Movement disorders are prominent in the clinical presentation of many autoimmune disorders (14; 36). These abnormal motor phenomena include faciobrachial dystonic seizures, neuromyotonia, chorea, myorhythmia, stereotypies, dystonia, tremor, parkinsonism, ataxia, and stiff-person like phenomena. Each type of autoimmune encephalitis presents with a different profile of abnormal movements for which a therapeutic response to immunomodulatory therapy suggests that these motor phenomena also have an autoimmune pathogenesis. However, symptomatic therapy of abnormal movement may contribute to clinical improvement and should be pursued in several cases. The prognosis will depend on the type of immune response, presence of underlying cancer (paraneoplastic disorder), evolution time, and promptness of therapy. This article focuses on disorders in which movement disorders are an integral part of autoimmune encephalitis.
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• Autoimmune encephalitis should be suspected in the context of new-onset movement disorders in an acute/subacute presentation and an accompanying neuropsychiatric syndrome.
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• Several motor phenomena with a presumed autoimmune pathogenesis may be observed in patients with autoimmune encephalitis, more commonly: faciobrachial dystonic seizures, neuromyotonia, chorea, myorhythmia, stereotypies, dystonia, tremor, parkinsonism, opsoclonus, myoclonus, and ataxia.
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• Early diagnosis and treatment are associated with a better prognosis and decreased risk of relapse.
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• Treatment of the underlying disorder usually improves the movement disorders, but symptomatic treatment may be necessary as well.
Historical note and terminology
The first identification of paraneoplastic neurologic syndromes occurred in the late 1940s, when neurologic symptoms were associated with a systemic cancer, but without an identifiable lesion in the nervous system (33). Later, specific antibodies to onconeural intracellular antigens (Hu, Yo, Ri, Ma2, Tr, CV2, etc.) were identified, usually manifesting as a paraneoplastic cerebellar degeneration or limbic encephalitis (63). In 2005, the identification of antibodies to neuronal surface antigens as a causal agent, often, but not always, associated with malignancies, revolutionized the field (02). Whereas “classical” paraneoplastic syndromes have a poor response to treatment, the autoimmune encephalitis with antibodies to cell surface or synaptic proteins are treatable, and clinical improvement can be observed even months after the initial episode (93).