Retrospective treatment comparisons in patients with Susac syndrome

Susac syndrome is a rare disease affecting arterioles in the brain, retina and inner ear. There is uncertainty about a clinical benefit of adding intravenous immunoglobulins or immunosuppressants to corticosteroid maintenance treatment.

This restrospective study identified adult patients from case records who met crite-ria for probable or definite Susac syndrome. Patients with a sole manifestation of arterial wall hyperintensity (AWH) on retinal fluorescein angiography (RFA) were also included. All clinically symptomatic disease activity and clinically asymptomatic AWH on RFA within a 3-month period from first signs were summarized as one event. Following an event, immunosuppressive treatments in consecutive 3-month observation periods were recorded until the next event has occurred or the treatment was discontinued.

Sixteen patients (9 female) were identified (mean age 34 years, range 2065 years). Median follow-up was 79 months (range 16-274 months). In a total of 69 observation periods in all patients, corticosteroids, IVIG, or both in combination, were applied with or without other immunosuppressants. Fewer events occurred in patients treated with IVIG (n = 6) compared to those treated with corticosteroids (n = 10) without statistical significance. Based on our data, a total of 126 observation periods would be required to obtain a statistically significant difference between both treatments, IVIG and corticosteroids. This corresponds to a total of 31.5 patient years needed for a prospective clinical trial.

This retrospective analysis in patients with Susac syndrome provides a basis for future structured prospective studies. From our data, a prospective evaluation of an additional clinical benefit of IVIG maintenance therapy in relapse prevention is supported.