Efficacy of a Modified Superficial Temporal Artery-Middle Cerebral Artery Bypass Using Superficial Temporal Artery Side-Branch Donors in Adult Moyamoya Disease: A Technical Note.

Background

Adult moyamoya disease (MMD) is a progressive steno-occlusive cerebrovascular disorder for which surgical revascularization is the primary treatment. The standard direct superficial temporal artery-middle cerebral artery (STA-MCA) bypass uses the frontal and/or parietal branch of the STA as the donor. However, in some patients, conventional STA-MCA bypass may be suboptimal because of a large mismatch in caliber between the STA branch and the recipient artery, increasing the risk of cerebral hyperperfusion. This study aimed to investigate the impact of a modified STA-MCA bypass on MMD treatment.

Methods

We retrospectively reviewed adult cases of MMD at our institution (2012-2025) for patients who underwent modified direct STA-MCA bypass using a small side branch of the STA as the donor artery. Surgical techniques and clinical outcomes of these cases were analyzed descriptively.

Results

Five cases (five hemispheres in four patients) underwent side-branch STA-MCA bypass. All procedures were completed successfully, with 100% graft patency confirmed by intraoperative indocyanine green angiography, and a mild increase in cerebral blood flow confirmed by postoperative single-photon emission computed tomography. No patients developed postoperative cerebral hyperperfusion syndrome or wound healing complications. Clinically, all patients experienced a stable or improved neurological status, with no reported new ischemic or hemorrhagic events during follow-up.

Conclusions

In this small feasibility series, the side-branch STA-MCA bypass was technically feasible and safe, with no cerebral hyperperfusion syndrome observed. Any risk-mitigating effect on hyperperfusion remains theoretical and requires confirmation in comparative studies.