Evaluation of Cortical Microvascularization by Preoperative Maximum Intensity Projection Method in Moyamoya Disease Reflects the Increase of Pial Arteries on the Brain Surface

Microvascular proliferation on the cerebral surface is a hallmark feature of Moyamoya disease (MMD); however, studies on this phenomenon are limited. This study evaluated whether preoperative cortical microvascularization on partial maximum intensity projection (MIP) using three-dimensional rotational angiography corresponds to increased intraoperative pial arteries in MMD. We analyzed 24 hemispheres from 22 patients with MMD who underwent cerebral angiography and bypass surgery between October 2018 and July 2023. Control groups included patients with unruptured cerebral aneurysms (n = 15) and major cerebral artery occlusion (n = 10). Microvascular density (MVD) was calculated by measuring vascular area surgical videos. Cortical artery and periventricular anastomosis development were graded (0-2) using MIP images, with grade 2 indicating well-developed vessels. The mean age of the 22 patients was 41.3 ± 13.7 years, of which and 4 (18.1%) were male. Cortical microvascularization was observed in 12 hemispheres (50%). The mean MVD in MMD was 24.8 ± 5.9%, which was significantly higher than that in unruptured cerebral aneurysms (17.5 ± 2.4%; p < 0.001) and major cerebral artery occlusion (18.0 ± 2.2%; p < 0.001). MVD was significantly higher in hemispheres with cortical microvascularization (p = 0.014) and in those with well-developed thalamic arteries (THA; p < 0.001), however not in those with developed lenticulostriate or choroidal arteries. Our findings demonstrate that elevated intraoperative pial arteries in MMD correlate with cortical microvascularization and THA development in preoperative imaging. Further investigation into the vascular pathophysiology of MMD may refine diagnostic and therapeutic approaches.