Temporary Occlusion of the Middle Cerebral Artery in the Monkey: Clinical and Pathological Observations

The right middle cerebral artery (MCA) was exposed in monkeys via a retro-orbital microsurgical approach. In 43 animals a temporary occlusive clip was placed on the MCA origin for one to 24 hours. In 20 animals, the origin of the MCA was permanently occluded. Clinical evaluation of the monkeys one to three days postoperatively showed that one to two-hour clipping caused no or mild neurological deficits, four-hour clipping caused mild to moderate deficits, six to eight-hour clipping caused moderate to severe deficits, and 24-hour clipping produced severe deficits or death, a result equivalent to that produced by permanent occlusion. Gross and microscopical evaluation of the brains showed that one to two-hour clipping usually caused no or mild damage, four-hour clipping caused mild to moderate damage (often with capsular sparing), and six to eight-hour clipping and 24-hour clipping produced severe extensive infarction not different from that caused by permanent occlusion. Six to eight-hour clipping and 24-hour clipping were associated with a high incidence of hemorrhagic infarction, but other clipping times were not, The results suggest that reestablishment of flow by surgical means within a few hours after MCA occlusion in selected patients might result in significant restoration of neurological function. If flow renewal were done within about four hours, an increased incidence of hemorrhagic infarction might be avoided.