Abstract
Movement disorders are extremely common and diverse manifestations in patients with autoimmune encephalitis (AE) and paraneoplastic neurological syndromes (PNS), presenting either as the primary symptom or as part of a complex clinical picture. Early diagnosis is critical since these conditions often respond well to immunotherapy, yet they are frequently misdiagnosed as infectious, metabolic, hereditary, or degenerative diseases. AE and PNS are classified into two main groups based on the target antigen location: (1) cell-surface antigens (rarely associated with cancer), including NMDA receptor encephalitis (orofacial dyskinesia, chorea, often linked to ovarian teratoma), LGI1 encephalitis (characteristic faciobrachial dystonia), CASPR2 encephalitis (peripheral nerve hyperexcitability, Morvan syndrome), DPPX encephalitis (tremor, myoclonus, hyperekplexia), and dopamine D2 receptor, VGCC, mGluR1, Tr/DNER, and glycine receptor encephalitis; (2) intracellular antigens (associated with cancer in >90% of cases), including anti-Hu, CV2/CRMP5, Ri, Yo, Ma2, amphiphysin, GAD65, and IgLON5 antibodies—with cerebellar ataxia being the most common movement disorder, alongside chorea, parkinsonism, and PERM (progressive encephalomyelitis with rigidity and myoclonus). Each encephalitis subtype shows relatively distinctive epidemiological and clinical features regarding age, sex, associated tumor type, and characteristic movement disorder pattern, aiding diagnostic orientation. The article emphasizes that accurately recognizing specific movement disorder patterns (such as faciobrachial dystonia in LGI1 encephalitis or orofacial dyskinesia in NMDA encephalitis) is crucial for early diagnosis, enabling timely immunotherapy and/or tumor treatment to improve patient prognosis.
