Is there a transitional zone between brain infarcts and the surrounding brain? A histological study.

Twenty-eight recent brain infarcts were studied histologically for the presence of zones of partial tissue destruction between the infarct border and the surrounding normal brain. Such transitional zones have been demonstrated in animals and might be suspected in humans from the broad zones of reduced blood flow that have been demonstrated around brain infarcts. Necrotic neurons were observed outside the infarct borders in 20 of 28 cases. However, the width of the peri-infarct border zone was less than 5 mm in 17 of 20 cases and between 7 and 10 mm in 2 cases. Only one section from one case showed necrotic neurons more than 20 mm from the infarct border. It is concluded that the large majority of the brain infarcts in man are sharply delimited and that the broad zones of reduced flow around the infarcts may be due to functional inactivity following partial denervation of the cortex rather than to true ischemia.