Chronic cerebral vasospasm after large subarachnoid hemorrhage in monkeys.

The authors have developed a model of chronic cerebral vasospasm analogous to the clinical situation, by inducing a large subarachnoid hemorrhage (SAH) in monkeys. With this model, the size of the SAH apparent on the first computerized tomography (CT) scan was correlated with the incidence and severity of cerebral vasospasm that developed. Indices monitored for up to 21 days after SAH included cranial CT scan, cerebral blood flow, vessel caliber, and neurological status. The 18 monkeys studied for 48 hours or more were divided into two groups according to the size of the SAH on CT scan. Vasospasm was more common in the group with large SAH. In this group, on Days 0, 7, and 14, the incidence of vasospasm was significantly higher than at other times (p less than 0.001, p less than 0.01, and p less than 0.05, respectively), and the percentage reduction in vessel caliber was significantly greater than in the group with small/medium SAH (Day 7, p less than 0.02; Days 0 and 14, p less than 0.05). Delayed neurological deficit developed in two monkeys with large SHA. Apathy was noted from Day 17 to Day 21 in one, and unsteadiness and drowsiness were noted on Days 4 and 5 in the other. Overall, the incidence, degree, and time course of vasospasm reflected the size of the hemorrhage.