Non-invasive assessment of cerebral microvascular changes for predicting postoperative cerebral hyperperfusion after surgical revascularisation for moyamoya disease: an arterial spin labelling MRI study.

Cerebral hyperperfusion syndrome (CHPS) can result after anastomotic surgery as the reperfusion is established in chronically ischemic cerebral territories in patients of moyamoya disease (MMD). In this study, we have evaluated the feasibility of arterial spin labelling (ASL) perfusion MRI to predict cerebral hyperperfusion syndrome based on changes of cerebral blood flow (CBF) after revascularisation surgery in patients of MMD.
Our prospective study included 25 patients with MMD who underwent superficial temporal artery-middle cerebral artery (STA-MCA) bypass with or without dural/muscle synangiosis. ASL MRI was performed before and 1-7 days after surgery. On the side planned for operation, 5-mm ROI circle was drawn on the predetermined regions in frontal lobe, temporal lobe, parietal lobe and basal ganglia in proximal and distal territories of MCA to calculate ipsilateral CBF values (CBFi). An attempt was made to select the same location on contralateral side (non-operative) (CBFc) for each measurement for calculation of hemispheric normalised CBF (nCBFh) ratios. To adjust for inter individual variation among MR imagers and CBF, additional regions of interest were drawn within the cerebellum (CBFcbl) for cerebellar CBF normalised ratios (nCBFCbl).
Of the 25 patients (26 operated hemispheres), 5 patients showed significant immediate postoperative symptoms suggestive of CHPS. Based on our findings, sensitivity and specificity of ASL perfusion to detect CHPS were evaluated. ASL was found to have 47-100% sensitivity and 45-88% specificity to detect CHPS. We have tried to calculate the prevalence of CHPS in postoperative patients of moyamoya disease, which in our study ranged from 6.83 to 40.70%.
Based on our results, we concluded that ASL perfusion is an appropriate alternative to standard nuclear medicine studies to monitor the changes in perfusion after STA-MCA bypass surgery in moyamoya patients. ASL MR perfusion can be used to identify changes in cerebral blood flow (CBF) for early detection of cerebral hyperperfusion syndrome in patients with otherwise normal conventional MRI sequences with very high sensitivity but moderate specificity.