ASSESSMENT AND DISORDERS OF VESTIBULAR SYSTEM

Dr.SUDEEP K.C.

THE END

Assessment of vestibular functions can be divided into two groups

A)Clinical tests

B)Laboratory tests

A)Clinical Tests

It includes 1)spontaneous Nystagmus

2)Fistula test

3)Romberg Test

4)Gait

5)Hall pike manoeuvre (Positional Test)

B)Laboratory Test

1)Caloric Test

2)Electro nystamography

3)Optokinetic Test

4)Rotation Test

5)Galvanic test

6)Posturography

Spontaneous nystagmus:

Nystagmus is an imp. Sign in the evaluation of vestibular system . To elicit this patient is seated in front of examiner .Examiner keeps his finger about 30cm from pt. eye in central position and moves it to right or left , up or down.

Presence of spontaneous nystagmus always indicates an organic lesion.

Peripheral vestibular nystagmus - lesion of labyrinth or viii nerve.

Central – Lesion in the central neural pathway(vestibular nuclei , brainstem , cerebellum.)

Fistula Test Induce nystagmus by producing

pressure changes in the external canal which are then transmitted to the labyrinth.

Stimulation of labyrinth results in nystagmus and vertigo.

The test is performed by applying intermittent pressure on tragus.

Normal –Test is negative

Fistula test is positive in: Erosion of horizontal semicircular canal like:

cholesteatoma , surgically created window in horizontal canal(Fenestration opt.) , abnormal opening in oval window(post stapedectomy fistula),or rupture of round window membrane.

Positive fistula also implies that labyrinth is still functioning and absent when labyrinth is dead.

3)Romberg Test

The patient is asked to stand with feet together and arms by the side with eyes first open and then closed.

With eyes open , patient can still compensate the imbalance but with eye closed, vestibular system is at more disadvantage.

Patient with vestibular lesion sways to the side of lesion.

Sharpened Romberg Test : Inability to perform this test indicate the vestibular impairment.

4)Gait

The patient is asked to walk along a straight line to a fixed point , first with eyes open and then closed.

In case of uncompensated lesion of peripheral vestibular system, with eyes closed ,patient deviates to the affected side.

5)Hallpike Manoeuvre(positional Test)

• This test is useful when patient complains of vertigo in certain head positions.It also helps to differentiate a peripheral from the central lesion.

• Method• Patient sits on couch . Examiner holds the

patients head , turns it 45 degree to right and then places in supine position so that head hangs 30 degree below horizontal . Patient eyes are observed for nystagmus .

• In BPPV nystagmus is seen

In peripheral type:Nystagmus appears after a latent period of

2-20 sec.Last for less then a minute and always in a

one direction i.e towards the ear that is undermost.

Fatiguable.

Central type:Nystagmus immediately appear as soon as

head is in critical position.Last as long as head is in critical position.Non fatiguable

B)Lab Tests

Caloric test The basis of this test is to induce

nystagmus by thermal stimulation. Method: Patient is seated with head tilted 60

degree backward to place horizontal canal in vertical position.Ear is irrigated with ice water for 60 sec,first with 5 ml and if no response then 10ml,20mland 40ml.

Normally : Nystagmus beating towards the opposite ear , will be seen with 5ml of ice water.

If response is seen with increased quantities of water between 5 and 40 ml, labyrinth is considered hypoactive.

No response to 40 ml of water indicates dead labyrinth.

Another method we use both the cold and warm water alternately .

In this method cold water induces nystagmus to opposite side and warm water to the same side.

ELECTRONYSTAGMOGRAPHY- METHOD OF DECTECTING & RECORDING OF

NYSTAGMUS WHICH IS SPONTANEOUS OR INDUCED BY CALORIC,POSITIONAL,ROTATIONAL OR OPTOKINETIC STIMULUS.

THE TEST DEPENDS ON THE PRESENCE OF CORNEORETINAL POTENTIALS WHICH ARE RECORDED BY PLACING ELECTRODES AT SUITABLE PLACES ROUND THE EYES. THE TEST IS ALSO USEFUL TO DETECT NYSTAGMUS WHICH NOT SEEN WITH THE NAKED EYES .

IT ALSO PERMITS KEEP A PERMANENT RECORD OF NYSTAGMUS.

OPTOKINETIC TEST PT IS ASKED TO FOLLOW A SERIES OF

VERTICAL STRIPES ON A DRUM MOVING FIRST FROM RIGHT TO LEFT & THEN FROM LEFT TO RIGHT.

NORMALLY PRODUCES NYSTAGMUS WITH SLOW COMPONENT IN THE DIRECTION OF MOVING STRIPES & FAST COMPONENT IN OPPOSITE DIRECTION .

OPTOKINETIC ABNORMALITIES ARE SEEN IN BRAIN STEM & CEREBRAL HEMISPHERE LESIONS.

THIS TEST IS USEFUL TO DIAGNOSE A CENTRAL LESION.

ROTATION TEST PT IS SEATED IN BARANY’S REVOLVING CHAIR

WITH HIS HEAD TILTED 30* FORWARD & THEN ROTATED TURNS IN 20 SECONDS. THE CHAIR IS STOPPED ABRUPTLY & NYSTAGMUS OBSERVED.

NORMALLY THER IS NYSTAGMUS FOR 24-40 SEC.

THE TEST IS USEFUL AS IT CAN BE PERFORMED IN CASES OF CONGENITAL ABNORMALITIES WHERE EAR CANAL HAS FAILED TO DEVELOP & IT IS IMPOSSIBLE TO PERFORM THE CALORIC TEST.

GALVANIC TEST IT HELPS DIFFERENTIATING AN END

ORGAN LESION FROM THAT OF VESTIBULAR NERVE.

PATIENT STANDS WITH HIS FEET TOGETHER , EYES CLOSE & ARMS OUTSTRETCHED & THEN A CURRENT OF 1mA IS PASSED TO ONE EAR

NORMALLY, PERSON SWAYS TOWARDS THE SIDE OF ANODAL CURRENT.

BODY SWAY CAN BE STUDIED BY SPECIAL PLATFORM.

POSTUROGRAPHY IT IS A METHOD TO EVALUATE VESIBULAR

FUNCTION BY MEASURING POSTURAL STABILITY & IS BASED ON THE FACT THAT MAINTENANCE OF POSTURE DEPENDS ON THREE SENSORY INPUTS- VISUAL, VESTIBULAR & SOMATOSENSORY.

IT USES EITHER A FIXED OR A MOVING PLATFORM.

VISUAL CUES CAN ALSO BE VARIED .THE CLINICAL APPLICATION OF POSTUROGRAPHY IS STILL UNDER INVESTIGATION

THANK YOU