Citations

Paraneoplastic neurological autoimmunity is often associated with small‐cell lung cancer (SCLC), a highly malignant neuroendocrine tumor. Paraneoplastic autoimmunity often correlates with longer survival. We describe the paraneoplastic neurological manifestations of patients with SCLC with and without SCLC‐predictive autoantibodies and the correlation between autoimmunity and survival. We reviewed the records of 116 patients (51% male) from the Mayo Clinic with histopathologically confirmed SCLC for whom stored serum was available for neural autoantibody testing. Cancer was limited stage in 41%; the median age at diagnosis was 64 years. Paraneoplastic neurological manifestations were recorded in 61% (decreasing frequency: peripheral neuropathy, dysautonomia, cognitive decline, cerebellar ataxia, neuromuscular junction disorder, seizures, cranial neuropathy, movement disorder, brainstem disorder, or myelopathy). Neural autoantibodies, some with pathogenic potential, were detected in the sera of SCLC patients with and without neurological autoimmunity. The most frequent among patients with neurological manifestations were: anti‐neuronal nuclear antibody‐type 1, voltage‐gated calcium channel (VGCC)‐N‐type, VGCC‐P/Q‐type, glutamic acid decarboxylase 65 (GAD65), SOX1, and muscle acetylcholine receptor (AChR); while the most common in patients without neurological manifestations were: GAD65, muscle‐AChR, and VGCC‐P/Q‐type. Neither cancer stage at diagnosis nor survival correlated with neurological manifestations or autoantibody‐positivity, except for shorter survival in patients with myelopathy. The only predictor of longer survival was limited‐stage disease at diagnosis.

Summary Objective Seizures develop in 80% of patients with anti– N ‐methyl‐ d ‐aspartate receptor (NMDAR) encephalitis, and these represent a major cause of morbidity and mortality. Anti‐NMDAR antibodies have been linked to memory loss in encephalitis; however, their role in seizures has not been established. We determined whether anti‐NMDAR antibodies from autoimmune encephalitis patients are pathogenic for seizures. Methods We performed continuous intracerebroventricular infusion of cerebrospinal fluid (CSF) or purified immunoglobulin (IgG) from the CSF of patients with anti‐NMDAR encephalitis or polyclonal rabbit anti‐NMDAR IgG, in male C57BL/6 mice. Seizure status during a 2‐week treatment was assessed with video‐electroencephalography. We assessed memory, anxiety‐related behavior, and motor function at the end of treatment and assessed the extent of neuronal damage and gliosis in the CA1 region of hippocampus. We also performed whole‐cell patch recordings from the CA1 pyramidal neurons in hippocampal slices of mice with seizures. Results Prolonged exposure to rabbit anti‐NMDAR IgG, patient CSF, or human IgG purified from the CSF of patients with encephalitis induced seizures in 33 of 36 mice. The median number of seizures recorded in 2 weeks was 13, 39, and 35 per mouse in these groups, respectively. We observed only 18 brief nonconvulsive seizures in 11 of 29 control mice (median seizure count of 0) infused with vehicle (n = 4), normal CSF obtained from patients with noninflammatory central nervous system (CNS) conditions (n = 12), polyclonal rabbit IgG (n = 7), albumin (n = 3), and normal human IgG (n = 3). We did not observe memory deficits, anxiety‐related behavior, or motor impairment measured at 2 weeks in animals treated with CSF from affected patients or rabbit IgG. Furthermore, there was no evidence of hippocampal cell loss or astrocyte proliferation in the same mice. Significance Our findings indicate that autoantibodies can induce seizures in anti‐NMDAR encephalitis and offer a model for testing novel therapies for refractory autoimmune seizures.

Purpose of review To describe a recently characterized autoimmune, inflammatory central nervous system (CNS) disorder known as autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy. Recent findings Affected patients present with symptoms of one or more of meningitis (headache and neck ache), encephalitis (delirium, tremor, seizures, or psychiatric symptoms), and myelitis (sensory symptoms and weakness). Optic disc papillitis (blurred vision) is common. CNS inflammation is evident in characteristic T1 postgadolinium enhancement of GFAP-enriched CNS regions, and lymphocytic cerebrospinal fluid (CSF) white cell count elevation. CSF is more reliable than serum for GFAP-immunoglobulin G (IgG) testing. Ovarian teratoma commonly coexists, particularly among patients with accompanying N-methyl-D-aspartate receptor or aquaporin-4 autoimmunity. Parainfectious autoimmunity is suspected in some other patients, though the culprit organism is rarely verified. Pathophysiologic relevance of T cells is underscored by neuropathology and cases of dysregulated T-cell function (HIV or checkpoint inhibitor cancer therapy). Corticosteroid-responsiveness is a hallmark of the disease. Relapses occur in approximately 20% of patients, necessitating transition to a steroid-sparing drug. Reported outcomes vary, though in the authors’ experience, early and sustained intervention usually portends recovery. Summary Autoimmune GFAP astrocytopathy is a treatable autoimmune CNS disease diagnosable by GFAP-IgG testing in CSF. This disease presents opportunities to explore novel mechanisms of CNS autoimmunity and inflammation.

ABSTRACTIntroduction: Antitumor immune responses are postulated to initiate paraneoplastic neurological disorders when proteins that are normally restricted to neural cells are expressed as oncoproteins. Mutated oncopeptides could bypass self‐tolerant T cells to activate cytotoxic effector T lymphocytes and requisite helper T lymphocytes to stimulate autoantibody production by B lymphocytes. Methods: We investigated muscle‐type nicotinic acetylcholine receptor (AChR) antigen expression at transcriptional and protein levels in a small‐cell lung cancer line (SCLC) established from a patient with AChR‐immunoglobulin G (IgG)‐positive myasthenia gravis. Results: We identified messenger RNA transcripts encoding the 2 AChR α1‐subunit isoforms and 7 alternative‐splicing products, 3 of which yielded premature stop codons. Despite detecting native muscle‐type AChR pentamers in the tumor, we did not identify mutant α1‐peptides. However, we found α1‐subunit‐derived peptides bound to tumor major histocompatibility complex (MHC)1‐protein. In a control SCLC from an antineuronal nuclear autoantibody, type 1 (anti‐Hu)‐IgG‐positive patient, we identified MHC1‐complexed Hu protein‐derived peptides but not AChR peptides. Discussion: Our findings support onconeural protein products as pertinent immunogens initiating paraneoplastic neurological autoimmunity. Muscle Nerve 58: 600–604, 2018

AbstractTo determine whether CSF leucine‐rich glioma‐inactivated 1(LGI1)‐IgG titer, index or IgG subclass has prognostic significance, we tested serum and CSF specimens collected concomitantly from 39 seropositive patients. LGI1‐IgG index was elevated (>1) in 21 patients (54%), suggesting intrathecal synthesis. Patients with worse outcome at last follow‐up (modified Rankin Scale >2) had significantly higher index (median 6.57 vs. 0.5, P = 0.048) compared to those with better outcome. Higher CSF LGI1‐IgG4 subclass‐specific titer and index correlated with worse outcome (P < 0.005 for both). These data suggest that evidence of intrathecal LGI1‐IgG synthesis may correlate with neuronal injury and warrant consideration of aggressive immunotherapy.