Sequential morphological changes of the constrictive basilar artery in a canine model of experimental cerebral vasospasm by talc injection.

To demonstrate the possible role of foreign-body reaction to extravasated blood in provoking chronic cerebral vasospasm, talc (crystallized hydrous magnesium silicate) was injected as a non-biologic foreign material into the canine-cisterna cerebellomedullaris, and pathologic changes were followed. Angiographically, this cisternal talc injection induced delayed and prolonged constriction of the basilar artery, without any evidence of so-called early phase cerebral vasospasm that should occur shortly after an insult. Pathologically, around the spastic artery in the subarachnoid space with talc injection, the appearance of a moderate cellular migration coincided with cerebral vasoconstriction, which took place 2 days after the talc injection. In the spastic basilar arterial wall, marked constrictive and degenerative changes including myonecrosis and subintimal proliferation were induced by cisternal talc injection as early as on day 2, and the changes were progressive with time. These pathologic changes were extremely analogous to those of the human autopsy cases with chronic cerebral vasospasm (chronic VS) but more prominent than those observed in the experimental autologous blood-induced model. The present study demonstrated that a foreign-body reaction to talc alone could induce chronic VS in the absence of extravasated blood. Thus, it is possible to consider that inflammatory reactions to extravasated autologous blood in subarachnoid hemorrhage may give rise to chronic VS.