Impact of cerebral microcirculatory changes on cerebral blood flow during cerebral vasospasm after aneurysmal subarachnoid hemorrhage

Background and Purpose-Cerebral microcirculatory changes during cerebral va sospasm after aneurysmal subarachnoid hemorrhage (SAH) are still controvers ial and uncertain. The aim of this study was to investigate the changes of cerebral microcirculation during cerebral vasospasm and to clarify the role s of microcirculatory disturbances in cerebral ischemia by measuring cerebr al circulation time (CCT) and regional cerebral blood flow (rCBF). Methods-In 24 cases with aneurysmal SAH, rCBF studies by single-photon emis sion CT and digital subtraction angiography (DSA) were performed on the sam e day between 5 and 7 days after SAH and/or within 4 hours after the onset of delayed ischemic neurological deficits. CCT was obtained by analyzing th e time-density curve of the contrast media on DSA images and was divided in to proximal CCT, which was the circulation time through the extraparenchyma l large arteries, and peripheral CCT, which was the circulation time throug h the intraparenchymal small vessels. They were analyzed in association wit h rCBF and angiographic vasospasm. Results-Severe angiographic vasospasm statistically decreased rCBF, and cor relation between the degree of angiographic vasospasm and rCBF was seen (r= 0.429, P=0.0006). Peripheral CCT showed strong inverse correlation with rCB F (r=-0.767, P<0.0001). Even in none/mild;or moderate angiographic vasospas m, prolonged peripheral CCT was clearly associated with decreased rCBF. Conclusions-In addition to the marked luminal narrowing of large arteries d etected as severe angiographic vasospasm, microcirculatory changes detected as prolonged peripheral CCT affected cerebral ischemia during cerebral vas ospasm. These results suggested that impaired autoregulatory vasodilation o r decreased luminal caliber in intraparenchymal vessels may take part in ce rebral ischemia during cerebral vasospasm.