Arnold-Chiari II奇形における第4脳室の嚢胞状拡張—症例報告と文献的考察

Cystic Dilatation of the Fourth Ventricle : Case Report

　Chiari奇形において，第4脳室と連続し，上位頸髄背側に存在する嚢胞形成の報告は，剖検例，あるいは小児例において時折みられるが，成人例の報告は極めて稀である。

　我々は複視・後頭部痛にて発症した25歳の男性で，第4脳室が嚢胞状に拡張し，第6頸椎レベルまで進展した1症例を経験した。治療として後頭下開頭，椎弓切除に加え第4脳室—腹腔短絡術を施行し，症状の改善を得た。神経放射線学的特徴，手術および病理所見，ならびに成因などにつき検討を加え報告した。

The patient, a 25-year-old male, was admitted with a 2-year history of double vision and recurrent suboccipital headache. Neurological findings on admission revealed nystagmus, double vision in the far field, bilateral abducense palsy, weakness in the bilateral legs, hypalgesia and hypesthesia under the L5 level, gait disturbance and hypotonia of the anal sphincter. Plain skull X-ray showed marked digitalimpression and disappearance of the posterior clinoid process and the dorsum sella. Myelography disclosed a filling defect dorsal to upper and midcer-vical cord. Intraventricular injection of metrizamide outlined cystic dilatation and caudal migration of the fourth ventricle. Occipital craniectomy and laminectomy from Cl to C6 was performed. Opera-tive findings showed thickened arachnoid mem-branes and cystic expansion of the fourth ventricle lying dorsal to the cervical cord. Caudal portion of the ventricle was removed, and V-P shunt was placed into the fourth ventricle to maintain decom-pression of the cystic part of the fourth ventricle. This patient is considered to represent a case of cystic dilatation (or ventricular diverticulum) of the fourth ventricle in Arnold-Chiari malformation. We stress that posterior decompression with V-P shunting procedure is recommended as the treat-ment of choice for such Arnold-Chiari type II malformation.