Postmortem evaluation of brain edema: An attempt with measurements of water content and brain-weight-to-inner-skull-circumference ratio.

INTRODUCTION: Postmortem evaluations of cerebral edema typically involve examinations of macroscopic features such as the presence of pressure signs and compression of the ventricles. Global massive edema is easily detectable in an autopsy, but less-extensive edema may be difficult to diagnose.

AIM: The aim of this study was to compare measurements of brain water contents, postmortem CT radiodensity and brain weight to skull size in edematous and nonedematous brains in order to develop an objective method for postmortem evaluations of brain edema.

METHOD: Fifty-four subjects autopsied at Oslo University Hospital underwent a standard forensic postmortem examination, including a computed axial tomography (CT) scan, measurement of brain weight, and macroscopic evaluation of the brain. CT images were used to roughly measure the inner skull circumference. The water content of the brain was determined by excising samples of approximately 1 g of brain tissue from eight different areas of the brain surface, drying them, and measuring their percentage water content.

RESULTS: The main finding was a significant relationship between brain weight and inner skull circumference, with the ratio between these two parameters being significantly higher in cases with severe postmortem brain edema than in cases with very little or no brain edema. The water content did not differ significantly between the edema and nonedema cases. There were no significant changes in radiodensity.

CONCLUSION: This indicates that the brain-weight-to-inner-skull-circumference ratio may serve as a good marker for severe brain edema in postmortem diagnostics, whereas measurements of water content can be misleading.