Auditory brainstem response testing in a 47-year-old man with asymmetric sensorineural hearing loss shows absolute latencies of waves I and V within normal limits individually, but the interpeak interval between waves I and V is prolonged on the affected side. What is the most likely explanation?
- A Outer hair cell dysfunction in the cochlea
- B Conduction delay along the auditory nerve and brainstem pathway, suggesting a vestibular schwannoma ✓
- C Middle ear effusion attenuating the stimulus
- D Normal age-related central auditory slowing requiring no investigation
Correct answer: B. Conduction delay along the auditory nerve and brainstem pathway, suggesting a vestibular schwannoma
Explanation
Wave I reflects the distal auditory nerve and wave V the lateral lemniscus and inferior colliculus region. A prolonged I to V interpeak interval with normal absolute wave latencies localises the delay to conduction between the eighth nerve and brainstem, the classic electrophysiological signature of a cerebellopontine angle tumour such as vestibular schwannoma. Cochlear dysfunction delays all waves including wave I, and middle ear pathology reduces amplitude and raises thresholds rather than selectively prolonging the central conduction time.
Reference: Cummings Otolaryngology Head and Neck Surgery, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.