急性期破裂脳動脈瘤のCT所見—とくに脳血管攣縮とHigh Densityとの関連について

COMPUTED TOMOGRAPHY OF RUPTURED INTRACRANIAL ANEURYSMS IN ACUTE STAGE : RELATIONSHIP BETWEEN VASOSPASM AND HIGH DENSITY ON CT SCAN

I．はじめに

　破裂脳動脈瘤におけるComputed Tomography （以下CTと略す）の診断的有用性に関しては，諸家によつて強調されているところである^{2,4,7,8,11）}。しかしCT所見と脳血管攣縮との関連について系統的に検討した報告はみあたらない。本研究の目的は，まず破裂脳動脈瘤急性期におけるCT上のHigh Density （extravasated blood，以下H．D．と略す）の出現頻度ならびにその消長を明らかにすることにある。さらにすすんで，このH．D．と脳血管攣縮発生との関連を検討したい。

Relationship between vasospasm and high density on CT-scan was studied in 73 patients with ruptured intracranial aneurysms in acute stage, and the fol-lowing conclusions were obtained;

1) High density area (extravasated blood) was found in 30 of 39 patients (77%) on CT-scan per-formed within 4 days after the onset of subarach-noid hemorrhage.

2) High density disappeared between 4 to 22 days after the bleeding on repeat CT-scans of 10 patients who were treated conservatively.

3) It is possible to anticipate whether vasospasm will develop by examining high density on CT-scan within 4 days after the onset. Vasospasm was observed on angiogram obtained between 5 to 14 days after the onset in 83% of the patients with high density in basal cisterns and 78% in Sylvian fissure, but no vasospasm developed in the patients without high density on CT-scan. On the other hand, there was no relationship between de-velopment of vasospasm and high density on CT-scan performed more than 4 days after the onset.

4) Location of high density (extravasated blood in subarachnoid space) on CT-scan performed with-in 4 days after the onset approximately coincided with the distribution of vasospasm demonstrated on angiogram.

5) Therefore, high density recognized on CT-scan performed within 4 days is considered to be es-sential for the development of vasospasm.

6) High density on CT-scan provides a guide to the indications and timing of surgical intervention. Early operation is recommended for the cases with-out high density on CT-scan performed within 4 days after the onset. For the cases with high density on CT-scan, it seems to be reasonable to remove subarachnoid clot as much as possible at surgery to prevent or minimize the future develop-ment of vasospasm.