Tone decay testing is performed at 4000 Hz in a patient with asymmetric sensorineural hearing loss. The threshold for continuous tone presentation drifts upward by 35 dB compared with the interrupted-tone threshold. This degree of tone decay indicates:

• A Normal adaptation, consistent with conductive loss
• B Mild decay typical of a cochlear lesion
• C Significant pathological decay suggesting a retrocochlear lesion ✓
• D An unreliable result requiring repeat tympanometry

Explanation

Tone decay measures auditory adaptation to a sustained suprathreshold tone. Decay up to about 15 to 20 dB can occur in cochlear lesions and even mild amounts are acceptable. Decay exceeding 30 dB is considered pathological and is characteristic of retrocochlear lesions such as vestibular schwannoma, where eighth nerve fibres fatigue rapidly. Conductive losses show essentially no tone decay.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.