Case Presentation:
A 34‐year‐old previously healthy male presented to an outside facility with rapidly progressive ataxia and encephalopathy over several months. CSF analysis showed slightly elevated protein, with no oligoclonal bands. Brain MRI showed scattered enhancing parenchymal lesions and leptomeningeal enhancement. Brain biopsy was nonrevealing. He was initially diagnosed with multiple sclerosis and placed on high‐dose steroids with minimal improvement. Worsening symptoms prompted transfer to a tertiary center. On arrival, the patient was encephalopathic and hyperreflexic. Further history revealed visual blurring but no subjective hearing loss. Audiologic evaluation revealed right greater than left sensorineural hearing loss and limited fluorescein angiography showed no retinal artery abnormalities. Repeat MRI brain showed disseminated lesions in the corpus callosum (Figure 1) and subacute evolving infarcts. Based upon clinical findings, diagnostic tests, and neuroimaging, a diagnosis of probable Susac syndrome was made. The patient was discharged to a rehabilitation center on immunosuppression. Unfortunately he continued to neurologically decline despite high dose steroids, plasma exchange, mycophenolate mofetil and rituximab.
Discussion:
Susac syndrome is characterized by the triad of encephalopathy, branch retinal artery occlusion, and sensorineural hearing loss. The disorder is presumed to be an autoimmune endotheliopathy affecting the microvessels of the brain, retina, and inner ear. A migrainous headache may herald this condition. Differential diagnosis includes multiple sclerosis, acute disseminating encephalomyelitis, central nervous system vasculitis or other white matter disease. Diagnostic studies characteristically reveal a snowball‐like lesion in the center of the corpus callosum on brain MRI (Figure 1) and branch retinal artery occlusions on fluorescein angiography. Other neuroimaging findings include perivascular leakage and leptomeningeal enhancement. CSF analysis may reveal a mild pleocytosis and an elevated protein. Treatment is immunosuppressive with steroids. Aspirin is added to treat the pro‐coagulopathy. In severe cases, IVIG, cyclophosphamide, mycophenolate mofetil, or rituximab may be utilized.
Conclusions:
Susac syndrome is a rare autoimmune disorder that is often confused with other white matter diseases such as multiple sclerosis and acute disseminated encephalomyelitis. Index of suspicion should be high in patients presenting with encephalopathy, auditory, and visual complaints. Early recognition may allow for early and appropriate treatment, with the intention of reducing long term neurologic sequelae.
