LAUSR

BACKGROUND Reports of cases diagnosed as Moyamoya disease (MMD) after stereotactic radiosurgery (SRS) for arteriovenous malformation (AVM) are extremely rare. In recent years, RNF213 has been identified as a susceptibility gene of MMD, but the mechanism by which MMD develops remains unclear. Those cases of de novo development of MMD may provide some clues to clarify the mechanism of progression of MMD. CASE DESCRIPTION We report the case of de novo MMD that developed after SRS for AVM. This patient presented with a variant of the RNF213 gene. The intracranial internal carotid artery (ICA) was not within the irradiation field; therefore, it was obvious that the development of MMD was not caused by the direct effect of radiation in the current case study. Moreover, we demonstrated the decrease in velocity in the ICA prior to the development of MMD using phase-contrast magnetic resonance angiography. Previous studies demonstrated that progression of the pathological condition in the cerebral arteries in response to hemodynamic changes is enhanced in patients with RNF213 variants. CONCLUSIONS Our findings indicate that the changes in the intracranial hemodynamics after SRS for AVM could trigger the de novo onset of MMD in patients with a genetic predisposition for the RNF213 variant.