いわゆる小脳橋角部原発性くも膜嚢腫—Luschka孔嚢腫

PRIMARY ARACHNOID CYST OF CEREBELLOPONTINE ANGLE: A CASE OF CYST OF FORAMINE LUSCHKA

Ｉ．はじめに

　くも膜嚢腫といわれているもののなかには，外傷性あるいは直接ないし間接の炎症による癒着性くも膜炎のあとの嚢腫形式，すなわち，二次性嚢腫と，それら外因関与が推定しにくい原発性嚢腫とがある。

　しかしながら，"各症例の原因的分類を行なうのは有用でないばかりか，むしろ混乱に陥るだけだ"とある著者^44）は述懐しているが，くも膜嚢腫の報告例をreviewしてみると，意外にもその組織学的検索が行なわれているものが少なく，はたして各報告者の想定している成因が妥当であるか危ぶまれるものもある。小脳橋角部くも膜嚢腫の報告は比較的少なく，その組織学的検索の行なわれた報告は，他の部のそれに比してはるかに少ない^{8）13）17）}。

The case of a 40-year-old man with primary cyst in the cerebellopontine angle producing the clinical picture of acoustic neurinoma with obstructive hy-drocephalus is reported. The surgical removal of the wall of the cyst produced excellent improvement. The cyst in this case was lined with ependymal lining.

The literature of arachnoid cyst in the posterior fossa was reviewd and we divided them into 4 groups (midline, cerebellopontine angle, ambient cisternal and superior cerebellar group) and discussed them from the clinical and histological points of view.

1) From the histological point of view, cerebello-pontine angle group were mostly ependymal in origin and superior cerebellar group belongs to meningoencephalccele. On the other hand, ambient cysternal and cerebellar midline groups were arachnoidal in origin, and occasionally had choroid plexus tufts. 2) From the clinical point of view : i) As to the cerebellopontine angle group, there were no infantile cases and usually acoustic neurinomas or cerebellar tumor had been suspected. Two phases distribution of onset age was recognized among those groups except pontin angle one, and their clinical manifestation was always hydrocephalus in the infants and also cerebellar tumor in more advanced age groups. ii) Intermittent symptoms (such as headache, vomiting or ataxia) were observ-ed high incidence of 85. 7% in the cerebellopon-tine angle group. On the other hand, no such intermittent symptoms were observed in the infan-tile cases, but 84.6% of adult cases in other groups. That is, as for the adult cases, the intermittent symptoms bares the significant diagnostic value.