Development of cortical microvascularization in Moyamoya disease using the maximum intensity projection method from three-dimensional rotational angiography

Background Neurosurgeons often experience increased cortical microvascularization in Moyamoya disease (MMD). However, there are no previous reports that radiologically evaluated preoperative cortical microvascularization. We investigated the development of cortical microvascularization and clinical characteristics of MMD using the maximum intensity projection (MIP) method. Methods We enrolled 64 patients at our institution, including patients with MMD ( n = 26), intracranial atherosclerotic disease (ICAD; n = 18), and unruptured cerebral aneurysms ( n = 20) as the control group. All patients underwent three-dimensional rotational angiography (3D-RA). The 3D-RA images were reconstructed using partial MIP images. Cortical microvascularization was defined as the vessels that branched off from the cerebral arteries and were classified as grade 0–2 depending on their development. Results Cortical microvascularization observed in patients with MMD was classified into grade 0 ( n = 4, 8.9%), grade 1 ( n = 17, 37.8%), and grade 2 ( n = 24, 53.3%). The development of cortical microvascularization was more common in the MMD group than in the other groups. The inter-rater reliability measured using weighted kappa was 0.68 (95% confidence interval = 0.56–0.80). There were no significant differences in cortical microvascularization according to the onset type and hemispheres. Cortical microvascularization correlated with periventricular anastomosis. Most patients with Suzuki classifications 2–5 developed cortical microvascularization. Conclusion Cortical microvascularization was characteristic of patients with MMD. These findings developed in the early stages of MMD and may act as a bridge to the development of periventricular anastomosis.