinations, e.g.

the magnetic search coil technique, electronystagmography,

video-oculography, vestibular-evoked myogenic potentials,

and posturography.

2. Background concepts

2.1. The vestibulo-ocular reflex (VOR) and the

classification of central vestibular disorders

The most important anatomical structure of the

vestibular system in the brainstem is the VOR. The

VOR has 3 major planes of action:

† horizontal head rotation about the vertical Z-axis (yaw).

† head extension or flexion about the horizontal Y-axis

(pitch).

† lateral head tilt about the horizontal X-axis (roll).

These 3 planes represent the three-dimensional space in

which the vestibular and ocular motor systems responsible

for spatial orientation, perception of self-movement,

stabilization of gaze, and postural control operate. The

neuronal circuitry of the horizontal and vertical semicircular

canals as well as the otoliths is based on a sensory

convergence that takes place within the VOR. The VOR

roughly connects a set of extraocular eye muscles that are

aligned with their primary direction of pull with the

respective spatial planes of the horizontal, anterior, and

posterior canals. The canals of both labyrinths form

functional pairs in the horizontal and vertical working

planes. In other words, the canals are excited/inhibited in

pairs: the horizontal right and left pair, and the vertical

anterior of one side along with the posterior canal of the

opposite side. The vertical planes of ‘pitch’ and ‘roll’ are a

result of the wiring connecting the two vertical canals that

are diagonal to the sagittal plane in the head. The pair of

canals function as a gauge of rotatory acceleration and react

to the rotational movements of the head in the correspond-

ing plane. The otoliths function as a gauge of gravity and

linear acceleration.

There is evidence that these 3 major planes of action of

the VOR allow a useful clinical classification of central

vestibular syndromes (Brandt, 1999). The plane-specific

vestibular syndromes are determined by ocular motor,

postural, and perceptual signs.

Yaw plane signs are horizontal nystagmus, past-pointing,

rotational and lateral body falls, horizontal deviation of

perceived straight-ahead.

Roll plane signs are torsional nystagmus, skew deviation,

ocular torsion, tilts of the head, body, and perceived vertical

(ocular-tilt reaction); see, for example, Fig. 2.

Fig. 1. Physiological vertigo (motion stimulation) and pathological vertigo (induced by lesion or stimuli) are characterized by similar signs and symptoms that

derive from the functions of the multisensory vestibular system (Brandt and Daroff, 1980).

T. Brandt, M. Strupp / Clinical Neurophysiology 116 (2005) 406–426 407

Pitch plane signs are upbeat or downbeat nystagmus,

forward or backward tilts and falls, vertical deviation of the

perceived straight-ahead.

2.2. Basic forms of vestibular dysfunction

Pathophysiologically, there are 3 basic forms of

vestibular dysfunction, each with its typical symptoms and

clinical signs:

† Bilateral (peripheral) loss of vestibular function. The

main symptoms are oscillopsia during head movements

(failure of the VOR), instability of gait and posture,

which increases in darkness or on uneven ground

(reduced or absent visual or somatosensory substitution

of vestibular loss), and only recently detected deficits in

spatial memory (lack of vestibular input for navigation

and spatial memory; Schautzer et al., 2003; Smith, 1997).

† Acute/subacute unilateral failure of vestibular function

(of the labyrinth, vestibular nerve, vestibular nuclei, or

central pathways), which causes a vestibular tonus

imbalance. The main symptoms are rotatory vertigo or

apparent body tilt (for a few days or weeks), nystagmus,

oscillopsia, nausea, and the tendency to fall in a direction

opposite to that of vertigo.

† Paroxysmal stimulation of the vestibular system of the

labyrinth (e.g. benign paroxysmal positioning vertigo),

the vestibular nerve (e.g. vestibular paroxysmia due to

vascular cross-compression), or the brainstem (e.g.

paroxysmal ataxia in MS). The main symptoms and

signs are short attacks of vertigo, dizziness, oscillopsia,

nystagmus, and postural imbalance.

Clinically, two major relevant areas of vestibular

dysfunction should be differentiated anatomically: periph-

eral vestibular disorders originating from the labyrinth

and/or vestibular nerve and central vestibular disorders.

Central vestibular forms of vertigo arise from lesions at the

neuronal connections between the vestibular nuclei and

the vestibular cerebellum as well as those between the

vestibular nuclei, the vestibular and ocular motor structures

of the brainstem, cerebellum, thalamus, and vestibular

cortex. On the one hand, these include clearly defined

clinical syndromes of various etiologies, for example,

upbeat or downbeat nystagmus (the quick phase of

nystagmus beats upward or downward). The occurrence of

these typical ocular motor findings in only the central

vestibular brainstem or in cerebellar disorders allows a

definite topical attribution. On the other hand, central

vestibular vertigo can also be part of a more complex

infratentorial clinical syndrome. In such cases other signs

and symptoms, such as supranuclear or nuclear ocular motor

disorders and/or other neurological brainstem signs (e.g.

Wallenberg’s syndrome), can also be observed. Vertigo/-

dizziness can manifest as attacks lasting for seconds or

minutes (vestibular migraine), for hours up to days

(brainstem infarction), or as a permanent syndrome (down-

beat nystagmus in cases of Arnold–Chiari malformation).

2.3. Semicircular canal or otolith dysfunction

There are several possible reasons why most vestibular

syndromes involve semicircular canal and otolith function.

The different receptors for perception of angular and linear

accelerations are housed in a common labyrinth. Their

peripheral (VIIIth nerve) and central (e.g. medial longitudi-

nal fascicle) pathways take the same course. Finally, there is

a convergence of otolith and semicircular canal input at all

central vestibular levels, from the vestibular nuclei to the

vestibular cortex.

Thus, most vestibular syndromes are mixed as regards

otolithic and canal function. A peripheral prototype of such

Fig. 2. Vestibular syndromes in the roll plane: Graviceptive pathways from

otoliths and vertical semicircular canals mediating vestibular function in

the roll plane. The projections from the otoliths and the vertical

semicircular canals to the ocular motor nuclei (trochlear nucleus IV,

oculomotor nucleus III, abducens nucleus VI), the supranuclear centers of

the interstitial nucleus of Cajal (INC), and the rostral interstitial nucleus of

the medial longitudinal fascicle (riMLF) are shown. They subserve VOR in

3 planes. The VOR is part of a more complex vestibular reaction which also

involves vestibular–spinal connections via the medial and lateral

vestibular–spinal tracts for head and body posture control. Furthermore,

connections to the assumed vestibular cortex (areas 2v and 3a and the

parieto-insular vestibular cortex, PIVC) via the vestibular nuclei of the

thalamus (VIM, Vce) are depicted. ‘Graviceptive’ vestibular pathways for

the roll plane cross at the pontine level OTR (skew torsion, head tilt, and tilt

of perceived vertical, SVV), which is depicted schematically on the right in

relation to the level of the lesion: ipsiversive OTR with peripheral and

pontomedullary lesions; contraversive OTR with pontomesencephalic

lesions. In vestibular thalamic lesions, the tilts of SVV may be

contraversive or ipsiversive; in vestibular cortex lesions they are most

often contraversive. OTR is not induced by supratentorial lesions above the

level of the INC (From Brandt, 1999).

T. Brandt, M. Strupp / Clinical Neurophysiology 116 (2005) 406–426408

a mixture is vestibular neuritis. It is mostly caused by failure

of the superior division of the vestibular nerve that

subserves the horizontal and the anterior semicircular canals

and the maculae of the utricle and the anterosuperior part of

the saccule (Balo, 2003; Buchele and Brandt, 1988; Fetter

and Dichgans, 1996; Murofushi et al. 2003). A central

prototype is Wallenberg’s syndrome, which involves the

medial and superior vestibular nuclei, where otolith and

canal input converge. This typically causes ocular and

body lateropulsion, and spontaneous torsional nystagmus

(Dieterich and Brandt, 1992).

It is, however, possible to selectively stimulate single

canals by caloric irrigation of the external auditory canal or

by the head-thrust test devised by Halmagyi and Curthoys

(Cremer et al., 1998; Halmagyi and Curthoys, 1988). The

prototype of a semicircular canal disease is benign

paroxysmal positioning vertigo of the posterior or horizon-

tal canal. Typical signs and symptoms of semicircular canal

dysfunction are rotational vertigo and deviation of

perceived straight-ahead, spontaneous vestibular nystagmus

with oscillopsia, postural imbalance in the Romberg test and

past-pointing, and nausea and vomiting, if severe. The

three-dimensional spatial direction of nystagmus and

vertigo depends on the spatial plane of the affected

semicircular canal and on whether the dysfunction is caused

by ampullofugal or ampullopetal stimulation or a unilateral

loss of afferent information. Malfunction of a single or more

than one semicircular canal can be detected by three-

dimensional analysis of spontaneous nystagmus (Bohmer

et al., 1997; Straumann and Zee, 1995), the head-thrust test

with individual semicircular canal plane head impulses

(Cremer et al., 1998), or perception of rotation (von Brevern

et al., 1997). Central vestibular syndromes may take

precedence over semicircular canal or otolith types. In

other words, ‘dynamic’, rotatory vertigo and nystagmus

represent (angular) canal function, whereas ‘static’ ocular-

tilt reaction, body lateropulsion, or tilts of the perceived

vertical represent (linear) otolithic function.

Although the pathophysiology of otolith dysfunction is

poorly understood, a disorder of otolithic function at

a peripheral or central level should be suspected if a patient

describes symptoms of falls, sensations of linear motion or

tilt, or else shows signs of specific derangements of ocular

motor and postural orienting and balancing responses

(Gresty et al., 1992). A significant number of patients

presenting to neurologists have signs and symptoms that

suggest disorders of otolithic function. Nevertheless,

diseases of the otoliths are poorly represented in our

diagnostic repertoire. Of these, posttraumatic otolith vertigo

(Brandt and Daroff, 1980) may be the most significant; the

rare otolith Tullio phenomenon may be the best studied

(Dieterich et al., 1989; Fries et al., 1993). Other examples

are vestibular drop attacks (Tumarkin’s otolithic crisis;

Baloh et al., 1990) and a number of central vestibular

syndromes that indicate tonus imbalance of graviceptive

circuits (skew deviation, ocular tilt reaction, lateropulsion,

or room-tilt illusion; Brandt, 1997; Brandt and Dieterich,

1994a; Brodsky, 2003; Tiliket et al., 1996), some of which

manifest without the sensation of dizziness or vertigo.

3. Approaching the patient

About 75% of all patients presenting with vertigo or

dizziness in a neurological dizziness unit will have one of

the 8 most common syndromes listed in Table 1. A clinician

not familiar with dizzy patients can best deepen his

knowledge by acquainting himself with these 8 most

frequently met but still challenging conditions. The

diagnosis of central vestibular disorders, however, com-

prises a variety of syndromes extending from the brainstem

to the vestibular cortex. Although most clinicians welcome

the effort being made to develop computer interview

systems for use with neuro-otological patients (O’Connor

et al., 1989) and expert systems as diagnostic aids in

otoneurology (Auramo et al., 1993; Mira et al., 1990), the

actual application of these systems in a clinical setting is

still quite limited.

Vertigo and dizziness are vexing symptoms. They are

sometimes difficult to assess because of their purely

Table 1

Relative frequency of different syndromes diagnosed in a special neurological dizziness unit (nZ4790 patients in 1989–2003)

Diagnosis Frequency (%)

Benign paroxysmal positioning vertigo 18.3 (Brandt and Steddin, 1993)

Phobic postural vertigo (PPV) 15.9 (Brandt, 1996)

Central vestibular disorders 13.5 (Brandt and Dieterich, 1994a)

Vestibular migraine 9.6 (Dieterich and Brandt, 1999; Neuhauser et al., 2001; 2004)

Vestibular neuritis 7.9 (Baloh, 2003)

Meniere’s disease 7.8 (James and Thorp, 2001)

Bilateral vestibulopathy 3.6 (Rinne et al., 1995)

Psychogenic vertigo (without PPV) 3.6

Vestibular paroxysmia 2.9 (Brandt and Dieterich, 1994b; Jannetta et al., 1984)

Perilymph fistula or superior canal dehiscence syndrome 0.4 (Minor et al., 1998)

Various other disorders 12.3

Unknown etiology 4.2


subjective character and the variety of sensations patients

report. The sensation of spinning or rotatory vertigo is much

more specific; if it persists, it undoubtedly indicates acute

pathology of the labyrinth, the vestibular nerve, or the

caudal brainstem, which contains the vestibular nuclei. The

diagnosis and management of vertigo syndromes always

require interdisciplinary thinking combined with a careful

taking of the patient’s history. The history is still much more

important than recording eye movements and postural sway

or using brain imaging techniques.

3.1. Diagnostic criteria

The important diagnostic criteria of vestibular syn-

dromes manifesting with vertigo or dizziness are as follows:

† Type of vertigo: Rotatory vertigo as experienced when

riding a merry-go-round (e.g. vestibular neuritis) or

postural imbalance as experienced during boat trips (e.g.

bilateral vestibulopathy) or dizziness/lightheadedness

(e.g. intoxication).

† Duration of vertigo: Attacks of vertigo lasting for

seconds to minutes (e.g. vestibular paroxysmia), over

hours (e.g. Meniere’s disease, vestibular migraine),

sustained vertigo for days to a few weeks (e.g. vestibular

neuritis), attacks of postural instability from minutes to

hours (e.g. transient ischemic attacks of the brainstem or

cerebellar structures).

† Trigger/exacerbation of vertigo: No trigger (e.g. vestib-

ular neuritis), walking (e.g. bilateral vestibulopathy),

head turning (e.g. vestibular paroxysmia), head position-

ing (e.g. benign paroxysmal positioning vertigo), cough-

ing, pressing, loud sounds of a certain frequency

(perilymph fistula or superior canal dehiscence syn-

drome), or certain social situations (phobic postural

vertigo).

† Vertigo associated with auditory dysfunction, non-

vestibular neurological signs and symptoms, or

headache.

3.2. Diagnostic categories

A thorough patient history allows the early differen-

tiation of vertigo and disequilibrium disorders into 9

categories that serve as a practical guide for the differential

diagnosis.

3.2.1. Dizziness and lightheadedness (Table 2)

Most of us have experienced presyncopal dizziness at

some time when rapidly standing up from a relaxed supine

or seated position. Such an experience best exemplifies this

category (Baloh and Halmagyi, 1996), which includes

orthostatic hypotension and cardiac arrhythmias as well as

hyperventilation syndrome and panic attacks.

3.2.2. Single or recurrent attacks of (rotatory) vertigo

(Table 3)

Recurrent vertigo attacks in children which last several

seconds or minutes are most likely due to benign

paroxysmal vertigo of childhood, a migraine equivalent.

In adults short attacks of rotatory vertigo may occur in

Meniere’s disease, vestibular migraine, or transient verte-

brobasilar ischemia.

3.2.3. Sustained rotatory vertigo (Table 4)

Sustained vertigo occurs either with acute unilateral

peripheral loss of vestibular function or with pontomedul-

lary brainstem lesion near the vestibular nuclei. Vestibular

neuritis is the most frequent cause and its diagnostic

Table 2

Dizziness and lightheadedness

Presyncopal dizziness

Orthostatic dysregulation

Vasovagal attacks

Neuro-cardiogenic (pre) syncope

Cardiac arrhythmia and other heart diseases

Psychiatric illnesses

Hyperventilation syndrome

Panic attacks

Agoraphobia

Acrophobia

Phobic postural vertigo

Metabolic disorders

Hypoglycemia

Electrolyte disorders (hypercalcemia, hyponatremia)

Intoxication

Alcohol

Medication

Toxic substances

Table 3

Episodic vertigo (diseases with recurrent attacks of vertigo)

Labyrinth/vestibulo-cochlear nerve

†Meniere’s disease

†Vestibular paroxysmia

†Perilymph fistula

†Superior canal dehiscence syndrome (induced by coughing, pressing,

or loud sounds of a specific frequency, i.e. a Tullio phenomenon)

†Benign paroxysmal positioning vertigo (only during changes of

head position relative to gravity)

†Cogan’s syndrome

†Cysts or tumors of the cerebellopontine angle

Central vestibular system

†Transient vertebrobasilar ischemia

†‘Rotational vertebral artery occlusion syndrome’

†Vestibular epilepsy

†‘Room-tilt illusion’

†Paroxysmal ataxia/dysarthrophonia (multiple sclerosis)

†Episodic ataxia types 1 and 2

†Paroxysmal ‘ocular tilt reaction’

Peripheral and/or central vestibular system

†Basilar/vestibular migraine

†Benign paroxysmal vertigo of childhood

†Vertebrobasilar transient ischemia (e.g. AICA)


hallmark is unilateral hyporesponsiveness to caloric irriga-

tion. Differential diagnosis of the pathologies of sustained

central vertigo involves all acute processes of the intraaxial

infratentorial structures (involving the root entry zone of the

VIIIth nerve or the vestibular nuclei) such as multiple

sclerosis, tumors, or brainstem infarctions.

3.2.4. Positional/positioning vertigo (Table 5)

In the majority of patients presenting with this condition,

positioning vertigo is due to canalolithiasis in the posterior

semicircular canal. All central forms of positional vertigo

involve the region around the vestibular nuclei and a

neuronal loop to the cerebellar vermis (Buttner et al.,

1999a,b).

3.2.5. Oscillopsia (apparent motion of the visual scene)

(Table 6)

Patients with involuntary ocular oscillations (acquired

pendular nystagmus, downbeat or upbeat nystagmus) not

only report a worsening of visual acuity but also apparent

motion of the visual scene (Bronstein, 2004). Patients with

extraocular muscle paresis or defects of the VOR are often

unable to recognize faces or to read while walking; they

may also report oscillopsia. Either the deficiency of

compensatory eye movements (due to an inappropriate

VOR) or the deficiency of visual fixation (due to ocular

Table 4

Sustained vertigo or dizziness

Infections

Viral

Vestibular neuritis

Herpes zoster oticus

Viral neuro-labyrinthitis

Bacterial

Bacterial meningitis

Tuberculous labyrinthitis

Syphilitic labyrinthitis

Rarely

Chlamydial labyrinthitis

Lyme borreliosis

Autoimmunological inner ear diseases

Cogan’s syndrome

Neurosarcoidosis

Behcet’s disease

Cerebral vasculitis

Systemic lupus erythematosus

Polychondritis

Rheumatoid arthritis

Polyarteritis nodosa

Wegener’s granulomatosis

Giant cell arteritis

Primary antiphospholipid syndrome

Tumorous

Vestibular schwannoma

Meningeoma

Epidermoid cyst

Glomus tumor

Metastasis

Meningeosis carcinomatosa

Cholesteatoma

Vascular

Labyrinthine infarction (AICA)

Pontomedullar brainstem infarction

Vertebrobasilar ectasia

Hyperviscosity syndrome

Traumatic

Temporal bone fracture (transverseOlongitudinal fracture)

Labyrinthine concussion

Posttraumatic otolith vertigo

Perilymph fistula

Superior canal dehiscence syndrome

Brainstem concussion

Iatrogenic

Temporal bone surgery

Systemic or transtympanic administration of aminoglycosides

Other ototoxic substances

Table 5

Positional/positioning vertigo and/or nystagmus

Elicited by changes of head position relative to gravity

†Benign paroxysmal positioning vertigo

†Positional alcohol vertigo/nystagmus

†Positional nystagmus with macroglobulinemia

†Positional ‘heavy water’ nystagmus

†Central positional nystagmus

†Positional down-beating nystagmus

†Central positioning vomiting

Elicited by lateral head rotation


†Rotational vertebral artery occlusion syndrome

†Compression of the VIIIth nerve due to cerebellopontine angle mass

†Carotid sinus syndrome

Table 6

Oscillopsia (illusionary movements of the surroundings)

Without head movements

†Spontaneous vestibular nystagmus (e.g. in vestibular neuritis)

†Congenital nystagmus (depending on direction of gaze)

†Downbeat nystagmus

†Upbeat nystagmus

†Acquired pendular nystagmus

†Periodic alternating nystagmus

†Opsoclonus

†Ocular flutter


†Myokymia of the superior oblique muscle (monocular)

†Paroxysmal ‘ocular-tilt reaction’

†Spasmus nutans (infants)

†Voluntary nystagmus

During head movements

†Bilateral vestibulopathy

†Disorders of the ocular motor system (peripheral or central)


†Benign paroxysmal positioning vertigo

†Central positional/positioning vertigo

†Vestibulo-cerebellar ataxia

†Perilymph fistula

†Superior canal dehiscence syndrome

†Posttraumatic otolith vertigo

†Rotational vertebral artery occlusion syndrome

†Intoxication (e.g. anticonvulsants, alcohol)


oscillation) causes undesired retinal image motion with

disturbing oscillopsia and sometimes unsteadiness.

3.2.6. Vertigo-associated with auditory dysfunction

(Table 7)

The presence of dizziness, vertigo, or disequilibrium

combined with sensorineural hearing loss or tinnitus

narrows down the differential diagnosis to certain peripheral

vestibular disorders. The rare central vestibular disorders

that manifest with audiovestibular symptoms are vestibular

epilepsy or caudal brainstem disorders, such as occur in

multiple sclerosis. Audiovestibular dysfunction associated

with interstitial keratitis indicates infectious or autoimmune

disease. Congenital unilateral and bilateral vestibular

disorders may be combined with sensorineural hearing loss.

3.2.7. Vertigo associated with brainstem and cerebellar

symptoms (Table 8)

Clinical studies of the differential effects of central

vestibular pathway lesions have increasingly shown that

vestibular syndromes are accurate indicators for a topo-

graphic diagnosis. Vestibular pathways run from the VIIIth

nerve and the vestibular nuclei through ascending fibers,

such as the ipsilateral or contralateral medial longitudinal

fascicle, brachium conjunctivum, or the ventral tegmental

tract to the ocular motor nuclei, the supranuclear integration

centers in the rostral midbrain, and the vestibular thalamic

subnuclei. From there they reach several cortex areas

through the thalamic projections. Another relevant ascend-

ing projection reaches the cortex from the vestibular nuclei

via the vestibular cerebellum structures, in particular the

fastigial nucleus. In the majority of cases, central vestibular

vertigo/dizziness syndromes are caused by dysfunction or a

deficit of sensory input induced by a lesion. In a small

proportion of cases they are due to pathological excitation of

various structures, extending from the peripheral vestibular

organ to the vestibular cortex. Since peripheral vestibular

disorders are always characterized by a combination of

perceptual, ocular motor, and postural signs and symptoms,

central vestibular disorders may manifest as ‘a complete

syndrome’ or as only single components. The ocular motor

aspects, for example, predominate in the syndrome of

upbeat or downbeat nystagmus. Lateral falls may occur

without vertigo in vestibular thalamic lesions (thalamic

astasia) or as lateropulsion in Wallenberg’s syndrome. Most

central vestibular syndromes have a specific locus but not a

specific etiology. The etiology may, for example, be

vascular, autoimmunological (e.g. in MS), inflammatory,

neoplastic, toxic, or traumatic.

3.2.8. Vertigo associated with headache (Table 9)

Various peripheral and central vestibular disorders are

typically associated with headache, such as basilar or

vestibular migraine. One-third of patients with vestibular

migraine, however, do not complain of headache associated

with vestibular aura deficits (Dieterich and Brandt, 1999;

Neuhauser et al., 2001).

3.2.9. Dizziness or to-and-fro vertigo with postural

imbalance

Dizziness and to-and-fro vertigo with postural imbalance

are non-specific but frequently described symptoms.

Differential diagnosis on the basis of such symptoms is

very difficult, because central and peripheral vestibular

disorders but also non-vestibular syndromes such as visual

vertigo, presyncopal faintness, or somatoform phobic

postural vertigo are all possible diagnoses in this category.

Table 7

Combination of vestibular and audiological symptoms

Meniere’s disease

Perilymph fistula or superior canal dehiscence syndrome

Vestibular paroxysmia

Cerebellopontine angle tumor

Cogan’s syndrome or other inner ear autoimmune diseases

Ear/head trauma

Pontomedullary brainstem infarct

Pontomedullary MS plaque

Labyrinthine infarct (AICA, labyrinthine artery)

Hyperviscosity syndrome

Neurolabyrinthitis

Zoster oticus

Cholesteatoma

Inner ear malformation

Vestibular epilepsy

Table 8

Vertigo with additional brainstem/cerebellar symptoms

Basilar/vestibular migraine

Intoxication

Craniocervical malformations (e.g. Arnold–Chiari malformation)

Lacunar or territorial infarcts

Hemorrhages (e.g. cavernoma)

Inflammation (e.g. MS plaque)

Brainstem encephalitis

Head trauma

Tumors of the cerebellopontine angle, brainstem, or cerebellum

Episodic ataxia type 2

Creutzfeldt–Jakob disease

Table 9

Vertigo with headache

Migraine without aura

Basilar/vestibular migraine

Brainstem/cerebellar ischemia

Vertebrobasilar dissection

Infratentorial hemorrhage

Inner/middle ear infection

Head trauma (especially transverse temporal bone fracture)

Infratentorial tumor

Zoster oticus


4. Clinical neuro-ophthalmological and neuro-otological

examinations

The major aim of the neuro-ophthalmological, neuro-

otological, and neuro-orthoptic examinations is to differen-

tiate between peripheral and central vestibular forms of

dysfunction. Since the disorders underlying vertigo and

dizziness are often combined with disturbances of the ocular

motor system due to anatomical proximity, ocular motor

examination techniques (how to) are also described and an

interpretation of the typical findings and their localizing

impact or topographic determination of the lesion is given.

This non-vestibular system must always be tested in patients

suffering from vertigo and disequilibrium. Then the simple

and reliable bedside test of the vestibulo-ocular reflex, the

most important anatomical and physiological structure of

the vestibular system, is presented (Halmagyi–Curthoys

head-impulse test) (Halmagyi and Curthoys, 1988; Halma-

gyi et al., 1990) together with a recently developed test of

otolith function (‘the head-heave test’ (Ramat et al., 2001)).

Finally, positioning tests for posterior and horizontal canal

benign paroxysmal positioning vertigo (BPPV), the exam-

ination with Politzer’s balloon for perilymph fistula or

superior canal dehiscence syndrome, and the tests of stance

and gait are demonstrated. The techniques of the different

tests and their typical questions are summarized in Table 10.

4.1. Eye position and nystagmus

Clinical examination of patients with suspected vestib-

ular disorders should begin with the examination of the eyes

in 9 different positions (i.e. looking straight ahead, to the

right, left, up, down as well as diagonally right up, right

down, left up, and left down) to determine ocular alignment

(for example, a possible misalignment of the eye axes,

which may be accompanied by a head tilt, Fig. 3) (Brandt

and Dieterich, 1994a), fixation deficits, spontaneous or

fixation nystagmus (Serra and Leigh, 2002), range of

movement, and disorders of gaze-holding abilities (Buttner

and Grundei, 1995). The examination can be performed

with an object for fixation or a small rod-shaped flashlight.

In primary position one should look for periodic eye

movements, such as nystagmus (e.g. horizontal-rotatory,

suppressed by fixation as in peripheral vestibular dysfunc-

tion), vertically upward (upbeat nystagmus) (Baloh and

Yee, 1989; Fisher et al., 1983) or downward (downbeat

nystagmus syndrome) (Baloh and Spooner, 1981; Bohmer

and Straumann, 1998; Glasauer et al., 2003), or horizontal

or torsional movements with only slight suppression (or

increase) of intensity during fixation as in a central

vestibular dysfunction. A (non-vestibular) congenital nys-

tagmus (Gottlob, 1998; Maybodi, 2003) beats, as a rule,

horizontally at various frequencies and amplitudes and

Table 10

Examination procedure for ocular motor and vestibular systems

Type of examination Question

Inspection

Head, body, and posture Tilt or turn of head/body

Position of eyelids Ptosis

Eye position/motility

Position of eyes during straight-ahead gaze Misalignment in primary position, spontaneous or fixation nystagmus

Cover test Horizontal or vertical misalignment

Examination of eyes in 8 positions (binocular and monocular) Determination of extent of motility, gaze-evoked nystagmus, end-position

nystagmus

Gaze-holding function: after 10–408 in the horizontal or 10–208 in the

vertical and back to 08

Gaze-evoked nystagmus: horizontal and vertical, rebound nystagmus

Smooth pursuit movements: horizontal and vertical Smooth or saccadic

Saccades: horizontal and vertical when looking around or at targets Latency, velocity, accuracy, conjugacy

Optokinetic nystagmus (OKN): horizontal and vertical with OKN

drum or tape

Inducible, direction, phase (reversal or monocularly diagonal)

Peripheral vestibular function: clinical testing of the VOR (Halmagyi–

Curthoys test): rapid turning of the head and fixation of a stationary target

Unilateral or bilateral, peripheral vestibular (semicircular canal) deficit

Fixation suppression of the VOR: turn of head and fixation of a target

moving at same speed

Failure of fixation suppression

Examination with Frenzel’s glasses:

Straight-ahead gaze, to the right, to the left, downward, and upward Spontaneous nystagmus

Head-shaking test Provocation-induced nystagmus

Positioning and positional maneuver (with Frenzel’s glasses): to the right,

left, head-hanging position, turning about the cephalocaudal axis

Peripheral positional or positioning nystagmus, central positional

nystagmus

Posture and balance control:

Romberg’s test and simple and difficult posture and gait tests: Instability, tendency to fall

Open-closed eyes

With/without reclining the head

With/without distraction (writing numbers on the skin, doing maths

mentally)

Psychogenic/functional components


increases during fixation. So-called square-wave jerks

(small saccades [0.5–58]) that cause the eyes to oscillate

around the primary position increasingly occur in progress-

ive supranuclear palsy or certain cerebellar syndromes

(Averbuch-Heller et al., 1999; Rascol et al., 1991; Shallo-

Hoffmann et al., 1990). Ocular flutter (intermittent rapid

bursts of horizontal oscillations without an intersaccadic

interval) or opsoclonus (combined horizontal, vertical, and

torsional oscillations) occur in various disorders (Helmchen

et al., 2003; Wong et al., 2001) such as encephalitis, tumors

of the brainstem or cerebellum, intoxication, or in

paraneoplastic syndromes (Bataller et al., 2003).

The examination of the eyes with Frenzel’s glasses

(Fig. 4) is a sensitive method for detecting spontaneous

nystagmus. This can also be achieved by examining one eye

with an ophthalmoscope (while the other eye is covered) and

simultaneously checking for movements of the optic papilla

or retinal vessels (Zee, 1978) even with low, slow-phase

velocities/frequencies or square-wave jerks (small saccades

[0.5–58] that are often observed in progressive supranuclear

palsy or certain cerebellar syndromes) (Leigh and Zee,

1999). Since the retina is behind the axis of rotation of the

eyeball, the direction of any observed vertical or horizontal

movement is opposite to that of the nystagmus detected with

this method, i.e. a downbeat nystagmus causes a rapid,

upward movement of the optic papilla or retinal vessels.

After checking for possible eye movements in primary

position and the misalignment of the axes of the eyes,

the examiner should then establish the range of eye

movements monocularly and binocularly in the 8 end-

positions; deficits found here can indicate, e.g. extraocular

muscle or nerve palsy. Gaze-holding deficits (Buttner and

Grundei, 1995; Leigh and Zee, 1999) can also be

determined by examining eccentric gaze position. Use of a

small rod-shaped flashlight has the advantage that the

corneal reflex images can be observed and thus ocular

misalignments can be easily detected (note: it is important to

observe the corneal reflex images from the direction of the

illumination and to ensure that the patient attentively fixates

the object of gaze.) The flashlight also allows one to

determine whether the patient can fixate with one or both

eyes in the end-positions. This is important for detecting a

defect of gaze holding. Gaze-evoked nystagmus can only be

clearly identified when the patient fixates with both eyes. It

is most often a side effect of medication (e.g. anti-

convulsants, benzodiazepines) or toxins (e.g. alcohol).

Horizontal gaze-evoked nystagmus can indicate a structural

lesion in the area of the brainstem or cerebellum (vestibular

nucleus, nucleus prepositus hypoglossi, flocculus, i.e. the

neural eye velocity to position integrator). Vertical

gaze-evoked nystagmus is observed in midbrain lesions

involving the interstitial nucleus of Cajal (Bhidayasiri et al.,

2000; Buttner and Grundei, 1995; Leigh and Zee, 1999). A

dissociated horizontal gaze-evoked nystagmus (greater in

Fig. 3. Measurement of head tilt. An abnormal head posture to the right or

left shoulder or a constant, abnormal tilt is especially observed in patients

with (a) paresis of the oblique eye muscles, e.g. in superior oblique palsy,

the head is turned to the non-affected side to lessen diplopia, or (b) an

ocular tilt reaction due to a vestibular tonus imbalance of the VOR in roll.

As a rule, the head is tilted to the side of the lower eye. Acute unilateral

lower medullary lesions (e.g. involvement of the vestibular nuclei in

Wallenberg’s syndrome) or acute unilateral peripheral vestibular lesions

cause an ipsiversive head tilt, whereas pontomesencephalic lesions of

vestibular pathways cause a contraversive head tilt.

Fig. 4. Clinical examination with Frenzel’s glasses. The magnifying lenses

(C16 diopters) with light inside prevent visual fixation, which could

suppress spontaneous nystagmus. Frenzel’s glasses enable the clinician to

better observe spontaneous eye movements. Examination should include

spontaneous and gaze-evoked nystagmus, head-shaking nystagmus (either

the examiner turns the subject’s head or the patient is instructed to quickly

turn his head to the right and to the left about 20–30 times; the eye

movements are observed after head shaking), positioning and positional

nystagmus, as well as hyperventilation-induced nystagmus. Spontaneous

nystagmus indicates a tonus imbalance of the vestibulo-ocular reflex; if it is

caused by a peripheral lesion—as in vestibular neuritis—the nystagmus is

typically dampened by visual fixation. Head-shaking nystagmus shows a

latent asymmetry of the so-called velocity storage, which can be due to

peripheral and central vestibular disorders.


the abducting than the adducting eye) in combination with

an adduction deficit points to internuclear ophthalmoplegia

due to a defect of the medial longitudinal fascicle (MLF),

ipsilateral to the adduction deficit. Downbeat nystagmus

usually increases in eccentric gaze position and when

looking down. To examine for a so-called rebound

nystagmus the patient should gaze at least 15 s to one side

and then return the eyes to the primary position; this can

cause a transient nystagmus to appear with slow phases in

the direction of the previous eye position. Rebound

nystagmus generally indicates cerebellar dysfunction or

damage to the cerebellar pathways (Hood, 1981; Hood et al.,

1973).

4.2. Smooth pursuit

The patient is asked to visually track an object moving

slowly in horizontal and vertical directions (10–208/s) while

keeping his head stationary. Corrective (catch-up or back-

up) saccades are looked for; they indicate a smooth pursuit

gain that is too low or too high (ratio of eye movement

velocity and object velocity). Many anatomical structures

(visual cortex, motion sensitive areas MT, V5, frontal eye

fields, dorsolateral pontine nuclei, cerebellum, vestibular

and ocular motor nuclei) are involved in smooth pursuit eye

movements, which keep the image of a moving object stable

on the fovea (Buttner and Grundei, 1995; Gaymard and

Pierrot-Deseilligny, 1999; Lisberger et al., 1987; Pierrot-

Deseilligny and Gaymard, 1992). These eye movements are

also influenced by alertness, various drugs, and age. Even

healthy persons exhibit a slightly saccadic smooth pursuit

during vertical downward gaze. For these reasons a saccadic

smooth pursuit as a rule does not allow either an exact

topographical or etiological classification. Marked asymme-

tries of smooth pursuit, however, indicate a structural

lesion; strongly impaired smooth pursuit is observed in

intoxication (anticonvulsives, benzodiazepines, or alcohol)

as well as degenerative disorders involving the cerebellum

or extrapyramidal system (Gaymard and Pierrot-Deseil-

ligny, 1999; Pierrot-Deseilligny and Gaymard, 1992). A

reversal of slow smooth pursuit eye movements during

optokinetic stimulation is typical for congenital nystagmus

(see above).

4.3. Saccades

First, it is necessary to observe spontaneous saccades

triggered by visual or auditory stimuli. Then the patient is

asked to glance back and forth between two horizontal or

two vertical targets. The velocity, accuracy, and the

conjugacy of the saccades should be noted. Normal

individuals can immediately reach the target with a fast

single movement or one small corrective saccade (Botzel

et al., 1993). Slowing of saccades—often accompanied by

hypometric saccades—occurs for example with intoxication

(medication, especially anticonvulsives or benzodiazepines)

(Thurston et al., 1984) or in neuro-degenerative disorders

(Troost et al., 1974). Slowing of horizontal saccades is

generally observed in brainstem lesions; there is often a

dysfunction of the ipsilateral paramedian pontine reticular

formation (PPRF) (Gaymard and Pierrot-Deseilligny,

1999). Slowing of vertical saccades indicates a midbrain

lesion in which the rostral interstitial medial longitudinal

fascicle (riMLF) is involved, not only in ischemic

inflammatory diseases but also in neuro-degenerative

diseases, especially progressive supranuclear palsy

(Bhidayasiri et al., 2001; Burn and Lees, 2002; Kuniyoshi

et al., 2002; Troost and Daroff, 1977). Hypermetric

saccades, which can be identified by a corrective saccade

back to the object, indicate lesions of the cerebellum

(especially the vermis) or the cerebellar pathways. Patients

with Wallenberg’s syndrome make hypermetric saccades

toward the side of the lesion due to a dysfunction of the

inferior cerebellar peduncle; defects of the superior

cerebellar peduncle, conversely, lead to contralateral

hypermetric saccades (Helmchen et al., 1994; Robinson et

al., 2002). A slowing of the adducting saccade ipsilateral to

a defective MLF is pathognomonic for internuclear

ophthalmoplegia (INO) (Cremer et al., 1999; Zee, 1992).

Delayed onset saccades are mostly caused by supratentorial

cortical dysfunction (Leigh and Zee, 1999).

4.4. Vestibulo-ocular reflex

One bedside test is of special clinical importance: the

head-impulse test of Halmagyi and Curthoys (Halmagyi and

Curthoys, 1988; Halmagyi et al., 1992); it allows the

examination of the horizontal VOR. This test is closely

related to the purpose and special properties of the VOR (see

above).

Fig. 5 summarizes how to do this test and how to

interpret the findings. The test also allows examination not

only of the horizontal, but also of the vertical canals,

because they can be stimulated in specific planes and sides,

e.g. the left anterior semicircular canal can be stimulated by

moving the head in the plane of this canal downward and

observing the induced eye movements. According to our

experience, the head-impulse test is very helpful; if it gives a

pathological finding, it is not necessary to do an additional

caloric irrigation.

Testing dynamic visual acuity (subject turns his head

horizontally to the right and left with a frequency of about

1 Hz and visual acuity is determined by, e.g. the Snellen

chart) is also helpful in diagnosing bilateral vestibular

failure (Burgio et al., 1992). A decrease of visual acuity by

at least 3 lines is pathological and indicates a bilateral deficit

of the VOR.

4.5. The head-heave test for otolith testing

This is a bedside test for utricular function and the trans-

lational VOR (Ramat et al., 2001). The head of the subject


has to be moved manually in a horizontal direction to the

right and left with brief but highly accelerated motions

(‘heaves’). The ocular response to the translation is a

compensatory eye movement to keep the target stable on

the retina. This eye movement response is asymmetrical in

patients with a unilateral peripheral vestibular lesion. For

instance, if the patient has a left-sided peripheral vestibular

lesion and his head is moved toward the affected side, the

examiner can easily observe a corrective saccade to the right.

This indicates a deficit of the translational VOR (Ramat et al.,

2001) on analogy to the ‘head thrust sign’ (Halmagyi and

Curthoys, 1988).

4.6. Positioning/positional maneuvers

All patients should also be examined with the so-called

Dix-Hallpike maneuver (Fig. 6) in order not to overlook the

most common form of vertigo, benign paroxysmal position-

ing vertigo (BPPV) (Brandt and Steddin, 1993; Schuknecht,

1969) of the posterior as well as central positioning/posi-

tional nystagmus or vertigo (Bertholon et al., 2002; Brandt,

1990; Buttner et al., 1999a,b). In addition, the ‘barbecue-

spit maneuvers’ should be performed to look for a BPPV of

the horizontal canal (Baloh et al., 1993; McClure, 1985;

Pagnini et al., 1989; Strupp et al., 1995), which is

characterized by a linear horizontal nystagmus beating in

most cases to the undermost ear (‘geotropic’), but in some

cases to the uppermost ear (Bisdorff and Debatisse, 2001).

4.7. Miscellaneous

4.7.1. Visual fixation suppression of the VOR

A disorder of visual fixation suppression of the VOR

(which as a rule occurs with smooth pursuit abnormalities,

as these two functions are mediated by common neural

pathways) (Takemori, 1983) is often observed in lesions of

the cerebellum (flocculus or paraflocculus) or of the

cerebellar pathways and in progressive supranuclear palsy

(see above). Anticonvulsants and sedatives can also impair

visual fixation of the VOR. Before testing visual fixation

suppression of the VOR, it is necessary to confirm that the

VOR is intact.

4.7.2. Head-shaking nystagmus

To test for head-shaking nystagmus (HSN), the examiner

turns the subject’s head by aboutG458 horizontally about 30

times within about 15 s or the patient does it by himself.

HSN is defined as the occurrence of at least 5 beats of

nystagmus immediately after the head-shaking maneuver,

which should be performed with Frenzel’s glasses. There is

good evidence that HSN reflects a dynamic (peripheral

and/or central vestibular) asymmetry of the velocity-storage

mechanism (Hain and Spindler, 1993; Hain et al., 1987). In

peripheral lesions, the ipsilateral dynamic VOR deficit leads

to an asymmetric accumulation within the velocity storage,

the discharge of which determines the direction of HSN,

usually toward the unaffected ear (Hain and Spindler, 1993).

Head-shaking nystagmus rarely beats toward the

affected ear; this may be related to recovery nystagmus

(‘Erholungsnystagmus’) when prior compensation becomes

inappropriately excessive as a peripheral function recovers.

Central vestibular lesions may also induce an asymmetry in

Fig. 5. Clinical examination of the horizontal vestibulo-ocular reflex (VOR)

by the head-impulse test (Halmagyi and Curthoys, 1988). To test the

horizontal VOR, the examiner holds the patient’s head between both hands,

asks him to fixate a target in front of his eyes, and rapidly and arbitrarily

turns the patient’s head horizontally to the left and then to the right. This

rotation of the head in a healthy subject causes rapid compensatory eye

movements in the opposite direction (a). In cases of unilateral labyrinthine

loss the patient is not able to generate the VOR-driven fast contraversive

eye movement and has to perform a corrective (catch up) saccade to re-

fixate the target. Part b explains the findings in a patient with a loss of the

right horizontal canal. During rapid head rotations toward the affected right

ear, the eyes move with the head to the right and the patient has to perform a

refixation saccade to the left; the latter can be easily detected by the

examiner.

Fig. 6. The so-called Dix-Hallpike maneuver is performed to determine

whether benign paroxysmal positioning vertigo (BPPV) is present. While

the patient is sitting, his head is turned by 458 to one side, and then he is

rapidly put in a supine position with head hanging over the end of the

examination couch. If a BPPV of the left posterior semicircular canal, for

example, is present, this maneuver will induce, with a certain latency, a

crescendo–decrescendo-like nystagmus, which from the patient’s view-

point beats counterclockwise toward the left ear and to the forehead. When

the patient is returned to a sitting position, the direction of nystagmus will

change.


velocity storage, which itself can produce HSN even though

the peripheral vestibular inputs are balanced. Furthermore,

horizontal head-shaking may also lead to a vertical

nystagmus due to cross-coupling of nystagmus, which is

also compatible with a central vestibular origin of HSN

(Leigh and Zee, 1999). Head-shaking nystagmus may

indicate a ‘latent’ (compensated) vestibular tonus imbal-

ance, since it has also been found in healthy control subjects

(12 of 50) (Asawavichiangianda et al., 1999).

4.7.3. Politzer’s balloon: testing for perilymph fistula or

superior canal dehiscence syndrome

Patients who report attacks of rotatory or postural vertigo

caused by changes in pressure, for example, by coughing,

pressing, sneezing, lifting, or loud noises and accompanied

by illusory movements of the environment (oscillopsia) and

instability of posture and gait with or without hearing

disturbances may suffer from perilymph fistula (Nomura,

1994) and should be tested with Politzer’s balloon. The

balloon can be used to apply positive and negative pressures

to the middle ear. One should look for eye movements,

especially nystagmus, vertigo, dizziness, oscillopsia, or

blurred vision induced by these changes in pressure. A

perilymph fistula may be caused by (a) a pathological

motility of the membrane of the oval or round window or the

ossicular chain with a hypermotility of the oval window

(Dieterich et al., 1989) or (b) bony defects in the region of

the lateral wall of the labyrinth (toward the middle ear)

together with a partial collapse of the perilymphatic space,

so-called ‘floating labyrinth’ (Nomura et al., 1992).

A bony defect toward the epidural space of the anterior

canal is the cause of the ‘dehiscence of the superior

semicircular canal,’ in which vertigo and/or eye movements

can also be induced by changes in pressure, e.g. by

Politzer’s balloon (Deutschlander et al., 2004; Minor et

al., 1998). The superior canal dehiscence syndrome can be

diagnosed by high resolution CT scan of the temporal bone

(Hirvonen et al., 2003).

4.7.4. Hyperventilation

Hyperventilation leads to alkalosis and changes in the

transmembraneous potential of cells which cause increased

excitability. It may induce a transient nystagmus in

vestibular paroxysmia, which is characterized by recurrent

but short attacks of vertigo due to a neurovascular cross-

compression of the VIIIth cranial nerve in the root entry

zone as in trigeminal neuralgia (Brandt and Dieterich,

1994b; Jannetta et al., 1984; Moller et al., 1986), and in

vestibular schwannoma (Minor et al., 1999). Downbeat

nystagmus due to cerebellar lesions may also worsen during

hyperventilation (Walker and Zee, 1999).

4.8. Stance and gait

Finally, the patient’s balance should be examined under

static conditions There are different variations of the

Romberg and one-leg stance test: feet next to each other

with eyes first open and then closed (to eliminate visual

cues); standing on one foot at a time with the head in normal

position or with reclining head (the latter creates extreme

imbalance). If a psychogenic disorder is suspected, the

examiner distracts the patient by writing numbers on her

arm or having her do maths mentally. If there is

improvement under the last condition, the stance disorder

has a psychogenic-functional origin. Another variation is

the Romberg test in tandem, during which the patient places

one foot directly in front of the other (the toes of one foot

touch the heel of the other). Excessive fore–aft, right–left, or

diagonal sway should be looked for. A peripheral vestibular

functional disorder typically causes ipsiversive falls; upbeat

and downbeat nystagmus syndromes are typically associ-

ated with increased body sway forward and backward once

the eyes are closed. The analysis of posture and gait

Table 11

Disturbance of posture and gait control in peripheral vestibular disorders

Illness Direction of deviation Pathomechanism

Vestibular neuritis Ipsiversive Vestibular tonus imbalance due to failure of the horizontal and anterior

semicircular canal and utricle (Strupp, 1999)

Benign paroxysmal positioning ver-

tigo (BPPV)

Forward and ipsiversive Ampullofugal stimulation of the posterior canal due to canalolithiasis that

leads to endolymph flow (Brandt and Steddin, 1993; Brandt et al., 1994)

Attacks of Meniere’s disease

(Tumarkin’s otolithic crisis)

Lateral ipsiversive or contraversive

(falls)

Variations of the endolymph pressure lead to an abnormal stimulation of

the otoliths and sudden vestibular–spinal tonus failure (Odkvist and

Bergenius, 1988; Schuknecht and Gulya, 1983)

Tullio phenomenon Backward, contraversive, diagonal Stimulation of the otoliths by sounds of certain frequencies, e.g. in cases

of perilymph fistulas or superior canal dehiscence syndrome (Tullio,

1927)

Vestibular paroxysmia Contraversive or in different direc-

tions

Neurovascular compression of the vestibulo-cochlear nerve and

excitation (rarely inhibition) of the vestibular nerve (Arbusow et al.,

1998; Brandt and Dieterich, 1994b)

Bilateral vestibulopathy All directions, especially forward

and backward

Failure of vestibular–spinal postural reflexes, exacerbated in the dark and

on uneven ground (Rinne et al., 1995)


instability frequently allows differentiation between periph-

eral (Table 11) and central vestibular disorders (Table 12)

(Bronstein et al., 2004; Jacobson et al., 1993).

5. Laboratory examinations

The laboratory examinations measure:

(a) eye movements by, e.g. electronystagmography (ENG),

video-oculography, and the magnetic search coil

technique;

(b) semicircular canal function by either caloric irrigation

for the horizontal canal, rotational testing or determi-

nation of the gain of the VOR for all 3 canals by

combining the head-impulse test (see above, Fig. 5);

(c) otolith function by assessing the eye position in roll by

the laser-scanning ophthalmoscope, ocular counterroll

(a test which still has to be established for general

vestibular testing), and vestibular-evoked myogenic

potentials for saccule function;

(d) spatial perceptional function, e.g. by determining the

subjective visual vertical; and

(e) postural control by means of posturography. Figs. 9–13

and Table 4 summarize the essential neuro-ophthalmo-

logical laboratory procedures of examination, give

typical findings, indicate how to interpret them, and

describe an orthoptic examination.

Table 13 shows the advantages and disadvantages of the

different laboratory examinations in comparison with the

neuro-ophthalmological and neuro-orthoptic examinations.

Table 13

Neuro-ophthalmological examination and laboratory diagnostics for vestibular and ocular motor disorders

Technique Features Advantages Disadvantages

Neuro-ophthalmological

examination

Total range of eye movements,

horizontal, vertical (torsional)

No technical requirements, simple,

resolution !18

No recording, eye movement velocity cannot

be judged

Orthoptic examination Fundus photography, determination

of eye misalignment and psycho-

physical determination of, e.g. the

subjective visual vertical

Precise measurement with docu-

mentation, non-invasive, well-toler-

ated

Expensive apparatuses (e.g. scanning laser

ophthalmoscope)

ENG Measurement rangeG408,

resolution of 18

Non-invasive, well-tolerated even

by children, caloric stimulation

possible, widespread method

No measurement of torsional and poor

measurement of vertical movements, eyelid

artifacts, baseline drift

Video-oculography Measurement rangeG408,

resolution of 0.1–18

Non-invasive, well-tolerated, poss-

ible to measure torsion

Measurement only possible with eyes open, 3-

D analysis is still complicated and expensive

Infrared system Measurement rangeG208,

resolution of 0.18

High resolution, non-invasive Measurements only possible with open eyes,

relatively expensive, vertical measurements

poor, torsional measurements not possible

Magnetic-coil technique Measurement rangeG408,

resolution of 0.028

Best resolution of horizontal, verti-

cal, and torsional movements

(research)

Semiinvasive, unpleasant, expensive, only

with cooperative patients, maximum of

30 min, local anesthetic necessary

Vestibular-evoked

myogenic potentials

Examination of saccular function Non-invasive, well-tolerated, simple

to perform

Still moderate clinical experience has been

made, some findings in part still contradictory

Table 12

Disturbance of posture and gait control in central vestibular disorders

Illness Direction Pathomechanism

Vestibular epilepsy

(rare)

Contraversive Focal seizures due to epileptic discharges of the vestibular cortex (Brandt

and Dieterich, 1993b)

Thalamic astasia (often

overlooked)

Contraversive or ipsiversive Vestibular tonus imbalance due to posterolateral lesions of the thalamus

(Masdeu and Gorelick, 1988)

Ocular tilt reaction Contraversive with mesencephalic lesions,

ipsiversive with pontomedullary lesions

Tonus imbalance of the vestibulo-ocular reflex in the roll plane with

lesions of the vertical canals or otolith pathways (Brandt and Dieterich,

1993a)

Paroxysmal ‘ocular tilt

reaction’

Ipsiversive with mesencephalic excitation,

contraversive with pontomedullary excitation or

excitation of the vestibular nerve

Pathological excitation of the otolith or vertical canal pathways (VOR in

the roll plane) (Dieterich and Brandt, 1993b)

Lateropulsion (Wallen-

berg’s syndrome)

Ipsiversive, diagonal Central vestibular tonus imbalance (‘roll and yaw planes’) with tilt of

subjective vertical (Dieterich and Brandt, 1992)

Downbeat nystagmus

syndrome

Backward Vestibular tonus imbalance in the ‘pitch plane’ (Brandt and Dieterich,

1995)


To clarify the cause of disorders (differential diagnoses:

ischemia, hemorrhage, tumor, or inflammation) additional

imaging techniques (Casselman, 2002; Mark and Fitzgerald,

1994) are necessary: primarily cranial magnetic resonance

imaging with precise sections of the brainstem, the

cerebellopontine angle, and the labyrinth; high resolution

CT of the temporal bone, e.g. in superior canal dehiscence

syndrome or temporal bone fractures; Doppler sonography;

and in some cases also a spinal tap, auditory evoked

potentials, and audiometry. As a rule, an otolaryngologist

gives a hearing test. In connection with the main symptom

of vertigo, audiometry is especially important for

diagnosing Meniere’s disease, labyrinthitis, vestibular

schwannoma, and other diseases of the vestibulo-cochlear

nerve as well as bilateral vestibulopathy. These techniques

are not described in this review.

5.1. Measurements of eye movements/eye position

5.1.1. Electronystagmography (ENG)

To quantitatively record eye movements, two electrodes

are placed horizontally and vertically on each eye so that the

changes in the dipole between the retina and cornea, which

occur with eye movements, can be recorded (Fig. 7)

Fig. 7. Electronystagmography (ENG). (a) Placement of the electrodes for monocular recording of horizontal and vertical eye movements. The

electrophysiological basis of the ENG is the corneo-retinal dipole (a potential difference of about 1 mV). The dipole is parallel to the longitudinal axis of the

eye, with the retina or the cornea having a negative potential. Changes in this dipole between the horizontal or vertical electrodes are DC-amplified. The ENG

allows non-invasive horizontal recordings of G408 with an accuracy of about 18 and vertical recordings of G208. Major disadvantages are susceptibility to

eyeblink artifacts, electromyographic activity, and unstable baseline; torsional eye movements cannot be recorded with the ENG. (b) Rotatory chair and

rotatory drum (with vertical stripes) with an apparatus that projects a laser spot (above the patient). This setup allows recordings of eye movements under static

conditions (e.g. test for spontaneous or gaze-evoked nystagmus, saccades, pursuit, and optokinetic nystagmus) and under dynamic conditions (per- and

postrotatory nystagmus, fixation suppression of the vestibulo-ocular reflex), as well as positional and positioning testing and caloric irrigation. (c) Caloric

testing by electronystagmography. By means of caloric testing, the excitability of the individual horizontal canals can be determined and thus whether or not

they are functioning. After excluding the possibility of a lesion of the eardrum, the head of the patient is tilted 308 upward, so that the horizontal semicircular

canals approach the vertical plane. This allows optimal caloric stimulation. The outer auditory canals on each side are separately irrigated under standard

conditions with 30 8C cool and 44 8C warm water. At the same time the horizontal and vertical eye movements are recorded by means of

electronystagmography. The irrigation with 44 8C warm water causes excitation of the hair cells of the horizontal canal and slow contraversive eye movements;

the 30 8C cool water leads to an inhibition of the slow ipsiversive eye movements.


(Furman et al., 1996; Jongkees et al., 1962). ENG also

allows documentation of the findings (important for

monitoring the course of the patient) and, for example,

exact measurements of saccade velocity and saccade

accuracy. In addition, irrigation of the external auditory

canal with 30 8C cool and 44 8C warm water (caloric

testing) can be used to detect loss of labyrinthine function

(horizontal canal). To quantify peripheral vestibular func-

tion the maximal velocity of the irrigation-induced eye

movements (peak slow phase velocity, PSPV) should be

measured; PSPV values less than 58/s are considered

pathological. Since there is considerable interindividual

variation of caloric excitability, the so-called ‘vestibular

paresis formula’ of Jongkees (Jongkees et al., 1962) is used

to compare the function of both labyrinths: (((R308CCR448C)K(L308CCL448C))/(R308CCR448CCL308CCL448C))!100, where for instance, R 308C is the PSPV

during caloric irrigation with 308C cool water. Values of

>25% asymmetry between the affected and non-affected

labyrinth are considered pathological and indicate, for

example, a unilateral peripheral vestibular disorder. This

formula allows a direct comparison of the function of the

horizontal semicircular canals of both labyrinths and is

highly reliable in detecting unilateral peripheral vestibular

loss (Fife et al., 2000). This is also a reliable parameter for

follow-up or treatment studies (Strupp et al., 2004).

Rotational chair testing requires that the subject sit on a

chair that rotates or oscillates with certain velocities/fre-

quencies, while his eye movements are being measured in

parallel by electronystagmography (or video-oculography,

see below). During longer rotations at constant speed,

however, the thus-induced rotational nystagmus resolves

(time constant about 20 s). If the rotational chair is then

suddenly stopped, postrotational nystagmus (P I) can also be

measured. The aim of rotational chair testing is to determine

the gain of the VOR, i.e. the slow component eye velocity:

head velocity (a gain of 1.0 indicates a perfect VOR). In

contrast to caloric irrigation (which tests the VOR at a

single, effectively very low frequency of 0.003 Hz),

rotational chair testing allows examination of the VOR at

different frequencies. Since rotation affects both labyrinths

simultaneously, it is not very helpful for diagnosing

unilateral vestibular hypofunction. However, it is the only

reliable test for bilateral vestibular failure (Baloh et al.,

1984a,b; Hess et al., 1985).

All in all, ENG including caloric irrigation and rotational

chair testing is the most important and clinically relevant

neuro-otological laboratory examination. Therefore, every

patient with vertigo or dizziness should be examined at least

once by this technique or by video-oculography (see 5.1.2).

Although widely used, electronystagmography has certain

limitations. The measurement of vertical eye movements is

not always reliable, especially due to artifacts of eyelid

movements. Other muscle artifacts and electronic noise

reduce its sensitivity, and there may be a baseline drift,

mainly due to the subject’s sweating (Baloh and Honrubia,

1979; Black and Hemenway, 1972).

5.1.2. Video-oculography

Video-oculography or video-nystagmography is another

non-invasive method that is now being used more frequently

(Vitte and Semont, 1995a,b; Schneider et al., 2002). It has

the same clinical relevance as ENG but is cheaper and easier

to handle. The eyes are first filmed by one or two video

cameras (i.e. monocular or binocular recording) integrated

in a mask attached to the head. Then a computer analysis of

the image of movements of the pupils and light reflexes is

performed to represent the eye movements in two dimen-

sions. This method allows rapid and reliable recording of

horizontal and vertical eye movements (without muscle

artifacts or unstable baseline). Recording is only possible

when the eyes are wide open, and the resolution is limited

due to the image repeat frequency of the video camera

(today generally limited to 100 Hz). There is a largely linear

resolution in the range of G308. The use of 3-D

representation of eye movements for research purposes

(i.e. additional measurement of torsion) requires an

extensive analysis of the image of the iritic structures or

of two additional marker dots applied to the sclera (Fig. 8)

(Schneider et al., 2002).

5.1.3. Magnetic search coil technique

The magnetic search coil technique (Fig. 9) is the gold

standard of scientific eye movement recordings for several

reasons (Bartl et al., 1996; Robinson, 1963). It allows the

recording of horizontal, vertical, and torsional eye move-

ments, i.e. in all 3 planes, including recordings of head

movements (see below). Its sensitivity is !5 min of an arc

and the drift is minimal. With the magnetic search coil

Fig. 8. Video-oculography performed with a mask attached to the head in

which a camera is integrated. An infrared headlight built into the mask also

allows measurement of eye movements in complete darkness. The signal of

the integrated camera is transmitted to a normal digital video camera and

finally stored on a PC. The pictures are analyzed offline by means of a

video-oculography program that calculates the eye movements. A Cajal dot

placed on the sclera simplifies the registration or analysis of eye movements

in the roll plane.


technique, eye movements can be recorded and analyzed

three-dimensionally and their trajectory reconstructed, thus,

the semicircular canal(s) involved can be determined. This

is important for the diagnosis of, e.g. superior canal

dehiscence syndrome (Cremer et al., 2000a,b), or detailed

analysis of BPPV (Fetter and Sievering, 2000), vestibular

neuritis (Fetter and Dichgans, 1996), isolated lesions of

certain semicircular canals (Cremer et al., 2000a,b), and

alcohol-induced nystagmus (Fetter et al., 1999).

The major disadvantage of this ‘semiinvasive’ method is

that a kind of contact lens has to be used which makes

necessary the application of topical anesthetic drops to the

cornea. These drops are rarely harmful to the cornea.

Recordings longer than 20–30 min should not be performed.

In general, the magnetic search coil technique is mainly

used as a research tool; its clinical relevance is limited.

5.1.4. Measurement of the static eye position

in the roll plane

Measurement of ocular torsion by fundus photography or

the ‘scanning laser ophthalmoscope’ (Ott and Eckmiller,

1989) (Fig. 10) is of special importance for the diagnosis of

central vestibular disorders that affect graviceptive path-

ways, e.g. the ocular tilt reaction and for the differentiation

of ocular tilt reaction (OTR) (Brandt and Dieterich, 1993a;

Dieterich and Brandt, 1993b; Strupp et al., 2003) and

trochlear palsy (Dieterich and Brandt, 1993a). This

technique has become more and more important in centers

specialized in the diagnosis and treatment of patients

suffering from vertigo or dizziness.

5.2. Measurements of the gain of the VOR and of otolith

function

5.2.1. Three-dimensional analysis of eye movements

and the VOR

Ewald’s first law predicts that the axis of the

nystagmus matches the anatomic axis of the semicircular

canal that generated it (Ewald, 1892). This law is

clinically useful when diagnosing the detailed pathology

of the vestibular end-organ. The magnetic search coil

technique (5.1.3 and Fig. 9) in combination with the head-

impulse test (4.4 and Fig. 5) allows calculation of the gain

of the VOR for each plane and thus, for each semicircular

canal (Cremer et al., 1988; Cremer et al., 2000a,b; Della-

Santina et al., 2001; Halmagyi et al., 1991; Halmagyi

et al., 1992). The involvement of certain canals, for

instance, in vestibular neuritis can be determined by this

method (Aw et al., 2001).

5.2.2. Measurement of otolith function

5.2.2.1. Vestibular-evoked myogenic potentials (VEMPs). In

response to loud clicks, a vestibular-evoked potential can be

recorded from sternocleidomastoid muscles. This is called a

‘vestibular-evoked myogenic potential’ (VEMP) (Fig. 11)

(Colebatch et al., 1994; Murofushi et al., 1996; Murofushi

et al., 2002). There is evidence that VEMPs originate in the

medial (striola) area of the saccular macula (Murofushi

et al., 1995). Therefore, they should test for otolith function

and also for central lesions, which may show pathological

latencies in case of multiple sclerosis (Murofushi et al.,

2001b). The findings for individual illnesses are as follows.

Vestibular neuritis: the VEMP is preserved in two-thirds of

the patients. This is due to the sparing of the pars inferior of

the vestibular nerve, which supplies the saccule and

posterior canal, among others (Colebatch, 2001; Murofushi

et al., 1996). Tullio phenomenon in cases of superior canal

dehiscence syndromes or perilymph fistula: here there is a

clearly lowered stimulus threshold, i.e. a stimulus reaction

occurs already at low dB values. Bilateral vestibulopathy:

Fig. 10. Measurement of the eye position in the roll plane. The scanning

laser ophthalmoscope (SLO) can be used to make photographs of the

fundus of the eye (examination is also possible with a fundus camera). The

rolling of the eye or eye torsion can be measured in degrees on the fundus

photographs as the angle between the horizontal and the so-called

papillofoveal meridian. The patient sits upright, looks into the SLO, and

fixates a dot. (It is not necessary to administer a mydriatic drug; however, it

is necessary if the measurement is made with traditional fundus

photography). Both eyes of healthy controls exhibit a slightly excyclotropic

position in the roll plane, i.e. counterclockwise rotation of the right eye,

clockwise rotation of the left eye (from the viewpoint of the examiner). The

normal range (G2 SDs) is from K1 to 11.5 degrees. Values outside this

range are considered pathological (e.g. patients with a peripheral vestibular

lesion show an ipsiversive ocular torsion).

Fig. 9. The magnetic search coil technique. Silastic annulus with imbedded

coils of fine wire is put on the cornea. The subject sits in a magnetic field

within a cage. Changes of the eye position cause a current that is amplified

and recorded, thus allowing the three-dimensional recording of eye

movements.


the VEMP is absent in only a portion of the patients; this

should be interpreted as a sign of additional damage to the

saccular function (Colebatch, 2001; Matsuzaki and Mur-

ofushi, 2001). Meniere’s disease: the VEMPs are frequently

reduced or absent (Murofushi et al., 2001a). The clinical

relevance of VEMP for general vestibular testing has still to

be evaluated.

5.3. Psychophysical procedures

5.3.1. Measurement of the subjective visual vertical

Recent years have witnessed the growing importance of

psychophysical examination procedures, in particular the

psychophysical determination of the subjective visual

vertical (SVV) (Fig. 12) (Bohmer and Mast, 1999; Bohmer

and Rickenmann, 1995). The topographical and diagnostic

significance of these procedures is particularly evident when

differentiating between peripheral and central vestibular or

ocular motor lesions and between OTR (Brandt and

Dieterich, 1993a) and trochlear palsy (Dieterich and Brandt,

1993a). In our experience the determination of SVV is an

important clinical tool for all patients suffering from vertigo,

dizziness, or ocular motor disorders. It is easy to handle and

the findings are easy to interpret.

5.4. Posturography

Posturography allows the examination and quantification

of postural stability under different conditions, such as

standing with the eyes open/eyes closed, standing on firm

ground, or standing on a foam rubber platform (Fig. 13) and

under static or dynamic conditions (Baloh et al., 1998;

Black, 2001; Black et al., 1989; Di Fabio, 1996; Furman,

1994; Hamid et al., 1991). From the raw data (measured

changes in the center of gravity to the right, left, forward,

Fig. 11. Vestibular-evoked myogenic potentials (VEMPs). The VEMP is

used to test the reflex arc of the saccule which extends over the vestibular

nerves, vestibular nuclei, interneurons, and motor neurons to the neck

musculature (sternocleidomastoid m.). It complements caloric testing, since

the latter tests only the canal system and not the otolith function. The

prerequisite for VEMP testing is an intact middle ear function; it is not

necessary that hearing be preserved, since the ‘sensitivity to sound’ of the

saccule can be used in the VEMP. The reflex is triggered by a loud click.

Surface EMG is used to record from both sternocleidomastoid muscles. (a)

Healthy subjects first show on the ipsilateral side a positive wave (about

14 s after the stimulus) as well as a negative wave (about 21 ms; lines 1 and

3). (b) The responses can as a rule not be recorded contralaterally (lines 2

and 4). Approximately 50–100 averagings are necessary for the recording.

It is important that the musculature is tense, e.g. for this the test person can

raise his head from the support surface. Evaluation criteria are the presence

of the waves P14 and N21 as well as their amplitude. The absence of these

waves as well as a clearly reduced amplitude are considered pathological;

the relevance of changes in latency must still be determined (Recording (b)

by K. Botzel, Munich).

Fig. 12. The subjective visual vertical (SVV). For determination of the SVV,

the patient sits upright in front of a hemispheric dome (60 cm in diameter)

and looks into it. The surface of the dome extends beyond the limits of the

patient’s visual field and is covered with a random pattern of dots. This

prevents the patient from orienting himself spatially by fixed external

structures. The hemispheric dome is connected axially to a motor and can

be rotated; a circular target disk (148 of visual field) with a straight line

through the center is 30 cm in front of the patient at eye level. The line is

also connected with a DC motor and can be adjusted by the patient by

means of a potentiometer until he has the subjective impression that the line

is ‘vertical’. The deviation of the line from the objective vertical axis is

measured in degrees and registered on a PC. The mean of 10 measurements

equals the SVV. Under these conditions, the normal range (meanG2 SDs)

of the SVV is 08G2.58. Measurements can be made under static (left) and

dynamic (right) conditions.


backward, upward, and downward directions), different

parameters can be calculated, for example, the sway path,

sway path histograms for determining the preferential

direction of sway, or a frequency analysis can be made

(Fourier power spectra). The results of posturography are

clinically significant, e.g. for documenting the direction of

falls (lateropulsion in Wallenberg’s syndrome or thalamic

astasia) and for monitoring the course of postural instability

in degenerative cerebellar disorders or during rehabilitation.

Posturography also plays an important role in clinical

research. In the analysis of sway direction, for example, it

may indicate the side of lesion (semicircular canal or otolith

organs) and the type of dysfunction (excitation or

inhibition). It is also used to measure postural sway activity,

e.g. in phobic postural vertigo (Holmberg et al., 2003;

Querner et al., 2000), during the treatment of vestibular

disorders (Strupp et al., 1998), and after the application of

pharmacological agents such as nicotine (Pereira et al.,

2001) or other agents. Despite its applications in research,

posturography is of limited usefulness for general vestibular

testing, because the findings are often non-specific for

certain disorders and, therefore, it does not help detect the

underlying dysfunction. However, there are exceptions,

such as the characteristic 3-Hz sway in (alcohol-induced)

anterior lobe cerebellar atrophy (Diener et al., 1984) and the

pathognomonic 14–18 Hz sway in orthostatic tremor

(Yarrow et al., 2001).

Acknowledgements

We thank J. Benson for copyediting the manuscript.

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