可逆性脳梁膨大部病変を有する脳炎・脳症（MERS）

Mild Encephalopathy with Reversible Splenial Lesion（MERS）

Point

・MERSは，脳梁膨大部にDWI高信号，ADC低下を示す可逆性の左右対称病変で，この病変自体は一過性で機能障害を残さないとされる．

・インフルエンザなどの感染症，薬剤性，代謝性など，さまざまな状態でみられることがある．

・脳梁を侵す疾患には，他にマルキアファーヴァ・ビニャミ病のように，脳梁を広範囲に傷害し後遺症を残すものもあり，注意が必要である．

　Mild encephalitis/encephalopathy with a reversible splenial lesion（MERS）is a clinically and radiologically benign condition that has been described within the past two decades. MRI findings include isolated symmetrical ovoid lesions of the splenium with a high-intensity signal on DWI and decreased apparent diffusion coefficient. These findings have been associated with viral infections, epilepsy, antiepileptic drug usage, and metabolic disturbances, among others. These conditions may present with severe clinical features, such as consciousness disturbance or cytokine storm; however, patients usually recover completely with optimal treatment. Some pathological conditions with splenic lesions, such as Marchiafava-Bignami disease, may be irreversible. Therefore, diseases with splenic lesions require careful attention.