MOHAMMAD S. ASGHAR AU.D (USA) , AUD (C), REG.CASLPO.

M.SC AUDIOLOGICAL MEDICINE (UK), M.B,B.S (PB) M.C.P.S (ENT)

CERTIFIED BY THE AMERICAN BOARD OF AUDIOLOGY (ABA)

DIRECTOR HEARING & BALANCE SERVICES

Dizzy battery at a Glance

Anatomy of the vestibular system

Anatomy of Vestibular System

Nerve supply of vestibular system

Blood supply of Inner Ear

Irrigation ParallelsInnervation

Blood supply Innervation

Basilar A VIIIth N

AICA

Labyrinthine A Common Cochlear Artery Main Cochlear Artery Cochlea Auditory

Nerve    Vestibulo Cochlear artery Vestibular N Post Vest A Post SCC Ampulla Inferior division Majority of Scaula   Ant Vestibular A Anterior SCC Ampulla Superior Division Horizontal SCC Ampulla Utricle Minority of Sacula 

Vestibular system: central connections

Anatomic and Basic Medical considerations:

Vestibular system consists of two groups of specialized sensory receptors.

1: Three semicircular canals Lateral or

horizontal, Posterior or inferior, Superior or

vertical SSC, which originate from utricle and

also end at utricle at a dilated end called

ampulla.

2: Two otolith organs: Utricular macula and

saccular macula.

Vestibular testing, (Introduction)

In vestibular testing we are always testing output of vestibular system.

We do not have any direct clinical measurement for vestibular testing.

1) For ENG, vHIT and Rotary Chair tests we use VOR

2) For Posturography we use VSR. 3) For VEMP we use vestibulocolic response (VCR) &VOR

4) For Meniere's Disease and endolymphatic Hydrops we use Ecoch.G and VEMP.

The Vestibulo-ocular reflex;

The VOR normally acts to maintain stable vision during head motion. This reflex has two components.

The angular VOR, mediated by the SCCs, compensates for rotation.

The linear VOR mediated by the otoliths, compensates for translation.

-- Tests based on VOR: ENG, rotary chair test, VAT, Active head rotation test, Dynamic visual acuity test, oVEMP & vHIT

The Vestibulospinal Reflex

The purpose of the VSR is to stabilize the body. The activity is induced on the side to which the head is inclined, and flexor activity s induced on the opposite side.

-- Tests Based on VSR: Computerized dynamic posturography (CDP, Sensory integration test).

The Vestibulocollic Reflex.

The VCR acts on the neck musculature to stabilize the head.

-- Tests Based on VCR: cVEMP

Tests involving Sup. and inf. divisions of vestibular Nerve:

Sup. Vestibular N: ENG, caloric test, High frequency head shake test, Rotary chair test, VAT, oVEMP & vHIT

Inf. Vestibular N: VEMP , This is the only test available to test the integrity of the Inf. Vestibular N of Vestibular nerve & Now vHIT can also test part of Inf Vest N.

What are we testing?

Five motion sensors – VOR (i.e. Input/output, ENG /R chair) lateral

canal only & now vHIT and oVEMP (Utricle and All SSC).

VCR (VEMP test) saccule only Abnormal gravity sensitivity (positional

nystagmus) - BPPV Tracking (pursuit, saccade test, OKN test) , Sensorimotor integration (posturography)

Tests only VSR, documents functional aspects of the balance system.

Believe in yourself (your own exam)

Quality control on vestibular testing is nonexistent

Computer software is crude No method exists of recording torsion (which you

need for BPPV) There are many places where corners can be cut

or things can go wrong Experienced eyes (with Frenzel's) are sometimes

are more reliable than most ENG’sSo no substitute for experience and your clinical

acumen.

VIII N

Cochlear N

Vestibular N

PTA

ABR

Ecoch.G

Sup. Vest. N

Inf. Vest. N

Ant.SCC

Baseline thresholdsShape of audiogramRetrocochlear pathology/VEMP may add credibility

MD/EHDrop attacks

Lat.SCC

Utricle

Post.SCC

Saccule

VAT/Positioning/

vHITCaloric/

Posiit.Rot Chair/vHIT

VAT/Positioning/

vHITcVEM

P

PTAABR

Ecoch.G

VEMP

VAT/vHITENG

oVEMP

VATENGVEM

P

Dizzy batter

yPTAABR

Ecoch.G

ENGRotaryChairVAT

oVEMPcVEMPvHIT

Flow chart

oVEMP

Conclusion

Assessment of vestibular function has advances from ENG being the only test to a test battery approach where we can actually diagnose the site of lesion to the exact receptor site in the ear.

Although we are still struggling to manage the dizzy patients after diagnoses but armed with the diagnoses we can better prepare the patient to deal with the problem and become a part of rehab team.

Conclusion

Lat. Canal: ENG, VAT, vHIT, Rotary ChairPost Canal: vHIT, VAT, Positional testSup Canal: vHIT, VATUtricle: oVEMPSaccule: cVEMPEcoch.G: MD/EH

What Next

If you are dizzy ask your doctor for vestibular testing as ear is the cause of vertigo in almost 50% of patient.