Objective: To describe the clinical and treatment characteristics of movement disorders associated with antibodies (Abs) against neuronal synaptic extracellular (NMDAR, LGI1, CASPR2, IgLON5, Glycine receptors (GLY-R)), intracellular (GAD65) and neuronal non-synaptic (Tr, Yo, Hu, SOX1, basal ganglia (BG)) targets from a tertiary neurology unit.

Background: Neuronal Abs are associated with an increasingly heterogeneous group of movement disorders. Although there are some characteristic associations e.g. LGI1-Abs and faciobrachial dystonic movements; there is increasing heterogeneity as testing has become more widely available. Furthermore, reported treatment regimens and response are variable.

Method: We performed a retrospective case record review of patients with neuronal Abs from 2010-20. All assays were performed by the regional UKAS accredited laboratory.

Results: Neuronal Abs were identified in 213 cases. A clinically relevant presentation (autoimmune encephalitis or paraneoplastic syndrome) was recorded in 88/213 (41%) cases. Of these, 45/88 (51%) presented with a movement disorder and more than one type was recorded in 15/45 (34%). Cerebellar ataxia (12/45; 26%) was the most common movement disorder (GAD-Ab=3, n=2; SOX-Ab, Yo-Ab, GAD65-Ab, NMDAR-Ab, n=1; Hu-Ab, Tr-Ab, BG-Ab). Orofacial dyskinesia/choreoathetosis was recorded in n/total (75%) of cases with NMDAR-Abs, faciobrachial dystonia in n/total (83%) cases with LGI1-Abs and myoclonus in all cases with GLY-R-Abs. Tumours were detected in 25% with NMDAR-Abs.

Immunotherapy was used in 25/45 (55%) of cases, most commonly when a neuronal synaptic extracellular Ab was present (94%). Prednisolone (80%) and IVIg (55%) were the commonly used 1^st and 2^nd line treatments. Chorea and paroxysmal dystonia showed complete remission with immunotherapy. The median times to diagnosis of autoimmune encephalitis were shorter when movement disorders were present with NMDAR-Ab (13 vs. 133 weeks) and LGI1-Ab (4 vs. 63 weeks).

Conclusion: Half of the patients with autoimmune encephalitis and a neuronal Ab presented with a movement disorder. This clinical feature appears to help with the diagnosis. Associated hyperkinetic movement disorders respond favourably to immunotherapy.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-clinical-spectrum-of-movement-disorders-associated-with-neuronal-antibodies/