[Latency changes in auditory brainstem response correlated with tympanic membrane temperature]

We had examined auditory brainstem responses (ABRs) of boxers in order to study human cerebral concussion. ABRs were not prolonged after bouts or knock-out but were unexpectedly shortened after any exertion with or without impact to the head. It was supposed that hyperthermia induced by exertion shortened brainstem conduction velocity as it occurred in peripheral nerve. We investigated correlation of ABR latency and tympanic membrane temperature, which indicated hypothalamic temperature or central nervous temperature, during exertion and body heating. I. Exertion group Six young males aged from 21 to 24 years old were examined (the two were examined twice). T ty (tympanic membrane temperature) and T rec (rectal temperature) were monitored. ABRs and carotid blood flow were examined (QFM). Then subjects were covered with PVC clothes and exercised on bicycle ergometer for 12 approximately 38 min. After T ty reached approximately one degree higher (degrees C) than base line, ABRs and carotid blood flow were recorded in the course of cooling down. T ty was elevated by 0.82 +/- 0.27 degrees C T rec, 0.60 +/- 0.26 degrees C after exertion. ABR I-V IPL was shortened from 4.24 +/- 0.60 to 4.10 +/- 0.11 msec (p less than 0.01) and it was correlated with T ty change rather than T rec or carotid blood flow. ABR IPL returned to base line as T ty came down. II. Heating group Six young males were examined. Hyperthermia was induced by electrical blanket or immersing in hot water (41 +/- 1 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)