小児ウィリス動脈輪閉塞症のMR診断—MRIおよびMRAの有用性と限界

Usefulness and Limitation of MR Imaging and MR Angiography in Diagnosis of Juvenile Moyamoya Disease

I．はじめに

　近年急速な発展を遂げるMRIは脳血管障害の診断において不可欠な検査法となってきており，殊に高磁場MRIでは脳実質病変のみならず頭蓋内血管の異常をも診断可能で，その有用性が報告されている^7,23,18）．またMRIの応用であるMR血管造影（MR angiography；MRA）は非侵襲的に血管構造を描出する新しい画像診断法であり，臨床的有用性が認められつつある^1-3,14）．今回，小児ウィリス動脈輪閉塞症の血管病変の描出能についてこれらMRL, MRA所見と脳血管撮影所見を比轍し，本疾患の診断における有用性と問題点につき検討を行ったので報告する．

Magnetic resonance (MR) images and MR angio-grams (MRA) were studied in 20 childhood cases of moyamoya disease. Both MRI and MRA successfully demonstrated moyamoya vessels in the basal ganglia in all cases, with a positive but not definite correlation tothe conventional angiographic findings. MRI depicted the stenotic and occlusive lesions of the carotid fork and horizontal portion of the middle cerebral artery effectively. MRA demonstrated some lesions which even MRI failed to prove, but it tended to overestimate the lesions. Post-operative state of collateral flow and the patency of EC-IC bypass graft could be evaluated as accurately with MRA as with conventional angiogra-phy, although MRA was limited in spatial resolution and evaluation of flow direction. In conclusion, MRI and MRA were considered to be useful in the diagnosis of moyamoya disease in stage 3and 4, but less effective in the evaluation of its angiographical stage.