Different perfusion responses to bypass surgery in moyamoya disease and intracranial atherosclerotic disease: a prospective perfusion MRI study

Objective Superficial temporal artery–middle cerebral artery (STA–MCA) bypass is a recommended treatment for moyamoya disease (MMD) but remains contentious for intracranial atherosclerotic disease (ICAD), due to uncertain haemodynamic alteration postoperatively. This study compared cerebral perfusion changes after STA–MCA bypass in patients with ICAD and MMD using dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI) and explored the association between haemodynamic alterations and postoperative ischaemic infarction.Methods Consecutive patients undergoing STA–MCA bypass for MMD or ICAD were prospectively enrolled. All patients received preoperative and postoperative (within 14 days) DSC-PWI. A subset of patients completed midterm follow-up (6–12 months) with a third DSC-PWI. Four normalised cerebral blood flow (nCBF) indices were calculated: central nCBF (caudate and lenticular nucleus), cortical nCBF, mean nCBF and haemodynamic stress distribution (hdSD). hdSD was defined as the ratio of central to cortical nCBF, reflecting perfusion distribution between deep and cortical regions. Perfusion indices were compared between groups and postoperative ischaemic infarction was assessed.Results The study included 64 consecutive patients. The cohort comprised 32 (50%) patients with ICAD and 32 (50%) MMD. The mean age was 52 years-old, and 37 patients (58%) were male. A significant increase in central nCBF (p=0.02), cortical nCBF (p<0.001) and mean nCBF (p<0.001) was observed postoperatively in patients with ICAD, while hdSD showed no significant change. For patients with MMD, a significant increase of cortical nCBF (p<0.001) and significant decreases of hdSD (p<0.001) and central nCBF (p<0.001) were observed. A further analysis identified a higher postoperative ischaemic infarction rate in ICAD (22.2%) than MMD (12.5%) patients, but with no significant differences (p=0.44).Conclusion STA–MCA bypass induced distinct haemodynamic changes in patients with MMD and ICAD. Baseline hdSD was associated with different postoperative perfusion redistribution between the two patient groups.