A 28-year-old woman with unilateral hearing loss undergoes the Short Increment Sensitivity Index (SISI) test. She correctly identifies 85% of 1 dB intensity increments superimposed on a continuous 4000 Hz tone. This result indicates:

• A Normal auditory adaptation
• B Conductive hearing loss with ossicular fixation
• C Retrocochlear lesion involving the VIII nerve
• D Cochlear (sensory) hearing loss with recruitment ✓

Explanation

SISI scores above 60 to 70 percent indicate a positive result, seen in cochlear lesions where outer hair cell damage produces recruitment, that is, abnormally rapid growth of loudness. Patients with cochlear loss detect small 1 dB increments far better than normal listeners. Retrocochlear lesions show low scores because neural encoding of small increments is impaired, and conductive loss simply attenuates the signal without altering increment detection.

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

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Written and medically reviewed by the StethoPrep medical team.