[The effect of repeated occlusions of the middle cerebral artery on pial arterial behavior and cerebral structure].

Temporary clipping of the major arterial trunk is a very important maneuver to control excessive unexpected bleeding during a neurosurgical operation, but repeated temporary clippings sometimes give rise to severe neurological deficits after surgery. In clinical practice, a major stroke can occur after many transient ischemic attacks without distinct angiographic occlusion. To confirm and explain these clinical experiences, the present study was performed. First, 20-min, 30-min and 1-h occlusion of the middle cerebral artery was performed in each of 5 cats, and pial arterial behavior, cerebral edema and infarction were observed. In the 20-min occlusion group, no abnormal change was found 5 hours after recirculation. In the 30-min occlusion group, cerebral edema was present in 10.5 +/- 4.2% of the hemisphere, but no infarction was observed, and pial arterial caliber remained in a 10% dilated state throughout the experimental periods. In the 1-h occlusion group, cerebral edema was present in 41.2 +/- 7.5% of the hemisphere and infarction was found in 34.5 +/- 9.5%. Pial arteries returned to a 20% dilated state but redilated by 45% at the end of experiment. As the second experiment, three 20-min occlusions at 1-h interval and two 30-min occlusions at 1-h interval were performed in each 10 cats. Pial arteries had dilated by 40% after release of the last occlusion in both groups. The extent of cerebral edema was 19.5 +/- 8.1% of hemisphere in the 20-min occlusions group and 36.6 +/- 9.7% in the 30 min occlusions group.(ABSTRACT TRUNCATED AT 250 WORDS)