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 extravasa ted blood in provoking chronic cerebral vasospasm, talc (crystallized hydrous magnesium silicate) was injected as a non-biologic foreign mat erial into the canine cisterna cerebellomedullaris, and pathologic cha nges were followed. Angiographically, this cisternal talc injection in duced delayed and prolonged constriction of the basilar artery, withou t any evidence of so-called early phase cerebral vasospasm that should occur shortly after an insult. Pathologically, around the spastic art ery in the subarachnoid space with talc injection, the appearance of a moderate cellular migration coincided with cerebral vasoconstriction, which took place 2 days after talc injection. In the spastic basilar arterial wall, marked constrictive and degenerative changes including myonecrosis and subintimal proliferation were induced by cisternal tal c injection as early as on day 2, and the changes were progressive wit h time. These pathologic changes were extremely analogous to those of the human autopsy cases with chronic cerebral vasospasm (chronic VS) b ut more prominent than those observed in the experimental autologous b lood-induced model. The present study demonstrated that a foreign-body reaction to talc alone could induce chronic VS in the absence of extr avasated blood. Thus, it is possible to consider that inflammatory rea ctions to extravasated autologous blood in subarachnoid hemorrhage may give rise to chronic VS.