Widespread microglial activation in patients deceased from traumatic brain injury

Primary objective: The role of microglial activation in traumatic brain injury (TBI) has been extensively described in established animal models. In contrast, very few studies have analysed this process in human patients, the majority being focused on the local reaction in the contused parenchyma. In this work, the main objective was the analysis of microglial activation in brain regions distant from the primary lesion. Research design: Morphological changes of microglia were evaluated in the cerebral cortex of patients deceased from TBI in comparison with control subjects. Methods and procedures: Cortical samples from five cases with TBI and 10 controls were evaluated using Ricinus communis lectin histochemistry and conventional Hematoxylin- eosin staining. Main outcomes and results: It was observed that microglial cells from patients with TBI presented shorter and thicker cellular projections compared with controls. Moreover, the percentage of histological area reactive to lectin was statistically higher in samples from subjects with TBI. These signs of microglial activation were observed in all of the analysed cortical areas, thus indicating a generalized effect on the whole cerebral cortex. The results are consistent with previous imaging PET studies performed in living patients with the C-11-PK11195 radiotracer. Conclusions: The findings indicate that TBI induces a widespread activation of brain microglia which affects all cortical areas, including those distant from the contusion site.