[Revascularization surgery for asymptomatic adult moyamoya disease presenting silent disease progression: report of two cases].

The authors describe two cases with asymptomatic moyamoya disease. Both of them demonstrated the progression of disease stage on follow-up MRA and DSA, although they were still asymptomatic. The intervals between initial diagnosis and disease progression were 10 and 36 months, respectively. Their SPECT or PET study also revealed a deterioration of cerebral hemodynamics in the involved hemispheres. They underwent superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis and indirect bypass on the involved hemispheres in order to reduce the risk of subsequent occurrence of ischemic stroke. Postoperative courses were uneventful. Follow-up radiological examinations showed well-developed surgical collaterals and improved cerebral hemodynamics on the operated hemispheres. In conclusion, the patients with asymptomatic moyamoya disease should be carefully followed up in order to avoid overlooking latent progression of disease stage. Surgical revascularization should be considered when disease stage progresses even if the patients are still asymptomatic, although further investigations are needed to establish the indication for surgical revascularization for asymptomatic moyamoya disease.