Resting-State Brain Temperature: Dynamic Fluctuations in Brain Temperature and the Brain-Body Temperature Gradient.

Abstract

While fluctuations in healthy brain temperature have been investigated over time periods of weeks to months, dynamics over shorter time periods are less clear. To identify physiological fluctuations in brain temperature in healthy volunteers over time scales of approximately 1 hour. Prospective. A total of 30 healthy volunteers (15 female; 26 ± 4 years old). 3 T; T1-weighted magnetization-prepared rapid gradient-echo (MPRAGE) and semi-localized by adiabatic selective refocusing (sLASER) single-voxel spectroscopy. Brain temperature was calculated from the chemical shift difference between N-acetylaspartate and water. To evaluate within-scan repeatability of brain temperature and the brain-body temperature difference, 128 spectral transients were divided into two sets of 64-spectra. Between-scan repeatability was evaluated using two time periods, ~1-1.5 hours apart. A hierarchical linear mixed model was used to calculate within-scan and between-scan correlations (Rw and Rb , respectively). Significance was determined at P ≤ .05. Values are reported as the mean ± standard deviation. A significant difference in brain temperature was observed between scans (-0.4°C) but body temperature was stable (P=.59). Brain temperature (37.9 ± 0.7°C) was higher than body temperature (36.5 ± 0.5°C) for all but one subject. Within-scan correlation was high for brain temperature (Rw =0.95) and brain-body temperature differences (Rw =0.96). Between scans, variability was high for both brain temperature (Rb =0.30) and brain-body temperature differences (Rb =0.41). Significant changes in brain temperature over time scales of ~1 hour were observed. High short-term repeatability suggests temperature changes appear to be due to physiology rather than measurement error. 2 TECHNICAL EFFICACY: Stage 1.