Lecture #23: Pathology of Auditory and Vestibular System

What does the term dizziness encompass clinically?

Dizziness is a nonspecific symptom patients use to describe sensations such as vertigo, near syncope, imbalance while walking, intoxicated feeling, psychiatric symptoms, or generalized lightheadedness.

What is vertigo?

Vertigo is the false sensation of movement, typically described as spinning of the patient or the environment.

Why is dizziness a challenging symptom to evaluate?

Patients use the term inconsistently, so clinicians must clarify the exact sensation, timing, triggers, and associated symptoms to determine the underlying cause.

What are the first critical questions when evaluating dizziness?

Determine whether the dizziness is dangerous, whether it is vestibular in origin, and whether it is peripheral or central.

What conditions make dizziness immediately dangerous?

Arrhythmias, transient ischemic attacks, strokes, and other central neurologic causes require urgent evaluation.

What distinguishes vestibular dizziness from non-vestibular dizziness?

Vestibular dizziness typically presents as vertigo with nausea and nystagmus, while non-vestibular causes involve presyncope, imbalance, or psychiatric symptoms.

What structures are involved in the vestibular system?

The vestibular system includes peripheral components (inner ear and vestibular nerve) and central components (brainstem and cerebellum).

What eye movement abnormalities suggest central pathology?

Disconjugate eye movements, poor smooth pursuit, and inaccurate saccades are more consistent with central nervous system disease.

What is nystagmus?

Nystagmus is an involuntary rhythmic oscillation of the eyes that reflects vestibular imbalance.

How does peripheral nystagmus differ from central nystagmus?

Peripheral nystagmus extinguishes with visual fixation and is suppressed by the brain, while central nystagmus does not extinguish and is not suppressed.

What is the fixation test used for?

The fixation test determines whether nystagmus extinguishes when the patient focuses on a fixed visual target.

What does extinguishing nystagmus indicate?

Extinguishing nystagmus indicates a peripheral vestibular cause.

What does persistent nystagmus with fixation indicate?

Persistent nystagmus suggests a central cause such as stroke or multiple sclerosis.

What is the vestibulo-ocular reflex (VOR)?

The VOR stabilizes vision by allowing the eyes to remain fixed on an object while the head moves.

How is the vestibulo-ocular reflex tested?

The patient fixates on a target while the examiner rapidly turns the patient’s head side to side.

What does an abnormal VOR suggest?

An abnormal VOR suggests a peripheral vestibular lesion.

What does an intact VOR suggest in vertigo?

An intact VOR suggests a central cause of vertigo.

How is gait evaluated in vestibular disorders?

Gait is usually normal in peripheral vertigo but often severely impaired in central vertigo.

What does inability to walk independently suggest?

Inability to walk independently strongly suggests a central cause such as stroke.

How does hearing involvement help localize vertigo?

Hearing loss, tinnitus, or roaring sounds usually indicate peripheral pathology, while complete hearing loss is more often central.

What is the ATTEST approach?

ATTEST evaluates dizziness using Associated symptoms, Timing and Triggers, Examination Signs, and Testing.

What is the HINTS exam used for?

The HINTS exam differentiates central from peripheral vertigo once vertigo has been identified.

What does HINTS stand for?

Head Impulse test, Nystagmus, and Test of Skew.

What is benign paroxysmal positional vertigo (BPPV)?

BPPV is a peripheral vestibular disorder caused by displaced otoconia in the semicircular canals.

What are the classic features of BPPV?

Brief episodes of vertigo lasting less than one minute, triggered by head movement, with latency before symptom onset.

Which semicircular canal is most commonly involved in BPPV?

The posterior semicircular canal.

What diagnostic maneuver confirms BPPV?

The Dix-Hallpike maneuver.

What treatment is used for BPPV?

The Epley maneuver, which repositions otoconia back into the utricle.

Why is the VOR normal in BPPV?

BPPV affects semicircular canals, not the vestibular nerve, which is tested by the VOR.

What is vestibulitis?

Vestibulitis is inflammation of the vestibular nerve, analogous to Bell’s palsy of cranial nerve VIII.

How does vestibulitis typically present?

Abrupt onset vertigo peaking within 24 hours, lasting days to weeks, often following a viral illness.

What are key exam findings in vestibulitis?

Nystagmus that extinguishes with fixation, abnormal VOR, and impaired balance with eyes closed.

How is vestibulitis treated?

Corticosteroids and antivirals, with limited use of vestibular suppressants to allow central compensation.

What is Meniere’s disease?

A peripheral vestibular disorder caused by endolymphatic hydrops in the inner ear.

What is the classic triad of Meniere’s disease?

Episodic vertigo, tinnitus, and sensorineural hearing loss.

How long do Meniere’s symptoms typically last?

Episodes last for hours rather than seconds or minutes.

What age group most commonly develops Meniere’s disease?

Onset is most common between ages 20 and 40 but can occur at any age.

How is Meniere’s disease evaluated?

Audiometry, vestibular testing, and imaging of the temporal bones when indicated.

What lifestyle modifications help manage Meniere’s disease?

Reducing sodium, caffeine, alcohol, stress, and environmental allergens.

What medications are used in Meniere’s disease?

Diuretics, benzodiazepines for acute attacks, antiemetics, and corticosteroids.

When is intratympanic gentamicin used?

In refractory Meniere’s disease to ablate vestibular hair cells.

What symptom duration helps distinguish vestibular conditions?

Seconds suggest BPPV, hours suggest Meniere’s or TIA, days suggest vestibulitis or stroke.

What are common causes of conductive hearing loss?

Cerumen impaction, otitis media, tympanic membrane perforation, otosclerosis, trauma, and Eustachian tube dysfunction.

What are common causes of sensorineural hearing loss?

Noise exposure, ototoxic drugs, congenital disorders, Meniere’s disease, presbycusis, and acoustic neuroma.

What is the goal of hearing loss evaluation?

To determine type, severity, location, and cause of hearing impairment.

What bedside tests differentiate conductive and sensorineural hearing loss?

The Weber and Rinne tuning fork tests.

How is the Weber test interpreted?

Sound lateralizes to the affected ear in conductive loss and to the unaffected ear in sensorineural loss.

How is the Rinne test interpreted?

Air conduction greater than bone conduction is normal or sensorineural loss; bone greater than air indicates conductive loss.

Why must Weber and Rinne be interpreted together?

Either test alone is insufficient to accurately localize hearing loss.

What is tinnitus?

Tinnitus is the perception of sound without an external source.

What conditions warrant ENT referral for tinnitus?

Pulsatile tinnitus, unilateral tinnitus, sudden hearing loss, dizziness, or ear or facial pain.

What are proposed mechanisms of tinnitus?

Loss of cochlear input, abnormal central neural firing, and altered inhibitory pathways.

What are key prevention strategies for hearing loss?

Treat infections promptly, monitor ototoxic drug levels, and avoid loud noise exposure.

Why is patient history emphasized in vestibular and hearing evaluation?

History provides the most critical clues for localization, diagnosis, and management.