Effects of hypothermia on the human brainstem auditory response.

Latency measurements between three potentials (waves I, III, and IV/V) of the human brainstem auditory response can allow early detection of certain posterior fossa lesions. The diagnostic use of these interwave latencies requires knowledge of what factors may prolong them in the absence of disease. Hypothermia appears to be one such factor--in 5 neurologically and audiometrically normal patients, mean esophageal temperatures as high as 34.5 degrees C resulted in prolongations of central auditory conduction time. Interwave latency prolongations that were abnormal relative to an age-matched normal population were seen at 32.1 degrees +/- 0.3 degrees C in patients with both spontaneous and induced hypothermia, and these abnormalities disappeared after rewarming to normothermia. Hypothermia often accompanies intoxication and coma and should therefore be considered when brainstem auditory response abnormalities are being interpreted in these two clinical conditions.