Speech discrimination score (SDS) obtained at suprathreshold levels (typically 40 dB above SRT) is used clinically to distinguish conductive, cochlear, and retrocochlear hearing losses. Which pattern is MOST suggestive of retrocochlear pathology?

• A SDS of 88% with hearing threshold of 50 dB SNHL — within expected limits
• B SDS of 60% in conductive hearing loss — expected with a 40 dB air-bone gap
• C SDS of 72% with a flat audiogram — consistent with cochlear noise-induced loss
• D SDS of 40% that is disproportionately poor relative to the degree of pure-tone average loss (roll-over phenomenon) ✓

Explanation

The 'rollover' phenomenon — where speech discrimination scores decrease (paradoxically worsen) as presentation intensity increases above the optimal level — is a hallmark of retrocochlear (VIII nerve or central auditory) pathology, such as acoustic neuroma. In normal hearing or cochlear loss, SDS remains stable or improves with increasing intensity. A rollover index >0.45 (difference between peak SDS and SDS at highest intensity divided by peak SDS) is considered significant for retrocochlear pathology. Disproportionately poor SDS relative to pure-tone average also suggests retrocochlear disease.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.