Susac's Syndrome--update

Abstract

Susac's Syndrome (SS) consists of the clinical triad of encephalopathy, branch retinal artery occlusion (BRAO), and hearing loss (HL). It is an autoimmune endotheliopathy affecting the precapillary arterioles of the brain, retina, and inner ear (cochlea and semicircular canals). The age range extends from 7 to 72 years, but young women (20-40) are most vulnerable. Headache routinely accompanies the encephalopathy and may be constant (best explained by leptomeningeal involvement), migrainous, or both. Multifocal neurological manifestations--particularly bilateral long-tract signs--commonly accompany the encephalopathy, which is laden with psychiatric features, confusion, memory loss and other cognitive changes. Left untreated, dementia can ensue. SS has an unexplained proclivity for attacking the central corpus callosum. In its encephalopathic form, pathognomonic callosal lesions permit an immediate diagnosis. We believe that the diagnosis of SS can be made when only the encephalopathy and pathognomonic MRI lesions are present; the BRAO and HL need not be present. We have also found the "string of pearls" MRI finding--the studding of the internal capsules with microinfarcts--to be most helpful--if not pathognomonic. This sign is always associated with the clusters of corpus callosum lesions, is especially striking on diffusion weighted imaging, and is associated with long-tract findings. We discuss the newly appreciated BRAO subset of SS and offer preliminary treatment suggestions for this subset. We also call attention to our development of an International Collaborative Study of SS and an educational website (http://www.ucalgary.ca/susac).