Paraneoplastic encephalitis: clinically based approach on diagnosis and management

Paraneoplastic neurological syndromes (PNSs) comprise a subset of immune-mediated nervous system diseases triggered by an underlying malignancy. Each syndrome usually shows a distinct clinical presentation and outcome according to the associated neural antibodies. PNSs generally have a subacute onset with rapid progression and severe neurological disability. However, some patients may have hyperacute onset or even show chronic progression mimicking neurodegenerative diseases. Updated diagnostic criteria for PNS have been recently established in order to increase diagnostic specificity and to encourage standardisation of research initiatives related to PNS. Treatment for PNS includes oncological therapy and immunomodulation to halt neurological deterioration although current treatment options are seldom effective in reversing disability. Nevertheless, growing knowledge and better understanding of PNS pathogenesis promise better recognition, earlier diagnosis and novel treatment strategies. Considering that PNSs provide a model of effective anticancer immunity, the impact of these studies will extend far beyond the field of neurology

Diagnostic criteria for primary autoimmune cerebellar ataxia—guidelines from an international task force on immune-mediated cerebellar ataxias

Aside from well-characterized immune-mediated ataxias with a clear trigger and/or association with specific neuronal antibodies, a large number of idiopathic ataxias are suspected to be immune mediated but remain undiagnosed due to lack of diagnostic biomarkers. Primary autoimmune cerebellar ataxia (PACA) is the term used to describe this later group. An International Task Force comprising experts in the field of immune ataxias was commissioned by the Society for Research on the Cerebellum and Ataxias (SRCA) in order to devise diagnostic criteria aiming to improve the diagnosis of PACA. The proposed diagnostic criteria for PACA are based on clinical (mode of onset, pattern of cerebellar involvement, presence of other autoimmune diseases), imaging findings (MRI and if available MR spectroscopy showing preferential, but not exclusive involvement of vermis) and laboratory investigations (CSF pleocytosis and/or CSF-restricted IgG oligoclonal bands) parameters. The aim is to enable clinicians to consider PACA when encountering a patient with progressive ataxia and no other diagnosis given that such consideration might have important therapeutic implications

Consensus Paper: Radiological Biomarkers of Cerebellar Diseases

Hereditary and sporadic cerebellar ataxias represent a vast and still growing group of diseases whose diagnosis and differentiation cannot only rely on clinical evaluation. Brain imaging including magnetic resonance (MR) and nuclear medicine techniques allows for characterization of structural and functional abnormalities underlying symptomatic ataxias. These methods thus constitute a potential source of radiological biomarkers, which could be used to identify these diseases and differentiate subgroups of them, and to assess their severity and their evolution. Such biomarkers mainly comprise qualitative and quantitative data obtained from MR including proton spectroscopy, diffusion imaging, tractography, voxel-based morphometry, functional imaging during task execution or in a resting state, and from SPETC and PET with several radiotracers. In the current article, we aim to illustrate briefly some applications of these neuroimaging tools to evaluation of cerebellar disorders such as inherited cerebellar ataxia, fetal developmental malformations, and immune-mediated cerebellar diseases and of neurodegenerative or early-developing diseases, such as dementia and autism in which cerebellar involvement is an emerging feature. Although these radiological biomarkers appear promising and helpful to better understand ataxia-related anatomical and physiological impairments, to date, very few of them have turned out to be specific for a given ataxia with atrophy of the cerebellar system being the main and the most usual alteration being observed. Consequently, much remains to be done to establish sensitivity, specificity, and reproducibility of available MR and nuclear medicine features as diagnostic, progression and surrogate biomarkers in clinical routine

Cytokine dynamics and targeted immunotherapies in autoimmune encephalitis

Autoimmune encephalitides constitute a diverse group of immune-mediated central nervous system disorders mainly characterized by the presence of antibodies targeting neuronal or glial antigens. Despite the notable contribution of antibody discovery to the understanding of their physiopathology, the specific immune cells and inflammatory mediators involved in autoimmune encephalitis are still poorly defined. However, cytokines have recently emerged as crucial signalling molecules in the pathogenesis of autoimmune encephalitis. Cytokines are biologically active, soluble, low-molecular-weight proteins or glycoproteins involved in a wide variety of physiological functions, including central nervous system development and homeostasis, immune surveillance, as well as proliferation and maturation of immune cells. Since unbalanced cytokine expression is considered a hallmark of many autoimmune central nervous system disorders, their identification and quantification has become an essential element in personalized medicine applied to the field of neuroimmunology. Several studies have explored the cytokine profile of autoimmune encephalitis, but their interpretation and comparison is challenging due to their small sample sizes and extremely high heterogeneity, especially regarding the cytokines analysed, type of sample used, and associated neural antibody. Only the cytokine profile of anti-N-methyl-D-aspartate receptor encephalitis has extensively been investigated, with findings suggesting that, although humoral immunity is the main effector, T cells may also be relevant for the development of this disorder. A better understanding of cytokine dynamics governing neuroinflammation might offer the opportunity of developing new therapeutic strategies against specific immune cells, cytokines, antibodies, or intracellular signalling cascades, therefore leading to better outcomes and preventing undesired side effects of the presently used strategies. In this review, we first summarize the current knowledge about the role of cytokines in the pathogenesis of autoimmune encephalitis, combining theoretical analysis with experimental validations, to assess their suitability as clinical biomarkers. Second, we discuss the potential applicability of the novel targeted immunotherapies in autoimmune encephalitis depending on the immunobiology of the associated antibody, their limitations, as well as the main limitations that should be addressed in future studies

Diagnostic yield of commercial immunodots to diagnose paraneoplastic neurologic syndromes

OBJECTIVE: To investigate the diagnostic yield of commercial immunodots to detect onconeural antibodies associated with paraneoplastic neurologic syndromes (PNSs), we analyzed the proportion of confirmed positive results using alternative techniques. METHODS: Sera (n = 5,300) of patients with suspected PNS were tested by PNS+2 blot (Ravo Diagnostika; January 2016-May 2017) or EUROLINE PNS 12 Ag (Euroimmun; July 2017-November 2018). Positive samples were further explored by in-house indirect immunofluorescence and a third in-house technique (Western blot or cell-based assay) using recombinant protein. Those found negative by these 2 techniques were considered as nonconfirmed. We analyzed the relationship between band intensity and final confirmation. Clinical data were collected for all confirmed results and nonconfirmed EUROLINE immunodots. RESULTS: PNS+2 blot was positive in 128/1,658 (7.7%) sera and confirmed in 47/128 (36.7%). EUROLINE was positive in 186/3,626 (5.1%) and confirmed in 56/186 (30.1%). Confirmation was highly variable among the antibodies tested, from 7.2% (PNS+2 blot) and 5.8% (EUROLINE) for anti-Yo to 88.2% (PNS+2 blot) and 65.0% (EUROLINE) for anti-Hu. None of the 27 weak positive sera by EUROLINE was confirmed. Band intensity in confirmed cases was variable among the antibodies from strong positive for all anti-Yo (n = 3) and anti-Hu (n = 11) to positive (n = 19) or strong positive (n = 9) for anti-SOX1. Among patients with a nonconfirmed EUROLINE result and available clinical information, all had an alternative diagnosis, and only 6.7% had cancer. CONCLUSIONS: Immunodots may be useful for PNS screening, but a threshold should be established for each antibody, and clinical information and confirmation by other techniques are essential. CLASSIFICATION OF EVIDENCE: The study provides Class IV evidence that immunodot assays for onconeural antibodies accurately identify patients with paraneoplastic neurologic syndromes

CRMP5 Regulates Generation and Survival of Newborn Neurons in Olfactory and Hippocampal Neurogenic Areas of the Adult Mouse Brain

The Collapsin Response Mediator Proteins (CRMPs) are highly expressed in the developing brain, and in adult brain areas that retain neurogenesis, ie: the olfactory bulb (OB) and the dentate gyrus (DG). During brain development, CRMPs are essentially involved in signaling of axon guidance and neurite outgrowth, but their functions in the adult brain remain largely unknown. CRMP5 has been initially identified as the target of auto-antibodies involved in paraneoplasic neurological diseases and further implicated in a neurite outgrowth inhibition mediated by tubulin binding. Interestingly, CRMP5 is also highly expressed in adult brain neurogenic areas where its functions have not yet been elucidated. Here we observed in both neurogenic areas of the adult mouse brain that CRMP5 was present in proliferating and post-mitotic neuroblasts, while they migrate and differentiate into mature neurons. In CRMP5−/− mice, the lack of CRMP5 resulted in a significant increase of proliferation and neurogenesis, but also in an excess of apoptotic death of granule cells in the OB and DG. These findings provide the first evidence that CRMP5 is involved in the generation and survival of newly generated neurons in areas of the adult brain with a high level of activity-dependent neuronal plasticity

Relapses in Anti-NMDAR Encephalitis: Clinical Characterization and Predictive Features

Background and ObjectivesDuring the recovery phase of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, up to 25% of relapses have been reported. Herein, we aimed to clinically characterize these relapses, analyze potential clinical predictors during the first episode, and evaluate the impact of immunotherapy in their occurrence.MethodsThis was a retrospective observational study of patients diagnosed with anti-NMDAR encephalitis relapses between January 2007 and June 2022 at the French Reference Center for Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis with a follow-up longer than 1 year.ResultsAmong 507 patients, 49 (9%) presented relapses after a median time of 720 days (range 149-8,280) and a median follow-up of 1752 days (range 390-9,229 days, interquartile range 1760 days). A total of 36 patients (73%) experienced 1 relapse, 9 (18%) had 2, and 4 (8%) had 3 relapses. Most patients presented an isolated core symptom (25/45, 55%). Relapses were less severe than the first episode, as reflected by a lower maximal modified Rankin Scale (median 5, range 3-5, vs median 3, range 0-6; p = 0.0001). At the first episode, patients experiencing relapses had shorter intensive care unit stays (22 days; vs 39 days; p = 0.04). In addition, presenting CSF pleocytosis >20 white blood cell decreased the risk of relapse by 71% (HR 0.29; CI 0.13-0.66; p = 0.003), and having a paraneoplastic etiology decreased the risk by 68% (HR 0.32; CI 0.12-0.87; p = 0.02). Moreover, during the first episode, they were treated less frequently with first-line (39/49, 79%, vs 190/197, 96%; p = 0.0001) and second-line immunotherapies (20/49, 40%, vs 142/197, 72%; p = 0.0001) and more frequently with delay >30 days (20/38, 52%, vs 58/185, 31%; p = 0.01) and >60 days (10/20, 50%, vs 39/138, 28%; p = 0.04), respectively. In addition, administering rituximab during the first episode with a delay <60 days decreased the risk of relapse by 60% (HR 0.40; CI 0.19-0.84; p = 0.01).DiscussionRelapses of anti-NMDAR encephalitis are uncommon, mostly monosymptomatic, and less severe than the first episode. At onset, presenting CSF pleocytosis or an underlying tumor decreases the risk of relapses. In addition, the early administration of first-line and second-line immunotherapies, particularly rituximab, could protect against further relapses

Predictors and Clinical Characteristics of Relapses in LGI1-Antibody Encephalitis

BACKGROUND AND OBJECTIVES: Relapses occur in 15%-25% of patients with leucine-rich glioma-inactivated 1 antibody (LGI1-Ab) autoimmune encephalitis and may cause additional disability. In this study, we clinically characterized the relapses and identified factors predicting their occurrence. METHODS: This is a retrospective chart review of patients with LGI1-Ab encephalitis diagnosed at our center between 2005 and 2022. Relapse was defined as worsening of previous or appearance of new symptoms after at least 3 months of clinical stabilization. RESULTS: Among 210 patients, 30 (14%) experienced a total of 33 relapses. The median time to first relapse was 23.9 months (range: 4.9-110.1, interquartile range [IQR]: 17.8). The CSF was inflammatory in 11/25 (44%) relapses, while LGI1-Abs were found in the serum in 16/24 (67%) and in the CSF in 12/26 (46%); brain MRI was abnormal in 16/26 (62%) relapses. Compared with the initial episode, relapses manifested less frequently with 3 or more symptoms (4/30 patients, 13% vs 28/30, 93%; p < 0.001) and had lower maximal modified Rankin scale (mRS) score (median 3, range: 2-5, IQR: 1 vs 3, range: 2-5, IQR: 0; p = 0.001). The median mRS at last follow-up after relapse (2, range: 0-4, IQR: 2) was significantly higher than after the initial episode (1, range: 0-4, IQR: 1; p = 0.005). Relapsing patients did not differ in their initial clinical and diagnostic features from 85 patients without relapse. Nevertheless, residual cognitive dysfunction after the initial episode (hazard ratio:13.8, 95% confidence interval [1.5; 129.5]; p = 0.022) and no administration of corticosteroids at the initial episode (hazard ratio: 4.8, 95% confidence interval [1.1; 21.1]; p = 0.036) were significantly associated with an increased risk of relapse. DISCUSSION: Relapses may occur years after the initial encephalitis episode and are usually milder but cause additional disability. Corticosteroid treatment reduces the risk of future relapses, while patients with residual cognitive dysfunction after the initial episode have an increased relapse risk

Revisiting anti-Hu paraneoplastic autoimmunity: phenotypic characterization and cancer diagnosis

Anti-Hu are the most frequent antibodies in paraneoplastic neurological syndromes, mainly associated with an often limited stage small cell lung cancer. The clinical presentation is pleomorphic, frequently multifocal. Although the predominant phenotypes are well characterized, how different neurological syndromes associate is unclear. Likewise, no specific study assessed the performance of new-generation CT and PET scanners for cancer screening in these patients. Herein, we aimed to describe the clinical pattern and cancer screening in a retrospective cohort of 466 patients with anti-Hu autoimmunity from the French Reference Centre on Paraneoplastic Neurological Syndromes registry. Clinical presentation, cancer screening and diagnosis were analysed. Among the 466 patients, 220 (54%) had multifocal neurological involvement. A hierarchical cluster analysis grouped the patients into (i) mainly limbic encephalitis, (ii) predominantly peripheral neuropathy and (iii) broad involvement of the nervous system (mixed group). Compared with limbic encephalitis and mixed groups, patients in the neuropathy group more frequently had a chronic onset of symptoms (29 versus 13 and 17%), elevated CSF proteins (83 versus 47 and 67%) and died from cancer progression (67 versus 15 and 28%; all P 2 years after clinical onset in few patients, screening should be extended up to 5 years. In addition, tumour regression was suspected in a substantial proportion of 'cancer-free' patients

Cerebellar Ataxia With Anti-DNER Antibodies: Outcomes and Immunologic Features

BACKGROUND AND OBJECTIVES: There is no report on the long-term outcomes of ataxia with antibodies against Delta and Notch-like epidermal growth factor-related (DNER). We aimed to describe the clinical-immunologic features and long-term outcomes of patients with anti-DNER antibodies. METHODS: Patients tested positive for anti-DNER antibodies between 2000 and 2020 were identified retrospectively. In those with available samples, immunoglobulin G (IgG) subclass analysis, longitudinal cerebellum volumetry, human leukocyte antigen isotyping, and CSF proteomic analysis were performed. Rodent brain membrane fractionation and organotypic cerebellar slices were used to study DNER cell-surface expression and human IgG binding to the Purkinje cell surface. RESULTS: Twenty-eight patients were included (median age, 52 years, range 19-81): 23 of 28 (82.1%) were male and 23 of 28 (82.1%) had a hematologic malignancy. Most patients (27/28, 96.4%) had cerebellar ataxia; 16 of 28 (57.1%) had noncerebellar symptoms (cognitive impairment, neuropathy, and/or seizures), and 27 of 28 (96.4%) became moderately to severely disabled. Half of the patients (50%) improved, and 32.1% (9/28) had no or slight disability at the last visit (median, 26 months; range, 3-238). Good outcome significantly associated with younger age, milder clinical presentations, and less decrease of cerebellar gray matter volumes at follow-up. No human leukocyte antigen association was identified. Inflammation-related proteins were overexpressed in the patients' CSF. In the rodent brain, DNER was enriched in plasma membrane fractions. Patients' anti-DNER antibodies were predominantly IgG1/3 and bound live Purkinje cells in vitro. DISCUSSION: DNER ataxia is a treatable condition in which nearly a third of patients have a favorable outcome. DNER antibodies bind to the surface of Purkinje cells and are therefore potentially pathogenic, supporting the use of B-cell-targeting treatments