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Otoneurology

Timothy C. Hain, MD

VestibularAnatomy

Ear Structures of importance

Inner ear is within the temporal bone –hardest in body.

Miniaturization: Everything is inthe bony labyrinth (size of dime)

Check an MRI of IAC if you are dubious.

Membranous Labyrinth

MRI of inner ear

The Labyrinth is filled withEndolymph and Perilymph

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Clinical Correlations

n Meniere’s diseaseMeningitis – cochlearaqueduct– Labyrinth may later ossify –

no fluid on MRI

n Perilymphatic fistula

Vestibular Hair cells – measure forcen Relative movement of hair cells to head

causes change in electrical potential

STARTING AND STOPPING =ACCLERATION (F=MA) Clinical Correlation – Hair Cells

n Aminoglycosides kill hair cells– Some just vestibular hair cells (gentamicin)

n Loop diuretics and NSAIDS are hair celltoxins (cochlear only)

Membranous LabyrinthNarrow lumen increases effect of viscosity

Allows mechanical integration to take place

Circulation to inner ear

n AICA– Labyrinthine aa– Vestibulocochlear aa

» PC, Saccule– Anterior vestibular aa

» AC, LC, Utricle

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Clinical correlates

AICA strokes generally take out everything(hearing and balance) on one side(labyrinthine artery)

PICA strokes rarely affect hearingNeither type of stroke can affect both ears at

the same timeVery improbable to get a branch occlusion

Cupula to Brain

Cupula

Scarpa’sganglion

VestibularNerve

VestibularNucleus

Cortex

Vestibular Nerve

n Superior vestibular nerve: AC, LC, Utriclen Inferior vestibular nerve: PC, Sacculen Scarpa’s ganglion

Clinical Correlations

n Vestibular neuronitis – Mainlyaffects superior division.Spares inferior.

n Acoustic Neurinoman Microvascular compression

syndrome. Blood vesselaccompanies nerve.

n Bad design – IAC/brainjunction vulnerable to sheartrauma.

Vestibular NucleusMajor Nuclei (4)

1. Superior, ‘S’, Bechterew, verticalcanals, VOR

2. Lateral (‘L’, Deiters), VSR

3. Medial (‘M”, Schwalbe), lateralcanals, VOR

4. Descending (‘D’), cerebellarconnections

Brodal

n Vertebral/PICAn AICA

VN is a BIG nucleus

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VestibularPhysiology

The ear is an inertial navigationdevice

n Semicircular Canalsare rate sensors.

n Otoliths (utricle andsaccule) are linearaccelerometers

n Bilateral symmetrymeans redundantdesign.

Vestibular Reflexes

n VOR: Vestibulo-ocular reflex

n VSR: Vestibulospinalreflex

Inertial navigation

n Three axes of rotation– Roll, pitch and yaw

n Three axes of translation– AP, Lateral, Vertical

6 degrees of freedom problem The Navigation Problem.

n Motion sensing is a "missioncritical" task -- for example,vestibular system is needed towalk reasonably safely in thedark.

n The vestibular systemincorporates considerableredundancy.

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5 sensors, 2 tests

n Clinical Correlate:can only measure2/5 -- lateral canaland saccule withavailable vestibulartests.

STARTING AND STOPPING =ACCLERATION

The otoliths sense tilt and linearacceleration

OTOLITHIC MEMBRANECalcite crystals

Utricle and Saccule orientation How the system deals withimperfections in Vestibular Sensors

n Imbalancen Timingn Gainn Noise

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Imbalance between ears

n Push-pull arrangementn Common mode

rejectionn Illusion of motion

when one side goes bad

Vestibular Nystagmus

1. Both sides – no nystagmus2. One side – lateral/rotatory3. One horizontal canal –

lateral nystagmus.4. One vertical canal – mixed

vertical/rotatory5. Vertical or torsional

nystagmus – usuallycentral

Imperfections in Vestibular Sensors

n Timing of canals isn’t good for eyes orbody– Need to extend timing for eyes– Need phasic emphasis for neck

Velocity Storage for VOR

Different timing needed for sluggishneck In vestibular lesions

n Velocity storage goes away for eyes (VOR).Time constant drops from 21 to 7 sec.

n Not clear what happens to timing in theneck/body – may be unchanged.

Hain TC, Zee D. S. : Velocity storage in labyrinthine disorders. New YorkAcademy of Sciences, 656, 1992, 297-304

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Ewald’s 3 Laws (1892)

n Eye and head movements occur in the planeof the canal being stimulated and in thedirection of endolymph flow

n In the lateral canal, ampullopetal flow causesa greater response than ampullofugal flow

n In the vertical canal the reverse is true

Observations made upon the exposed membranous labyrinthof Pigeons (Ewald’s pneumatic hammer)

Ewald JR. 1882. Physiologische Untersuchungen uber dasEndorgan des Nervus Octavus. Bergman, Wiesbaden.

Ewald’s 2nd Law

Wilson/Melville Jones

Ewald’s Compensationneed for both eyes and neck

Saturation Anti-Saturation

Linearbehavior

In unilateral vestibular loss, Ewald's2nd law probably causes head-shaking nystagmus, positive rapid-dolls head reflex. We are not surewhat happens to VCR/VSR.

Hain TC, Fetter M and Zee DS: Head-shaking nystagmus in unilateral peripheralvestibular lesions. American J. Otolaryngology., 8:36-47, 1987.

VNS L

Imperfections in Vestibular Sensorsn Gain

– Ewald’s 2nd law – built inproblem

– Growth and development– adapt to bigger head,

» loss of 50% inner ear byage 80

– Disease – bilateralvestibular loss

Noise in Vestibular Sensors

n Noise – a commonproblem– Fluctuations in vestibular

function» Ménière's, Fistula

n Noise makes vestibularinput unreliable– Logical consequence is to

decrease weighting ofvestibular input

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Clinical correlations

n Grocery Store Syndrome(AKA visual dependence)– Unable to tolerate busy visual

environments– Normally people switch

between most salient sensorymode –visual/vestibular/somatosensory

– Can’t switch -> bothered byTarget

Higher Level Vestibular Problems

n Coordinate rotation is needed tocommunicate with VCR and VSR

n Integration is needed of vision andsomatosensation with vestibular input

n Estimation is needed to process multipleunreliable sensors

Coordinate Rotation is neededbetween head and body

n Ears are in head which canturn on body

n Must rotate vestibularsignals into bodycoordinates (Nashner,1974)

n This is probablycomputationally intensiveand slow. http://i.pbase.com/u17/j_nasche/upload/39144467.012805.jpg

Sensory Integration

nVisual, vestibular, somatosensory sensesmust be integrated to form best estimate.n If incorrect estimate

– Motion sickness– Visual dependence

» Grocery store syndrome» Simulator sickness

Internal Model Theory(how the brain works ?)

n Outgrowth of Space programn Space Shuttle – 100’s of inputs and outputs

– Some intermittent– Some more reliable than others– Some sluggish, some rapid– Some are noisy

n Needed a method of formally computingbest estimate of Space Shuttle State

Kalman Filter (internal model)

n Grew out of work by Kalman at MIT

Wolpert, 1997

Formal method offorming “optimalestimate”.

Integrates efferencewith afference

Accounts for noise,sensor differences.

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VestibularDisorders

Otologic (Ear) Dizziness

n BPPV (benign paroxysmalpositional vertigo) -- about50% of otologic, 20% all

n Meniere’s disease -- about20%

n Vestibular neuritis andrelated conditions (15%)

n Bilateral vestibular loss(about 1%)

n SCD and Fistula (rare butworth knowing)

Positional VertigoThe most common syndrome

nBenign ParoxysmalPositional Vertigo(BPPV) -- bed spins

n Orthostatic hypotension (dizzy upright)n Central positional nystagmus (dizzy everywhere)n Low CSF pressure syndrome (dizzy upright)

Benign Paroxysmal PositionalVertigo (BPPV)

61 Y/O man slipped on wet floor.

LOC for 20 minutes.

In ER, unable to sit up because ofdizziness

Hallpike Maneuver: Positive

Positional VertigoDix-Hallpike Maneuver

Benign Paroxysmal PositionalVertigo (BPPV)

n 20% of all vertigon Brief and strongn Provoked by change of head positionn Definitively diagnosed by Hallpike test

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BPPV Mechanism: Utricular debris migrates toposterior canal BPPV treatment

n Medication (e.g. antivert) –minor benefit– May avoid vomiting by

pretreatingn Excellent response to PTn Surgery – canal plugging if

rehab fails (need morerehab after plug). Rarelydone.

Helminski, J. O., D. S. Zee, et al. (2010). "Effectiveness of particle repositioning maneuvers in the treatment of benignparoxysmal positional vertigo: a systematic review." Phys Ther 90(5): 663-678.

Unilateral Vestibular lesions

n Vestibular Neuritis/Labyrinthitis (common)n Meniere’s disease (unusual, 1/2000

prevalence)n Acoustic Neuroma (very rare)n Vestibular paroxysmia (not sure how

common)

Vestibular Neuritis: Case

56 y/o woman began to become dizzy after lunch.Dizziness increased over hours, and consisted of aspinning “merri-go-round” sensation, combinedwith unsteadiness.

Vomiting ensued 2 hours later, and she was broughtby family members to the ER.

Vestibular Spontaneous Nystagmusseen with video Frenzel Goggles Aside : how to examine for SN

n Frenzel Goggles (best)n Ophthalmoscope (good –but

backwards)n Gaze-evoked nystagmus

(Alexander’s Law)n Sheet of white paper (neat,

Ganzfeld)

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Vestibular Neuritis -- rxn Disturbance of unknown

cause (Viral ? Vascular)involving vestibular nerveor ganglion

n Disability typically lasts 2weeks.

n Symptomatic Rx(meclizine, phenergan)

n Rehab if still symptomaticafter 2 months.

n These patients can still getBPPV !

Meniere’s Disease

n Prosper Meniere– Hearing loss (fluctuating)– Episodic Vertigo– Fluctuating (roaring) Tinnitus– Aural Fullness

n About 1/2000 people in populationn Chronic condition – lasts lifetime

Etiology of Meniere’s (Dogma)n Dilation and episodic rupture of inner ear membranes

(Endolymphatic Hydrops)n As endolymph volume and pressure increases, the

utricular/saccular and Reissner’s membranes rupture,releasing potassium-rich endolymph into the perilymphcausing cochlear/vestibular paralysis

Meniere’s disease – symptoms

n Progressive hearing loss -- sometimes godeaf

n Episodic vertigo – dizzy for several daysn Ataxia – gradually increases over yearsn Visual sensitivity à

Visual Sensitivity is common

n Sensory integrationdisorder – upweightvision, downweighteverything else

n Grocery store,Omnimax, Target, etc

n Typical of disorderswith intermittentvestibular problems

Otolithic Crises of Tumarkin

n Drop attacksn Go from upright to

on floor in fractionof second

n No LOCn Very dangerousn Destructive

treatment is best

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Treatments of Menieres

n Medical management –– Usually ineffective

n Bad rehab candidate while fluctuatingn Surgery

– Low dose gentamicin treatment works nicely– High dose gentamicin treatment (overkill)

Hain TC, Ostrowski T. Unsteady Influence. Menieres disease. Advancesfor directors in rehabilitation October 2007, 51-51

Acoustic Neuroma

Acoustic Neuroma

n Rare cause ofunilateral loss

n Generally also deafn Slowly progressive –

little or no vertigon 1 mm/year growth

Treatment of Acoustic Neuroma

n Watchful waiting (about 25%)n Operative removal (about 50%) – losing

groundn Gamma Knife (about 25%) – gaining

ground because effective and noninvasiven Good rehab candidate

Vestibular Paroxysmia (AKAmicrovascular compression)

n Irritation of vestibular nerven Quick spins, tilts, dipsn May follow 8th nerve surgery, Gamma knife

treatment, acoustic neuroma, vestibularneuritis, vascular loop

n Wastebasket syndrome in some cases ?

Clinical Diagnosis of MVC

n Quick spinsn May have

nystagmus onhyperventilation

n Response toanticonvulsant

n No rehab potential

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Bilateral Vestibular Loss

A stewardess developed a toe-nail infection. Sheunderwent course of gentamicin andvancomycin. 12 days after starting therapy shedeveloped imbalance. 21 days after starting, shewas “staggering like a drunk person”. Meclizinewas prescribed. Gentamicin was stopped on day29. One year later, the patient had persistentimbalance, visual symptoms, and had notreturned to work. Hearing is normal. Sheunsuccessfully sued her doctor for malpractice.

SYMPTOMS OF BILATERALVESTIBULAR LOSS

l OSCILLOPSIA

Understanding your Dizziness and BalanceDisorder Video, Zee/Hain

Gentamicin is a problem SYMPTOMS OF BILATERALVESTIBULAR LOSS

l ATAXIAl Oscillopsia

DIAGNOSIS IS EASY

l History of recent IV antibiotic medicationl Eyes closed tandem Romberg is positivel Dynamic illegible ‘E’ test (DIE) failedl Ophthalmoscope test failed

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Dynamic Illegible ‘E’ test(DIE test)

n Distance vision with headstill

n Distance vision with headmoving

n Normal: 0-2 lines change.n Abnormal: 4-7 lines

change

http://www.dizziness-and-balance.com/practice/images/equipment/die%20chart.pdf

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Rapid Dolls failed

n VOR: Vestibulo-ocular reflex

Ophthalmoscope Test

LABORATORY DIAGNOSISEverything should be “dead”

l ENGl Rotatory chairl VEMP

DIAGNOSIS Continued

l Rotatory chair confirms diagnosis

DIAGNOSIS Continued

l ENG showslittle or noresponse

Treatment Bilateral

n No medical management (other thanavoiding more damage)

n Outstanding rehab candidaten Be prepared for a deposition

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Superior canal dehiscence Case: WSRetired plastic surgeon, with impaired hearingrelated to war injuries, found that when he wentto church, when organ was playing, certain notesmade him stagger. His otolaryngologist noted thatduring audiometry (with hearing aid in), certaintones reliably induced dizziness and a mixedvertical/torsional nystagmus. This “Tullio’sphenomenon” could be easily reproducedexperimentally. MRI scan was normal.

Tullio in SCD Valsalva in SCD

Diagnosis of SCD

n History of sound and pressure sensitivityn Valsalva test is easiest bedside testn Temporal Bone CT scan (0.6 mm high

resolution)n VEMP: Vestibular evoked myogenic

potentials, bigger on bad side

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Superior Canal Dehiscence

n Etiology:– Congenital bone defect

(2% ?)– Trauma/Age may

exacerbaten Treatment:

– Surgical» Plug» Resurface

n Most patients choseto “live with it”

Summary of Otologic Vertigo

More details

Hain, T.C. Approach to the patientwith Dizziness and Vertigo. Practical

Neurology (Ed. Biller), 2011.Lippincott-Raven

More movieswww.dizziness-and-hearing.com