Clinical Analysis of Cerebral Vasospasm following Subarachnoid Hemorrhage

—Part 2 Disturbance of Cerebral Circulation and Cerebral Infarction Associated with Cerebral Vasospasms—

Abstract

Eighty-four patients with ruptured intracranial aneurysms were analyzed to investigate relationship of cerebral vasospasms to subarachnoid clots and to cerebral circulation and the effect of vasospasms upon the development of cerebral infarction.
The extent of vasospasms was classified into four types: diffuse (narrowing over 2 cm in length in at least one of the C₁, A₂ and M₁ portions), peripheral (narrowing over 2 cm in length in the distal portions), multi-local (multiple localized narrowing) and local (single localized narrowing). The diffuse type of vasospasm was further divided into two grades of severity: diffuse severe (reduction of the caliber by more than 50%) and diffuse mild (reduction of the caliber by 25 to 50%). As an indicator of objective estimation of vasospasms, the ratio of the diameter of the arteries at the C₁, A₂ and M₁ portions to that of the canalicular portion of ICA was calculated from 32 normal angiograms. Measurement of the rCBF was undertaken by the intra-arterial xenon-133 injection method. The degree of subarachnoid clot was graded according to the high density area in the CT from 0 (no clot) to II (diffuse and severe clot in the basal cisterns, especially around the midbrain). The extent of the vasospasm was estimated by angiography performed 4 to 20 days after the subarachnoid hemorrhage.
The results were as follows: 1) There was a good correlation between the degree of subarachnoid clot within 3 days after the subarachnoid hemorrhage and the types and the severity of the vasospasm. Fifteen out of 18 patients with grade I or II subarachnoid clot developed the diffuse type of vasospasm (nine severe and six mild), while only three cases developed the diffuse type of vasospasm (one severe and two mild) out of eight patients with grade 0 or I. 2) Most of the patients with the diffuse type of vasospasm, especially with the diffuse severe type, showed decreases of mean CBF and impaired CO₂ response, while mean CBF of the patients with the multi-local or the local type ofvasospasm showed no meaningful decrease when compared to the patients without vasospasms. Focal ischemia was frequently shown in regions supplied by the involved arteries in the patients with vasospasms. Increase of cerebrovascular resistance was seen in patients with the diffuse-severe type of vasospasm. 3) Twenty out of 38 patients with the diffuse type of vasospasms developed cerebral infarctions (12/20 severe, 4/14 mild and 4/4 peripheral), while none of the 14 patients with no, vasospasm or local and multi-local type of vasospasm developed cerebral infarctions. 4) Development of cerebral infarctions after subarachnoid hemorrhages depended not only on the severity of vasospasms but also on the duration of the vasospasm and interval between onset of the vasospasm and the subarachnoid hemorrhage.