Absent auditory brain stem response: peripheral hearing loss or brain stem dysfunction?

Interpretation of auditory brain stem response (ABR) findings can be problematic in cases where waves III and V are absent. Such findings can be attributed to profound hearing loss, brain stem neuropathology, or both. Over a 3-year period, 48 patients with no known brain stem damage and on whom audiologic data were available were found to have no response by ABR or absent waves III and V. Severe to profound hearing loss was documented in 38 cases, audiometric data were equivocal in 3 cases, and 7 patients showed pure tone sensitivity ranging from normal hearing to moderate impairment. Thus 15% had better hearing sensitivity than might have been expected from their ABR findings. Each of these patients also exhibited abnormal acoustic reflex findings. We report the electrophysiological (ABR, MLR, acoustic reflex), medical (history, neurological, EEG, CT scan) and behavioral (audiometric, speech and language, learning disabilities, psychological) data which characterize this group of patients.