Acoustic reflex decay testing is performed by presenting a continuous tone at 10 dB above the reflex threshold for 10 seconds. A decay exceeding 50% of the initial reflex amplitude is recorded. This result localizes the lesion to the:

• A Eighth nerve or cerebellopontine angle ✓
• B Cochlea
• C Facial nerve distal to the stylomastoid foramen
• D Middle ear effusion

Explanation

Abnormal acoustic reflex decay, defined as more than 50% reduction in reflex amplitude during sustained stimulation, reflects impaired neural encoding and adaptation failure of the auditory nerve, and it is a classic indicator of retrocochlear pathology such as vestibular schwannoma. Cochlear lesions typically show strong, easily elicited reflexes at reduced sensation levels, while middle ear pathology abolishes reflexes altogether rather than causing selective decay. Facial nerve lesions affect the efferent motor limb but decay testing targets the sensory pathway.

Reference: Katz's Handbook of Clinical Audiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.