小脳形成不全を伴ったHoloprosencephalyの検討

Holoprosencephaly Accompanied with Dysgenesis of the Cerebellum

I．はじめに

　Holoprosencephalyは胎生期初期の三脳胞期から五脳胞期への分化が不十分であったために生じる奇形と考えられており，Demyerら^1）による重症度に従ったalobar, semilobar, lobarの分類が広く用いられている．holoprosencephalyでは従来から後頭蓋窩の構造は正常であるといわれてきたが，holoprosencephalyにDandy-Walker syndromeを合併した症例の報告が散見されている^{2,3,5-7,9-11）}．われわれはこれまでに9例のholoprosencephalyを経験してきたが，この内の4例に小脳形成不全を認めたので報告する．

We have encountered 9 cases of holoprosencephaly, four of them with abnormalities of the posterior fossa. Three cases of semilobar type had severe cerebellar hypoplasia and a large cyst continuing to the fourth ven-tricle. They were diagnosed as Dandy-Walker syndrome. A case of lobar type had a relatively mild form of cere-bellar hypoplasia and it was thought to be a Dandy-Walker variant. MRI was able to clarify the anatomical relationship of the intracranial construction, for example monoventricle, dorsal sac or large cyst in the posterior fossa, and it was very useful for the diagnosis of these congenital anomalies. All of them showed hydrocephalus and required treatment with ventriculoperitoneal or cyst-peritoneal shunt.

With the availability of MRI, easy diagnosis of the mild forms of holoprosencephaly has been facilitated, and accompanying anomalies are also able to be dia-gnosed. Up to now, the structure of the posterior fossa in holoprosencephaly was thought to be normal. However, several cases of holoprosencephaly accompanied with cerebellar hypoplasia and cystic lesion of the post-erior fossa, revealed by MRI or autopsy, have been re-ported. It was suggested that holoprosencephaly with anomalies of the posteior fossa may be less rare than has been thought, so far.