A case of eight-and-a-half syndrome due to malignant lymphoma of the brainstem

one-and-a-half症候群は一側の傍正中橋網様体 (paramedian pontinereticular formation,PPRF)や 外転神経核の障害による一側への側方共同注視障害 と同側の内側縦束(medial longitudinal fasciculus, MLF)の障害による単眼の内転障害(MLF症候 群,核間性眼筋麻痺)を併発したものである。 健側眼の外転は可能である。One-and-a-half症候群 に顔面麻痺を伴うものは Eight-and-a-half症候群と 呼ばれており,PPRF及びMLFに隣接する顔面神 経核も障害を受けることで発症する。今回,左顔 面麻痺とMLF症候群,側方共同注視麻痺を呈した Eight-and-a-half症候群をきたした脳幹部悪性リンパ 腫の1例を経験したので文献的考察を含めて報告す る。 症 例 患者:60歳,男性。 主訴:左顔面麻痺 X-2年前から飛蚊症・霧視を認め近医眼科を受 診し原因不明のまま通院を自己中断していた。XPurpose: To discuss the mechanism of development of eight-a-half syndrome in a case with a pontine lesion. Case: A 60-year-old man presented with left facial palsy and abnormal eye movements. Neuro-ophthalmologic examination showed conjugate leftward gaze palsy, impaired left eye adduction, rightward gaze-evoked nystagmus of the right eye on looking rightward, and upward gaze-evoked nystagmus. Vergence movements of the eyes were preserved. Contrast-enhanced MRI revealed an approximately 3-cm lesion in the dorsal paramedial pons. Histopathology revealed diffuse large-cell malignant lymphoma. He was diagnosed as having eight-a-half syndrome due to malignant lymphoma of the pons. Eight-a-half syndrome is one-and-a-half syndrome, characterized by impairment of both the medial longitudinal fasciculus (MLF) and paramedian pontinereticular formation (PPRF), accompanied by facial palsy. Ipsilateral facial palsy can be associated with one-and-a-half syndrome, because the facial nuclei and nerve are adjacent to the MLF, PPRF, and the abducens nucleus. Conclusion: In a patient with the eight-and-a-half syndrome, neurophysiologic information would be useful to speculate the extent of the lesion. 原 著