Non-traumatic recurrent dissection and its spontaneous repair in the circle of Willis: report of two autopsy cases.

Post-mortem examinations of the circle of Willis in two cases of subarachnoid hemorrhage disclosed a wide spectrum of vasculopathy ranging from a minimal tear between the intima and media, and between the media and adventitia, to complete transmural disruption leading to the formation of pseudoaneurysms. The presence of coexistence of the focal lesions with complete replacement of the entire arterial wall with thick fibrous connective tissues and the vasculopathy was suggestive of the spontaneous repair of recurrent non-traumatic dissection of intracranial arteries. The patients were 58-year-old and 43-year-old females. There was no history of injury to the head or neck in either case. They were hypertensive, but the degree of atherosclerotic changes in the circle of Willis was compatible with age. There was no histological evidence of vasculitis. The role of hypertension and medial mucoid degeneration in the genesis of non-traumatic dissection of intracranial arteries was discussed.