Early Cerebral Circulatory Disturbance in Patients Suffering Subarachnoid Hemorrhage Prior to the Delayed Cerebral Vasospasm Stage: Xenon Computed Tomography and Perfusion Computed Tomography Study

Abstract

Subarachnoid hemorrhage (SAH) causes dynamic changes in cerebral blood flow (CBF), and results in delayed ischemia due to vasospasm, and early perfusion deficits before delayed cerebral vasospasm (CVS). The present study examined the severity of cerebral circulatory disturbance during the early phase before delayed CVS and whether it can be used to predict patient outcome. A total of 94 patients with SAH underwent simultaneous xenon computed tomography (CT) and perfusion CT to evaluate cerebral circulation on Days 1-3. Cerebral blood flow (CBF) was measured using xenon CT and the mean transit time (MTT) using perfusion CT and calculated cerebral blood volume (CBV). Outcome was evaluated with the Glasgow Outcome Scale (good recovery [GR] ). Hunt and Hess (HH) grade II patients displayed significantly higher CBF and lower MTT than HH grade IV and V patients. HH grade III patients displayed significantly higher CBF and lower MTT than HH grade IV and V patients. Patients with favorable outcome (GR or MD) had significantly higher CBF and lower MTT than those with unfavorable outcome (SD, VS, or D). Discriminant analysis of these parameters could predict patient outcome with a probability of 74.5%. Higher HH grade on admission was associated with decreased CBF and CBV and prolonged MTT. CBF reduction and MTT prolongation before the onset of delayed CVS might influence the clinical outcome of SAH. These parameters are helpful for evaluating the severity of SAH and predicting the outcomes of SAH patients.

Are We Barking Up the Wrong Vessels?

“…29,32 However, despite normal CPP, the early phase following SAH may be accompanied by a severe reduction in CBF, approaching ischemic levels as shown in patients and experimental animals. 23,24,27 Because large cerebral vessels were not spastic at this early time after SAH, perfusion deficits on the level of the cerebral microcirculation were the only mechanisms left to explain the observed cerebral ischemia. The degree of posthemorrhagic oligemia/ischemia was associated with an unfavorable outcome and high mortality.…”

“…22 Recent clinical studies demonstrated a significant long-lasting reduction in CBF, independent of cerebral perfusion pressure, and occurring within the first day after SAH, that is, long before onset of delayed large artery vasospasm. 23,24 Other studies also failed to identify a consistent correlation between large artery vasospasm and ischemia in the parenchyma perfused by spastic arteries. 25,26 Hence, as Bederson et al 27 hypothesized already 20 years ago, posthemorrhagic ischemia may be caused by changes at the level of the cerebral microcirculation.…”

“…В последних клинических исследованиях выявили выра-женное стойкое снижение CBF независимо от цереб-рального перфузионного давления, которое развивалось в течение первых суток после САК, т.е. задолго до того отсроченного спазма крупных артерий [23,24]. В других исследованиях также не удалось обнаружить законо-мерной корреляции между спазмом крупных артерий и ишемией вещества головного мозга, кровоснабжаемого спазмированными артериями [25,26].…”

“…После оста-новки кровотечения внутричерепное давление снижа-ется до уровня, определяемого размером гематомы, и ЦПД нормализуется [29,32]. Однако, несмотря на нормальное ЦПД, острый период САК может сопро-вождаться резким снижением CBF, приближаясь к ишемическим уровням, как показано у людей и экспе-риментальных животных [23,24,27]. Поскольку в ост-ром периоде САК еще не развивается спазм крупных сосудов головного мозга, дефицит перфузии на уровне церебральной микроциркуляции был единственным механизмом, который позволял объяснить наблюда-емую церебральную ишемию.…”

Early whole-brain CT perfusion for detection of patients at risk for delayed cerebral ischemia after subarachnoid hemorrhage

“…18,30 Computed tomography perfusion (CTP) allows visualization of brain perfusion and has been applied in brain tumors, ischemic stroke, and aSAH. 1,4,10,12,14,15,[17][18][19]23,25,28,33,[36][37][38] A disadvantage of CTP is the exposure to radiation, which precludes its frequent use. This is reflected by available studies, in which CTP was performed once between Days 5 and 14, which represent the days with the highest probability of vasospasm occurrence.…”