Postmortem changes in stereological parameters of cerebral neurons.

The form and size of neurons in the cat cerebral cortex were stereologically investigated intravitally, and 30 sec., 5 hours, and 22 hours postmortem. For comparison, the human cerebral cortex of a 60 year old male subject was deep frozen 16 hours postmortem, and fixed in formalin. The stereologic parameters of the cat experiment included neuronal surface Ai, perimeter LPi, and formfactor fi. In our experiment, the neurons showed swelling and metachromasia 30 sec. postmortem, which disappeared with progressive autolysis. Postmortem neuronal swelling was attributed to circulatory disturbances in the course of fatal cardiac arrest, whereas metachromasia of nucleoli and Nissl bodies appeared together with increased lysosomal acid phosphatase activity. "Dark neurons were only found in the human cerebral cortex fixed by immersion, and are thus recognized as artefact due to fixation. The intravital occurence of "dark" neurons could not be excluded, however. Size and form determinations of the neuronal perikaryon are expected to give additional information on pathologic changes during the aging process of the human brain, especially in senile dementia and organic brain syndrome.