Venous angiomaにより中脳水道狭窄症をきたした稀な1例

A Rare Case of Aqueductal Stenosis due to Venous Angioma

　要旨　Venous angiomaにより中脳水道狭窄症をきたした稀な1例を経験し，第三脳室開窓術により良好な経過を得たので報告する。Venous angiomaによる中脳水道狭窄症は，これまでに5例の報告があるのみであり稀な疾患と考えられる。本症例を含めいずれも青年期から成人期に発症し，緩徐な症状の進行を認めている。これまでにも水頭症が緩徐に進行する理由について様々な議論がなされてきたが，本症例を検討したところ，1）延髄，小脳桃の大孔への陥入に伴う大槽，延髄槽の狭小化，2）鞍上槽，中脳周囲槽の狭小化の所見が認められた。以上から，venous angiomaによる中脳水道の狭窄がinitiationとなり水頭症を引き起こし，側脳室，第三脳室が徐々に拡大，テント上容積の増大が1），2）を招き，その結果，髄液循環の抵抗が増大するという悪循環に陥ることにより，多段階的に水頭症が進行した可能性が推察された。

　Aqueductal stenosis is induced by widely various causes. These causes include congenital stenosis, tumor or inflammation. Among them vascular malformation is a very rare cause. In this paper we present a rare case of aqueductal stenosis caused by venous angioma.

　The patient was a 28-year-old female, who suffered from headache and double vision. On admission, CT and MRI showed lateral and third ventricular dilatation not but fourth ventricle, suggested aqueductal stenosis. Gd-DTPA enhanced T1-weighted MR image showed an abnormal draining vein passing through the orifice of the aqueduct. Angiography demonstrated the umbrella sign which was specific sign of the venous angioma. We performed endoscopic third ventriculostomy. Postoperative neuroradiological examination showed shrinkage of the ventricles and the symptom of the patient improved markedly.

　In the past literatures, five cases of aqueductal stenosis due to venous angioma have been reported. Although venous angioma is congenital, all five cases had been symptomatic at adult stage. Detailed evaluation of pre-and post-operative MRIs suggest that aqueductal stenosis induced enlargement of the lateral and third ventricles, which led narrowing of the suprachiasmatic cistern and the peri-mesencephalic cistern, and downward displacement of medulla and tonsil into the foramen magnum. As a result, hydrocephalus is aggravated gradually.

（Received : October 8, 2004）