It's pretty warm in a healthy brain. At 38.5 degrees Celsius, the average brain temperature is more than two degrees higher than that in the mouth, as a British research group reports in the specialist magazine »Brain«. In the deeper brain regions it often exceeds 40 degrees - a value that would be diagnosed as a fever in other places in the body.
The team led by Nina Rzechorzek from the MRC Laboratory for Molecular Biology in Cambridge recruited 40 healthy volunteers between the ages of 20 and 40 and determined the temperature in different brain regions in the morning, afternoon and evening by magnetic resonance spectroscopy (MRS). In all subjects, the values fluctuated by almost one degree Celsius over the course of the day. In the evening the temperature dropped, during the day it rose again. The highest values were measured in the afternoon. The record was set by a woman: 40.9 degrees Celsius in the thalamus – in the brain region where it was warmest on average.
The brain temperatures of women achieved about 0.4 degrees Celsius more than that of men. The researchers suspect that this probably has to do with the menstrual cycle. As is known, the temperatures after ovulation are higher than usual, and most women were in the measurement in this phase. The temperature also increased with age, especially in deeper brain regions.
From the data, the researchers created what they claim is the first 4-D map of brain temperature - "a much–needed reference source," says study leader Nina Rzechorzek. The team compared the results with measurements from more than 100 intensive care patients who had a traumatic brain injury. The brain temperature in them was on average one degree lower than in the healthy ones, in addition, it fluctuated between 32.6 and 42.3 degrees Celsius and thus more than in the volunteers of the first examination (36.1 to 40.9). Only a quarter of the sick had the daily rhythm typical of healthy people. If there was no rhythm, the risk of death increased by a factor of 20.
"The daily rhythm of the brain temperature correlates strongly with the survival of a traumatic brain trauma," says Rzechorzek in a press release. However, it cannot be assumed that it was the cause and effect - rather a risk marker.
