To evaluate the effectiveness of superficial temporal artery-middle cerebral artery (STA-MCA) bypass in improving cerebrovascular reserve (CVR) in Moyamoya syndrome.

This prospective study included 10 consecutive patients treated for Moyamoya syndrome by STA-MCA bypass in our institution between June 2016 and January 2018. Perfusion MRI, transcranial Doppler and 99m Tc-HMPAO SPECT with acetazolamide challenge were performed before and after treatment to evaluate perfusion and cerebrovascular reserve. STA-MCA bypass was indicated for patients with history of ischemic or hemorrhagic stroke and when CVR was diminished on both transcranial Doppler and 99m Tc-HMPAO SPECT with acetazolamide challenge or brain perfusion was deteriorated on MRI.

Bypass anastomosis was patent in all patients at end of surgery. One patient presented partial postoperative sensorimotor deficit related to an ischemic lesion in the frontal cortical area. One patient presented regressive chronic subdural hematoma without neurological deficit. Three months after treatment, CVR was significantly improved in 8 patients and unchanged in 2, probably related to low flow. Further follow-up found CVR deterioration in 1 patient, with anastomosis occlusion at 1 year.

Our data suggest that improvement in cerebral perfusion and CVR depends on flow in the STA-MCA anastomosis in patients with Moyamoya syndrome. Systematic long-term follow-up of anastomosis flow, brain perfusion and CVR improves quantification of the benefit of STA-MCA anastomosis in terms of disease progression.