てんかんの神経画像

Neuroimaging in Epilepsy

はじめに

　てんかんの診断における検査としては，脳波検査（光刺激，過呼吸，睡眠を含む）と神経画像検査が重要であり，必要に応じてビデオ脳波同時記録も行う。

　てんかん発作を起こした患者は，頭蓋内病変の検索のためにMRI（magnetic resonance imaging）またはCT（computed tomography）を施行することが推奨され，特にMRI検査は局在関連てんかん患者には重要である（『てんかん治療ガイドライン2010』推奨度A)¹⁾。

　一般的に，てんかんの画像検査は，純粋に形態学的評価が主体でその性状によりてんかん原性が経験的に示唆されるものと，十分な局在情報を有する機能検査（脳機能イメージング：脳機能画像検査）の2種類に分けることができる。前者はMRI，CTによる解剖学的評価であり，後者は，局所ブドウ糖代謝，局所脳血流評価，酸素代謝，受容体イメージングなどである。本稿では，てんかん患者における画像検査（形態学的評価および脳機能神経画像）と，関連する手法による統合的なてんかん焦点，脳機能診断について概説する。

Abstract

　It is now recommended that magnetic resonance imaging (MRI) or computed tomography (CT) be carried out in all patients with at least partial- and hopefully also generalized epilepsy to help identify intracranial lesions, such as hippocampal sclerosis, focal cortical dysplasia, brain tumor, cavernous malformation, and arteriovenous malformation. In order to identify epileptic focus, other neuroimaging tools, such as positron emission tomography (PET), single photon emission computed tomography (SPECT), and magnetoencephalography (MEG), are also useful, because an epileptogenic area is not necessarily located within these intracranial lesions. With regard to epilepsy surgery, neuroimaging is also required for the identification of functionally essential cortices, such as motor and language areas. MEG and functional MRI are noninvasively, and tractography with diffusion-weighted imaging (DWI) is also useful for visualizing relevant white matter tracts. Recently, it has been reported that the cortico-cortical network plays an important role in preservation of brain function. Thus, cortico-cortical evoked potentials (CCEP) and resting state fMRI are candidate methods to help clarify brain network. While good seizure control is an important treatment outcome for patients with intractable partial epilepsy, the preservation of brain function is equally important. For this reason, further development and clinical application of sophisticated imaging technique are required.