Perfusion-weighted MRI to evaluate cerebral autoregulation in aneurysmal subarachnoid haemorrhage
The aim of this study was to evaluate autoregulatory mechanisms in different vascular territories within the first week after aneurysmal subarachnoid haemorrhage (SAH) by perfusion-weighted magnetic resonance imaging (PW-MRI). For this purpose, regional cerebral blood flow and volume (rCVF and rCBV) were measured in relation to different degrees of angiographically visible cerebral vasospasm (CVS). In 51 SAH patients, PW-MRI and digital subtraction angiography were performed about 5 days after onset of SAH. Regional CBF and rCBV were analysed in the territories of the anterior cerebral artery (ACA), the middle cerebral artery (MCA) and the basal ganglia of each hemisphere in relationship to the degree of CVS in the particular territory. Correlations between rCBF, rCBV and CVS were analysed. CVS was found in 22 out of 51 patients in at least one territory. In all territories, rCBV decreased with increasing degree of CVS, correlated with a decrease of rCBF. In the ACA territories, SAH patients with severe CVS had significantly lower rCBF compared to healthy subjects and to SAH patients without CVS. In the basal ganglia, rCBF and rCBV of the control group were significantly higher compared to the patients without and with moderate vasospasms. PW-MRI showed simultaneous decrease of rCBF and rCBV in patients with SAH. The fact that rCBV did not increase in territories with CVS to maintain rCBF reveals dysfunctional vascular autoregulation. Vasospasms in the microvasculature are most evident in the basal ganglia, showing decreased rCBV and rCBF even in SAH patients without CVS.