Abstract Details

Title Frequency and clinical significance of seronegative anti-NMDAR encephalitis

Topic Autoimmune Neurology

Presentation(s) P10 - Poster Session 10 (5:30 PM-6:30 PM)

Poster/Presentation
Number 15-011

Objective To determine the frequency of anti-NMDAR encephalitis without detectable serum NMDAR antibodies (NMDAR-abs) and the potential changes in the syndrome presentation.

Background Some patients with anti-NMDAR encephalitis do not have detectable NMDAR-abs in serum. The clinical implications are unknown.

Design/Methods Retrospective assessment of patients with anti-NMDAR encephalitis and available paired serum/CSF samples examined at Hospital Clínic-IDIBAPS, Barcelona, between January 2007 and December 2017. NMDAR-abs were determined with (1) rat brain immunostaining, (2) in-house cell-based assay (CBA), and (3) a commercial CBA. Patients were considered seronegative if NMDAR-abs were undetectable in serum using the 3 indicated techniques (NMDAR-abs only present in CSF).

Results Among 578 patients with anti-NMDAR encephalitis, 75 (13%) were seronegative. Compared with seropositive patients, the seronegative were older (23.5 years [IQR: 17-43] vs 20.5 [IQR: 14-31]; p<0.0001), less frequently female (39 [52%] vs 313 [76%]; p<0.001), and less frequently had a tumor (6 [9%] vs 128 [32%]; p<0.001). Additionally, seronegative patients were less likely to have seizures (44 [60%] vs 294 [73%]; p= 0.028), movement disorders (52 [69%] vs 355 [86%]; p<0.001), hypoventilation (12 [16%] vs 132 [32%]; p=0.008), and intensive care admissions (27 [43%] vs 283 [69%]; p<0.001). Treatment with immunotherapy and outcome were similar in seronegative and seropositive patients (mRS>2 at one year follow-up, 8 [19%] vs 60 [27%]; p=0.265). In multivariate analysis, older age at diagnosis, absence of tumor and less need for ICU admission were independent variables associated with seronegativity. No differences were observed in time from symptom onset to diagnosis (median days 30 [21-60] vs 35 [21-63]; p=0.3792), or frequency of relapses (one or more in 9 [16%] vs 28 [11%]; p=0.307).

Conclusions 13% of patients with anti-NMDAR encephalitis are seronegative. These patients are more likely to be male, with milder forms of the disease, and without tumors.

Authors/Disclosures
PRESENTER	No disclosure on file
	No disclosure on file
Thais Armangue, MD (IDIBAPS-HClinic)	Dr. Armangue has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Roche. The institution of Dr. Armangue has received research support from ISCIII(Spanish institute of health) -PI21/00316, Marato TV3, La Caixa Research Foundadion, Pablove Foundation (689368), Torrons Vicens Foundation (PFNR0144), 2021 Invest AEP.
Josep O. Dalmau, MD, PhD, F�鶹��ýӳ��	Dr. Dalmau has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Astellas Research Institute of America. Dr. Dalmau has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Janssen Research & Development . Dr. Dalmau has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for �鶹��ýӳ��. An immediate family member of Dr. Dalmau has received personal compensation in the range of $5,000-$9,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Springer Nature. The institution of Dr. Dalmau has received research support from Sage Therapeutics. The institution of Dr. Dalmau has received research support from Edmond J.Safra Foundation . The institution of Dr. Dalmau has received research support from La Caixa Foundation. The institution of Dr. Dalmau has received research support from Spanish Ministry of Health (ISCIII). The institution of Dr. Dalmau has received research support from Euroimmun, Inc. Dr. Dalmau has received intellectual property interests from a discovery or technology relating to health care. An immediate family member of Dr. Dalmau has received intellectual property interests from a discovery or technology relating to health care. Dr. Dalmau has received intellectual property interests from a discovery or technology relating to health care. An immediate family member of Dr. Dalmau has received intellectual property interests from a discovery or technology relating to health care. Dr. Dalmau has received publishing royalties from a publication relating to health care. Dr. Dalmau has received publishing royalties from a publication relating to health care. Dr. Dalmau has received publishing royalties from a publication relating to health care.
Francesc R. Graus, MD (IDIBAPS)	Dr. Graus has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for MedLink. Dr. Graus has received intellectual property interests from a discovery or technology relating to health care.

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