Constrictive structural elements in human cerebral arteries following aneurysmal subarachnoid haemorrhage.

Histoimmunological, histochemical, and histological studies were conducted on cerebral arteries from four living patients with a recent aneurysmal subarachnoid haemorrhage. There appeared to be a correlation between the severity of vasospasm and the magnitude of pathological findings. Large myofibroblast cells and type V collagen within the medial layer were abundant in arteries showing marked vasospasm, but were less conspicuous in those showing milder involvement. Intracranial arteries from patients who died from non-cerebral causes did not demonstrate these changes. In ruptured vessels, there was also a positive fluorescence for actin-myosin filaments in layers of the arterial wall other than the media. It is postulated that the intimal and adventitial actin-myosin, myofibroblasts and type V collagen may contribute to cerebral vasospasm by holding the damaged vessel in a contracted phase during the healing period.