嚢胞を形成した，脳動静脈奇形による脳内血腫の1例

A chronic encapsulated expanding hematoma with cyst formation caused by rupture of arteriovenous malformation:a case report

I．はじめに

　出血したAVMの手術待機中に，脳内血腫の周囲に被膜が形成されて血腫が拡大し，後に嚢胞化した症例を経験した．嚢胞被膜の病理組織学的検討を行った結果，慢性に経過する頭蓋内血腫の被膜構造に共通点を見出したので文献的考察を加える．

A 57-year-old male was admitted to our hospital complaining of a headache with disturbance of con-sciousness on November 7, 1994. CT scans revealed an intracerebral hematoma of 25ml in volume in the left frontal lobe with adjacent spotty calcification. An arte-riovenous malformation (AVM) with a nidus of 2.0×2.0cm in size was found to be the cause of the hemato-ma by cerebral angiography. Since the patient com-plained of mild right hemiparesis 10 days after the onset, CT scans were taken and a slightly enlarged hematoma with capsule formation was observed. On the 31st day after the onset, the hematoma had li-quefied and the surrounding capsule was clearly visible on CT. Since the patient's only symptom was a slight headache, and he displayed no other serious conditions, a palliative operation was planned. The AVM was re-moved and the capsule was resected 41 days after the onset.

The capsule or cyst wall of the liquefied hematoma was composed of three layers: a granulation layer with a neovascular system on the inside, a collagenous layer in the middle, and a reactive brain tissue layer on the outside. The structure of the capsule was the same as the structure of the cyst wall in chronic hematomas that have been reported as cystic AVM or encapsulated expanding hematoma in the literature. We would there-fore like to propose that chronic encapsulated expand-ing hematomas form with time due to intermittent bleeding or exudation form the neovascular system of a cyst wall.