[A Case of a Ruptured Cerebral Aneurysm Associated with Microscopic Polyangiitis]

A 71-year-old woman was receiving dialysis for microscopic polyangiitis(MPA). She was transported to the emergency room after developing a headache and losing consciousness. She was in a coma and had dense left paralysis. Head computed tomography(CT)showed a subarachnoid hemorrhage. Head three-dimensional CT angiography showed an aneurysm proximal to the right M2(inferior trunk), which was considered as the source of bleeding. We performed an emergency aneurysm clipping surgery. However, we placed a permanent clip on the arterial wall defect when the clip detached from the parent artery. Pathological examination of the aneurysm revealed that the layered structure of the artery was damaged because of fibrin degeneration, suggesting that the aneurysm was caused by vasculitis. Coma persisted after surgery, and the patient was transferred to another hospital.

We found only one report demonstrating an association between a cerebral aneurysm and MPA. Aneurysms resulting from vasculitis are common at the periphery, rather than at vessel bifurcations. Cyclic inflammatory activity causes progressive destruction of the blood vessel wall, further expanding the lumen and forming an aneurysm. Therefore, such aneurysms are more fragile than true aneurysms, and are more likely to be damaged or detached during surgery, as in the present case. Trapping of the parent artery should be considered when the aneurysm is damaged or detached. Accordingly, preoperative planning could anticipate the need for superficial temporal artery to middle cerebral artery bypass.