Validation of a risk score to differentiate autoimmune and viral encephalitis: a Nationwide Cohort Study in Denmark.

BACKGROUND: A score to differentiate autoimmune (AE) and viral encephalitis (VE) early upon admission has recently been developed but needed external validation. The objective of this study was to evaluate the performance of the score in a larger and more diagnostically diverse patient cohort. METHODS: We conducted a retrospective nationwide and population-based cohort study including all adults with encephalitis of definite viral (2015-2022) or autoimmune aetiology (2009-2022) in Denmark. Variables included in the score-model were extracted from patient records and individual risk scores were assessed. The performance of the score was assessed by receiver-operating characteristics (ROC) curve analyses and calculation of the area under the curve (AUC). RESULTS: A total of 496 patients with encephalitis [AE n = 90, VE n = 287 and presumed infectious encephalitis (PIE) n = 119] were included in the study. The score was highly accurate in predicting cases of AE reaching an AUC of 0.94 (95% CI 0.92-0.97). Having a score ≥ 3 predicted AE with a PPV of 87% and an NPV of 91%. The risk score was found to perform well across aetiological subgroups and applied to the PIE cohort resulted in an AUC of 0.88 (95% CI 0.84-0.93). CONCLUSION: The excellent performance of the score as reported in the development study was confirmed in this significantly larger and more diverse cohort of patients with encephalitis in Denmark. These results should prompt further prospective testing with wider inclusion criteria.

Fatigue predicts quality of life after leucine-rich glioma-inactivated 1-antibody encephalitis.

Patient-reported quality-of-life (QoL) and carer impacts are not reported after leucine-rich glioma-inactivated 1-antibody encephalitis (LGI1-Ab-E). From 60 patients, 85% (51 out of 60) showed one abnormal score across QoL assessments and 11 multimodal validated questionnaires. Compared to the premorbid state, QoL significantly deteriorated (p < 0.001) and, at a median of 41 months, fatigue was its most important predictor (p = 0.025). In total, 51% (26 out of 51) of carers reported significant burden. An abbreviated five-item battery explained most variance in QoL. Wide-ranging impacts post-LGI1-Ab-E include decreased QoL and high caregiver strain. We identify a rapid method to capture QoL in routine clinic or clinical trial settings.

Tick-borne encephalitis as a trigger for anti-N-Methyl-d-aspartate receptor encephalitis.

Tick Borne Encephalitis (TBE) is endemic to an increasing number of countries and is a common cause of meningoencephalitis in Europe and Asia making any potential complications of the disease increasingly relevant to clinicians. We present, what is to our knowledge, the second reported case of N-methyl-d-aspartate receptor (NMDAR) encephalitis following Tick Borne Encephalitis (TBE) in a 47-year-old Lithuanian man. The case provides further evidence of TBE being a possible trigger of NMDAR encephalitis and highlights the importance of being aware of symptoms of autoimmune encephalitis in patients with infectious encephalitis.

Pathophysiological Effects of Autoantibodies in Autoimmune Encephalitides.

The heterogeneity of autoantibody targets in autoimmune encephalitides presents a challenge for understanding cellular and humoral pathophysiology, and the development of new treatment strategies. Thus, current treatment aims at autoantibody removal and immunosuppression, and is primarily based on data generated from other autoimmune neurological diseases and expert consensus. There are many subtypes of autoimmune encephalitides, which now entails both diseases with autoantibodies targeting extracellular antigens and classical paraneoplastic syndromes with autoantibodies targeting intracellular antigens. Here, we review the current knowledge of molecular and cellular effects of autoantibodies associated with autoimmune encephalitis, and evaluate the evidence behind the proposed pathophysiological mechanisms of autoantibodies in autoimmune encephalitis.

NMDA-receptor encephalitis in Denmark from 2009 to 2019: a national cohort study.

BACKGROUND: To describe the national Danish N-methyl-D-aspartate receptor encephalitis (NMDARE) cohort. METHODS: All NMDAR immunoglobulin G (IgG) positive cases in Denmark from 2009 to 2019 were included. Medical information was assessed retrospectively for clinical phenotype, workup, treatment and outcome. RESULTS: Seventy-seven patients were NMDAR IgG positive in serum/CSF. Fifty-five fulfilled the criteria of NMDARE, 18 did not and 4 had missing data. Incidence was 0.17/100,000 persons per year in 2018, and incidence rates increased since 2009. Of the 55 NMDARE patients (median age 27; 60% female), 9 had post-herpes simplex (HSE) NMDARE and 7 had a tumor (four teratomas). MRI was normal in 51% of patients. Brain FDG PET was performed in 17 patients, and was abnormal in 47% of patients with a normal MRI. First-line therapy was administered to 91%, and 24% required second-line therapy. Maintenance therapy during recovery was given 84% of patients, with no effect on relapse-risk. ICU admission occurred in 29%. Poor outcome (mRS > 2) was reported in 27% and dependent on age and etiology. Patients > 45 years had a poorer outcome (71% vs 8%, p < 0.0001), more frequently post-HSE NMDARE (47% vs 3%, p < 0.0001) and underlying malignancies (18% vs 0%). CONCLUSION: The incidence of NMDARE in Denmark is currently 0.17/100,000 persons per year, and has increased since 2009. NMDARE patients in Denmark display a higher median age, lower female:male ratio, a less frequent tumor association and need for ICU admission. Maintenance therapy did not reduce relapse rate. Poor outcome was seen with higher age, likely related to underlying etiology.

[Autoimmune encephalitis].

Autoimmune encephalitis is an important, treatable subtype of acute encephalitis where autoantibodies target intra- or extracellular neural antigens. Despite research advances, diagnosis is often delayed or incorrect, which affects outcome negatively. We summarise clinical features of the most common autoantibody-mediated autoimmune encephalitis subtypes and focus on classification, current diagnostic challenges using commercially available diagnostic assays, in an attempt to increase awareness.

CSF-Neurofilament Light Chain Levels in NMDAR and LGI1 Encephalitis: A National Cohort Study.

Background and Objectives: The two most common autoimmune encephalitides (AE), N-methyl-D-Aspartate receptor (NMDAR) and Leucine-rich Glioma-Inactivated 1 (LGI1) encephalitis, have been known for more than a decade. Nevertheless, no well-established biomarkers to guide treatment or estimate prognosis exist. Neurofilament light chain (NfL) has become an unspecific screening marker of axonal damage in CNS diseases, and has proven useful as a diagnostic and disease activity marker in neuroinflammatory diseases. Only limited reports on NfL in AE exist. We investigated NfL levels at diagnosis and follow-up in NMDAR and LGI1-AE patients, and evaluated the utility of CSF-NfL as a biomarker in AE. Methods: Patients were included from the National Danish AE cohort (2009-present) and diagnosed based upon autoantibody positivity and diagnostic consensus criteria. CSF-NfL was analyzed by single molecule array technology. Clinical and diagnostic information was retrospectively evaluated and related to NfL levels at baseline and follow-up. NMDAR-AE patients were subdivided into: idiopathic/teratoma associated or secondary NMDAR-AE (post-viral or concomitant with malignancies/demyelinating disease). Results: A total of 74 CSF samples from 53 AE patients (37 NMDAR and 16 LGI1 positive) were included in the study. Longitudinal CSF-NfL levels was measured in 21 patients. Median follow-up time was 23.8 and 43.9 months for NMDAR and LGI1-AE respectively. Major findings of this study are: i) CSF-NfL levels were higher in LGI1-AE than in idiopathic/teratoma associated NMDAR-AE at diagnosis; ii) CSF-NfL levels in NMDAR-AE patients distinguished idiopathic/teratoma cases from cases with other underlying etiologies (post-viral or malignancies/demyelinating diseases) and iii) Elevated CSF-NfL at diagnosis seems to be associated with worse long-term disease outcomes in both NMDAR and LGI1-AE. Discussion: CSF-NfL measurement may be beneficial as a prognostic biomarker in NMDAR and LGI1-AE, and high CSF-NfL could foster search for underlying etiologies in NMDAR-AE. Further studies on larger cohorts, using standardized methods, are warranted.

Autoimmune Encephalitis: Current Knowledge on Subtypes, Disease Mechanisms and Treatment.

Autoimmune Encephalitides (AE) comprises a group of diseases with antibodies against neuronal synaptic and cell surface antigens. Since the discovery of the most common subtype, NMethyl- D-Aspartate (NMDA) receptor encephalitis, an astonishing number of novel disease-causing antibodies have been described. This includes other glutamatergic and GABAergic receptor antibodies and antibodies against various other surface proteins. Many of these novel conditions present as limbic encephalitis with memory impairment, psychiatric features and epileptic seizures, often alongside subtype specific clinical features. Others present with a clinical disease course specific to the antibody. In contrast to the well-known paraneoplastic syndromes with antibodies directed against intracellular antigens (e.g. limbic encephalitis with Hu antibodies), autoimmune encephalitides are often highly responsive to immunotherapy, with a good outcome if diagnosed and treated early. Prognosis depends on aggressive immunotherapy, often with a combination of corticosteroids, intravenous immunoglobulin, plasma exchange or in some cases anti-CD20 therapy and cyclophosphamide. Other treatment regimens exist, and prognosis varies between disease subtypes and occurrence of underlying cancer. We review current knowledge on subtype-specific clinical presentation, disease mechanisms, diagnosis including pitfalls, treatment paradigms and outcome in autoimmune encephalitides, and provide suggestions for future research.

Anti-IgLON5 Disease: A Case With 11-Year Clinical Course and Review of the Literature.

Background: Anti-IgLON5 disease is a novel disorder with a complex interplay between inflammation and neurodegeneration. Patients develop antibodies against IgLON5 but also deposition of neuronal tau protein. Symptoms often have an insidious onset, slow progression and mimic other neurological disorders. Here we report a case with severely prolonged 11-year disease course and provide a review of current reported cases with focus on presentation, work-up, treatment, and outcome. Method: All reported cases of anti-IgLON5 disease were evaluated. Cases reported twice (in case series and as single case reports), were carefully excluded. Results: Most patients display a characteristic sleep disorder with severe insomnia, non rapid eye movement (NREM) parasomnia, with finalistic movements and sleep disordered breathing (stridor and obstructive sleep apnea). Other symptoms are bulbar involvement, gait instability, movement disorders, oculomotor abnormalities, dysautonomia, and peripheral symptoms. Antibodies are present in both serum and CSF and there is a strong correlation with human leukocyte antigen (HLA) DRB1*10:01 and HLA-DQB1*05:01. Neuropathological examination reveals neurodegeneration with neuronal tau deposits in regions that correlate with the clinical presentation (e.g., predominantly hypothalamus and tegmentum of the brain stem). Majority of cases respond partially to immunotherapy. Cases, who received no treatment or treatment with IV corticosteroids alone, had a higher mortality than cases treated with more potent immunotherapy. Conclusion: The clinical spectrum of Anti-IgLON5 disease continues to expand. Further studies are needed to elucidate the pathophysiology, therapeutic strategies and outcome in this novel disorder. Aggressive immunotherapy seems to increase survival.

[Stiff person syndrome: still a difficult and overlooked diagnosis].

We present a case of stiff person syndrome (SPS) with a description of the diagnostic challenges and a discussion of the implication of novel antibodies. SPS is a rare neurological disorder presenting with severe rigidity, muscle spasms and impaired gait function, and diagnosis is often delayed due to low awareness. SPS is classically associated with antibodies directed against glutamic acid decarboxylase or amphiphysin. However, recent advances have contributed to our understanding because of detection of several new antibodies, which cause SPS, mostly with additional neurological/systemic manifestations.

Use of Cerebrospinal Fluid Biomarkers in Diagnosis and Monitoring of Rheumatoid Meningitis.

Rheumatoid meningitis is a rare extra-articular manifestation of rheumatoid arthritis, often with non-specific symptoms. In most cases brain MRI shows a patchy lepto- and pachymeningeal enhancement, but the diagnosis currently relies on examination of a meningeal biopsy with presence of plasma cells and rheumatoid noduli. Presence of IgM rheumatic factor (RF) has been found in several cases and recently four cases have shown high titer anti-cyclic citrullinated peptide (anti-CCP) in CSF, suggesting this as a potential marker for rheumatoid meningitis. We present a 62 year-old woman with sero-positive (IgM RF and anti-CCP) rheumatoid arthritis, presenting with headache and gait impairment. Brain MRI revealed the classical patchy meningeal enhancement and the diagnosis of rheumatoid meningitis was confirmed by neuropathological examination of a meningeal biopsy. Analysis of the CSF revealed positive IgM RF (92.7 IU/mL) and strongly positive anti-CCP (19,600 IU/mL) and CXCL-13 (>500 ng/L). After treatment with high-dose steroid and Rituximab the clinical symptoms resolved. A 6 month follow-up analysis of CSF showed a dramatic decrease in all these markers with negative IgM RF and a decrease in both anti-CCP (64 IU/mL) and CXCL-13 (<10 ng/L). Our case further underlines the potential use of CSF anti-CCP and IgM RF in the diagnosis of RM and the use of these markers and CXCL-13 in evaluation of treatment response. A case review of 48 cases of rheumatoid meningitis published since 2010, including, symptoms, serum, and CSF findings, treatment, and outcome is provided.