Axial Magnetic Resonance Angiography in Evaluating Revascularization after Indirect Bypass Surgery for Moyamoya Axial Magnetic Resonance Angiography after Indirect Bypass.

Introduction: At our institution, revascularization after indirect moyamoya surgery is routinely evaluated using magnetic resonance angiography (MRA) rather than catheter angiography. In this paper, we review how revascularization can be visualized on axial MRA and compare its visualization on MRA to that on catheter angiography. We also compare clinical outcomes of patients followed with routine postoperative MRA with outcomes of patients followed with routine catheter angiography.

Methods: We retrospectively reviewed the records of all patients treated at our institution who underwent unilateral encephaloduroarteriosynangiosis (EDAS) and/or pial synangiosis between the ages of 1 and 21 years and between December 31, 2003, and May 1, 2021. We included patients who underwent EDAS/pial synangiosis at other hospitals as long as they met all inclusion criteria. Inclusion criteria included having a preoperative MRA within 18 months of surgery and a postoperative MRA 3-30 months after surgery. Clinical outcomes included development of postoperative stroke and transient ischemic attacks (TIAs) and changes in symptoms (improved, unchanged, or worsened), including seizures, balance issues, and headaches. Clinical outcomes were compared between patients who had routine postoperative MRA only versus those who had routine postoperative angiograms, with or without routine MRA. For each surgery, we determined the ratios of the diameters and areas of the donor vessel and the contralateral corresponding vessel, as well as the relative signal intensities of these two vessels, on preoperative and 3- to 30-month postoperative MRA. We did the same for the middle meningeal artery (MMA) ipsilateral to the donor artery and the contralateral MMA. We assessed changes from pre- to post-operation in diameter ratios, area ratios, relative signal intensity, ivy sign, and in brain perfusion on arterial spin labeled (ASL) imaging. MRI and MRA measures of revascularization and flow were compared to Matsushima grades in patients who had postoperative catheter angiograms.

Results: Fifty-one operations for 42 unique patients were included. There were no significant differences in the rates of postoperative strokes, postoperative TIAs, changes in symptoms, or new symptoms after surgeries evaluated by routine postoperative MRA versus catheter angiogram (p = 0.282, 1, 0.664, and 0.727, respectively). There were significant associations between greater collateralization on postoperative MRA and greater median increases in preoperative-to-postoperative ratios of donor-vessel-over-contralateral-vessel diameter (p = 0.0461), ipsilateral-MMA-over-contralateral-MMA diameter (p = 0.0135), and the summed donor and ipsilateral MMA diameters over the summed contralateral vessel diameters (p < 0.001). The median increase in the ratio of the donor vessel and contralateral corresponding vessel diameters was significantly higher for Matsushima grade A versus B (p = 0.036). The median increase in the ratio of the sum of donor and ipsilateral MMA diameters over the sum of the contralateral vessel diameters was significantly higher for improved-versus-unchanged perfusion on ASL imaging (p = 0.0074). There was a nonsignificant association between greater postoperative collateralization on MRA and Matsushima grade (p = 0.1160).

Conclusion: Cerebral revascularization after EDAS and pial synangiosis can be evaluated on axial MRA by comparing the diameter and/or signal intensity of the donor vessel and corresponding contralateral vessel, as well as the ipsilateral and contralateral MMA, on postoperative-versus-preoperative MRA. The use of routine postoperative MRA rather than catheter angiography does not appear to negatively affect outcomes.