てんかん焦点部における微小形成不全の形態と機能

Histopathological and functional features of microdysgenesis

微小形成不全は側頭葉てんかんなどにおいて，しばしば認められる。病理組織学的には様々な所見が示されているが，perivascular glial satellitosisのような明確な基準所見をもとに病理診断基準が検証されることが必要である。微小形成不全の画像や脳波所見などの検討は，意外にも少ない。通常のMRI撮影では特異的な所見はなく，MRSで白質の異常が指摘される場合がある。［¹⁸F］FDG-PETで低代謝を示すことが半数程度あり，［¹¹C］flumazenil PETでは取り込み増加がみられる。頭皮脳波では微小形成不全の領域から異常波が検出され，術中皮質脳波で激しい棘波が出現するのが確認された。

Microdysgenesis（MD）is an important disorder of cortical development commonly associated with epilepsy. Although several authors demonstrated neuropathological abnormalities of MD, there are a few studies about imaging and electrophysiologic features. We reviewed the histopathological, neuroimaging and EEG features of MD. The histopathological findings of MD are too various to be always found. The pathological standard such as prerivascular glial satellitosis should be confirmed for an accurate diagnosis of MD. MD may be not visible on routine MRI, and the majority of our patients had normal MRI. Magnetic resonance spectroscopy（MRS）is able to indicate pathological changes of MD in the white matter. MD may explain changes in the volume of interest by increasing the volume of the grey matter by MRI volumetry.［¹⁸F］FDG-PET showed hypometabolism in half of our patients.［¹¹C］flumazenil PET finding is increased flumazenil volume of distribution（FMZ-Vd）in the white matter, and this finding is due to an increased number of neurons in the white matter. There was a strong correlation between EEG abnormalities and the extent of MD. Intraoperative electrocorticogram showed severe spikes in the area of MD. In our series, non-MD patients tended to have a better surgical outcome, but the other studies demonstrate a better outcome for MD patients. Widespread MD that is not able to be resected sufficiently indicates a poorer prognosis. In contrast, excision of focal MD is enough to achieve freedom from seizures. Furthermore, relationships between pathology and imaging and electrophysiology in the patients of MD provide useful information of epileptogenesis.