Progression of unilateral moyamoya disease: A clinical series.

BACKGROUND The natural history of unilateral moyamoya disease (MMD) in adult patients is not clearly described in the literature. We present a series of 18 patients with unilateral MMD and analyze the risk factors for progression to bilateral disease. METHODS A retrospective review of 157 MMD patients treated at Stanford University Medical Center from 1991 to 2005 identified 28 patients with unilateral MMD (defined as none, equivocal or mild involvement on the contralateral side). RESULTS Eighteen patients (5 males and 13 females) were identified with unilateral MMD and angiographic follow-up of > or =5 months. Mean radiologic follow-up (+/- standard error of the mean) was 19.3 +/- 3.4 months and mean clinical follow-up was 24.5 +/- 3.7 months. Five patients had childhood onset MMD and 13 patients had adult onset disease. Angiographic progression from unilateral to bilateral disease was seen in 7 patients (38.9%) at a mean follow-up of 12.7 +/- 2.4 months. Four of the 7 patients had significant clinical and radiologic progression requiring surgical intervention. Five of 7 patients that progressed had adult onset MMD. The presence of equivocal or mild stenotic changes of the contralateral anterior cerebral artery (ACA), middle cerebral artery (MCA) or internal carotid artery (ICA) was an important predictor of progression (p < 0.01); 6 of 8 patients (75%) with equivocal or mild contralateral disease progressed, whereas only 1 of 10 patients (10.0%) with no initial contralateral disease progressed to bilateral MMD. One patient had mild or equivocal MCA, ICA and ACA stenosis at the time of initial diagnosis and this patient progressed. CONCLUSIONS Contralateral progression in the adult form occurs more commonly than previously reported. The presence of minor changes in the contralateral ACA, intracranial ICA and MCA is an important predictor of increased risk of progression. Patients with a completely normal angiogram on the contralateral side have a very low risk of progression.