破裂脳動脈瘤術前後の大脳半球の脳代謝および高次脳機能の変化—1H-MR spectroscopyおよびWAIS-Rを用いた検討

Changes in Proton Magnetic Resonance Spectroscopy and Wechsler Adult Intelligence Scale Revised after Clipping of Unruptured Aneurysms

Ⅰ．はじめに

　近年，MR装置の進歩や脳ドックの普及に伴い，破裂以前の脳動脈瘤の診断率が向上し，未破裂脳動脈瘤の手術件数が各施設で増加している．未破裂脳動脈瘤の開頭による根治術は，手術の適応基準，手術法および注意点などについて様々な報告があり，ほぼ確立されつつある．開頭術に伴うmorbidityは3-5％とされており，安全に遂行される手術と考えられている．しかし，このmorbidityは主に神経学的あるいは神経放射線学的視点からの検討であり，高次脳機能の変化は考慮されていない．従来，くも膜下出血後の高次脳機能や脳循環代謝に関する研究^{4,7,9,10,20）}は散見されるが，未破裂脳動脈瘤術後の高次脳機能や脳代謝物質の変化に関する報告^2）は少ない．未破裂脳動脈瘤の手術はあくまで予防外科である．今後も増加するであろう未破裂脳動脈瘤術後の評価には，高次脳機能や脳代謝についての検討も必要であると考えられる．

　今回われわれは，未破裂脳動脈瘤患者に対し，手術前後にWechsler Adult Intelligence Scale re-vised（WAIS-R）^13,19）およびmagnetic resonancespectroscopy（MRS）を計測し，本手術が高次脳機能および大脳半球の脳代謝に与える影響について検討したので報告する．

The purpose of this study is to evaluate the influence of surgery for unruptured aneurysms on neuro-psychological status and cerebral metabolism. We studied 21 patients with unruptured aneurysms treated with direct surgery accompanied by craniotomy, rather than by the endovascular method. Patients were evaluated before and after surgery, using the Wechsler adult intelligence scale revised (WAIS-R) and pro-ton magnetic resonance spectroscopy which measured the ratio of N-acetyl-aspartate to creatine (NAA/ Cr).Although the results of WAIS-R (total IQ, verbal IQ and performance IQ) was not significantly diffe-rent after surgery in any of the patients, the total IQ of the patients with anterior communicating artery aneurysms (AcoA) showed a significant decline compared with patients with other aneurysms after surgery. Five of eight AcoA patients showed a specific reduction in verbal IQ, suggesting deterioration of recent memory. The NAA/Cr remained within the normal range and was not significantly different before and after surgery. However, the NAA/Cr in the white matter of the frontal lobe of AcoA patients showed a significant reduction compared with that of non-AcoA patients. All three elderly patients older than 70 showed a reduction in NAA/Cr of more than one standard deviation from normal subjects in their frontal or parietal lobes. These results indicated that operation for unruptured aneurysms is reliable and well established but they also show that careful consideration should be given to possible deterioration in neuropsychological status and cerebral metabolism after operation in AcoA and elderly patients.