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Vestibular Disorders - Detailed Clinical Notes

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1. ANATOMY AND PHYSIOLOGY OF THE VESTIBULAR SYSTEM

Peripheral Vestibular Apparatus

• Anterior (superior), posterior, and horizontal (lateral) canals
• Detect angular acceleration (rotational movement)
• Each canal has an ampulla containing the crista ampullaris with hair cells embedded in the cupula
• Hair cell deflection toward kinocilium = excitation; away = inhibition
• Ewald's Laws: (1) nystagmus occurs in the plane of the stimulated canal; (2) ampullopetal flow in horizontal canal is excitatory; (3) ampullofugal flow in vertical canals is excitatory

• Utricle: horizontal plane; detects linear acceleration and head tilt
• Saccule: vertical plane; detects vertical linear acceleration
• Hair cells embedded in the macula covered by the otolithic membrane with calcium carbonate crystals (otoconia/otoliths)

• Superior division: innervates utricle, anterior and horizontal canal cristae
• Inferior division: innervates saccule and posterior canal crista
• Cell bodies in Scarpa's ganglion
• Projects to 4 ipsilateral vestibular nuclei (superior, inferior, medial, lateral) in the brainstem

Vestibulo-Ocular Reflex (VOR)

• Generates compensatory eye movements opposite to head movement to stabilize gaze
• Three-neuron arc: hair cell afferents → vestibular nuclei → extraocular motor neurons
• The Head Impulse Test (HIT) tests VOR integrity: a corrective saccade (catch-up saccade) seen after a rapid head thrust indicates ipsilateral canal hypofunction

Vestibulospinal Reflex

• Lateral vestibulospinal tract (from Deiter's nucleus): facilitates extensor muscle tone ipsilaterally
• Medial vestibulospinal tract: maintains head-neck posture

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2. CLASSIFICATION OF VESTIBULAR DISORDERS

Key Feature: Central vs. Peripheral Vertigo

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3. BENIGN PAROXYSMAL POSITIONAL VERTIGO (BPPV)

Overview

Pathophysiology

1. Canalithiasis (most accepted): Free-floating otoconia (canaliths) migrate from the utricle into a semicircular canal (usually posterior), causing cupular deflection with position change
2. Cupulolithiasis: Otoconia adhere directly to the cupula, making it gravity-sensitive

Clinical Features

• Paroxysmal vertigo lasting < 60 seconds (usually < 30s), triggered by:
  • Lying down or rolling over in bed
  • Bending over and straightening up
  • Tilting the head backward (looking up)
• Accompanied by oscillopsia and nausea
• No change in hearing, no tinnitus
• Symptoms often worse in the morning
• May be preceded by head trauma (17%) or viral neurolabyrinthitis (15%)
• Association with osteoporosis noted in some studies

Diagnosis: Dix-Hallpike Maneuver

• Patient seated; examiner rapidly lowers patient to supine with head turned 45 degrees to affected side, extended 30 degrees below horizontal
• Positive test (posterior canal BPPV):
  • Latency of 2-10 seconds before nystagmus onset
  • Upbeat-torsional nystagmus with torsional component toward the lower (affected) ear
  • Duration < 60 seconds
  • Fatigability: nystagmus diminishes with repeated testing
  • Reversal of nystagmus on returning to seated position
• If nystagmus lasts > 90 seconds → consider central positional nystagmus (CNS pathology)

Management

1. Patient seated with head turned 45° toward affected side
2. Rapidly lie back with head hanging over the edge of the bed (position 1, hold 20 seconds)
3. Rotate head 90° to face opposite shoulder, maintaining head-hanging position (position 2, hold 20 seconds)
4. Roll patient onto side; rotate head further face-down (position 3, hold 20 seconds)
5. Return to seated position

• Success rate: 50-90% with a single maneuver; 85% in large series of 965 patients
• The Semont maneuver has similar efficacy (~90%)
• Post-procedure: maintain upright head position for 24 hours
• Surgical options (for refractory cases): singular neurectomy (risk of hearing loss up to 41%) or posterior semicircular canal occlusion (94 of 97 cured in reported series)

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4. MENIERE DISEASE (Idiopathic Endolymphatic Hydrops)

History

• First described by Prosper Meniere in 1861 (proposed labyrinthine origin)
• Histopathological confirmation of hydrops demonstrated in 1938

Epidemiology

• Incidence: ~1 in 500 in the US; 13.1 per 100,000 person-years in the UK
• Peak onset: 4th-5th decade; can occur at any age
• Slight female predominance in some series
• Bilateral disease: 19-24% (true incidence; may develop years later)
• Familial occurrence: 10-20%; autosomal dominant pattern suggested
• HLA associations: B8/DR3 and Cw7

Pathophysiology

• Ruptures of Reissner's membrane
• Mixing of endolymph and perilymph causing potassium toxicity to vestibular hair cells
• Possible immune dysfunction (HLA associations; responds to steroids in some cases)
• Etiology remains elusive despite 70+ years of research

Classic Tetrad (VETH)

1. Vertigo - episodic, spontaneous, rotational, lasting 20 min to several hours (rarely >24h)
2. Ear fullness (aural fullness)
3. Tinnitus - usually low-pitched, louder during attacks
4. Hearing loss - sensorineural, fluctuating, typically low-frequency initially

Unique Features

• Otolithic crises of Tumarkin (drop attacks): Sudden falls without loss of consciousness or vertigo, due to abrupt otolithic dysfunction generating erroneous gravity reference. Occur in 2-6% of patients; often in clusters then spontaneously remit
• Lermoyez variant: Tinnitus and hearing loss precede and worsen before the attack, then dramatically resolve when vertigo begins
• Attacks are preceded by aura: increasing fullness, worsening tinnitus, hearing decrease

AAO-HNS Diagnostic Criteria (1995, revised)

Management

1. Low-salt diet (< 1500 mg/day sodium) + diuretics (acetazolamide, hydrochlorothiazide) - first-line, though evidence is modest
2. Vestibular suppressants (acute attacks): meclizine, diazepam, promethazine
3. Intratympanic (IT) steroids: Dexamethasone (4-12 mg/mL); multiple protocols; vertigo relief in 80%, tinnitus in 74% in early series. Avoids ablative surgery in 81-91% of patients in retrospective studies

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5. VESTIBULAR NEURITIS (Vestibular Neuronitis)

Overview

Pathophysiology

• Vestibular nerve degeneration with sparing of peripheral receptor structures (confirmed on temporal bone histology)
• Most likely etiology: reactivation of herpes simplex virus type 1 (neurotropic virus in Scarpa's ganglion)
• Borrelia infection implicated in some cases
• Superior vestibular nerve more commonly affected than inferior division (longer, narrower bony canal → more susceptible to compressive swelling)

Clinical Features

• Sudden onset of severe vertigo lasting days with gradual improvement
• Accompanying nausea, vomiting, diaphoresis
• Head movement-related balance complaints may persist for months
• No hearing change, no focal neurologic complaints
• BPPV can develop subsequently in a small percentage
• Can recur (less intense subsequent attacks)
• Bilateral disease can occur (consider in bilateral vestibular loss)

Diagnosis

• Caloric testing: Reduced or absent response on the affected side (canal paresis)
• Head Impulse Test (HIT): Corrective catch-up saccade toward the affected side (positive = peripheral lesion)
• MRI with gadolinium: Enhancement of vestibular nerve (less common, useful to rule out central)
• VEMP testing rarely useful (inferior nerve usually spared)

Management

• Vestibular suppressants: meclizine, diazepam, ondansetron, promethazine
• Corticosteroids (methylprednisolone): Historically used; some evidence supports benefit if given within 3 days
• Supportive care (IV fluids if unable to tolerate oral)
• Antivirals: Evidence weak; not routinely recommended

• Vestibular rehabilitation exercises (VRT): Begin as soon as tolerated; critical for central compensation
• Gaze stability exercises, balance training
• Vestibular suppressants should be weaned to avoid impairing central compensation

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6. LABYRINTHITIS

Serous (Toxic) Labyrinthitis

• Inflammation without direct invasion of the labyrinth
• Caused by toxins from adjacent otitis media or meningitis
• Presents with vertigo + mild hearing loss
• Hearing usually recovers with treatment of primary cause

Suppurative (Bacterial) Labyrinthitis

• Direct bacterial invasion of the labyrinth
• Complication of: acute otitis media, meningitis, cholesteatoma
• Severe vertigo + profound sensorineural hearing loss
• May lead to permanent labyrinthine destruction
• Treatment: IV antibiotics, surgical drainage of source; cochlear implant may be needed if ossification (labyrinthitis ossificans) develops

Viral Labyrinthitis

• Distinguished from vestibular neuritis by PRESENCE of sensorineural hearing loss
• Same viral etiologies (herpes, influenza, mumps)
• Treatment: supportive; antivirals may be considered

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7. VESTIBULAR MIGRAINE

Overview

Diagnostic Criteria (Barany Society / IHS joint criteria)

• A. ≥5 episodes of vestibular symptoms, moderate-severe intensity, lasting 5 min to 72 hours
• B. Current or prior history of migraine (ICHD criteria)
• C. ≥1 migrainous feature in ≥50% of vestibular episodes: migraine headache, photophobia/phonophobia, or visual aura
• D. Not better accounted for by another vestibular or ICHD diagnosis

• Criteria A + C but only ONE of criteria B or C fulfilled
• Not better accounted for by another diagnosis

Treatment

• Lifestyle modification: Identify triggers (specific foods, sleep irregularities, hormonal changes), stress reduction
• Acute: triptans, NSAIDs, antiemetics
• Preventive: Beta-blockers (propranolol), tricyclic antidepressants (amitriptyline), SSRIs, anticonvulsants (topiramate, valproate)
• Diet manipulation and close follow-up important for compliance

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8. SUPERIOR CANAL DEHISCENCE SYNDROME (SCDS)

Pathophysiology

• Absence of bone over the superior semicircular canal creates a "third mobile window" into the inner ear
• Normally, sound pressure enters via stapes footplate (oval window) and exits via round window
• The dehiscence diverts sound/pressure to the superior canal, causing abnormal vestibular activation
• Ewald's first law predicts the eye movement direction based on the plane of the superior canal

Clinical Features

• Tullio phenomenon: vertigo and nystagmus induced by loud sounds (Hennebert sign variant)
• Hennebert sign: vertigo/nystagmus with tragal compression or Valsalva (pressure changes)
• Autophony: Sensation of increased loudness of one's own voice/footsteps/heartbeat
• Conductive hearing loss (not due to middle ear pathology - bone conduction enhanced)
• Pulsatile tinnitus
• Nystagmus in the plane of the superior canal (upbeat-torsional, with torsion of superior pole away from affected ear)

Diagnosis

• High-resolution CT scan with reconstructions in the plane of the superior canal and orthogonal plane
• cVEMP (cervical vestibular evoked myogenic potential): enhanced responses
• oVEMP (ocular VEMP): present with normal thresholds

Management

• Conservative: most patients managed with lifestyle modifications (avoid loud sounds, Valsalva)
• Surgical repair (middle fossa craniotomy or transmastoid approach): resurfacing or plugging the dehiscent canal; indicated when symptoms are debilitating

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9. VESTIBULAR PAROXYSMIA

Overview

• Brief (seconds to minutes) episodes of vertigo occurring suddenly without apparent trigger
• Analogous to hemifacial spasm and trigeminal neuralgia
• Postulated mechanism: neurovascular compression of cranial nerve VIII (usually AICA)

Diagnosis

• Unilateral dysfunction on vestibular/auditory testing in some patients
• MRI may show vascular contact with CN VIII (though asymptomatic vascular contact is common in general population)

Treatment

• Carbamazepine (first-line)
• Oxcarbazepine
• Gabapentin
• Surgical microvascular decompression: rarely indicated; most have favorable course with medication

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10. PERILYMPH FISTULA

Pathophysiology

• Abnormal communication between perilymph-filled inner ear and middle ear (through oval or round window rupture)
• Causes: barotrauma (heavy lifting, Valsalva, air travel), trauma, iatrogenic (stapedectomy)

Clinical Features

• Fluctuating sensorineural hearing loss
• Vertigo/dizziness, especially with pressure changes (straining, nose-blowing, heavy lifting)
• Positive fistula test: pressure in EAC → vertigo/nystagmus

Management

• Conservative: bed rest, head elevation, avoid Valsalva for 4-6 weeks
• Surgical repair (patch graft of fat/perichondrium) if conservative management fails

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11. VESTIBULAR SCHWANNOMA (Acoustic Neuroma)

Overview

• Benign tumor of Schwann cells of the vestibular division of CN VIII (not truly "acoustic")
• Most common neoplasm causing vertigo; accounts for ~6-8% of all intracranial tumors

Clinical Features

• Progressive unilateral sensorineural hearing loss (most common initial symptom)
• Tinnitus (usually unilateral, high-pitched)
• Disequilibrium (often mild, as slow growth allows central compensation; true vertigo is uncommon)
• Large tumors: facial numbness, facial weakness (CN VII compression), cerebellar signs, elevated ICP

Diagnosis

• MRI with gadolinium (investigation of choice): "ice cream cone" appearance on axial cuts
• Audiology: asymmetric SNHL, poor speech discrimination disproportionate to pure tone threshold
• ABR (auditory brainstem response): prolonged or absent wave V

Management

• Observation (small tumors in elderly): serial MRI every 6-12 months
• Microsurgical resection: translabyrinthine (no hearing preservation), retrosigmoid (hearing preservation possible), or middle fossa approaches
• Stereotactic radiosurgery (Gamma Knife): tumor control ~90-95%; reasonable alternative for small-medium tumors

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12. THE HINTS EXAMINATION

• Sensitivity 88-100%, specificity 85-99% for central cause in high-risk AVS populations
• More sensitive than early MRI/CT for posterior fossa stroke (especially within 24-48h)

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13. PERSISTENT POSTURAL-PERCEPTUAL DIZZINESS (PPPD)

Overview

• Functional vestibular disorder (previously called phobic postural vertigo, chronic subjective dizziness)
• Characterized by: persistent (≥3 months) non-spinning dizziness, unsteadiness, or non-spinning vertigo
• Exacerbated by upright posture, motion, and visually complex environments

Diagnostic Criteria (Barany Society 2017)

• Persistent dizziness/unsteadiness on most days for ≥3 months
• Symptoms vary throughout the day, worse with upright stance, motion, complex visual stimuli
• Triggered by: acute vestibular disorder, other neurological event, anxiety/panic
• Not better explained by another diagnosis

Pathophysiology

• Maladaptive postural control strategy: over-reliance on high-acuity visual processing and somatosensory information rather than vestibular input
• Anxiety and autonomic hyperarousal play a significant role

Management

• Vestibular rehabilitation therapy (VRT)
• SSRIs/SNRIs (sertraline, venlafaxine): first-line pharmacotherapy
• Cognitive behavioral therapy (CBT)
• Avoid vestibular suppressants (counterproductive)

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14. CENTRAL CAUSES OF VERTIGO

Vertebrobasilar Ischemia / Posterior Circulation Stroke

• Involves PICA (AICA, SCA, or basilar artery)
• PICA infarct (Lateral Medullary/Wallenberg syndrome): vertigo, ipsilateral facial numbness, contralateral body numbness, ipsilateral Horner's, dysphagia, dysarthria, ipsilateral limb ataxia
• AICA infarct: vertigo + ipsilateral hearing loss + facial palsy
• Cerebellar hematoma: sudden vertigo + severe ataxia; emergency (obstructs 4th ventricle → hydrocephalus)
• Dizziness is the most frequent presenting symptom of vertebral artery dissection (VAD) - present in 58% of presentations

Vertebral Artery Dissection (VAD)

• Tear in vertebral artery wall → false lumen → stenosis/dilation
• Results in stroke in ~2/3 of presentations
• Mean age 46 years (2 decades younger than typical stroke population)
• Accounts for ~2% of ischemic strokes; larger fraction of strokes in patients < 45 years
• Annual incidence: ~1 in 100,000
• Diagnosis: CT/MRI angiography
• Treatment: antiplatelet agents or anticoagulation; endovascular options

Multiple Sclerosis

• Demyelinating plaques in brainstem (vestibular nuclei) or cerebellum
• Internuclear ophthalmoplegia (INO) is a classic finding
• Pendular or gaze-evoked nystagmus

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15. VESTIBULAR TESTING

Caloric Testing

• Warm (44°C) and cool (30°C) water irrigations of external auditory canal
• Warm = ipsilateral slow-phase nystagmus; mnemonic COWS (Cold Opposite, Warm Same)
• Canal paresis: reduced response on one side → peripheral hypofunction
• Directional preponderance: asymmetry in responses → central or peripheral

Videonystagmography / Electronystagmography (VNG/ENG)

• Records eye movements during positional testing, caloric testing, and oculomotor testing
• Identifies site of lesion (peripheral vs. central)

Video Head Impulse Test (vHIT)

• Quantitative measurement of VOR gain for all 6 semicircular canals
• Gain < 0.8 = reduced VOR; covert/overt saccades confirm hypofunction

Rotary Chair Testing

• Low-frequency sinusoidal rotation testing
• Useful for bilateral vestibulopathy

Vestibular Evoked Myogenic Potentials (VEMP)

• cVEMP (cervical): tests saccular function + inferior vestibular nerve
• oVEMP (ocular): tests utricular function + superior vestibular nerve
• Enhanced cVEMP thresholds in SCD; absent in vestibular neuritis (inferior nerve)

Posturography (Balance Platform Testing)

• Computerized dynamic posturography (CDP)
• Tests sensory organization (visual, vestibular, somatosensory contributions to balance)

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16. VESTIBULAR REHABILITATION THERAPY (VRT)

Mechanisms

• Habituation: repeated exposure to symptom-provoking stimuli reduces response amplitude
• Adaptation: VOR gain recalibration via repetitive head movements
• Substitution: development of alternative strategies (increased reliance on visual/somatosensory cues)

Components

• Gaze stabilization exercises (x1 and x2 viewing paradigms)
• Balance/gait training
• Canalith repositioning (for BPPV)
• Fall prevention strategies

Indications

• Unilateral vestibular hypofunction (vestibular neuritis, schwannoma post-surgery)
• Bilateral vestibular hypofunction (ototoxicity)
• Presbystasis (age-related vestibular decline)
• PPPD (with cognitive behavioral therapy)

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17. PRESBYSTASIS (Age-Related Vestibular Decline)

• 35.4% of adults ≥40 years have vestibular dysfunction (NHANES 2001-2004 data; 69 million Americans)
• Age-related hair cell and neuron degeneration in semicircular canals, utricle, saccule
• Degeneration most prominent at central area of cristae (SCC); more diffuse in maculae
• Strong association with cognitive impairment (spatial navigation, financial management)
• Diabetes mellitus: vestibular dysfunction is a recognized complication, mediates fall risk
• Treatment: VRT, fall prevention (night lights, removal of throw rugs, ambulatory aids), address underlying causes (postural hypotension, medications, endocrine disorders)
• Vestibular suppressants relatively contraindicated in bilateral hypofunction (further reduces vestibular input)

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Summary Table: Common Peripheral Vestibular Disorders

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