Cerebrovascular instability in a subset of patients with stroke and transient ischemic attack.

In six patients, we observed remarkably unsteady blood flow and indications of vasospasms on the arteriolar level in connection with episodes of focal cerebral ischemia. The patients originated from a prospective consecutive study of 53 patients with stroke and transient ischemic attack who had been examined by cerebral angiography and rapidly repeated regional cerebral blood flow measurements using the intracarotid xenon 133 method. In 47 patients, regional cerebral blood flow values, flow patterns, and clinical condition were stable during the repeated regional cerebral blood flow measurements. In six patients, pronounced regional hypoperfusion and hyperperfusion developed during the course of examination. In the hypoperfused regions, flow was transiently reduced to values consistent with ischemia, and in four of these patients this was accompanied by transient neurological deficits. The arteriogram and isotope angiograms ruled out spasms of large arteries or thromboembolism. A condition of cerebrovascular instability on the arteriolar level probably was induced by the examination procedure. These patients were hypersensitive to the provoking stimuli either habitually or as a consequence of previous ischemic accidents. It is suggested that in some patients with focal cerebral ischemia, the primary cause might be spasms of the smallest resistance vessels rather than thromboembolism.