The temperature within the circle of Willis versus tympanic temperature in resting normothermic humans.

We measured the temperature of arterial blood within the circle of Willis (T(Willis)) in seven normothermic patients undergoing carotid arteriography. We found this temperature to be lower by 0.13 to 0.30 degrees C than tympanic temperature and by 0.30 to 0.55 degrees C lower than rectal temperature. By imposing this data on calculated cerebral heat balance it can be suggested that the average cerebral temperature of a resting subject is somewhat higher than tympanic temperature. These findings would also support indirectly the thesis that temperature gradients may exist within the brain.