A 52-year-old man presents with asymmetric sensorineural hearing loss and unilateral tinnitus. Immittance audiometry is performed, and the acoustic reflex decay test shows the pattern marked **B** in the diagram—reflex amplitude decays to less than 50% of its initial value within 5 seconds at 500 Hz and 1000 Hz. Which of the following is the most likely diagnosis that this finding is designed to screen for?

Why Vestibular schwannoma (acoustic neuroma) is right

The acoustic reflex decay test (Anderson reflex decay test) is a screening tool for retrocochlear pathology, with vestibular schwannoma being the most important diagnosis to exclude in patients with asymmetric sensorineural hearing loss. The pattern marked B—decay to <50% of initial amplitude within 5 seconds at 500 and 1000 Hz—represents pathologic reflex decay characteristic of neural adaptation/fatigue at the level of the eighth nerve or brainstem. This occurs because the reflex arc (afferent via cochlear nerve → central processing in superior olivary complex → efferent via facial nerve to stapedius) is disrupted by the mass effect or demyelination caused by retrocochlear lesions. Vestibular schwannoma is the classic retrocochlear pathology that presents with asymmetric SNHL and unilateral tinnitus and produces positive reflex decay. (Cummings Otolaryngology 7e; Katz Handbook of Clinical Audiology 7e)

Why each distractor is wrong

Cummings Otolaryngology 7e; Katz Handbook of Clinical Audiology 7e