Diencephalic cyst

A CASE OF DIENCEPHALIC CYST

I．はじめに

　脳梁欠損症と呼ばれる脳の奇型は，1812年，Reilが初めて剖検所見を記載して以来，現在まで200以上の報告例を数える^{12）8）6）}。それらの症例は，holoprosencepha—lyからspleniurnのみが欠けるpartial agenesisに到るまで幅広いスペクトルムを呈している。一方porence—phalyなどの他の奇型や，水頭症の合併する症例も見られる。

　1973年，Brocklehurst　＆　Chir^1）は，「脳梁欠損を伴つて，第III脳室が？胞状に著明に拡大した症例」を4例紹介し，"diencephalic cyst"と名付けた。興味あることに4例全てに交通性水頭症が合併している。彼らは，この病態をひとつのclinical entityとしようと提唱しているが，われわれも最近，この範疇に含まれる一症例を経験したので報告する。

A 2 months old girl was admitted to our depart-ment because of an enlarged head. She showed normal neurological function and was robust.

A ventriculogram was obtained by injecting air through the open anterior fontanel, which revealed not only the typical pattern of agenesis of the corpus callosum but also a large midline cyst. The cyst was in continuity with the third ventricle and extended hugely upwards and backwards between hemispheres to reach almost up to the calvaria. The pneumoencephalogram indicated a communi-cating type of hydrocephalus.

A carotid angiogram demonstrated that the two pericallosal arteries were separated by the dience-phalic cyst away from the midline.

A ventriculoperitoneal shunt was performed and subsequent course was satisfactory. There occurred no further abnormal increase of the head circum-ference. At the age of 5 months gross mental retardation and physical underdevelopment were recognized.

A case of extensive cystic dilatation of the third ventricle associated with agenesis of the corpus callosum was described. This is coincident with "diencephalic cyst" termed by Brocklehurst.