左前頭葉背外側部梗塞により記憶力障害を呈した1例

Memory Impairment Due to Circumscribed Infarct at the Left Dorsolateral Prefrontal Lobe

はじめに

　記憶の中枢として側頭葉内側部，間脳，前脳基底部などがよく挙げられる部位であるが，前頭葉背外側部の障害による記憶力障害の報告は比較的稀である。今回われわれは，左前頭葉背外側部の限局性梗塞による記憶障害例を経験したので報告する。

Abstract

　A 65-year-old man experienced an embolism at the left dorsolateral prefrontal region of the brain (the inferior frontal gyrus and a part of the middle frontal gyrus).　He was a known case of diabetes mellitus and atrial fibrillation.　On evaluation his Mini-Mental State Examination (MMSE) score was 26, indicating the absence of dementia.　His chief complaint was episodic memory impairment.　On the Wechsler Memory Scale-Revised (WMS-R), he had lower scores for general memory, visual memory and verbal memory.　In particular, his verbal memory was markedly impaired compared to visual memory.　Tests performed to assess working memory, such as evaluation on the WMS-R for attention/concentration in WMS-R and both parts A and B of the trail making test, revealed normal findings; this indicated that the patient had normal working memory.　However, he complained of forgettingess of either phone numbers or routes, and this suggested the impairment of working memory in his daily life.　In summary, he suffered from either episodic verbal memory or working memory impairment.　His executive function test revealed a slight disturbance of set-exchange on the Wisconsin Card Sorting Test-Keio version.　Such a case of memory impairment caused by a lesion in the left dorsolateral prefrontal lobe has rarely been reported.