Cell density and cortex thickness in the border zone surrounding old infarcts in the human brain.

Six cases of completed ischemic stroke in the middle cerebral artery territory of more than two months' duration were selected for this study of neuropathology. Coronal brain slices of the entire brain were cut for histology and stained with Klüver-Barrera's stain. Neuronal and glial cell density, and cortex thickness were measured at various distances from the border of the infarct. Corresponding counting points in the contralateral hemisphere served as control in all cases. The density of histologically intact neurons was in all cases normal at a distance of 0.5 cm or more from the border of the infarcts. In one half of the cases the border zone between infarcted and normal tissue was less than a few cells in thickness. This study of old brain infarcts confirms the commonly held view that there is an abrupt transition between infarcted and normal tissue. This observation suggests that the wide zone of low blood flow and metabolism surrounding cerebral infarcts is not caused by selective loss of neurons. Instead, we hypothesize that such change in blood flow and metabolism is the result of neuronal disconnection and cortical deactivation.