Our findings suggest that autoimmunity should be considered an important etiology in patients with late-onset seizures. Testing for neural antibodies and brain MRI may be worthwhile in this patient group.

Background and ObjectivesTo assess seizure characteristics in antibody (ab)-associated autoimmune encephalitis (ab + AE) with the 3 most prevalent abs against N-methyl-d-aspartate receptor (NMDAR), leucine-rich glioma-inactivated protein 1 (LGI1), and glutamic acid decarboxylase (GAD).MethodsMulticenter nationwide prospective cohort study of the German Network for Research in Autoimmune Encephalitis.ResultsThree hundred twenty patients with ab + AE were eligible for analysis: 190 NMDAR+, 89 LGI1+, and 41 GAD+. Seizures were present in 113 (60%) NMDAR+, 69 (78%) LGI1+, and 26 (65%) GAD+ patients and as leading symptoms for diagnosis in 53 (28%) NMDAR+, 47 (53%) LGI+, and 20 (49%) GAD+ patients. Bilateral tonic-clonic seizures occurred with almost equal frequency in NMDAR+ (38/51, 75%) and GAD+ (14/20, 70%) patients, while being less common in LGI1+ patients (27/59, 46%). Focal seizures occurred less frequently in NMDAR+ (67/113; 59%) than in LGI1+ (54/69, 78%) or in GAD+ patients (23/26; 88%). An aura with déjà-vu phenomenon was nearly specific in GAD+ patients (16/20, 80%). Faciobrachial dystonic seizures (FBDS) were uniquely observed in LGI1+ patients (17/59, 29%). Status epilepticus was reported in one-third of NMDAR+ patients, but only rarely in the 2 other groups. The occurrence of seizures was associated with higher disease severity only in NMDAR+ patients.DiscussionSeizures are a frequent and diagnostically relevant symptom of ab + AE. Whereas NMDAR+ patients had few localizing semiological features, semiology in LGI1+ and GAD+ patients pointed toward a predominant temporal seizure onset. FBDS are pathognomonic for LGI1 + AE. Status epilepticus seems to be more frequent in NMDAR + AE.

Introduction: Free light chain kappa (FLCκ) are a newer sensitive biomarker to detect intrathecal immunoglobulin synthesis. Here we report the study protocol of the ORCAS study which will evaluate a novel laboratory work flow recently proposed including FLCκ analysis simplifying cerebrospinal fluid (CSF) analysis. Methods: The ORCAS study is a prospective multicenter diagnostic biomarker study across at least 4 study sites. The study protocol does not specify which assays should be applied in the participating laboratories to detect oligoclonal bands (OCB) or measure FLCκ or Ig synthesis to represent real world data. Primary outcome parameter is the sensitivity and negative predictive value of the absence of local FLCκ synthesis for the absence of intrathecal synthesis according to OCB and/or intrathecal IgG, IgA, IgM synthesis in quotient diagrams. The reference range of FLCκ will be indicated by the FLCκ quotient diagram. This study was designed according to the STARD criteria. Perspective: The establishment of a newer biomarker in routine practice is associated with significant difficulties, such as the inconsistent comparability of different measurement platforms, the establishment of suitable cut-offs or insufficient knowledge regarding sensitivity and specificity of the biomarker. If the ORCAS study objective is achieved, the use of the proposed workflow integrating FLCκ analysis in routine practice in CSF diagnostics could help to better characterize the intraindividual and disease-specific intrathecal humoral immune response in a resource-efficient manner.