Susac Syndrome

The clinical trial of this rare, apparent autoimmune process consists of CNS involvement, branch retinal artery occlusions, and sensorineural hearing loss. As of a review published in 2012, 304 cases of this syndrome had been reported worldwide at that time [85]. There is an inflammatory process affecting microvessels of the brain, retina, and inner ear. It has most commonly been reported in young women and is felt to be underdiagnosed [86]. Retinal artery branch occlusions can be documented by fluorescein angiography, and compatible changes on MRI brain scan have been reported in patients presenting with the triad. Antiendothelial cell antibodies are found in some patients [86]. Response to immunosuppression has been reported with corticosteroid therapy as the usual initial first choice.

Cryoglobulinemia-Associated CNS Vasculitis

Vasculitic involvement in cryoglobulinemia is characterized by the triad of purpura, weakness, and arthralgia [12]. The presentation can be quite insidious, but aggressive multi-organ involvement can be life threatening. This smaller vessel arteritis is related to the deposition of cryoglobulins within the vessel wall with activation of the complement cascade. Type I represents single monoclonal immunoglobulin formation related to B-cell lymphoproliferative disorders, while types II and III are often referred to mixed cryoglobulinemias. These are reflective of polyclonal IgG immunoglobulin formation with or without monoclonal IgM associated with rheumatoid factor activity [87]. Hepatitis C virus infection is observed to be the most common cause of mixed cryoglobulinemic vasculitis [88].

There can be associated cerebral infarction, and there is also the potential for the associated hyperviscosity to promote cerebral ischemia. The treatment consists of various forms of immunosuppression with the potential for rituximab to be particularly effective [89, 90]. Hyperviscosity in cryoglobulinemia is best managed with early plasma exchanges.

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