Arterial spin-labeling imagingが診断に有用であったてんかん発症の前頭蓋窩硬膜動静脈瘻の1例

A Case of Anterior Cranial Fossa Dural Arteriovenous Fistula Involving Uncontrolled Seizures Diagnosed Based on Characteristic Findings on Arterial Spin-labeling Imaging

Ⅰ．はじめに

　前頭蓋窩硬膜動静脈瘻（anterior cranial fossa dural arteriovenous fistula：ACF-DAVF）は全DAVF中6％程度の頻度の稀な疾患であるが，そのうち61〜91％は脳出血を契機に発見されると報告されており^1,5,9)，てんかん発作で発見される症例はさらに稀である．一般的に，DAVFは発生部位・症状が多様であり，神経学的症候のみで積極的にこの疾患を疑うことが困難な場合もあり，診断に苦慮することも珍しくはない．画像診断のgold standardは脳血管造影（digital subtraction angiography：DSA）検査であるが，侵襲度が高い検査であり，強く疑われる症例にのみ適応されるべきと考えられる．Arterial spin-labeling imaging（ASL画像）は，造影剤を用いずに脳組織灌流状態を撮像できるMRI検査法の1つであり，脳血管障害や脳腫瘍などの血流評価に臨床応用されている．

　今回，特徴的なASL画像所見に基づき診断に至った，てんかん発症のACF-DAVFの症例を経験したので報告する．

　We report a case of anterior cranial fossa dural arteriovenous fistula（ACF-DAVF）in a patient whose diagnosis was made according to characteristic findings on arterial spin labeling（ASL）MRI.

　CASE:A 68-year-old man was admitted to our hospital because of intractable epilepsy. Based on the initial MRI findings, an initial diagnosis of limbic encephalitis was made. Steroids and anticonvulsant drugs were administered;however, the seizures could not be controlled. A second MRI with ASL revealed abnormal vessel signals in the base segments of the left frontal and temporal lobes toward the basal vein of Rosenthal. Digital subtraction angiography（DSA）revealed an arteriovenous shunt in the left anterior cranial fossa, which drained toward the medial side of the left temporal lobe. A diagnosis of ACF-DAVF with status epilepticus was made, and the main drainer was cauterized. After the surgical procedure, the epilepsy was controlled with antiepileptic drugs, and postoperative MRI revealed obliteration of ACF-DAVF, disappearance of the high-intensity area on FLAIR sequences, and disappearance of the high-intensity signal area on ASL.