Cerebral vasospasm is the delayed narrowing of cerebral arteries exposed to blood. Although vasospasm typically occurs after subarachnoid hemorrhage (SAH) from rupture of a cerebral aneurysm, it can also develop after trauma (1,2) and infections (3). In humans, vasospasm presents as a biphasic phenomenon. Whereas acute vasospasm generally presents immediately after SAH and typically resolves within hours, chronic vasospasm occurs at 4 to 21 days and peaks 7 to 10 days after hemorrhage, with an overall angiographic incidence of 67% (4) and a clinical incidence of 37% (4). Chronic vasospasm causes delayed ischemic deficits, stroke, and death.

The etiology of vasospasm remains unclear. Current hypotheses include endothelial dysfunction secondary to inflammation of the arterial wall and transendothelial migration of macrophages and neutrophils (5,6 ), nitric oxide (NO) scavenging by such blood-degradation products as oxy-hemoglobin (7), depletion of NO secondary to NO synthase dysfunction (8), direct vasoconstriction due such to spasmogenic proteins as endothelin-1 (9), and dysregulation of electrolyte channels in the smooth muscle cell, such as K+ (10) and Mg2+ (11).

In 1949, Robertson at the Royal Melbourne Hospital in Melbourne, Australia, was the first to describe delayed ischemia after SAH and to suggest that the ischemic changes could be related to temporary spasm of the supplying vessels (12). The first angiographic description of cerebral vasospasm after SAH was reported in 1951 (13). Since then, this condition has been studied extensively in experimental models.

Studies on the pathophysiology of cerebral vasospasm in humans have been attempted using postmortem specimens (14-18). Delayed postmortem artifacts, however, have prevented adequate analyses of genomic and proteomic variables, as well as testing of physiologic responses. To study cerebral vasospasm under more physiologic conditions, several experimental models have been developed. We present an overview of the different experimental models that have been used to date and comment on their technical and scientific characteristics.

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