Assessment of Heat Stroke-Induced Brain Injury: A Preclinical Study with a Rat Model Using <SUP>18</SUP>F-FDG Brain PET

Abstract

PurposeHeat stroke is the most serious heat-related illness and is recognized as a worldwide public concern as global temperatures continue to rise. Although the clinical neurological complications of heat stroke are relatively well described, a limited number of studies exist that document imaging findings. Therefore, in this preclinical study, we aimed to identify the imaging findings of 18F-FDG brain PET following heat stroke and elucidate the utility of FDG PET in the evaluation of heat stroke-induced brain injury.MethodsHeat stroke was induced in Sprague Dawley rats by placing them in a hot and humid chamber maintained without food and water until they exhibited the heat stroke onset diagnostic criterion. Three hours after the induction ended, 18F-FDG brain PET images were acquired in 7 controls and 14 rats with heat stroke. Between groups, region-based (standardized uptake values were normalized to the whole brain and SUV of the whole brain (SUVWB), and voxel-based analyses were performed.ResultsOf the 14 rats with heat stroke, 8 survived, whereas 6 did not. In the region-based and voxel-base analyses, the rats that did not survive showed significantly higher SUVRHB in the hypothalamus and significantly lower SUVRHB in several cortical regions than the controls as well as the survived rats. In the region-based analysis, the survived rats showed a significant increase or decrease in SUVRHB compared to the controls in a few cortical regions. However, no difference was observed in the voxel-based analysis.ConclusionsThe 3-h post-injury PET scan showed a distinctly different regional distribution of 18F-FDG in the brains of lethally injured heat stroke rats compared to the controls as well as the survived rats. The 18F-FDG brain PET may have the potential to provide early indicators of catastrophic injury and reflect the early neurological pathophysiology of heat stroke.