Downbeat nystagmusを呈した扁平頭蓋底，頭蓋底陥入症，Klippel-Feil症候群の合併例

Klippel-Feil Syndrome with Platybasia and Basilar Impression Presenting with Downbeat Nystagmus

　I．はじめに

　垂直性下眼瞼向き眼振（downbeat nystagmus）は，その責任病巣部位は下部脳幹，特に延髄から小脳虫部にかけてであり^1），下方向への滑動眼球運動の障害^2）が惹起されるとされている。多くの場合扁平頭蓋底，Amold-Chiari奇形に髄伴して出現してくる眼振^{3,11,12,14）}である。筆者らは，downbeat nystagmusを示した1例を経験し，耳神経学的検査を施行し得たので報告する。

　A 18-year-old female with downbeat nystagmus is reported. She complained of hypesthesia and motor weakness of her left extremity. Skull and cervical x-ray films showed synostosis of the atlas and axis, flattening of the base of the skull and an anomaly of the occipitocervical junction where the upper cervical segments and foramen magnum protruded into the cranial cavity. Neurotological examinations revealed downbeat nystagmus during right and left gaze, disturbance of horizontal OKN, saccadic eye movement of ETT and overshot on calibration. These findings suggested brainstem and cerebellar lesions. The patient underwent suboccipital decompression and after operation her condition was stabilized although downbeat nystagmus still persisted.