Clinical, radiological and laboratory comparison between autoantibody-negative and autoantibody-positive Autoimmune Encephalitis patients. (P2.2-006)

Objective: To compare clinical, radiological and laboratory features of two groups of patients with autoimmune encephalitis (AE): autoantibody-positive AE patients (AE+) and autoantibody-negative AE patients (AE-).

Background: Recognition of AE is important because patients may benefit from several lines of immunomodulatory tre atment, which is more effective as soon as it is started. Prompt laboratory essays are not easily available, especially amongst small peripheral hospitals. In literature, no work has been published which compare clinical, radiological and laboratory characteristics of patients with definite autoantibody-positive AE and autoantibody-negative AE.

Design/Methods: We retrospectively selected patients admitted to our department between September 2010 and October 2018. In AE+ group we included 18 patients with clinical diagnosis of AE, accompanied by the positivity in serum and/or CSF for known neuronal antibodies (NMDAR: 4 patients, LGI-1: 9, GAD: 2, Ma2: 2, Hu: 1). In AE-group we included 14 patients, who fulfilled the following criteria: a) clinical, MRI and CSF data suggestive of autoimmune encephalitis, b) extensive neuronal antibodies (NMDAR, LGI-1, CASPR2, GAD, Ma1, Ma2, Ro, Yo, Hu, Ri, CV2, GABAR, AMPAR) testing in serum and cerebrospinal fluid (CSF) resulted negative, c) reasonable exclusion of other causes. Between these two groups we compared the following data: demographics, signs and symptoms, association with malignancy, EEG, CSF, MRI and treatment administered.

Results: We did not find any significant differences between the two groups. Clinical picture was homogenous between AE+ and AE-, as well as MRI features, EEG, CSF data.

Conclusions: AE-patients show similar features if compared to AE+ patients, except for autoantibody detection. As outlined by recent guidelines, our work suggests that, if clinical picture is highly suggestive for AE, antibody detection is not mandatory for diagnosis and, therefore, immunomodulatory treatment must not be delayed.

Disclosure: Dr. Giordano has nothing to disclose. Dr. Fazio has nothing to disclose. Dr. Gelibter has nothing to disclose. Dr. Volonté has nothing to disclose. Dr. Magnani has nothing to disclose. Dr. Comi has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Actelion, Bayer, Biogen, Merck Serono, Novartis, Sanofi, Serono Symposia International Foundation, and Teva. Dr. Martinelli has nothing to disclose.