Brain temperature and its fundamental properties: a review for clinical neuroscientists

Abstract

Brain temperature, as an independent therapeutic target variable, has received increasingly intense clinical attention. To date, brain hypothermia represents the most potent neuroprotectant in laboratory studies. Although the impact of brain temperature is prevalent in a number of common human diseases including: head trauma, stroke, multiple sclerosis, epilepsy, mood disorders, headaches, and neurodegenerative disorders, it is evident and well recognized that the therapeutic application of induced hypothermia is limited to a few highly selected clinical conditions such as cardiac arrest and hypoxic ischemic neonatal encephalopathy. Efforts to understand the fundamental aspects of brain temperature regulation are therefore critical for the development of safe, effective, and pragmatic clinical treatments for patients with brain injuries. Although centrally-mediated mechanisms to maintain a stable body temperature are relatively well established, very little is clinically known about brain temperature's spatial and temporal distribution, its physiological and pathological fluctuations, and the mechanism underlying brain thermal homeostasis. The human brain, a metabolically "expensive" organ with intense heat production, is sensitive to fluctuations in temperature with regards to its functional activity and energy efficiency. In this review, we discuss several critical aspects concerning the fundamental properties of brain temperature from a clinical perspective.

Keywords: brain; cerebral blood flow; hyperthermia; hypothermia; temperature.

Figure 1

Thermal map of the brain. The results of measurements of the temperature difference between arterial blood and 100 brain and subarachnoid sites in 16 monkeys during 347 experiments. Values expressed are T_i–T_a temperature of intracranial site minus the temperature of the aortic arterial blood measured simultaneously, and are all positive values). The major regions which have been studied in the primate brain have been placed on two representative frontal sections, A, frontal 14.5 and B, front 0.3. Values are expressed to the nearest 0.1 C. Reprinted with permission from The American Journal of Physiology, Hayward and Baker (1969).

Figure 2

Local brain temperature change during activity and active cooling. Example studies documenting localized phasic temperature changes after an increase in activity or a stimulus presentation (plotted over red background) or to external cooling (plotted over blue background). Brief experiment description, species, and brain area written inside oval and reference displayed on opposite side of abscissa.