NeurologyTier 2Topic

Audiometry

What it measures

Quantifies hearing threshold by frequency - pure-tone audiometry measures the quietest sound heard at each frequency (typically 250Hz-8kHz), separately for air conduction (outer/middle/inner ear + nerve) and bone conduction (bypasses outer/middle ear, tests cochlea/nerve directly)
First-line objective test for suspected hearing loss - localises to conductive, sensorineural, or mixed

Patterns

Pattern	Air conduction	Bone conduction	Air-bone gap
Conductive loss	Reduced	Normal	Present (>10dB)
Sensorineural loss	Reduced	Reduced (parallels air)	Absent
Mixed loss	Reduced	Reduced (less than air)	Present

Bedside and adjunct tests

Weber and Rinne tuning fork tests - a rapid bedside screen before formal audiometry: Weber lateralises to the affected ear in conductive loss, away from the affected ear in sensorineural loss; Rinne is negative (BC>AC) in conductive loss, positive (normal) in sensorineural loss
Tympanometry - assesses middle ear compliance/pressure, complementing audiometry in a conductive loss workup

Acting on the result

Conductive loss -> ENT workup (otosclerosis, effusion, cerumen, ossicular chain disease) - often surgically correctable
Sensorineural loss -> hearing aids, cochlear implant if severe; sudden sensorineural hearing loss is an emergency (urgent ENT referral, often for corticosteroids)

Associations

NF2 (bilateral vestibular schwannoma - progressive sensorineural loss), ototoxic drugs (aminoglycosides, cisplatin, loop diuretics), presbycusis, Meniere's disease, otosclerosis

Serial testing

Serial audiometry monitors progression in known pathology (NF2 surveillance, ototoxic drug monitoring) and response to intervention (hearing aids/implants)

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