側脳室脈絡叢乳頭腫に合併した天幕下ventricular diverticulumの1例

A CASE OF SUBTENTORIAL VENTRICULAR DiVERTICULUM ACCOMPANIED WITH CHOROID PLEXUS PAPILLOMA IN THE LATERAL VENTRICLE

　抄録　Ventricular diverticulumは，著明な非交通性水頭症の結果脳室の一部が破綻し，脳室と連続した嚢胞が異所性に形成される極めて稀な現象である。今回我々は，側脳室脈絡叢乳頭腫に同側脳室三角部内側山来の天幕下ventricular diverticulumが合併した9歳女性例を経験した。脳室破綻現象の他の一型として，脳室とクモ膜下腔との間に交通が生じるspontaneous ventriculostomyがあるが，側脳室腫瘍を原因疾患とする脳室破綻例はこのタイプをも含めて本症例が最初の報告例と思われた。またその発生機序の上では，腫瘍による脳室伸展に加え，三角部内側の著明な内方偏位とその局所的髄液循環障害等，破綻部位に対する腫瘍の直接的諸作用が重要であり，単に非交通性水頭症によるものではないと考えられた点で，特異な1例と思われた。更に組織学的にはdiverticulum壁に軟膜のほかにグリア組織が認められたことから，脳実質組織が断裂することなく形成されたventricular diverticulumと考えられ，軟膜のみが残存するとされたこれまでの多くの報告例とは異なるものであった。これらの興味深い諸特徴を有するventricular di-verticulumの1例を文献的考察を加えて報告した。

Marked non-communicating hydrocephalus may rarely cause ventricular rupture producing either a dilated cystic cavity (ventricular diverticulum) or communication between ventricle system and subarachnoid space (spontaneous ventriculostomy). Ventricular diverticulum has been believed to be collection of cerebrospinal fluid which escaped beneath the pia mater after rupture of ependymal layers and cerebral parenchyma.

We proposed herein to report a case of subten-torial ventricular diverticulum which accompanied with choroid plexus papilloma of the lateral vent-ricle. A nine year-old girl admitted to our hospital complaining of clumsiness of hands and walking, disability of reading, headache and vomi-ting. The neurological examination revealed a-lexia, papilledema, anisocoria, right hemianopsia, weakness of right upper limb, and cerebellarataxia. CT brain scan showed a large high den-sity area at the trigon of the left lateral ventricle with non-communicating hydrocephalus and an extra-axial low density area in the posterior fossa. The medial space of the left trigon was especially balooned and is just shifted above incisura tentorii by the tumor. The intraventricular tumor was totally removed by operation and proved to be benign choroid plexus papilloma microscopically. The subtentorial mass was confirm-ed to be a cyst contiguous to the medial trigon of the lateral ventricle, namely ventricular diver-ticulum.

Three special features were recognized in this case. The first, this was the first example of ventricular rupture accompanied with tumor in the lateral ventricle reviewing all reports of both ventricular diverticulum and spontaneous ventricu-lostomy. The second, this ventricular diverticulumwas not produced merely by hydrocephalus alone but mainly by direct effects of the tumor. Namely, the wall of the left medial trigon was markedly stretched by the tumor itself, and was thinned more by local blockade of cerebrospinal fluid circulation at this site. Furthermore, medial wall of the trigon lost support of tentorium cerebelli by its unusual shift above incisura tentorii, which finally produced ventricular diverticulum. The third, glial tissue was recognized in addition to pia mater and arachnoid mater microscopically. This suggested it a very rare ventricular diverti-culum without any rupture of cerebral parenchyma. Similar cases were only reported by Macfarlane (1947) and Kajtor (1950). But exact reasons were not evident on that cerebral parenchyma was preserved.