Vestibular function test (dr.rajeev gupta,igmc shimla)

Vestibular function test

Dr. Rajeev gupta

Igmc shimla

h.p.

Vestibular anatomy

• Inner ear (labyrinth) - BonyMembranous

• Endolymph• Perilymph

Bony labyrinth - vestibulesemi circular canalscochlea

• Membranous laby. - cochlear duct

utricle/ saccule

semicircular ducts

endolymphatic sac / duct

Maculae

• Vestibular nerve - vestibular / scarpa’s ganglion situated in the lateral part of IAM.

• Bipolar neurons – distal process innervate sensory epithelium of labyrinth.

- central process aggregate to form vestibular nerve.

• these fibers end in vesti. Nuclei and some go to directly to cerebellum.

• 4 vesti. Nuclei – sup. / medial / lateral/ descending

Affrents come from to these nuclei –

peripheral vestibular receptors

cerebellum

reticular formation

spinal cord

C/L vesti. Nuclei

• Effrents from nuclei go to -

1- nuclei of C.N iii / iv/ vi via medial longi. Bundle , ( pathway of vestibulo ocular reflexes) causes - nystagmus.

2- motor part of spinal cord- (vestibulo spinal reflex)- coordinates head , neck , body

3- cerebellum- vestibulocerebellar fibers- maintain body balance

4- ANS- explains nausea , vomiting , palpitations ,sweating

5- vestibular nuclei of C/L side

6-cerebral cortex - responsible of subjective awareness of motion.

Physiology

• Vestibular system- peripheral

central

• Semicircular canals - 3 canals lie at right angle to each other , but one which lies right angle to axis of rotation is stimulated the most . Thus HSCC respond max. to rotation on vertical axis.

• Stimulation of SCC produces nystagmus and direction of nystagmus is determined by plane of canal being stimulated.

• So, HSCC produces- horizontalSSCC - rotatoryPSCC - vertical

• Stimulus to SCC is flow of endolymph which displaces cupula. Flow may be towards cupula (ampullopetal/ utriculopetal), away to cupula(ampullofugal/ utriculofugal)

• Slow component of nystagmus is always towards the side of flow of endolymph and fast component is always opposite to it.

• SCC responds to angular acceleration and deceleration.

• Utricle / saccule-

• Stimulated by linear acceleration / deceleration or gravitational pull during head tilts.

• Saccule also responds to sound stimuli also.

• Sensory hair cells of macula stimulated by displacement of otolithicmembrane during head tilts.

• These information sent to CNS where information from other system also reached and then integrated and used to regulate equilibrium and body posture.

• Maintenance of body equilibrium –

two sided push and pull system

Disorder of vestibular system

Peripheral

BPPV

Vestibular neuronitis

Labyrinthitis

Perilymphatic fistula

Acoustic neuroma

Meniere’s disease

Head trauma

Vestibulotoxic drugs

central

• Vertebrobasilarinsufficiency

• Migrane

• Cerebellar disease

• Multiple sclerosis

• Tumors of brainstem

• Epilesy

• Cervical vertigo

• Post.inf. Cerebellar artery syndrome

Vestibular function tests

• History

• Examinations- neuro-otologicalexamination

special laboratory tests

• Radiological investigations

• Serological investigations

History

1. Nature of the sensation:dizziness, vertigo, oscillopsia, disequilibrium, syncope.

2. timing of initial spell:

3. frequency and duration of symptoms:Short term symptomsMedium length symptomsLonger spells

4. precipitating / mitigating factors:5. associated symptoms:6. medical conditions and family history

Examinations

• Neurotological Examinations:

1. otoscopy with audiometric evaluation

2. eye movements: spon. / gaze nystagmussmooth pursuit movement

saccadic eye movementsoptokinetic nystagmus

3 . vestibular ocular reflexes: doll’s head maneuveredynamic visual acuityhead impulse testvor suppression test

4. Postural test : romberg testgaitpast pointing test

• 5. positioning test :

• 6. positional test :

• 7. fistula test :

• Laboratorical test :

For VOR testing 1. caloric test2. rotatory test3. electronystagmography

For VSR testing1. craniocorpography2. posturography3. VEMP

• Radiological tests

• Serological test

• EYE MOVEMENTS

1. spontaneous nystagmus:

• Presents in straight ahead positon of eyes.• Should note direction and waveform.• It enhances by convergence,by moving an object in and out along visual axis.• Absence of convergence occurs in midbrain lesion and also present in > 60 yr age

persons.• The cover test should be done to rule out diplopia and ocular alignment and latent

nystagmus.• If Spon. Nyst. In primary gaze present with acute vertigo and severe nausea and

unsteadiness. May be due to central/peripheral lesion.• But, pt .comes as a routine ambulatory patient and does not look acutely ill,

nystagmus is more likely of central origin.

• Smooth pursuit eye movements:

• When we track an object with our eyes ,there are a combination of fast (saccades) and slow phase (pursuit) movements.

• Velocity of smooth pursuit movement is limited to 40-50 degree/ second.• When pursuit is abnormal called as broken up pursuit.• So, presence of normal pursuit rules out a central vestibular disorder or

broken up pursuit almost certainly has neurological rather than labyrinthine disorder.

• Examination procedure include two precaution-• Because pursuit are visually guided so subject is able to target correctly.• Target has to be moved slowly ,4-5 seconds to travel from right to left and

vice versa.

• Gaze evoked nystagmus:

• Soon after the acute stage of a peripheral vestibular lesion , nystagmus is not visible in primary gaze but only on deviation of gaze to opposite side of lesion( in fast phase direction)

• Classification to check the severity of nystagmus

• ALEXANDER’S LAW:

• 1 degree: weak nystagmus which present only when pt.look in direction of fast component.

• 2 degree: moderate nystagmus which present when pt. looks straightly ahead.

• 3 degree: strong nystagmus which present when pt. looks in direction of slow component.

• Saccadic eye movement:

• Saccadic are fast movements of the eyes (200-500degree/ sec.) which allows shift gaze from one object to another.

• Saccades does not require visible moving target, it can be generated at will or command without a specifically command.

• Three properities are assessed velocity, accuracy, binocular conjugacy.

Optokinetic nystagmus

• Vestibulo- ocular reflexes:

1. Doll’s head maneuvere -

Dynamic visual acuity

Head impulse test

Vestibulo ocular reflex suppression test

• Positioning test: • most frequently employed test is dix-hallpike maneuver.• 4 features:

1. it has a delayed onset.(2-20 sec.)2. it is always transient.3. it is always accompanied by vertigo.4. it is usually fatigable.

• Limitation : can not be done in cervical spine disease patient.

• By these methods , we can detect BPPV easily.

Dix - hallpike maneuver

Supine roll test (pagnini- maccluremaneuver)

• Positional test:

• Done to determine if different head positions induce or modify vestibular nystagmus.

• In this , pt. eye movements are monitored while the head is in at least four positions:

• Supine , head right (rt. Ear down), head left (lt. ear down), sitting position.

• Eye movements are noted in each positions for about 20 sec. in both visual fixatation and without visual fixatation.

• Positional nystagmus may be intermittent or persistent.

• FISTULA TEST:

• Producing pressure changes in EAC which stimulate labyrinth induces nystagmus and vertigo.

• Test done by siegel’s speculum , pressure on tragus• Normally it is negative.• Positive in :• Erosion in HSCC by choleasteatoma , fenestration operation.

Abnormal opening in OW / RW.• False positive: without presence of fistula seen in congenital syphilis

meniere’s disease (hennebert’s sign)• False negative : when choleasteatoma covers site of fistula and does not

allow pressure changes.

Vestibulo ocular testing

Electronystagmography:

Most commonly laboratory evaluation method.It documents, analyze the eye movements and assesses

labyrinthine function, degree of dysfunction.Various methods for recording eye movements-

1. Electrooculography2. Magnetic potentials (search coils)3. Videonystagmography4. Infrared technology

Procedure

• The pt. is instructed to avoid alcohol and certain drugs for at least 48 hours.

• Ear examination should be done prior.

• Electrodes applying area are cleansed with spirit and alcohol.

• Corneoretinal potential: EOG depends upon that there is a steady DC potential, termed as CRP.

• CRP is ,between the cornea and retina .• These potentials create an electric field at the front of head

that rotates as the eyes rotate.• The CRP is generated by the metabolic activity of the retinal

pigment epithelium. Retina is negative charged relative to the cornea which is measured by skin surface electrodes.

• Horizontal eye position is monitored by electrodes placed on temples, vertical eye position is monitored by electrodes placed above and below one eye.

• By Traditional EOG ,it is difficult to detect torsionalnystagmus because rotation of eye about the axis of the pupil does not effect a change in the CRP.

• Videonystagmography :

• Method of oculography in which eye movements are recorded by a video camera not by changes in CRP.

• So , eye blinking artifacts and artifacts due to contraction of facial muscle which alters ENG results ,do not effect VNG result.

• VNG can record torsional movements also.• Disadvantage that , VNG can record eye movements at a speed of

60hz ,whereas during saccadic tests and other occulomotor tests the eye movements need to be recorded at speed of 175hz .ENG is a superior option.

• Another that, it records when eyes are open.• Difficult in children, and more expensive.

• Magnetic search coil technique:

• pt. sitting in a low strength ,alternating magnetic field by wearing a soft contact lens in which a wire coil is embedded.

• The contact lens fits around but does not directly contact the cornea. motion of the coil of wire in the alternating magnetic field induces a very small current wire and this signal can be used to obtain measurement of eye position.

• Two major adv. are provides very precise determination of eye position in 3 dimensions and recorded very rapidly.

• Disadv. Are that it requires a sophisticated laboratory and trained persons.

• Infrared oculography:

• Based upon the differing reflectance properties of iris compared to sclera . In this, photocells of eye remain stationary while the edge of iris move with the eye and light sensed by the photocells differs according to eye positions.

• Adv. that direct estimate of eye position as a function of time can be calculated.

• Disadv. That it include the bulk of equipments which limit visual stimulations and interfere blink movements and makes vertical recording difficult.

• All types of visual oculomotor tests including saccades, smooth pursuit and optokinetic eye movements and gaze evoked nystagmus are recorded and analyzed .

• Both positional / positioning test are done with help of ENG and interpreted.

• Two main test bithermal caloric test and rotatory test are done with help of ENG.

Rotational test

• To maintain equilibrium , the subject has to attain a sense of spatial stability , so that , he feels that surrounding environment is stable.

• To achieve this goal , the image of objects in the visual field have to be retained in the same place of retina.

• When head moves or visual field moves in relation to subject the image of visual field on the retina displaced, called as retinal slip, which produces vertigo.

• In normal persons it is prevented by a corrective movement of the eyes which occurs reflexly by VOR.

• In the rotatory test, the head is rotated and eye movements are monitored to assess whether the compensatory or corrective eye movements is occuring properly or not.

• Movement occurs in horizontal plane so stimulates HSCC.• This test first carried out by Barany .

• In this test ,pt,. is made sit on a special chair and rotated for 20 seconds and then rotation stops abruptly.

• This sudden stop sets nystagmus due to resultant deceleration which stimulates the HSCC on both sides.

• Nystagmus are recorded for both clockwise and anticlockwise rotation of chair by EOG.

• Indication:

1. when ENG suggest well compensated state, despite clinically significant U/L caloric weakness with active symptomatology.

2. when caloric test cannot be performed, results in two ears may not be compared because of anatomic variablity.RCT is used to define B/L weakness of vestibular system.

3. To check B/L vestibular system at same time.

• The computer compares head velocity, slow phase eye velocity and calculates phase ,gain, symmetry for each of the test frequency.

• Gain is slow eye velocity divided by head velocity. Reduction in gain seen in B/L vestibular disease.

• Phase angle measures the temporal relationship between eye and head velocity and measured in degrees. It has greatest clinical significance. increase phase implies in peripheral vestibular system and decreased phase suggest cerebellar lesion.

• Symmetry is ratio of rightward to leftward slow phase eye velocity. Asymmetry seen in peripheral vestibular system weakness.

• Abnormalities in RCT are classified in 4 categories:

1.vestibular habituation and asymmetry-Abnormal low frequency phase leads and high frequency asymmetry ( always towards the side of lesion) is most often seen in acute peripheral U/L peripheral dysfunction.

2.vestibular habituation-Consist solely of abnormally large phase leads at the lower frequency. Often seen in patients with a chronic ,U/L peripheral vestibular lesion.

3.vestibular deficit-Slow harmonic acceleration test shows abnormalities in patients with B/L loss of vestibular function.

4.vestibular asymmetryCharacterized by an asymmetry at high frequency seen in patients of acute peripheral lesion.

Caloric test

• Caloric test are highly sensitive for unilateral lesion because in this we stimulate each ear separately.

• Nystagmus produced by this is analyzed and assess the activity of vestibular system

3 types :

1. modified kobrak test

2. bithermal caloric test

3. cold air caloric test

Modified kobrak test:

• Office procedure• Pt. seated with head tilted 60 degree backwards to place

HSCC in vertical position.• Ear irrigated by ice cool water for 60 sec. with 5/ 10/20/40

ml.• Response seen with 5ml of water towards opposite ear –

normal • Response seen with 5 to 40 ml water –hypoactive labyrinth• No response seen with 40 ml –dead labyrinth

• Bithermal caloric test-

• Fitzgerald – hallpike test

• Pt. lies supine with head tilted 30 degree forward so that HSCC is vertical.

• Ear is irrigated for 40 sec. with water at 30 degree and 44 degree and nystagmus are noted till its end point.

• If no nystagmus appeared from any ear ,test iarepeated with water at 20 degree water for 4 minute before labeling the labyrinth dead.

• Responses of caloric test are analyzed by calculating the velocity of each of slow phase nystagmus and interpreted in terms of unilateral weakness and directional preponderance.

Jongkees and colleagues formula

• On canal pareasis (UW) if values is greater than 20% is considered significant.

• Less or no response from particular side indicative of depressed function of I/L labyrinth and vestibular nerve / nuclei , seen in meniere’s disease, acoustic neuroma , postlabyrinthectomy, vestibular nerve section.

• On directional preponderance, duration of nystagmus to rt/left irrespective of side of ear stimulation is considered.

• If nystagmus is 25-30% or more on one side than the other , is called as directional preponderance to that side.

• It occurs towards the side of central lesion , away from peripheral lesion but it does not localise the lesion in central vestibular pathway.

Results found in

U/L meniere’s disease – canal paresis on one side and diectional preponderance to opposite side.

Acoustic neuroma – canal paresis and directional preponderance towards same I/L side.

Cold air caloric test :

• Test done in perforated TM because irrigation is contraindicated.

• Done with DUNDAS GRANT TUBE , coiled copper tube wrapped in cloth, air is cooled by mixing with ethyl chloride and then blown to ear.

• Problem with this tube is that we can not control on temperature and amount of air to be used.

• So new device “varioair” is used now a days which has precise control over amount and temperature of air.

Vestibulospinal reflexes testing

1. CRANIOCORPOGRAPHY(CCG)

• Described by claussen• Procedure and interpretation:1. The stepping test-• Visual and proprioceptive inputs are cut off• Pt deviate / rotate to side of weaker hypoactive vestibule. • Parameters evaluated in test

DisplacementAngular deviationAngular rotationBreadth of lateral sway

• Interpretation:

• Displacement : walk forwards/ backwards

• Angular deviation : normal range70 degree to rt. And 50 degree left to midline. Any deviation beyond suggest hypoactivity of vestibular periphery on the side of deviation.

• Angular rotation : 85 degree to rt. And 60 degree to left from midline. Any rotation beyond this suggest hypoactivityof vestibular on side of rotation.

• Breadth of lateral sway : normally 3cm to 15 cm.

• Any sway more than 15cm. Suggest of central lesion.

• So, stepping test CCG is a very effective to evaluate peripheral vestibular compensation, which is not possible by ENG.

2. romberg test:• Pt. blind folded and stands erect with feet close together

for 1 minute.• Max. breadth of sway is 10 cm .if it is more than it

considered abnormal and indicates a central lesion.

3. WOFEC test:• Graybiel and fregly• Pt is asked to walk on floor on a imaginary straight line with

tandem walk and eyes closed.• In central lesion and acute peripheral lesion , pt can not

perform this test and falls repeatedly.

Advantage:

Quick , noninvasive , can be repeated often.Does not require vestibular stimulation as in caloric

test.In Large screening of vestibular system for job

persons.For drug trials To detect malingerers.With perforated ear patients.

• POSTUROGRAPHY:

• CDP is more sophisticated and sensitive test for vestibulospinal test.

• It check overall balance function and capacity of body to maintain erect posture and gait

• Usually done to detect vertigo in whom ENG are normal.

Methods:

• The Sensory organisation test• The motor coordination test

• In these, pt is made to stand on a platform and in front of his eyes a screen is placed that entire vision field is covered.

• Whole purpose is manipulate somatosensory and visual inputs to vestibular system.

• In sensory organisation test, analyse the capacity of patient to maintain equilibrium during a variety of changing sensory input conditions.

• 1. support fixed, eyes open, visual fixed

• 2. support fixed, eyes closed, visual fixed

• 3.support fixed,eyes open,visual sway-refrenced

• 4.support swayed, eyes open,visual fixed

• 5.support swayed,eyes closed, visual fixed

• 6support swayed,eyes open,visual sway-refrenced

• The pt. is subjected to each test condition 3 times, and an equilibrium score is calculated for each condition .it was compared with theoretical limits of antero-posterior sway.

• The results of SOT inform us whether pt. is able to properly utilise the three main sensory inputs ( visual, somatosensory, vestibular) to CNS for maintaining posture and equilibrium.

• A score of 100% implies little sway and lower scores corresponds to greater amounts of sway.

• The motor coordination test:

• In this platform is made to undergo sudden translations forwards and backwards and the pt. sway is monitored and analyzed by the computer.

• An EMG of gastrocnemius is documented and shows that muscular contractions in responses to destabilizing forces is adequate or not.

• In this somatosensory inputs to brainstem pathway is checked.

• New version is “lucerne measuring plate” which documents , analyze ,and provide objective information on the functional vestibular deficiency.

• VESTIBULAR EVOKED MYOGENIC POTENTIALS:

• Depends upon vestibulo- colic reflexes.

• Loud sounds - stapes movement- mechanical stimulation of saccule - mech.energy converted into electrical energy in saccule - impulse passes through IV N -reaches lat. Vesti. Nucleus in brainstem - I/L SAN nucleus - impulse passes through medial vestibulospinal tract-reaches SAN branch to SCM – contraction of SCM.

• These are recorded and documented by the EMG.

• VEMP are generated by the loud sound (95 -105db) of pure tones of 500hz with rate of 3-5 stimuli/ sec.

• For proper recording of EMG ,sternocleidomastoid should be in contracted position.

• EMG recorded wave morphology , amplitude ,latency but amplitude is most important.

• Decreased amplitude on one side is corelated with peripheral vestibular dysfunction from paretic lesion such as vesti. Neuronitis, meniere’s disease, acoustic neuromaand intratympanic gentamycin therapy.

• An increased ampiltude is seen in irritative lesions as meniere’s disease and sup. Canal dehiscence syndrome.

• So disorder of saccule are practically impossible to diagnose other than VEMP.

• in these cases ENG will normal but VEMP are absent or abnormally low amplitude.

Vestibular rehabilitation

• Apart from drugs which affect on labyrinth ,there are various vestibular exercises .

• Three targets for these regimens are

adaptation

sensory substitution

habituation

CAWTHRONE –COOKSEY EXERCISE

NORRE’S APPROACH( habituation)

• Based on concept of the error signal driven adapatation and assumption that repetition of same stimulus causes a decline in responses which is stimulus specific.

• It includes 19 positional maneuvers.

BRANDT DAROFF EXERCISE

GAZE STABILIZATION EXERCISES

Canalith Repositioning

• Posterior Canal (85-95% success)–Epley

–Semont

• Horizontal Canal (100% success)–Barbecue Roll (270 degree)

– baloh 360 degree yaw rotation

–GUFONI

EPLEY’S MANOUVERE

MODIFIED EPLEY’S

SEMONT’S MANOUVERE

BARBECUE/ LEMPERT MANOUVERE

GUFONI’S MANOUVERE

360 YAW ROTATION

THANK YOU