Comparative evaluation of acute cerebral vasospasm by the microsphere and the angiography techniques

Experimental subarachnoid haemorrhage (SAH) induces an acute transient cerebral vasospasm. The goal of this study was to compare angiography with iterative measurements of regional cerebral blood flow (rCBF) by the microsphere technique for tracking acute cerebral vasospasm after SAH. Cerebral vasospasm was induced in anaesthetised rabbits by injecting 1 ml of fresh blood in the cisterna magna. In a first experiment, the diameter of the basilar artery was measured by repeated angiograms over 60 min. In a second experiment, rCBF was measured over 60 min by the radioactive microspheres method without and with bilateral ligation of the carotid artery. Without carotid ligation, despite a profound transient vasospasm of the basilar artery, rCBF was unchanged in the cerebellum and cerebrum and was not statistically decreased in the brain stem. However, with bilateral carotid ligation, rCBF dramatically decreased at 5 and 15 min after haemorrhage. At 30 min, despite a persistent 50% decrease in the basilar cross-sectional area, rCBF was no longer different from the control group. Thus in a model of acute vasospasm of the basilar artery, rCBF evaluation by the microsphere technique parallels the cerebral vasospasm evaluated by angiography only when both carotid arteries are ligated.