The relationship between directly measured human cerebral and tympanic temperatures during changes in brain temperatures.

The present study was performed to investigate the relationship between noninvasive measurements of core temperature and intracranial temperature measurements in humans. At 2-3 weeks following minor subarachoid haemorrhage, five patients were studied during open brain surgery. All patients were fully conscious and free of neurological symptoms at the time of surgery. During craniotomies in the frontotemporal region, temperatures between the dura and brain surface were on average 0.58 (SD 0.51) degrees C lower than those near the mesencephalon. During the 60-90 min following the initial exposure of the brain surface to the ambient temperature of 24 degrees C, subdural temperature at the convexity decreased by 0.72 (SD 0.43) degrees C and subdural temperature at the basis decreased by 0.36 (SD 0.17) degrees C. During the same period, mesencephalon temperature decreased by 0.22 (SD 0.10) degrees C. The decreases of cerebral temperatures were followed by a similar decrease in tympanic temperature of 0.28 (SD 0.10) degrees C but by an increase in rectal temperature of 0.22 (SD 0.13) degrees C and an increase in oesophageal temperature of 0.20 (SD 0.20) degrees C. The maximal shift of frontal skin temperature during the same period amounted to +0.04 (SD 0.21) degrees C. The findings would seem to support the thesis that a direct relationship does exist between tympanic and brain temperatures in humans and that of the externally accessible body temperatures, tympanic temperatures giving the best approximation of average cerebral temperature.