Incidence and prevalence of multiple system atrophy: a nationwide study in Iceland

Background Multiple system atrophy (MSA) is a neurodegenerative disorder characterised by autonomic dysfunction with parkinsonism (MSAp) or cerebellar (MSAc) symptoms. At autopsy, α-synuclein inclusions in glial cells of the brain are needed to confirm a definite diagnosis. We determined the 10 year incidence of MSA, point prevalence and survival in a well defined population with a high number of neurologists. Methods Cases were identified from the only neurology department and all practising neurologists in Iceland, over a 10 year period. The diagnosis of MSA was in accordance with the Second Consensus Criteria of MSA. Findings 19 incidence cases were diagnosed with MSA (11 women, eight men) during the study period, giving an average annual incidence of 0.7:100 000 (95% CI 0.4 to 1.1). Ten cases were alive on the prevalence day, giving a point prevalence of 3.4:100 000 (95% CI 1.6 to 6.3). 16 of the cases had probable and three possible MSA; 16 had MSAp and three had MSAc. Mean age at symptom onset was 65 years and mean age at diagnosis was 68 years. Patients were followed for an average of 31 months, and 15 died during the follow-up period. Survival from symptom onset was mean 5.7 years. The 1 and 5 year survival rates from diagnosis were 74% and 28%, respectively. Interpretation We reported on the incidence of MSA (both MSAp and MSAc) in a nationwide study where a definite diagnosis of MSA was confirmed in four out of five patients autopsied. We found survival to be shorter than reported in other studies.