The Influence of Dual Revascularization Techniques on Middle Meningeal Artery Collateral Networks in Moyamoya Angiopathy

BACKGROUND AND OBJECTIVES: Moyamoya disease is characterized by spontaneous and progressive occlusion of the intracranial internal carotid arteries and their proximal branches. Combined surgical revascularization uses a superficial temporal artery to middle cerebral artery direct bypass with concomitant indirect revascularization, most commonly encephaloduroarteriosynangiosis. The role and evolution of collaterals, particularly from the middle meningeal artery (MMA), is incompletely understood in combined revascularization. METHODS: Patients undergoing combined revascularization for Moyamoya disease at a single center were retrospectively reviewed. Preoperative and postoperative cerebral angiograms were analyzed for the presence of MMA collaterals, as well direct bypass patency at the last postoperative follow-up. Preoperative and postoperative noninvasive optimal vessel analysis from quantitative magnetic resonance angiography provided quantitative measurements of total hemispheric and direct bypass blood flow. RESULTS: Twenty-nine patients met inclusion criteria and underwent combined revascularization, with a total of 36 hemispheres treated. All had patent direct bypasses immediately postoperatively. Postoperative angiography (at median 13 months postsurgery) showed 24 (66.6%) direct bypasses remained robustly patent, while 12 (33.3%) had regressed. Preoperative MMA collaterals were identified in 11 patients (30.6%) and increased to 23 (63.9%) postrevascularization (P < .01). In the patent direct bypass group, MMA collaterals were present in 54.2% of cases, compared with 91.7% in the regressed direct bypass group (P = .03). Three (10.3%) patients had minor ischemic strokes during the follow-up period. Overall, postoperative total hemispheric blood flow did not decrease significantly (311 ± 150 mL/min to 275 ± 85 mL/min; P = .33). CONCLUSION: Long-term regression of direct bypasses is associated with increased MMA collateral networks. While direct bypass immediately enhances cerebral perfusion, MMA collaterals improve cerebral perfusion in the long term, is associated with reduced contribution of the direct bypass at follow-up. These findings suggest a potential hemodynamic relationship, although causality cannot be determined. This phenomenon is not associated with increased stroke rates.