Objective The contemporary diagnosis of paraneoplastic neurologic syndromes (PNSs) requires an increasing understanding of their clinical, immunologic, and oncologic heterogeneity. The 2004 PNS criteria are partially outdated due to advances in PNS research in the last 16 years leading to the identification of new phenotypes and antibodies that have transformed the diagnostic approach to PNS. Here, we propose updated diagnostic criteria for PNS. Methods A panel of experts developed by consensus a modified set of diagnostic PNS criteria for clinical decision making and research purposes. The panel reappraised the 2004 criteria alongside new knowledge on PNS obtained from published and unpublished data generated by the different laboratories involved in the project. Results The panel proposed to substitute “classical syndromes” with the term “high-risk phenotypes” for cancer and introduce the concept of “intermediate-risk phenotypes.” The term “onconeural antibody” was replaced by “high risk” (>70% associated with cancer) and “intermediate risk” (30%–70% associated with cancer) antibodies. The panel classified 3 levels of evidence for PNS: definite, probable, and possible. Each level can be reached by using the PNS-Care Score, which combines clinical phenotype, antibody type, the presence or absence of cancer, and time of follow-up. With the exception of opsoclonus-myoclonus, the diagnosis of definite PNS requires the presence of high- or intermediate-risk antibodies. Specific recommendations for similar syndromes triggered by immune checkpoint inhibitors are also provided. Conclusions The proposed criteria and recommendations should be used to enhance the clinical care of patients with PNS and to encourage standardization of research initiatives addressing PNS.

Objective: To define the clinical characteristics, management, and outcome of neurological immune-related adverse events (n-irAEs) of immune checkpoint inhibitors (ICIs). Methods: Systematic review of the literature following the PRISMA guidelines. Results: A total of 694 articles were identified. Two hundred fifty-six articles, with 428 individual patients, met the inclusion criteria. Reports regarding neuromuscular disorders (319/428, 75%) were more frequent than those on central nervous system (CNS) disorders (109/428, 25%). The most common n-irAEs reports were: myositis (136/428, 32%), Guillain-Barré syndrome and other peripheral neuropathies (94/428, 22%), myasthenic syndromes (58/428, 14%), encephalitis (56/428, 13%), cranial neuropathies (31/428, 7%), meningitis (13/428, 3%), CNS demyelinating diseases (8/428, 2%), and myelitis (7/428, 2%). Other CNS disorders were detected in 25/428 (6%) patients. Compared to the whole sample, myasthenic syndromes were significantly more Ab-positive (33/56, 59%; p<0.001). Anti-PD-1/PD-L1 were more frequent in myasthenic syndromes (50/58, 86%; p=0.005) and less common in meningitis (2/13, 15%; p<0.001) and cranial neuropathies (13/31, 42%; p=0.005). Anti-CTLA-4 ICIs were more frequent in meningitis (8/13, 62%; p<0.001) and less common in encephalitis (2/56, 4%; p=0.009) and myositis (12/136, 9%; p=0.01). Combination of different ICIs was more frequent in cranial neuropathies (12/31, 39%; p=0.005). Melanoma was more frequent in patients with peripheral neuropathies (64/94, 68%; p=0.003) and less common in encephalitis (19/56, 34%; p=0.001). The highest mortality rate was reached in myasthenic syndromes (28%). Conclusion: Considering the increasing use of ICI therapy in the forthcoming future, this information can be valuable in assisting neurologists and oncologists in early n-irAEs diagnosis and treatment.

Background and Objectives To report the clinical, biological, and imaging features and clinical course of a French cohort of patients with glial fibrillary acidic protein (GFAP) autoantibodies. Methods We retrospectively included all patients who tested positive for GFAP antibodies in the CSF by immunohistochemistry and confirmed by cell-based assay using cells expressing human GFAPα since 2017 from 2 French referral centers. Results We identified 46 patients with GFAP antibodies. Median age at onset was 43 years, and 65% were men. Infectious prodromal symptoms were found in 82%. Other autoimmune diseases were found in 22% of patients, and coexisting neural autoantibodies in 11%. Tumors were present in 24%, and T-cell dysfunction in 23%. The most frequent presentation was subacute meningoencephalitis (85%), with cerebellar dysfunction in 57% of cases. Other clinical presentations included myelitis (30%) and visual (35%) and peripheral nervous system involvement (24%). MRI showed perivascular radial enhancement in 32%, periventricular T2 hyperintensity in 41%, brainstem involvement in 31%, leptomeningeal enhancement in 26%, and reversible splenial lesions in 4 cases. A total of 33 of 40 patients had a monophasic course, associated with a good outcome at last follow-up (Rankin Score ≤2: 89%), despite a severe clinical presentation. Adult and pediatric features are similar. Thirty-two patients were treated with immunotherapy. A total of 11/22 patients showed negative conversion of GFAP antibodies. Discussion GFAP autoimmunity is mainly associated with acute/subacute meningoencephalomyelitis with prodromal symptoms, for which tumors and T-cell dysfunction are frequent triggers. The majority of patients followed a monophasic course with a good outcome.

Objective To describe the spectrum and outcome of central nervous system complications associated with immune checkpoint inhibitors (CNS-ICI). Methods Patients with CNS-ICI were identified and their characteristics compared with ICI-related peripheral neuropathy (PN-ICI). Results We identified 19 patients with CNS-ICI. The patients were receiving nivolumab (n=8), pembrolizumab (n=6), a combination of ipilimumab-nivolumab (n=3), ipilimumab-durvalumab (n=1), or atezolizumab (n=1). Underlying malignancies included non-small-cell lung cancer (n=8), melanoma (n=3), and other less common tumours (n=8). Neurological phenotypes were limbic encephalitis (n=8), meningoencephalitis (n=4) and cerebellitis (n=4). Two patients developed isolated confusion and one parkinsonism. Associated autoantibodies included onconeural (Ma2, n=7; Hu, n=1), astrocytic (glial fibrillar acidic protein, n=2) and neuronal surface (contactin-associated protein-like 2, n=1) specificities. ICIs were withheld and corticosteroid treatment was given in all cases. Five patients received intravenous immunoglobulin, two rituximab, one plasmapheresis and one infliximab. Overall, six patients died. Readministration of ICI was attempted in three patients, without further relapses. Non-small-cell lung cancer was significantly more frequent in patients with CNS-ICI (p<0.01), while melanoma and ipilimumab treatment were more common in PN-ICI (p<0.01 and p=0.01). Conversely, CNS-ICI cases were more frequently antibody-positive than PN-ICI (p<0.01) and showed a strong trend towards poorer outcome (p=0.053). Conclusion Three main clinical phenotypes characterise CNS complications of ICIs, each with distinct immunological background, disease course and response to treatment. Other clinical manifestations (including parkinsonism and steroid-responsive confusion) are also possible. Underlying cancers, antibody prevalence and outcome appear different from those of patients with PN-ICI.

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.