側副血行路として遺残した網状血管に生じた脳動脈瘤が破裂し，くも膜下出血を来した内頚動脈終末部形成不全（C1 dysplasia）の1小児例

A Case of Pediatric C1 Dysplasia with Ruptured Aneurysm in Collateral Plexiform Arterial Network

Ⅰ．はじめに

　Internal carotid bifurcationにおける内頚動脈（internal carotid artery：ICA）形成不全（C1 dysplasia）は極めて稀な奇形であり，aplastic/twig-like middle cerebral artery（MCA）のように原始血管網の遺残を伴うことがある．今回，C1 hypoplasiaと考えられる小児の症例で，網状血管内に発生した脳動脈瘤が破裂し，くも膜下出血（subarachnoid hemorrhage：SAH）を来した稀な1例を経験したので報告する．

　A 3-year-old girl was admitted to our hospital with symptoms including headache, nausea, and vomiting. Head CT scan showed subarachnoid hemorrhage in the right carotid cistern. Digital subtraction angiography revealed right internal caortid artery（ICA）malformation at the C1 segment with collateral plexiform arterial network. The right ICA branched into posterior communicating artery and anterior choroidal artery（AChoA）and the ICA was decreased in caliber. The distal portion of the C1 segment of the ICA continued to the collateral plexiform arterial network, forming a saccular aneurysm. The plexiform arterial network connected to the right AChoA and the anterior communicating artery and continued to the distal portion of the right M1 segment. Right cervical carotid artery was normal. There was no transdural collateral flow from the right external carotid artery. Genetic analysis of a variant of RING finger protein 213 was negative. We diagnosed this patient with C1 dysplasia. We performed coil embolization for the aneurysm. The patient was discharged without any neurological deficit. Four months after the surgery, recurrence of the aneurysm was observed. We suspected that the aneurysm was formed due to hemodynamic mechanism and vulnerability of the collateral plexiform arterial network.