Susac syndrome, a rare but probably underdiagnosed combination of
encephalopathy,
hearing loss, and visual deficits due to
branch retinal artery occlusion of unknown aetiology has to be considered as differential diagnosis in various conditions. Particularly, differentiation from
multiple sclerosis is often challenging since both clinical presentation and diagnostic findings may overlap. Optical coherence tomography is a powerful and easy to perform diagnostic tool to analyse the morphological integrity of
retinal structures and is increasingly established to depict characteristic patterns of
retinal pathology in
multiple sclerosis. Against this background we hypothesised that differential patterns of
retinal pathology facilitate a reliable differentiation between
Susac syndrome and
multiple sclerosis. In this multicenter cross-sectional observational study optical coherence tomography was performed in nine patients with a definite diagnosis of
Susac syndrome. Data were compared with age-, sex-, and disease duration-matched
relapsing remitting multiple sclerosis patients with and without a history of
optic neuritis, and with healthy controls. Using generalised estimating equation models, Susac patients showed a significant reduction in either or both
retinal nerve fibre layer thickness and total macular volume in comparison to both healthy controls and
relapsing remitting multiple sclerosis patients. However, in contrast to the
multiple sclerosis patients this reduction was not distributed over the entire scanning area but showed a distinct sectorial loss especially in the macular measurements. We therefore conclude that patients with
Susac syndrome show distinct abnormalities in optical coherence tomography in comparison to
multiple sclerosis patients. These findings recommend optical coherence tomography as a promising tool for differentiating
Susac syndrome from MS.