Gilligan, Michael

ABSTRACT Objective We sought to characterize the sixth most common finding in our neuroimmunological laboratory practice (tissue assay‐observed unclassified neural antibodies [UNAs]), combining protein microarray and phage immunoprecipitation sequencing (PhIP‐Seq). Methods Patient specimens (258; 133 serums; 125 CSF) meeting UNA criteria were profiled; October 2022–September 2023. Top‐ranking candidate antigens were validated in silico, by dual‐staining confocal microscopy, and ≥ 1 protein‐specific assay. Clinical data were reviewed. Results Among 21 patients, 11 autoantibodies were characterized (serum, 19; CSF, all 9 available). Autoantigens were CACNA1I, 1; CAMK2B, 2; CLIP2, 1; FMN2, 2; MAP1A, 2; MAP2, 5; NECAB1, 1; SNAP91, 3; SRCIN1, 1; SYNJ1, 1; SYT3, 2. Analytical validation was by confocal TIIFA (all), western blot (10/10 available), and cell‐based assay (5/5 performed). Clinical accompaniments were: encephalitis, 6; brainstem encephalitis, 2; encephalomyelitis, 2; cerebellar ataxia, 2; longitudinally extensive transverse myelitis (LETM), 2; sensory neuronopathy, 1; peripheral neuropathy, 4, and movement disorders, 2. Inflammatory MRI abnormalities were identified in 5/16 patients (31%) with CNS disorders: T2 signal change (2), LETM (2), leptomeningeal enhancement (1). Seven of 8 (88%) had inflammatory CSF (pleocytosis, 5 [median 25.5 cells, range 7–294]; elevated IgG index/synthesis rate, 4; CSF‐exclusive oligoclonal bands, 4). Six had paraneoplastic causation (lung cancer, 2; other, 4); 3 were postinfectious (1 each of COVID‐19, HSV‐1, and post‐Group A streptococcal infection). Of 9 immunotherapy‐treated patients, 5 improved. Interpretation UNAs are partly accounted for by a repertoire of diverse mostly intracellular synaptic antigens. Their characterization is expedited by protein arrays and PhIPSeq. Further individual studies are needed to assess them as disease biomarkers.

Background Data regarding long-term recovery from autoimmune encephalitis (AE) remain limited. Methods This retrospective observational study investigated outcomes in 182 patients who met the 2016 criteria for definite AE. Recovery data were available in 172 patients. Follow-up data at ≥24 months post-attack were available for 119. Recovery trajectory, residual symptoms, outcome predictors and causes of post-AE death were assessed. Results Of 172 patients, 138 (80%) achieved good recovery (modified Rankin Scale (mRS) ≤2) with a median recovery time of 4 months (95% CI: 2 to 6 months). Recovery varied by associated neural antibody, with the best recovery observed in leucine-rich glioma-inactivated 1 (97% good recovery, median recovery time 0 (0 to 2) months). Paraneoplastic AE (p=0.007), severe attacks (eg, mRS ≥4 at attack, p=0.007) and cerebrospinal fluid pleocytosis (p=0.005) were associated with a lower likelihood of good recovery, while seizure presentation (p=0.026) was associated with better recovery. Despite good recovery, several residual symptoms persisted ≥24 months post-AE, including cognitive deficits (53%), seizures (26%), depression (23%), sleep disorders (25%), brainstem/cerebellar symptoms (13%), other movement disorders (14%) and autonomic symptoms (12%). Predictors of long-term sequelae included disabling cognitive deficit at onset and delayed immunotherapy for post AE-dementia, and medial temporal atrophy as well as escalation to cyclophosphamide therapy for both drug-resistant epilepsy and chronic depression. Of 182 patients, 20 (11%) died; the most common cause of death was progression of AE (6/20 (30%)). Conclusion While the majority of patients achieved functional independence after AE, several residual symptoms persisted. Several clinical and paraclinical features were associated with long-term sequelae.

AbstractObjectiveWe describe neurologic phenotype, clinical associations, and outcomes in autoimmune brainstem encephalitis.MethodsMedical records of neural‐IgG positive autoimmune brainstem encephalitis patients diagnosed at Mayo Clinic (January 1, 2006–December 31, 2022) were reviewed.ResultsNinety‐eight patients (57 male) were included. Median age of symptom onset was 51 years (range, 8 months‐85 years). Frequent presenting features were ≥1: diplopia (80%), ataxia (78%), dysarthria (68%), vestibulocochlear symptoms (67%), dysphagia (61%), nausea/vomiting (42%), and facial weakness (32%). Altered mental status (11%) was uncommon. Neural antibodies detected were as follows: KLHL‐11 (26 patients), GAD65 (high titer, 12), ANNA‐1 (anti‐Hu, 8), ANNA‐2 (anti‐Ri, 8), Ma2 (7), IgLON‐5 (6), AQP4 (6), MOG (4), glycine receptor (4), GQ1B (4), PCA‐1 (anti‐Yo, 4), DPPX (2), neurochondrin (2), neurofilament (2), NMDA‐R (2), AGNA‐1 (SOX‐1, 1), ANNA‐3 (DACH1, 1), amphiphysin (1), CRMP‐5 (1), ITPR‐1 (1), PCA‐Tr (DNER, 1), and PDE10A (1). Cancer was identified in 55 patients: germ cell (23 patients; 3 extra‐testicular), ductal breast adenocarcinoma (8), small cell carcinoma (6, lung 4), adenocarcinomas (6), neuroendocrine carcinoma (3), hematologic (2), squamous cell (2), and other (7). Median modified Ranking score (mRS) at last follow‐up was 3 (range, 0–6). Factors associated with poor outcome included abnormal brain MRI, bulbar symptoms, and elevated CSF IgG index. Kaplan–Meier analysis revealed faster progression to wheelchair in patients who were immunotherapy refractory and with elevated CSF IgG index. Diagnostic criteria for autoimmune brainstem encephalitis (definite and probable) are proposed.InterpretationAutoimmune brainstem encephalitis is a distinct clinical subphenotype of autoimmune encephalitis. Abnormal brain MRI, bulbar symptoms, and elevated CSF‐IgG index associate with poor outcome.

AbstractBackgroundThere are more than 30 immunoglobulin G (IgG) autoantibody biomarkers of autoimmune cerebellar ataxia reported.ObjectiveTo describe a novel IgG biomarker targeting neurobeachin, a scaffolding protein integral to synapse formation and function.MethodsClinical and laboratory‐based assessment was used for a novel diagnostic biomarker of autoimmune ataxia.ResultsA 46‐year‐old woman had ataxia onset followed by bilateral knee pain, attributable to rheumatoid arthritis. She was negative for standard neural antibodies. Her ataxia stabilized and tremor initially improved after corticosteroid treatment, but she progressed to wheelchair‐dependence (on methotrexate and then rituximab) over 4 years, in keeping with the trajectory encountered by many with autoimmune ataxia. In contrast, her inflammatory arthritis remitted with immunotherapy. Neurobeachin‐IgG was unmasked in serum and cerebrospinal fluid using protein arrays and confirmed using neurobeachin‐specific confocal immunofluorescence and Western blot.ConclusionsNeurobeachin‐IgG is a new neural antibody biomarker of cerebellar ataxia among a growing antibody repertoire, collectively common but often individually rare. © 2024 International Parkinson and Movement Disorder Society.

ObjectivesTo report an autoimmune paraneoplastic encephalitis characterized by immunoglobulin G (IgG) antibody targeting synaptic protein calmodulin kinase‐like vesicle‐associated (CAMKV).MethodsSerum and cerebrospinal fluid (CSF) samples harboring unclassified antibodies on murine brain‐based indirect immunofluorescence assay (IFA) were screened by human protein microarray. In 5 patients with identical cerebral IFA staining, CAMKV was identified as top‐ranking candidate antigen. Western blots, confocal microscopy, immune‐absorption, and mass spectrometry were performed to substantiate CAMKV specificity. Recombinant CAMKV‐specific assays (cell‐based [fixed and live] and Western blot) provided additional confirmation.ResultsOf 5 CAMKV‐IgG positive patients, 3 were women (median symptom‐onset age was 59 years; range, 53–74). Encephalitis‐onset was subacute (4) or acute (1) and manifested with: altered mental status (all), seizures (4), hyperkinetic movements (4), psychiatric features (3), memory loss (2), and insomnia (2). Paraclinical testing revealed CSF lymphocytic pleocytosis (all 4 tested), electrographic seizures (3 of 4 tested), and striking MRI abnormalities in all (mesial temporal lobe T2 hyperintensities [all patients], caudate head T2 hyperintensities [3], and cortical diffusion weighted hyperintensities [2]). None had post‐gadolinium enhancement. Cancers were uterine adenocarcinoma (3 patients: poorly differentiated or neuroendocrine‐differentiated in 2, both demonstrated CAMKV immunoreactivity), bladder urothelial carcinoma (1), and non‐Hodgkin lymphoma (1). Two patients developed encephalitis following immune checkpoint inhibitor cancer therapy (atezolizumab [1], pembrolizumab [1]). All treated patients (4) demonstrated an initial response to immunotherapy (corticosteroids [4], IVIG [2]), though 3 died from cancer.InterpretationCAMKV‐IgG is a biomarker of immunotherapy‐responsive paraneoplastic encephalitis with temporal and extratemporal features and uterine cancer as a prominent oncologic association. ANN NEUROL 2024;96:21–33

Objective The aim of this study was to assess the diagnostic utility of cerebrospinal fluid (CSF) myelin oligodendrocyte glycoprotein antibodies (MOG‐IgG) testing. Methods We retrospectively identified patients for CSF MOG‐IgG testing from January 1, 1996, to May 1, 2023, at Mayo Clinic and other medical centers that sent CSF MOG‐IgG for testing including: controls, 282; serum MOG‐IgG positive MOG antibody‐associated disease (MOGAD), 74; serum MOG‐IgG negative high‐risk phenotypes, 73; serum false positive MOG‐IgG with alternative diagnoses, 18. A live cell‐based assay assessed CSF MOG‐IgG positivity (IgG‐binding‐index [IBI], ≥2.5) using multiple anti‐human secondary antibodies and end‐titers were calculated if sufficient sample volume. Correlation of CSF MOG‐IgG IBI and titer was assessed. Results The pan‐IgG Fc‐specific secondary was optimal, yielding CSF MOG‐IgG sensitivity of 90% and specificity of 98% (Youden's index 0.88). CSF MOG‐IgG was positive in: 4/282 (1.4%) controls; 66/74 (89%) serum MOG‐IgG positive MOGAD patients; and 9/73 (12%) serum MOG‐IgG negative patients with high‐risk phenotypes. Serum negative but CSF positive MOG‐IgG accounted for 9/83 (11%) MOGAD patients, and all fulfilled 2023 MOGAD diagnostic criteria. Subgroup analysis of serum MOG‐IgG low‐positives revealed CSF MOG‐IgG positivity more in MOGAD (13/16[81%]) than other diseases with false positive serum MOG‐IgG (3/15[20%]) ( p = 0.01). CSF MOG‐IgG IBI and CSF MOG‐IgG titer (both available in 29 samples) were correlated (Spearman's r = 0.64, p < 0.001). Interpretation CSF MOG‐IgG testing has diagnostic utility in patients with a suspicious phenotype but negative serum MOG‐IgG, and those with low positive serum MOG‐IgG results and diagnostic uncertainty. These findings support a role for CSF MOG‐IgG testing in the appropriate clinical setting. ANN NEUROL 2024;96:34–45