Susac's syndrome: clinical course and epidemiology in a Central European population.

Objective: Susac's syndrome is characterized by inflammation and occlusion of pre-capillary arterioles with the clinical triad of branch retinal artery occlusion (BRAO), encephalopathy and hearing loss. No epidemiological data are available for the disease.

Methods: All neurology departments in Austria were addressed to report adult patients who were on immunosuppressive treatment for a diagnosis of Susac's syndrome between 1 August 2010 and 1 August 2015. Clinical course, treatment regimens, period and point prevalence rates, and annual incidence of Susac's syndrome in Austria in people over 19 years of age are reported.

Results: Ten patients with Susac's syndrome were identified, and eight of them were newly diagnosed within the five-year timeframe. Minimum five-year period prevalence of the disease is 0.148/100,000 (95% confidence interval (CI) 0.071-0.272), annual incidence is 0.024/100,000 (95% CI 0.010-0.047). Minimum point prevalence rates varied from 0.030/100,000 (95% CI 0.004-0.108) to 0.088/100,000 (95% CI 0.032-0.192). Of all 10 patients, 8 showed typical callosal or internal capsule magnetic resonance imaging lesions at first presentation, 7 presented with BRAO and 5 had hearing loss or tinnitus at the beginning of the disease. Four patients developed the complete clinical triad of Susac's syndrome during the observation period.

Conclusions: We provide for the first time population-based data about the clinical course, prevalence and incidence of Susac's syndrome.