Distinctive seizure semiology in the first video study of a naturally-occurring feline autoimmune encephalitis model

<h3>Introduction</h3> Frequent focal seizures are a hallmark of encephalitis with antibodies to leucine-rich glioma-inactivated 1 (LGI1-Ab-E) in humans. Recently, LGI1-Ab-E has emerged as an important cause of encephalitis in pet cats. This video study aimed to characterise feline LGI1-Ab-E seizure semiology, draw parallels to human LGI1-Ab-E, and inaugurate collaboration between human and veterinary neurologists. <h3>Methods</h3> Videos of LGI1-antibody positive and negative cats had been recorded in the domestic or ward setting. Five independent reviewers (three veterinary and two human neurologists) blind-rated each clip against pre-defined features on a standardised spreadsheet. Analysis was conducted in R (v4.0.3). <h3>Results</h3> 35 clips depicted 24 cats (16 seropositive; 13 female). Four semiologies were statistically significantly enriched in LGI1-Ab-E after multiple comparison correction. These included the most commonly observed features: orofacial automatisms (88/120 observations; 73%), salivation (87/120; 73%); and mydriasis (79/120; 66%). LGI1-Ab-E episodes could include aggression and/or circling behaviour, rarely or never visualised in seronegative clips. A temporal lobe origin was suggested in 67% of ratings for seropositive, compared to 28% of ratings for seronegative cats (p=4.18e-06). <h3>Conclusions</h3> Feline LGI1-Ab-E presents a distinctive seizure disorder. Further work will delineate inter-rater agreement and clinical associations. This will be a multi-media presentation with illustrative video clips.