On tone decay testing at 1000 Hz, a continuous tone presented just above threshold becomes inaudible, and the patient needs an additional 35 dB of intensity within 60 seconds to keep it audible. This degree of tone decay is most consistent with:

• A Normal auditory adaptation
• B Cochlear lesion such as Meniere disease
• C Conductive hearing loss
• D Retrocochlear lesion such as vestibular schwannoma ✓

Explanation

Normal ears show 0 to 15 dB of tone decay, reflecting ordinary physiological adaptation. Decay of 15 to 25 dB occurs in some cochlear lesions, but decay greater than 30 dB at any single frequency is considered diagnostic of a retrocochlear lesion, typically an eighth nerve tumour, where pathological fatigue causes rapid loss of audibility of a steady tone. Conductive loss does not produce abnormal tone decay.

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

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Written and medically reviewed by the StethoPrep medical team.