Which ABR finding would most strongly suggest a retrocochlear lesion?

• A. Prolonged wave I–V latency
• B. Absent Wave I
• C. Reduced amplitude of Wave II
• D. Normal wave I–V latencies

Answer: (D)

ABR captures the timing of neural transmission from the auditory nerve through brainstem pathways. When a retrocochlear lesion is present, conduction along these pathways is slowed, and the most telling sign is a lengthened interval between the earliest and later ABR waves. Specifically, a prolonged interpeak latency from Wave I to Wave V reflects delayed transmission from the auditory nerve up to higher brainstem centers. This slowing is the strongest clue that the problem lies beyond the cochlea. In contrast, normal Wave I–V latencies argue against a retrocochlear lesion, and other patterns (like an absent Wave I or reduced Wave II amplitude) are less specific to retrocochlear pathology.