虚血脳におけるcritical flow level—II．クモ膜下出血後脳血管攣縮

CRITICAL FLOW LEVELS IN CEREBRAL ISCHEMIA : II.VASOSPASM FOLLOWING SUBARACHNOID HEMORRHAGE.

I．はじめに

　クモ膜下出血における現在の最大の未解決の問題は脳血管攣縮にある。高度の脳血管攣縮は脳梗塞を紹来し，クモ膜下出血の予後を著しく低下させるが，その確固たる対応方法はいまだ確立されていない。それは従来脳血管攣縮の情報を脳血管写のみに頼らざるを得なかつたからであり，脳血管攣縮による虚血の程度を正確に定量することが困難であつたことにも由来していうと思われる。また脳血管攣縮により血流がどの程度低下すると脳組織が梗塞に陥るかということについてはいまだ未知の問題であり，臨床的な報告はほとんどみられていない。

　本報告における目的は¹³³Xe動注法による局所脳血流測定法（rCBF）およびCTスキャンを用いて脳血管攣縮のcritical flow level，すなわち乏血により神経脱落症状の出現する脳血流レベルおよび脳梗塞に陥る脳血流レベルを知ることにある。脳血管攣縮による血流低下は徐々に進行するものであり，そのcritical flow levelを知ることは脳血管攣縮の治療を行なう上で重要な指針となると考えられる。

Critical level of cerebral blood flow was assessed in 21 selected patients with angiographically proved vasospasm following subarachnoid hemorrhage. The patients with severe primary brain damage due to intracerebral hematoma, hydrocephalus and/or the patients with vasospasm mainly in anterior cere-bral artery territory were excluded. The each levels of regional cerebral blood flow (rCBF) which may cause neurological symptoms (symptomatic flow level) and may cause cause cerebral infarction (in-farcted flow level) were estimated using both com-puted tomography (CT) and rCBF measurment. Regional CBF was measured 23 times in 21 cases by ¹³³Xe intracarotid injection method with 16 scintillation detectors from 7th day to 14th day after subarachnoid hemorrhage. The mean value, rCBF in motor area and rCBF in speech area (10 cases with dominant side lesion) were calculated according to the initial slope index.

In seven patients without neurological symptoms the value of mean rCBF, motor rCBF and speech rCBF were ranged 33-49, 35-45 and 30-48ml/100g/min. respectively. In ten patients with neurologi-cal symptoms without obvious low density area on CT, the value of mean rCBF, motor rCBF and speech rCBF were ranged 26-34, 22-31 and 27-33 ml/100g/min. respectively. In 6 patients with low density area on CT, the value of mean rCBF, motor rCBF and speech rCBF were ranged 19-26, 19-23 and 22-24ml/100g/min. respectively.

Therefore, the symptomatic flow level was asses-sed at 33-34ml/100g/min., of mean flow (approxi-mately 55% of normal value) and 30-33ml/100g/min. of rCBF (approximately 53% of normal value).The infarcted flow level was assessed at 25-26ml/100g/min. of mean flow (approximately 40% of normal value) and 18~22ml/100g/min. of rCBF (approximately 35% of normal value).

About half of the patients with neurological de-ficit alone showed a full recovery within one month after the onset showing no low density area on CT. These facts suggest that the measurement of rCBF in the patients with vasospasm may give an im-portant information for the prognosis.