Moyamoya disease in a European setting: a Danish population‐based study

Background and purpose The incidence of moyamoya disease (MMD) in Europe is not well known. In those affected, the risk of brain hemorrhage is considered low. The present study aimed to investigate the incidence and clinical presentation of MMD in the Danish population. Methods Eligible patients were identified in the Danish National Patient Register from 1994 to 2017. We collected clinical and radiological data from individual patient records from neurological, neurosurgical and paediatric units across Denmark. The diagnosis was validated according to established criteria. We also extracted basic demographic data on the cohort from the Danish Civil Registration System. Results A total of 52 patients fulfilled the diagnostic criteria for MMD. Most patients were native Danes and only 15% had an East Asian background. The ratio of female to male patients was 1.8, and the incidence had two peaks: one in childhood and another in young middle age. Until 2007, MMD was only diagnosed sporadically. From 2008 onwards, the incidence rate was 0.07 per 100 000 person‐years (95% confidence interval 0.05–0.09 per 100 000 person‐years). The most common mode of presentation was ischaemic stroke (33%), followed by hemorrhage (23%), headache (17%) and transient ischaemic attack (14%). Conclusions Moyamoya disease is rare in Denmark, but is associated with a considerable risk of hemorrhage. Thus, MMD should be considered in the evaluation for ischaemic as well as hemorrhagic stroke paediatric and middle‐aged Caucasians.