Longitudinal time course of reversible and irreversible components of chronic cerebrovasospasm of the rabbit basilar artery.

Multiple injections of autologous blood were made around the basilar artery of rabbits through a silicone catheter placed into the prepontine cistern. The total blood injected was 3 ml/kg in aliquots of 0.5 to 0.8 ml over a 4-hour period. Control angiograms were obtained 7 days before this procedure. Groups of animals were examined by angiography on each of 9 days after the injections of blood. An angiogram was obtained 15 minutes after the first injection of blood, 20 seconds after the intra-arterial injection of a maximum dilating dose of papaverine. All surviving animals showed basilar artery narrowing, which was greatest 24 hours after the hemorrhage, when the vessel diameter was reduced to 54% of the control value. The narrowing then decreased to a reduction of about 30%, which was maintained throughout the rest of the study period. A papaverine-resistant component of narrowing was not seen until the 3rd day. It increased progressively to Day 9 when it represented 63% of the total. This model has a number of features that are reminiscent of human cerebrovasospasm, including the fact that there is an initial phase of narrowing that is completely reversed by an intra-arterially administered vasodilator, and a second phase beginning on Day 3 which exhibits a progressively increasing papaverine-resistant component.