LGI1-antibody encephalitis is characterised by frequent, multifocal clinical and subclinical seizures

PURPOSE: To describe clinical and electrographic characteristics of seizures LGI1-antibody encephalitis, and their correlations with two-year outcomes. METHODS: Video-electroencephalography recordings were performed on a cohort of 16 consecutive patients with LGI1-antibodies from two UK neuroscience-centers over five-years. RESULTS: From 14 of 16 patients (13 males; age-range 53-92years), 86 faciobrachial dystonic seizures were recorded at a median frequency of 0.4 per hour (range 0.1-9.8), and ictal EEG changes accompanied 5/86 events. In addition, 11/16 patients showed 53 other seizures - subclinical (n=18), motor (n=16), or sensory (n=19) - at a median of 0.1 per hour (range 0.1-2) associated with temporal and frontal discharges. The sensory events were most commonly thermal sensations or body-shuddering, and the motor events were frequently automatisms or vocalisations. Furthermore, multifocal interictal epileptiform discharges, from temporal, frontal and parietal regions, and interictal slow-wave activity were observed in 25% and 69% of patients, respectively. Higher observed seizure frequency correlated with poorer functional recovery at two-years (p=0.001). CONCLUSIONS: Multiple frequent seizure semiologies, in addition to numerous subclinical seizures and interictal epileptiform discharges, are hallmarks of LGI1-antibody encephalitis. High overall seizure frequency may predict more limited long-term recovery. These observations should encourage closer monitoring and proactive treatment of seizure activity in these patients.