MRI拡散強調画像で経時変化を確認しえた一過性全健忘の1例

Temporal Changes of Diffusion-weighted MR Images in a Patient with Transient Global Amnesia

要旨　一過性全健忘（transient global amnesia : TGA）は特徴的な臨床像の一方で，その病因は不明である。われわれはTGAの1例で，発症30時間後のMRI拡散強調画像（diffusion-weighted image : DWI）で側脳室に接する左海馬CA1領域に病変を認めた。同病変は発作9日後のfluid-attenuated inversion recovery（FLAIR）画像でも確認され，遷延性に経過した小梗塞と判断された。7日後に行ったSPECT，PETで側頭葉の血流・代謝の低下が遺残し，合致する所見であった。しかし，支配血管の異常やvascular risk factorを認めず，微小循環障害の原因は不明であった。

The pathogenesis of transient global amnesia （TGA） remains uncertain, although it is featured by characteristic clinical symptoms. We present a patient with TGA, in which diffusion-weighted MR image showed a punctuate hyperintense lesion in the left CA1 subfield of the hippocampus adjoining the lateral ventricle 24 hours after the onset. This lesion was observed with FLAIR image after 9 days from the onset, and therefore was considered to be a delayed ischemic lesion. A SPECT and PET studies 7 days after the onset showed a decrease of the CBF, CMRO₂ and CMRglu, and was compatible with a delayed ischemic lesion. However, there were no cardiovascular risk factors nor abnormalities of vascular supply, and therefore the reason for microcirculatory disturbances remained unclear.

（Received : February 2, 2005）