Postmorten changes in the chemistry and histology of normal and edematous brains.

The brains of 18 patients were examined post mortem for histologic criteria of edema, and samples of white and gray matter were analyzed for water, sodium, and potassium content. In a parallel experimental study, brains of cats with unilateral freezing lesions and resulting cerebral edema were similarly examined immediately after death and up to 18 hours post mortem. In both types of material, in gray matter there was a relatively rapid (within less than 4 hours) increase in water and sodium content and fall in potassium content. In normal and edematous white matter, little change was observed post mortem. No correlation could be demonstrated in any of the material studied between water content and histologic grading for cerebral edema. It is concluded that determination of water content in the white matter postmortem could be a useful tool for the neuropathologist. Histologic assessment of cerebral edema is of little value.