Nystagmus

Presenter:Dr.Vikram S Nakhate

Moderator: Dr.Atul Seth

Defination Nystagmus is a regular,repetitive to and fro

movement of the eyes (horizontal,vertical or torsional) with 2 phases

1. slow drift from the target of interest f/b2. corrective saccade back to the target

Terminologies

• Amplitude• Frequency • Intensity• Null zone• Pursuit / Saccade• Conjugate / Dissociated• Jerk / Pendular

Amplitude Amplitude is the excursion of the nystagmus

and described asFine : less than 50

Moderate: 50-150

Large greater than 150

Frequency Frequency is the number of to and fro

movements in one secondDescribed an cycles/sec or Hertz (Hz)Slow : (1-2 Hz)Medium : (3-4 Hz)Fast: (5 Hz or more)

Intensity Intensity = amplitude * frequency

Null zone: position where nystagmus is minimised

Patient assumes a head posture, such that the eyes are in null zone

Pursuit /SaccadePursuit eye movements allow the eyes to

closely follow a moving object.Pursuit differs from the vestibulo-ocular

reflex, which only occurs during movements of the head and serves to stabilize gaze on a stationary object

Saccades are quick, simultaneous movements of both eyes in the same direction

Conjugate/DissociatedConjugate : nystagmus which is symmetric in

direction,amplitude and rate

Dissociated: when it differs in any one of the parameters between two eyes

Jerk / PendularJerk nystagmus Pendular nystagmus

Alternation of slow phase drift f/b rapid corrective saccade in opp direction

Sinusoidal oscillation with slow phase in both directions and no corrective saccade

Direction of jerk nystagmus= direction of the fast phase

Pendular nystagmus may be horizontal or vertical

Right or left beating nystagmusUpbeat or downbeat nystagmus

Not characterised by right,left,up,down beating as there is no fast phase

Alexanders lawIt states that the amplitude of jerk nystagmus

is largest in the gaze of direction of fast component

1 degree: nystagmus only in the direction of the fast component

2 degree: nystagmus in primary gaze position 3 degree: nystagmus in addition to above

gazes,also present in the direction of the slow component

Mechanism of nystagmusFoveal centration of an object of regard is

necessary to obtain the highest level of visual acuity

Three mechanisms are involved in maintaining foveal centration of an object of interest:

FixationThe vestibulo-ocular reflex The neural integrator.

Fixation Fixation in the primary position involves the

visual system's ability to detect drift of a foveating image and signal an appropriate corrective eye movement to refoveate the image of regard.

The vestibular system is intimately and complexly involved with the oculomotor system

Vestibulo-ocular reflexThe vestibulo-ocular reflex is a complex

system of neural interconnections that maintains foveation of an object during changes in head position.

The proprioceptors of the vestibular system are the semicircular canals of the inner ear.

The semicircular canals respond to changes in angular acceleration due to head rotation

Neural integratorWhen the eye is turned in an extreme

position in the orbit, the fascia and ligaments that suspend the eye exert an elastic force to return toward the primary position

To overcome this force, a tonic contraction of the extraocular muscles is required.

A gaze-holding network called the neural integrator generates the signal. The cerebellum, ascending vestibular pathways, and oculomotor nuclei are important components of the neural integrator.

Classification CongenitalAcquired

Infantile nystagmus

Usually not noted at birth but becomes apparent during first few months of life

Characteristics Horizontal nystagmus ( mixed pendular and

jerk)b/l conjugate movements of the eyesNystagmus not present during sleepAssociated latent nystagmusHead turn to achieve null pointDecreases with convergence Increases with fixation

Reverse response to OKN stimulus ( fast phase in direction of moving OKN drum)

May be seen in isolation or associated with strabismus,afferent visual defects

Treatment Base out prisms to induce convergence

( dampens the nystagmus and may improve visual acuity)

Use of prisms to shift the viewing position to null position

Contact lenses may dampen nystagmusGabapentine may dampen nystagmus

Surgical Includes moving the extraocular muscles to

place the null zone in primary position(kestenbaum procedure)

Recessing all 4 rectus muscles to decrease tension (large recession procedure)

Spasmus nutansTriad of symptoms: NystagmusHead noddingTorticollis (head tilt or head turn)

Onset usually in the first year of life (3-15 months)

Disappears by 3-4 yrs of ageThe nystagmus typically consists of small-

amplitude, high frequency oscillations and usually is bilateral, but it can be monocular, asymmetric, and variable in different positions of gaze

Usually benignNeuroimaging recommended ( gliomas may

mimic spasmus nutans)

Infantile monocular pendular nystagmus

Usually due to visual loss( often optic neuropathy or chiasmal glioma)

In cases of b/l visual loss,there is b/l nystagmus ,with nystagmus greater in eye with poorest vision

AcquiredPhysiological:

End point nystagmusVestibular (caloric or rotational) nystagmusOptokinetic nystagmus

End point nystagmusJerk nystagmusOn looking extreme lateral or upwardsAngle of gaze > 450

Vestibular nystagmusJerk nystagmusAltered inputs from vestibular nuclei to PPRFDemonstrated by caloric test: normal

responseCold water : opposite sideWarm water : same sideCold water in both ears: upwardsWarm water in both ears : downwards

Optokinetic nystagmusJerk nystagmusInduced by moving a full visual field stimulusSlow phase (pursuit) : eye follows the targetFast phase ( saccade): eye fixates on next

targetUses: Detecting malingering

Testing visual potential in children

Pathological causesNystagmus associated with poor vision

(sensory)

Anterior segment: cataract,aniridiaRetinal diseases: RB,ROP,Intrauterine

infections

Nystagmus associated with neurological diseases (motor)

1.End gaze paretic nystagmus ( horizontal gaze center)

2.Convergence retraction nystagmus( vertical gaze,parinaud’s)

3.Vestibular nystagmus:Central ( brainstem nuclei)Peripheral ( labyrinths, VIII CN)

4.Downbeat nystagmus( cervicomedullary junction)

5.Upbeat nystagmus( cerebellum,medulla)

6. Seesaw nystagmus (parasellar lesions)7. periodic alternating nystagmus

Gaze paretic nystagmusMost common typeAbsent in primary position and is not visually

disablingBeats in the direction of gazeCauses: anticonvulsants brainstem lesions cerebellar lesions

Convergence-retraction nystagmus

Not truly a nystagmusb/l adducting saccades causing convergence

of both eyesElicited by having the patient to look up,at

which time the eyes converge & retractCauses: midbrain lesions

Vestibular nystagmusFeature Peripheral Central

Disease of vestibular origin

Disease of the brainstem

Direction Intensity increases when the eyes are turned in direction of fast phase

Direction of nystagmus may change with gaze

Visual fixation Inhibits nystagmus No inhibition

Severity of vertigo Severe Mild

Induced by head movements

Often Rare

Associated eye movement deficits

None Pursuit or saccadic defects

Other findings Hearing loss CNS involvement

Upbeat nystagmusType of jerk nystagmus with fast phase

upward in primary positionOften worsens in upgazeCauses: lesions of medulla,

cerebellar vermis,midbrainRx: base up prisms in reading glasses can be

used to force the eyes downward

Downbeat nystagmusType of jerk nystagmus with fast phase

downward in primary positionOften worsens in downgazeOscillopsia is usually prominentCauses: lesions at cervicomedullary junctionRx: base down prisms in reading glasses can

be used to force the eyes upward

Seesaw nystagmusDefined as pendular nystagmus with

elevation and intorsion of one eye simultaneous with depression and extorsion of other eye

Followed by reversal of cycle,so that the eyes move like a seesaw

Causes: parasellar lesions,pituitary tumorsProduces very disabling oscillopsia that

responds poorly to any Rx

Periodic alternating nystagmus(PAN)PAN is a conjugate, horizontal jerk

nystagmus with the fast phase beating in one direction for a period of approximately 1-2 minutes.

The nystagmus has an intervening neutral phase lasting 10-20 seconds

The nystagmus begins to beat in the opposite direction for 1-2 minutes then, the process repeats itself

Periodic alternating head turn to minimise nystagmus & oscillopsia

Causes: lesions of the cerebellum

Acquired Congenital

Form Pure sinusoidal Variable waveform

Direction Omnidirectional (vertical,torsional)

Horizontal,uniplanarRarely vertical or torsional

OKN reversal Never Frequent

Oscillopsia Frequent Mild (if present)

Nystagmus associated with strabismus

Latent /manifest-latent nystagmusManifest nystagmusNystagmus blockage syndrome

Manifest nystagmus Manifest-latent nystagmus

Pendular nystagmus Jerk nystagmus

No change on abduction Increased on abduction

No change on covering one eye Increase on covering one eye

Null zone is present Fast phase always towards fixing eye

Less commonly associated with infantile esotropia

Always associated with esotropia

Binocular visual acuity same as uniocular

Binocular visual acuity better than uniocular

Nystagmus blockage syndromeInverse relationship with esotropiaEsotropia is a mechanism of blocking the

nystagmusThe fixing eye is preferred to be in

adduction ,face turn is in the direction of fixing eye

Nystagmoid conditionsMovements which are not regular and

rhythmic:

Oculopalatal myoclonusOpsoclonusOcular bobbing

Oculopalatal myoclonusType of vertical pendular nystagmus Coexisting with tremor of the facial

muscles,larynx,palatePresent during sleepCause : usually develops months after an

infarction or h’hage involving mollaret triangle

Rx: Gabapentine

Ocular bobbingCharacterised by conjugate eye movements,beginning with a fast downward movementf/b slow drift back to midlineCauses: 1. comatose patients with massive

pontine lesion 2.metabolic encephalopathy

Superior oblique myokymiaDefined as oscillation of one eye due to

intermittent firing of the superior oblique muscle

Produces oscillopsia or intermittent diplopia elicited by having the patient look in the direction of the superior oblique muscle

Characterised by monocular,rapid,intorsional movements

Usually benignNo underlying etiology is foundNeuroimaging : r/o post fossa tumorsRefractory cases: surgical weakning of the

superior oblique muscle can be performed

Treatment Nonsurgical : non neurological causes1.Optical devices Glasses: overminus lenses stimulate

accomodative convergence and thus dampens nystagmus

Contact lenses: helpful in high refractive errors by giving good visual stimulus for fusional control

Prisms : can be used for 2 purposes1. to induce fusional convergence by using 7

PD base out prism in front of each eye2. pre op evaluation in a patient with face

turn prisms are inserted with the apex in

direction of gaze

Useful as a diagnostic trial ,but as a therapeutic alternative are not helpful

Occlusion therapy:Trials with conventional occlusion have been

found to be effective As amblyopia gets corrected and vision

improves,nystagmus finally decreases

Pharmacologic MxThese drugs hypothetically inhibit excitatory

neurotransmitters within CNSBaclofen : congenital nystagmus, seesaw

nystagmus,periodic alternating nystagmusCarbamazepine: widely used for superior

oblique myokymia

Pharmacologic denervationBotulinum toxin A act by blocking the

neuromuscular transmission used in 2 distinct ways to dampen nystagmus3 units of toxin is injected in each of the 4

horizontal rectus musclesSingle large dose of drug into the retrobulbar

space Effect last for only few months

Surgical Based on 3 principles:To shift the null position if any to the primary

positionTo induce extra convergence innervation by

weakening medial recti,to dampen nystagmusTo reduce the amplitude of the nystagmus by

weakening the muscle force of all recti

Kestenbaum surgeryDevised first surgical approach using

recession-resection of all four horizontal rectiAdvocated an equal amount of 5 mm for all

rectiLeft face turn (null in dextroversion):Right eye: LR recession & MR resectionLeft eye : MR recession & LR resection

Anderson surgeryAdvocated only recessionsLeft face turn (null in dextroversion):Right eye : LR recessionLeft eye : MR recession

Parks surgeryRecommended lesser amount of recessions

and for medial rectus surgery compared to lateral rectus surgery.

Advocated a 5,6,7,8 planMR recession : 5 mmMR resection : 6 mmLR recession : 7 mmLR resection : 8 mm

Carlow TJ : medical treatment of nystagmus and ocular motor disorders.Int Ophthalmol Clin 1986;28:355

Rosenberg ML,Glaser JS:Superior oblique myokymia.Ann Neurol 1983;13:667

Helveston EM, Pogrebniak AE : Treatment of acquired nystagmus with botulinum toxin A. Am J Ophthalmol 1988;106:584