A. Sebastian Lopez-Chiriboga

Metabotropic glutamate receptor type 1 autoimmunity Clinical features and treatment outcomes

Objective: To describe retrospectively the clinical associations of immunoglobulin G (IgG) targeting metabotropic glutamate receptor 1 (mGluR1-IgG). Methods: Specimens of 9 patients evaluated on a service basis in the Mayo Clinic Neuroimmunology Laboratory by tissue-based immunofluorescence assay (IFA) yielded a robust, synaptic immunostaining pattern consistent with mGluR1-IgG (serum, 9; CSF, 2 available). Transfected HEK293 cell-based assay (CBA) confirmed mGluR1 specificity in all 11 specimens. A further 2 patients were detected in Germany primarily by CBA. Results: The median symptom onset age for the 11 patients was 58 years (range 33–81 years); 6 were male. All 9 Mayo Clinic patients had subacute onset of cerebellar ataxia, 4 had dysgeusia, 1 had psychiatric symptoms, and 1 had cognitive impairment. All were evaluated for malignancy, but only 1 was affected (cutaneous T-cell lymphoma). One developed ataxia post–herpes zoster infection. Head MRIs were generally atrophic or normal-appearing, and CSF was inflammatory in just 1 of 5 tested, though mGluR1-IgG was detected in both specimens submitted. Five patients improved (attributable to immunotherapy in 4, spontaneously in 1), 3 stabilized (attributable to immunotherapy in 2, cancer therapy in 1), and 1 progressively declined (untreated). The 2 German patients had ataxia, but fulfilled multiple sclerosis diagnostic criteria (1 relapsing-remitting, 1 progressive). However, both had histories of hematologic malignancy (acute lymphocytic leukemia and mantle cell lymphoma), and had mGluR1-IgG detected in serum by CBA (weakly positive on tissue-based IFA). Conclusions: mGluR1 autoimmunity represents a treatable form of cerebellar ataxia. Dysgeusia may be a diagnostic clue. Paraneoplastic, parainfectious, or idiopathic causes may occur.

Glycine receptor modulating antibody predicting treatable stiff-person spectrum disorders

Background Glycine receptor alpha-1 subunit (GlyRα1)-immunoglobulin G (IgG) is diagnostic of stiff-person syndrome (SPS) spectrum but has been reported detectable in other neurologic diseases for which significance is less certain. Methods To assess GlyRα1-IgGs as biomarkers of SPS spectrum among patients and controls, specimens were tested using cell-based assays (binding [4°C] and modulating [antigen endocytosing, 37°C]). Medical records of seropositive patients were reviewed. Results GlyRα1-IgG (binding antibody) was detected in 21 of 247 patients with suspected SPS spectrum (8.5%) and in 8 of 190 healthy subject sera (4%) but not CSF. Among 21 seropositive patients, 20 had confirmed SPS spectrum clinically, but 1 was later determined to have a functional neurologic disorder. Sera from 9 patients with SPS spectrum , but not 7 controls, nor the functional patient, caused GlyRα1 modulation (100% specificity). SPS spectrum phenotypes included progressive encephalomyelitis with rigidity and myoclonus (PERM) (8), classic SPS (5), stiff limb (5), stiff trunk (1), and isolated exaggerated startle (hyperekplexia, 1). Neuropsychiatric symptoms present in 12 patients (60%) were anxiety (11), depression (6), and delirium (3). Anxiety was particularly severe in 3 patients with PERM. Objective improvements in SPS neurologic symptoms were recorded in 16 of 18 patients who received first-line immunotherapy (89%, 9/10 treated with corticosteroids, 8/10 treated with IVIg, 3/4 treated with plasma exchange, and 1 treated with rituximab). Treatment-sparing maintenance strategies were successful in 4 of 7 patients (rituximab [2/3], azathioprine [1/1], and mycophenolate [1/3]). Conclusions GlyRα1-modulating antibody improves diagnostic specificity for immunologically treatable SPS spectrum disorders. Classification of evidence This study provides Class IV evidence that GlyRα1-modulating antibody accurately identifies patients with treatable SPS spectrum disorders.

Autoimmune septin-5 cerebellar ataxia

Objective To report a form of autoimmune cerebellar ataxia in which antibodies target septin-5, a guanosine triphosphate (GTP)-binding neural protein involved in neurotransmitter exocytosis. Methods Archived sera and CSF specimens with unclassified synaptic antibodies were re-evaluated by tissue-based indirect immunofluorescence assay. Autoantigens were identified by Western blot and mass spectrometry. Recombinant protein assays (Western blot, cell based, and protein screening array) confirmed antigen specificity. Results Serum and CSF from 6 patients produced identical synaptic immunoglobulin G (IgG) staining patterns of synaptic regions (neuropil) of the mouse cerebrum and cerebellum. The molecular layer of the cerebellum and the thalamus demonstrated stronger immunoreactivity than the midbrain, hippocampus, cortex, and basal ganglia. The antigen revealed by mass spectrometry analysis of immunoprecipitated cerebellar proteins and confirmed by recombinant protein assays was septin-5. All 4 patients with records available had subacute onset of cerebellar ataxia with prominent eye movement symptoms (oscillopsia or vertigo). None had cancer detected. Improvements occurred after immunotherapies (2) or spontaneously (1). One patient died. Conclusion Septin-5 IgG represents a biomarker for a potentially fatal but treatable autoimmune ataxia.

Association of MOG-IgG Serostatus With Relapse After Acute Disseminated Encephalomyelitis and Proposed Diagnostic Criteria for MOG-IgG–Associated Disorders

Importance Recent studies have reported a higher relapse rate following an initial inflammatory demyelinating disorder in pediatric patients with persistent seropositivity of antibodies targeting myelin oligodendrocyte glycoprotein (MOG-IgG1). To date, the clinical implications of longitudinal MOG-IgG1 seropositivity using live cell assays with IgG1 secondary antibodies in adults after acute disseminated encephalomyelitis (ADEM) are unknown. Objective To determine whether MOG-IgG1 serostatus (transient vs persistent) and titer change over time provide clinical utility in predicting the likelihood of relapse after ADEM. Design, Setting, and Participants This cohort study identified patients with an initial diagnosis of ADEM evaluated at a single referral center between January 1, 1990, and October 1, 2017. Fifty-one patients were included, including 31 children and 20 adults. Longitudinal serologic testing was performed detecting autoantibodies targeting aquaporin 4 (AQP4-IgG) and MOG-IgG1 with clinically validated fluorescence-activated cell sorting assays. Patients were divided into 3 cohorts: persistent seropositivity, transient seropositivity, and seronegativity. Main Outcomes and Measures Clinical demographic characteristics, longitudinal AQP4-IgG and MOG-IgG1 serostatus, titers, relapses, use of immunotherapy, and Expanded Disability Status Scale score at follow-up. Results Of 51 patients presenting with an initial diagnosis of ADEM, 20 (39%) were adult, 24 (47%) were female, and ages ranged from 12 months to 57 years. Seventeen patients fulfilled criteria for persistent seropositivity; of those, 8 of 9 children (89%) and 7 of 8 adults (88%) had at least 1 relapse after median (range) follow-up periods of 75 (15-236) months and 39 (9-161) months, respectively. Eight patients (16%), including 4 adults, fulfilled criteria for transient seropositivity; of those, no children and 1 of 4 adults (25%) relapsed after median (range) follow-up periods of 32 (24-114) months and 16 (13-27) months, respectively. Of 24 patients with AQP4-IgG and MOG-IgG seronegativity, 6 of 17 children (35%) and 2 of 7 adults (29%) had at least 1 relapse after median (range) follow-up periods of 36 (3-203) months and 34 (15-217) months, respectively. There were only 2 patients, including 1 adult, with AQP4-IgG seropositivity, and both relapsed. The hazard ratio for relapses in those with persistent MOG-IgG1 positivity compared with AQP4-IgG and MOG-IgG1 seronegativity was 3.1 (95% CI, 1.1-8.9; P = .04) in children and 5.5 (95% CI, 1.4-22.5; P = .02) in adults. Immunotherapy was used in 5 of 9 children (56%) and 6 of 8 adults (75%) with persistent seropositivity and in 3 of 17 children (18%) and 1 of 7 adults (14%) with AQP4-IgG and MOG-IgG seronegativity. Conclusions and Relevance Relapse occurred in 15 of 17 patients (88%) with persistent MOG-IgG1 seropositivity after ADEM; only 1 patient with transient seropositivity experienced relapse. Our data extend the clinical utility of MOG-IgG1 serological testing to adult patients and highlights that longitudinal serologic evaluation of MOG-IgG1 could help predict disease course and consideration of immunotherapy.

Emerging Subspecialties in Neurology: Autoimmune neurology

Autoimmune neurology is one of the most rapidly evolving fields in modern neurology. Autoantibodies that recognize nervous system self-antigens, including ion channels, receptors for neurotransmitters, and neuronal intrinsic and extrinsic proteins involved in synaptic transmission, are all recognized as targets of pathogenic autoantibodies. The accelerating rate of new antigen discovery in recent decades is impressive (figure). The diversity of neurologic presentations, the unique pathophysiology, and the complexity of treating these disorders justifies dedicated fellowship training to acquire the expertise needed to diagnose and optimally manage these patients. The requisite training is distinct from the classical exposure provided by traditional neuroimmunology fellowships that focus on multiple sclerosis. As a new subspecialty, autoimmune neurology intersects all neurologic subspecialties and other medical specialties, including but not limited to clinical immunology, infectious disease, rheumatology, gastroenterology, oncology, and psychiatry. While this article focuses on autoimmune neurology fellowships currently available in the United States, historically many current leaders in the field trained nationally and internationally under Dr. Jerome Posner, Dr. John Newsom-Davis, and Dr. John Trotter, to name a few of the pioneers.

Diagnostic and Therapeutic Approach to Autoimmune Neurologic Disorders

Abstract The field of autoimmune neurology is evolving rapidly. The discovery of autoantibodies that target neural antigens has expanded swiftly in the last decade. Recognition of the clinical syndromes associated with autoimmune neurologic disorders, and our understanding of the pathophysiology, has progressed significantly. Radiographic, electrophysiological, and laboratory testing (particularly neural autoantibody testing) are fundamental in the diagnosis of autoimmune neurological disorders and in the exclusion of mimics. Furthermore, investigations may serve as a baseline from which objective assessment of improvement or detection of relapse can be made. These disorders can be associated with underlying neoplasms, and screening for malignancy is an essential component of the investigations. Early diagnosis and prompt initiation of immunotherapy can improve neurologic function. The use of immunotherapy, however, can be associated with diverse side effects, and careful monitoring is crucial to prevent complications. Herein the authors address the diagnostic and treatment approach of autoimmune neurologic disorders, with particular focus on antibody‐mediated neurologic autoimmunity.

Posttransplant autoimmune encephalitis

The causes of encephalopathy in the posttransplant setting are diverse and include medication toxicity (e.g., posterior reversible encephalopathy syndrome), infections (e.g., human herpes virus type 6 [HHV-6]), and neoplastic disease (posttransplant lymphoproliferative disorder). Autoimmune etiologies are not well recognized in this setting, although a few cases are described.1–5 Herein, we report 3 patients with posttransplant autoimmune encephalitis (AE).

Granulomatous Angiitis of the Central Nervous System Associated with Hodgkin's Lymphoma: Case Report and Literature Review

Granulomatous angiitis of the central nervous system (GACNS) is a rare cerebrovascular disorder. It usually presents with multifocal neurologic symptoms symptoms including stroke, encephalopathy, and headache. A limited number of case reports describe neurological deficits resulting from GACNS as the manifesting symptoms of Hodgkins lymphoma (HL). We describe the case of a patient with neurological symptoms from GACNS that led to the diagnosis of HL, as well as a literature review focusing on the association between GACNS and HL.

LGI1 and CASPR2 neurological autoimmunity in children

The clinical phenotype of leucine‐rich glioma‐inactivated protein 1 (LGI1) and contactin‐associated proteinlike 2 (CASPR2) autoimmunity is well defined in adults. Data for children are limited (<10 cases). Among 13,319 pediatric patients serologically tested for autoimmune neurological disorders (2010–2017), 264 were seropositive for voltage‐gated potassium channel‐complex–IgG (radioimmunoprecipitation). Only 13 (4.9%) were positive by transfected cell‐binding assay for LGI1‐IgG (n = 7), CASPR2‐IgG (n = 3), or both (n = 3). This is significantly less than in adults. Encephalopathy, seizures, and peripheral nerve hyperexcitability were common, as was coexisting autoimmunity. No faciobrachial dystonic seizures or cancers were identified. Functional neurologic disorders were frequently the initial diagnosis, and immunotherapy appeared beneficial. Ann Neurol 2018;84:473–480

Paroxysmal sneezing in NMOSD: Further evidence of the localization of the human sneeze center

Intractable nausea, vomiting, and hiccups are characteristic symptoms associated with neuromyelitis optica spectrum disorder (NMOSD) as the result of immune-mediated lesions affecting the area postrema and medullary floor of the fourth ventricle. Reports of paroxysmal sneezing as part of the NMOSD phenotype are rare. We present a case of a patient who developed symptoms of NMOSD associated with prominent paroxysmal sneezing as a heralding symptom. The precise location of the human sneeze center has not been identified; this case provides further evidence for its location in the dorsolateral medulla as previously proposed.1