Sensorineural Hearing Loss

Cochlear loss shifts every wave rightward in parallel and preserves interpeak intervals. The latency–intensity function shifts right but stays parallel.

Pattern

Cochlear sensorineural loss arises from outer hair-cell or stria vascularis dysfunction. All ABR waves are delayed by a similar amount, so the interpeak intervals (I–III, III–V, I–V) remain within normal limits1. The latency–intensity function for wave V is shifted to the right but maintains the canonical 0.03 ms/dB slope. Foundation

Threshold and amplitude

Wave V threshold rises in step with the behavioural threshold, corrected for the laboratory's dB nHL→dB eHL offset2. Wave V amplitude is typically reduced, but amplitude is more variable than latency and weighed less in interpretation.

The wave-I correction Trainee

For asymmetric SNHL with one severely affected ear, the absent wave I makes IPL I–V uncomputable on that side. The clinical workaround is to compare interaural wave V latency with a correction factor — roughly 0.1 ms subtracted per 10 dB of high-frequency loss above 50 dB HL — so that the cochlear-induced shift is not mistaken for a retrocochlear one3.

Ototoxicity monitoring Clinician

Platinum-based chemotherapy (cisplatin, carboplatin) and high-dose aminoglycosides damage outer hair cells in a basal-to-apical progression. Extended high-frequency audiometry (above 8 kHz) is more sensitive than the standard audiogram for early changes; click ABR — biased toward 1–4 kHz — lags the earliest changes but captures progression once mid frequencies are involved7. Children and adults with cognitive impairment, where behavioural audiometry is unreliable, are the populations for whom serial objective monitoring matters most. ASHA-style monitoring criteria (≥ 20 dB threshold shift at any single frequency, ≥ 10 dB at two adjacent frequencies, or loss of response at three consecutive previously-responding frequencies) trigger oncology consultation8. The ABR signature is the cochlear pattern of this page — parallel L–I shift, IPLs preserved — applied serially over the treatment course.

What argues against pure cochlear loss

Disproportionate IPL prolongation, asymmetric interaural V difference exceeding 0.4 ms, or a steeper-than-normal L–I slope — any of these moves the workup toward retrocochlear pathology and an MRI of the IACs.