During acoustic reflex decay testing, a tone 10 dB above the reflex threshold is presented to the affected ear for 10 seconds. The recorded reflex amplitude falls to less than half its initial value before the end of the stimulus. This result is characteristic of:

• A Normal neural adaptation
• B Eighth nerve lesion, such as vestibular schwannoma ✓
• C Cochlear hearing loss with recruitment
• D Fixation of the stapes in otosclerosis

Explanation

Normally the stapedius reflex can be sustained for the full duration of a stimulus with little decline in amplitude. Decay to half or less of the initial amplitude within 10 seconds reflects pathological fatigue of the reflex arc and is a classic indicator of a retrocochlear lesion involving the auditory nerve, classically vestibular schwannoma. Cochlear lesions produce recruitment and brisk reflexes at low sensation levels rather than decay, and otosclerosis raises reflex thresholds or abolishes the reflex altogether.

Reference: Dhingra, Diseases of Ear, Nose and Throat, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.