片側顔面痙攣に対するmicrovascular decompressionの新しい術前画像評価：3D MR cisternogram/angiogram fusion imagingの応用

Preoperative Assessment of Microvascular Decompression for Hemifacial Spasm with Fusion Imaging of 3D MR Cisternogram/Angiogram

Ⅰ．は じ め に

　片側顔面痙攣に対するmicrovascular decompression（MVD）^1-3)の術前画像評価には，神経，血管，脳実質が同時に描出されるMRI元画像が使用され，顔面神経root exit zone（REZ）近傍での圧迫責任血管を元画像上で推測することが可能となってきた^1,4-6,10,11)．しかし，これらは2次元平面画像のため，REZでの神経と血管との解剖学的位置関係を立体的に把握することは困難である．

　今回，片側顔面痙攣症例において，責任血管による顔面神経REZの圧迫状況を立体的に表示する目的で，3D MR cisternogram/angiogram fusion imaging ^8,9)を応用し，術前にMVD術野に相応するthree-dimensional（3D）simulation画像をprospectiveに作成し，手術所見と対比検討した．3D MR cisternogram/angiogram fusion imageを用いて顔面神経REZでの神経血管圧迫状況を小脳橋角部脳槽内の様々な観察視点から術前検討した結果，片側顔面痙攣に対するMVDの適応の判断，手術難易度の推定，手術戦略，informed consentなどに有用と考えられたので報告する．

　The preoperative assessment of microvascular decompression (MVD) for hemifacial spasm has been performed with MRI,but assessment of the compressive status by 2D imaging has a number of limitations. We used a fusion image of the 3D MR cisternogram and co-registered 3D MR angiogram,reconstructed from MR cisternogram,obtained by 3D fast spin-echo sequence,and MR angiography,3D time-of-flight and spoiled-gradient recalled sequences,for the preoperative assessment of the offending artery in 10 patients with hemifacial spasm. The anatomical relationship of the nerve-vessel complex was assessed on the simulated images,and compared with the intraoperative findings. The fusion image of the 3D MR cisternogram/angiogram depicted contours of the brain,nerves,and vessels clearly,and that allowed precise assessment of the pathogenic compression of the facial nerve by the offending vessels,comparative to the operative findings. The fusion imaging of the 3D MR cisternogram/angiogram may provide useful information in the surgical planning of MVD for hemifacial spasm.