Acoustic reflex decay testing is performed in a 45-year-old with asymmetric sensorineural hearing loss. Presenting a sustained tone at 500 Hz for 10 seconds just above reflex threshold causes the reflex amplitude to fall by more than 50%. This finding localizes the lesion to:

• A Cochlear hair cells
• B Ossicular chain
• C Eighth nerve or lower brainstem (retrocochlear) ✓
• D Facial nerve distal to the stapedius branch

Explanation

Reflex decay greater than 50% of initial amplitude within 10 seconds of continuous stimulation reflects abnormal neural adaptation and is characteristic of retrocochlear pathology such as vestibular schwannoma. Cochlear lesions show strong, easily elicited reflexes with little decay because of recruitment, which kills distractor A. Facial nerve lesions abolish the reflex entirely rather than causing gradual decay, eliminating D.

Reference: Cummings Otolaryngology: Head and Neck Surgery, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.