Cerebral vasospasm in conditions other than subarachnoid hemorrhage.

Intracranial arterial spasm is an arteriographically evident narrowing of the lumen of one or more of the major intracranial arteries at the base of the brain that develops in some patients 1 or more days after the rupture of an intracranial aneurysm. If it is severe enough, such cerebral vasospasm may be accompanied by cerebral ischemia or infarction. Because of its usual setting, cerebral vasospasm is thought to arise from some chemical factor or factors in the blood that accumulates within the basal subarachnoid cisterns and bathes the arteries that subsequently develop spasm. There seem to be exceptions to this basic plan, however. In patients with a ruptured aneurysm, only some of the arteries bathed in subarachnoid blood develop spasm. Of more significance, some patients develop intracranial arterial spasm without apparent subarachnoid bleeding. Until the development of CT scanning, the evidence for the lack of subarachnoid hemorrhage in such patients was weak. We now have the ability to assess cerebral vasospasm repetitively in a noninvasive manner with TCD ultrasonography and to quantitate subarachnoid hemorrhage by CT scanning. We should take advantage of this opportunity to document cases that are exceptions to the rule. Does hypothalamic damage explain such cases, or is there some other explanation? This question may be the key for unlocking the mysteries of the pathogenesis of cerebral vasospasm.