Sen, Arjune

Abstract Background N‐methyl‐D‐aspartate receptor antibody encephalitis (NMDAR‐Ab‐E) is an autoantibody‐mediated disorder, characterized by acute development of neuropsychiatric symptoms, seizures, movement disorders, and autonomic instability. Objectives To describe acute seizure semiology and electroencephalogram (EEG) findings in patients with a first episode of NMDAR‐Ab‐E. Methods Medical records and EEG results were retrospectively evaluated from 14 adult patients with definite NMDAR‐Ab‐E, recruited between April 2009 and September 2017, and followed up until October 2024. Results A total of 92.8% (13/14) were women with a mean age of 29.6 years. 85.7% (12/14) patients experienced seizures. Focal and/or generalized seizures were described at presentation or in the first days of the illness in 57% (8/14). EEGs showed diffuse slowing in 13/14 and this coexisted with epileptiform activity in 10/13; fast frequencies in 7/13 (potentially owing to a benzodiazepine effect); and asymmetric focal slowing in 6/13. Six patients had periods of rhythmic slow activity (focal or diffuse), without evolution to electrographic seizures. An extreme delta brush (EDB) pattern was recorded in 2/13 patients, and this was associated with non‐convulsive status epilepticus in one of these individuals. Significance Most patients in this case series of NMDAR‐Ab‐E were young adult females with early focal and/or generalized seizures. Diffuse slowing in theta/delta range was the most common EEG finding, with or without epileptiform discharges, focal slowing, superimposed fast activities, and focal or diffuse rhythmic slowing. An EDB pattern was rare. Even with non‐specific findings, EEG seems to be a sensitive tool to aid diagnosis and decision‐making in NMDAR‐Ab‐E.

Abstract Objective Differentiating forms of autoimmune encephalitis (AE) from other causes of seizures helps expedite immunotherapies in AE patients and informs studies regarding their contrasting pathophysiology. We aimed to investigate whether and how Nuclear Magnetic Resonance (NMR)‐based metabolomics could differentiate AE from drug‐resistant epilepsy (DRE), and stratify AE subtypes. Methods This study recruited 238 patients: 162 with DRE and 76 AE, including 27 with contactin‐associated protein‐like 2 (CASPR2), 29 with leucine‐rich glioma inactivated 1 (LGI1) and 20 with N‐methyl‐ d ‐aspartate receptor (NMDAR) antibodies. Plasma samples across the groups were analyzed using NMR spectroscopy and compared with multivariate statistical techniques, such as orthogonal partial least squares discriminant analysis (OPLS‐DA). Results The OPLS‐DA model successfully distinguished AE from DRE patients with a high predictive accuracy of 87.0 ± 3.1% (87.9 ± 3.4% sensitivity and 86.3 ± 3.6% specificity). Further, pairwise OPLS‐DA models were able to stratify the three AE subtypes. Plasma metabolomic signatures of AE included decreased high‐density lipoprotein (HDL, −(C H 2 ) n −, –C H 3 ), phosphatidylcholine and albumin (lysyl moiety). AE subtype‐specific metabolomic signatures were also observed, with increased lactate in CASPR2, increased lactate, glucose, and decreased unsaturated fatty acids (UFA, –C H 2 CH=) in LGI1, and increased glycoprotein A (GlycA) in NMDAR‐antibody patients. Interpretation This study presents the first non‐antibody‐based biomarker for differentiating DRE, AE and AE subtypes. These metabolomics signatures underscore the potential relevance of lipid metabolism and glucose regulation in these neurological disorders, offering a promising adjunct to facilitate the diagnosis and therapeutics.