By Amanda L. Piquet, MD | Autoimmune Neurology is a rapidly evolving field in Neurology. Autoimmune diseases that target the central nervous system involve a variety of diseases that are distinctly different from multiple sclerosis. An example of an antibody-mediated disease is Neuromyelitis Optic (NMO); once thought to be a form of multiple sclerosis (MS), NMO has now been defined as a distinct clinical–pathological disorder, although the initial clinical presentation often mimics MS. Additionally, newly recognized autoantibody-mediated neurological diseases include autoimmune encephalitis and autoimmune epilepsy. In fact, studies show that up to 11 percent of patients with epilepsy are found to have autoantibodies1.
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Encephalitis is a common neurological disease and a major public health concern in the United States with more than 20,000 hospitalizations per year and a fatal outcome in 5.8 percent2. It is estimated that over 50 percent of patients remain without a clear diagnosis and etiology (or cause) despite an extensive work up. However, recent research shows that autoimmune encephalitis is not as uncommon as previously thought.
Particularly in young patients, autoimmune encephalitis is found more frequently than viral encephalitis3. Forms of autoimmune encephalitis include paraneoplastic disorders, classically associated with cancer, and other antibody-mediated diseases associated with cell-surface antibodies that may or may not be associated with cancer. One well-known example is anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. NMDAR encephalitis was first described in 2007 as a syndrome of memory problems and confusion, psychiatric symptoms, seizures, hallucinations and movement disorders in four young women with ovarian teratomas4. Since that time, there have been many causes reported in children, as well as, young to middle age adults including men and woman without an underlying tumor. Now over the last decade numerous other autoantibodies have been identified at a rapid pace.
The discovery of new neural autoantibodies has revealed that these conditions are much more common than previously appreciated and often times patients are misdiagnosed or remain undiagnosed. As the increased awareness of autoimmune neurological disease continues to increase, it is likely more patients will be diagnosed and will need to be treated appropriately with immunotherapy. Immunomodulatory therapies are commonly used as a treatment, some of which overlap treatment approaches used in multiple sclerosis and some of which are much different. Rapid diagnosis and early treatment is essential in the treatment of autoimmune neurological disease, particularly in the setting of cell-surface antibody-mediated encephalitis such as NMDAR encephalitis. Treatment approaches are largely based on expert opinion currently and there is a strong need for future research with prospective trials.
1. Brenner T, Sills GJ, Hart Y, et al. Prevalence of neurologic autoantibodies in cohorts of patients with new and established epilepsy. Epilepsia 2013;54:1028–1035.
2. Vora NM, Holman RC, Mehal JM, Steiner CA, Blanton J, Sejvar J. Burden of encephalitis-associated hospitalizations in the united states, 1998–2010. Neurology 2014;82:443-451.
3. Gable MS, Sheriff H, Dalmau J, Tilley DH, Glaser CA. The frequency of autoimmune N-methyl-D-aspartate receptor encephalitis surpasses that of individual viral etiologies in young individuals enrolled in the California Encephalitis Project. Clin Infect Dis 2012; 54:899–904.
4. Dalmau J, Tüzün E, Wu HY, Masjuan J, Rossi JE, Voloschin A, et al. Paraneoplastic anti-N-methyl-D-aspartate receptor encephalitis associated with ovarian teratoma. Ann Neurol. 2007;61(1):25-36.