初診時Fisher症候群が疑われたone-and-a-half症候群の1例

A case of one-and-a-half syndrome masquerading as Fisher syndrome

要約　16歳女性に右上下肢のしびれが突発し，外眼筋麻痺，運動失調，深部腱反射の消失を伴っていた。磁気共鳴画像検査（MRI）で中枢神経系に異常がなく，Fisher症候群が疑われた。発症の2日後に眼科を受診した。矯正視力は右0.8，左0.5であり，両眼の輻輳反応が消失していた。両眼とも垂直方向での運動障害はなく，右眼に内転障害，左眼に内外転障害があり，いわゆるone-and-a-half症候群を呈していた。再度のMRIで左側の橋背側部に高信号域があった。当初のFisher症候群ではなく，多発性硬化症が強く疑われた。副腎皮質ステロイド薬のパルスと漸減療法で眼球運動は改善し，橋の病巣が縮小した。

Abstract.　A 16-year-old girl developed numbness in her right upper and lower extremities. She also showed external ophthalmoplegia,ataxia,and absence of deep tendon reflexes. The central nervous system was apparently normal by magnetic resonance imaging（MRI）. She was tentatively diagnosed with Fisher syndrome. She was referred to us on day 3 of the disease. Her corrected visual acuity was 0.8 right and 0.5 left. Convergent reflex was absent in either eye. Vertical eye movement was normal. The right eye showed impaired adduction and the left eye showed impaired adduction and abductlon. These findings were compatible with the diagnosis of one-and-a-half syndrome. Repeat MRI showed a high-density signal in the dorsal pontine area,suggesting a high possibility of multiple sclerosis. Pulsed corticosteroid therapy followed by tapering resulted in improved eye movements and decrease in the size of pontine lesion.