MRI hallmarks of LGI1- and CASPR2-antibody encephalitis (P7-5.032)

Abstract

<h3>Objective:</h3> To identify common imaging characteristics in LGI1- and CASPR2-antibody mediated disorders, and how these differ from non-autoimmune disorders such as infectious encephalitis and Creutzfeld-Jakob Disease; CJD. <h3>Background:</h3> LGI1- and CASPR2-antibody encephalitis can present with acute to subacute onset confusion, amnesia and seizures. Early recognition and treatment help optimise patient outcomes and salient MRI features can aid diagnosis. Two disorders commonly confused with these syndromes are viral encephalitis and CJD. Here, we asked whether patients with LGI1- and CASPR2-Antibody mediated encephalitis showed characteristic findings on MRI brain to help expedite diagnosis and distinguish the illness from these differentials. <h3>Design/Methods:</h3> This was a retrospective cross-sectional analysis of patients referred to the Oxford Autoimmune Neurology Group. MRI brains from 97 patients were reviewed blinded and independently by two neuroradiologists. Patients included those with antibodies against LGI1 (N=44), CASPR2 (N=17), LGI1 and CASPR2 (N=4),patients with proven viral encephalitis (N=22) and CJD (N=10). Statistical analyses (e.g. Chi-square test) were performed to identify differences between and within groups, and correlate imaging findings with clinical syndromes. <h3>Results:</h3> T2 hyperintensity of the mesial temporal lobe was common in LGI1- and CASPR2-Antibody mediated disease (43/65, 66%). Compared to viral encephalitis, this is more likely to be bilateral (24/43; 56% vs 5/18; 28%. P=0.046), and less likely to extend to other structures (8/43; 19% vs 17/18; 94%. P&lt;0.001), or be associated with oedema (12/65; 19% vs 13/22; 59%, P&lt;0.001). Notably, true diffusion restriction was not seen in any antibody-mediated cases (0/60 vs 16/22; 73%. P&lt;0.001) and contrast enhancement was rare (1/22; 5% vs 7/17; 41%. P=0.013). <h3>Conclusions:</h3> In the correct clinical context, highly characteristic imaging findings may be used to assist the diagnosis of LGI1- and CASPR2-Ab mediated encephalitis. In particular, the absence of diffusion restriction and contrast enhancement supports these diagnoses and differentiates them from other common differentials. <b>Disclosure:</b> The institution of Dr. Kelly has received research support from The Health Research Board / Wellcome Trust. Dr. Grant has nothing to disclose. Andrew Murchison has nothing to disclose. Dr. Uy has nothing to disclose. The institution of Ms. Binks has received research support from Wellcome Trust. The institution of Ms. Binks has received research support from PetSavers. The institution of Ms. Binks has received research support from PetPlan. Ms. Binks has received intellectual property interests from a discovery or technology relating to health care. Ms. Binks has a non-compensated relationship as a Speaker with Encephalitis Society UK that is relevant to AAN interests or activities. Dr. Sheerin has received personal compensation in the range of $5,000-$9,999 for serving as an officer or member of the Board of Directors for Indigo Silver Neuroimaging Ltd. Dr. Irani has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Immunovant, UCB, Cerebral therapeutics, Roche and Janssen. Dr. Irani has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for UCB. Dr. Irani has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Roche. Dr. Irani has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Brain. Dr. Irani has received personal compensation in the range of $50,000-$99,999 for serving as an Expert Witness for LLPs. Dr. Irani has received intellectual property interests from a discovery or technology relating to health care. Dr. Irani has received intellectual property interests from a discovery or technology relating to health care. Dr. Irani has received intellectual property interests from a discovery or technology relating to health care.