Speech Arrestの頻発にて発症した前頭葉てんかんの1例

A Case of Frontal Lobe Epilepsy Presenting with Recurrent Speech Arrest

　症例は55歳の男性で，高血圧，高脂血症および高尿酸血症ににて通院中。会話中に突然，発声および発語不能の発作が出現するようになった。この発作中，意識障害はなく，周囲の状況を十分に認知していた。1日に十数回と頻発するようになってきたため発症3日目に左内頸動脈系の一過性脳虚血発作の疑いで当科に入院した。CT・MRIでは左前頭葉皮膚下に石灰化を認めた。脳血管と撮影では異常所見は認められなかった。脳波では左前頭部および中心部を焦点とする速波が出現し，数秒で対側へ波及、さらに律動波に発展し，不規則性棘徐波複合に変わるというパターンが60分間に合計9回（1回の持続は1〜2分）出現し，これらの発作波の出現中に発声・発語不能が認められた。Phenytoinの内服にて発作は消失し，脳波上も正常化した。本症例はSpeech arrestのみの頻発にて発症した前頭葉てんかんの稀な例である。

We report a 55-year-old right-handed man with frontal lobe epilepsy manifesting recurrent speech arrest. He was known to have hypertension, hyper-triglyceridemia, and gout. In the three days prior to admission, he had episodes of sudden inability to talk. These episodes lasted 10 to 30 seconds andrecurred ten to twenty times a day. On admission, speech comprehension and other mental functions were normal, as were findings on neurologic exami-nation. During the period of speech arrest, he under-stood spoken commands, and there was no abnor-mal motor activity or paresis. The episodes of speech arrest were thought to be short aphasic periods due to transient ischemic attacks in the left carotid territory. Computed tomography and mag-netic resonance imaging demonstrated a small calcified lesion in the upper medial portion of the left frontal lobe. Left internal carotid angiography demonstrated no abnormal findings. After neurora-diological examination finished, he suddenly raisedhis right hand and followed it with his gaze and a right head turn. The EEG seizure pattern in which 20-25 Hz activity began in the left fronto-central region and spread rapidly to the right fronto-central region, which after about 8 seconds was replaced by 12-14 Hz flattening rhythmic polyspikes was detect-ed 9 times within 60 minutes. It is most unusual for supplementary motor area seizure to present pure paroxysmal speech arrest without accompanying paroxysmal motor activity. As in our case, epileptic arrest of speech may be confused with a transient ischemic attack of the dominant hemisphere.