脳アミロイド・アンギオパチーと脳出血：出血源を求めて

Cerebral amyloid angiopathy and cerebral hemorrhage：Where is the origin of the hemorrhage?

　脳アミロイド・アンギオパチー（CAA）による脳出血の機序は，アミロイドが沈着した皮質内血管が破れるため，皮質下白質に血腫を作ると考えられてきた。またCAAによる皮質下出血例ではくも膜下出血を伴うことが多いが，これは皮質下出血がくも膜下腔に破れ，二次的にくも膜下出血を引き起こしたものと考えられてきた。筆者らは，CAAにおける出血は脳溝を含むくも膜下腔に最初に起こり，それが周囲の大脳皮質に出血性ないし貧血性梗塞を起こし，くも膜下腔の血腫がこの壊死性となった大脳皮質を破壊して脳内に進展し，最終的に脳実質内に血腫を形成する可能性について最近報告した。これまで，CAAにおける血管破綻の機序についての関心は皮質内血管に向けられてきたように思われる。今後，髄膜血管についての検討も重要となってくると思われる。

　The subcortical hemorrhages in cerebral amyloid angiopathy（CAA）has been said to originate from the rupture of the cortical vessels which are infiltrated with amyloid. CAA-related hemorrhage frequently occures subarachnoid hemorrhage, which is said to the secondary evidence. Recently, we have studied six autopsied cases associated with CAA-related hemorrhages and obtained the findings as follows；1）all of our examined cases had multiple hematomas in the subarachnoid space, mainly in the cerebral sulci, as well as intracerebral hematomas, 2）each intracerebral hematoma was connected to the subarachnoid hematomas at the depth of cerebral sulci or through the lateral side of the cortex, 3）in one case, another solitary subarachnoid hematoma, which was not connected to any intracerebral hematoma, was seen, 4）in all of these subarachnoid hematomas, many ruptured amyloid-infiltrated arteries up to 300μm in diameter were observed, and 5）there were no ruptured vessels within the intracerebral hematomas. Our study indicates that in some cases of CAA-related hemorrhage origenates from the rupture of the meningeal vessels, particular in the cerebral sulci. Infarction occurs subsequently in the cortex around the subarachnoid hematoma, the hematoma penetrates into the brain parenchyma, and finally, a subcortical hematoma is formed.