Microcirculatory changes during acute phase of aneurysmal sub-arachnoid hemorrhage evaluated by clinical and experimental studies

Abstract

Cerebral microcirculatory changes during cerebral vasospasm after aneurysmal sub-arachnoid hemorrhage (SAH) are still controversial and uncertain. Experimental and clinical investigations of cerebral microcirculation after SAH were performed.Experimental SAH was produced by a canine two-hemorrhage method, and the dogs were perfusion-fixed at 3, 7 and 14 days after SAH. Specimens of the anterior sylvian gyri and pons were produced by three methods. Microvascular corrosion casts produced by arterial injection of polyester resin were examined by scanning electron microscopy (SEM). Sectioned slices parallel to the brain surface were examined by SEM and by light microscopy with morphometric analysis of the luminal diameter and wall thickness of the small arteries. Corrosion casts showed tapered narrowing in the arterioles and irregular width with folds in the perforating arteries 3 to 7 days after SAH. Sectioned slices showed increased wall thickness and decreased internal diameter of the arterioles and the perforating arteries 3 to 7 days after SAH.In cases with aneurysmal SAH, regional cerebral blood flow (rCBF) and digital subtraction angiography (DSA) were performed. Also, cerebral circulation time (CCT) obtained by analyzing the time–density curve of the contrast media on DSA images was evaluated in association with rCBF and angiographic vasospasm. In addition to correlation between the degree of angiographic vasospasm and rCBF, CCT showed strong inverse correlation with rCBF, and even in mild angiographic vasospasm, prolonged peripheral CCT was clearly associated with decreased rCBF.These results suggest that intraparenchymal small arteries decrease their caliber, which results in increased small-vessel resistance and affects cerebral ischemia during cerebral vasospasm.