Parallel Session 2: Neurodegeneration| Wed 18 May, 1115 – 1230|4 Novel complex motor behaviours in LGI1-autoantibody encephalitis

BackgroundPathognomonic clinical signs are increasingly well recognised across the autoim- mune encephalitides. Faciobrachial dystonic seizures (FBDS) are exclusively present in patients with LGI1-autoantibodies. Owing to their recent description and rarity, however, the wider clinical phenotypes remain less well-defined.AimsTo describe novel clinical features in a large cohort of patients with LGI1-autoantibodies.MethodsPatients were recruited for clinical research following either direct referral to the Oxford Autoim- mune Neurology Service, or via notification to the national Association of British Neurologists Rare Disease Ascertainment and Recruitment (RaDaR) Surveillance Unit. Novel clinical signs were identified through clinical assessment of 107 LGI1-autoantibody patients. We use video footage to present the phenotypes.Results5/104* (5%) of patients with LGI1-autoantibodies displayed highly unusual manual stereotypies which we have termed ‘complex motor behaviours’. These behaviours consisted of the patients acting out intricate manual behaviours using imaginary objects, for example drinking from a cup, writing, and imitation of winding a piece of string around the fingers. They typically occurred during sleep or periods of relaxed wakefulness, were of short duration (30-60 seconds), and were associated with loss of awareness. All patients had multiple seizure semiologies (3-5) and associated visual hallucinations and sleep disorder.ConclusionsComplex motor behaviours were observed in 5% of patients with LGI1-autoantibodies and may represent either a novel seizure semiology or the sleep disorder agrypnia excitata. These findings expand the clinical phenotypes of LGI1-autoantibody encephalitis.