Diagnosing progressive multifocal leukoencephalopathy: Positive predictive value of CSF JC virus quantitative PCR and importance of recognizing suggestive neuroimaging findings.

Objective: To determine the positive predictive value (PPV) of CSF John Cunningham virus (JCV) quantitative PCR (qPCR) for progressive multifocal leukoencephalopathy (PML), and highlight neuroimaging findings reported to be suggestive of this disease.

Methods: We reviewed patients at London Health Sciences Centre with a positive CSF JCV qPCR result. Patients were classified as true-positive if they had a clinico-radiographic presentation compatible with PML and no more likely alternative diagnosis.

Low Yield of Routine Cerebrospinal Fluid Analysis to Assess for An Autoimmune Etiology in Patients with Chronic Seizures of Unknown Cause.

In this study, we examined the yield of routine cerebrospinal fluid (CSF) analysis to assess for an autoimmune etiology in patients with chronic seizures of unknown cause. Forty-seven patients were included. Six of 47 (13%) had inflammation on routine CSF analysis, none of whom were diagnosed with seizures related to autoimmune encephalitis (AE).

Autoimmune-associated seizure disorders.

With the discovery of an expanding number of neural autoantibodies, autoimmune etiologies of seizures have been increasingly recognized. Clinical phenotypes have been identified in association with specific underlying antibodies, allowing an earlier diagnosis. These phenotypes include faciobrachial dystonic seizures with LGI1 encephalitis, neuropsychiatric presentations associated with movement disorders and seizures in NMDA-receptor encephalitis, and chronic temporal lobe epilepsy in GAD65 neurologic autoimmunity.

Case report: Headache as the sole neurological symptom in autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy.

Autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy is a recently emerging autoimmune disease of the central nervous system (CNS); GFAP astrocytopathy is characterized by optic neuritis and meningoencephalomyelitis. We report the case of a 55-year-old man, otherwise healthy, who presented with isolated headaches for three months, without other features of meningoencephalitis or myelitis. His neurological examination and fundoscopy were unremarkable.

Myelin oligodendrocyte glycoprotein antibody titers by fixed cell-based assay: positive predictive value and impact of sample collection timing.

Introduction: In January 2023, our laboratory began performing serum myelin oligodendrocyte glycoprotein antibody (anti-MOG) titers by fixed cell-based assay (CBA). As a quality assurance (QA) assessment, we evaluated titer positive predictive value (PPV) as well as impact of sample collection timing on titers.

Methods: Among patients who underwent antibody titers to distinguish between low-positive (<1:100) and clear-positive (≥1:100) anti-MOG, records were reviewed to classify results as true-positive (TP) or false-positive (FP) and facilitate PPV calculation.

Optimizing the diagnostic performance of neural antibody testing for paraneoplastic and autoimmune encephalitis in clinical practice.

The detection of neural antibodies in patients with paraneoplastic and autoimmune encephalitis has majorly advanced the diagnosis and management of neural antibody-associated diseases. Although testing for these antibodies has historically been restricted to specialized centers, assay commercialization has made this testing available to clinical chemistry laboratories worldwide. This improved test accessibility has led to reduced turnaround time and expedited diagnosis, which are beneficial to patient care.

Antibodies to neural cell surface and synaptic proteins in paraneoplastic neurologic syndromes.

Among patients with paraneoplastic neurologic syndromes (PNS), emphasis has historically been placed on neural antibodies against intracellular proteins that have a strong association with malignancy. Because of the intracellular location of their antigenic targets, these antibodies are typically considered to be non-pathogenic surrogate markers of immune cell-mediated neural injury. Unfortunately, patients with these antibodies often have suboptimal response to immunotherapy and poor prognosis.

Exclusion of alternative diagnoses: A component of the 2023 MOGAD criteria that belongs at the forefront, not in the background.

A recent study evaluating the diagnostic performance of the 2023 MOGAD criteria found that it had relatively low specificity. However, this study did not apply the component of these criteria that requires exclusion of alternative diagnoses (item C) when evaluating its performance, raising questions surrounding the relevance of the study's findings to the use of these criteria in routine practice. This correspondence acknowledges the challenge of clinically applying this component of diagnostic criteria, discusses what exclusion of alterative diagnoses actually entails conceptually, and emphasizes the importance of its inclusion in future studies aimed at evaluating the performance of proposed criteria.

Positive predictive value of myositis antibody line blot testing in patients with suspected idiopathic inflammatory myopathy.

Introduction/aims: Line blot (LB) is in widespread use for myositis antibody detection. Yet, studies of its positive predictive value (PPV) in patients with suspected idiopathic inflammatory myopathy (IIM), which would be of particular relevance to neuromuscular clinicians, are lacking. We aimed to determine the PPV of myositis antibody LB testing in patients with suspected IIM, and examine whether PPV was significantly impacted by intensity of antibody positivity.

Canadian Consensus Guidelines for the Diagnosis and Treatment of Autoimmune Encephalitis in Adults.

Autoimmune encephalitis is increasingly recognized as a neurologic cause of acute mental status changes with similar prevalence to infectious encephalitis. Despite rising awareness, approaches to diagnosis remain inconsistent and evidence for optimal treatment is limited. The following Canadian guidelines represent a consensus and evidence (where available) based approach to both the diagnosis and treatment of adult patients with autoimmune encephalitis.

Evaluating yield and utilization of ganglioside antibody testing in clinical practice.

Background And Objectives: Ganglioside antibodies can help diagnose distinct acute and chronic inflammatory neuropathies including axonal variants of Guillain-Barre syndrome, Miller-Fisher syndrome (MFS), multifocal motor neuropathy, and chronic sensory ataxic neuropathies. Because ganglioside antibody testing may be routinely ordered in patients with suspected inflammatory neuropathy, we sought to evaluate its yield and utilization in clinical practice.

Methods: We performed a retrospective chart review of all patients at London Health Sciences Centre who underwent ganglioside antibody testing between April 2019 and August 2023.

Teaching NeuroImage: Unilateral Primary Angiitis of the CNS.

A 48-year-old woman was referred with an 18-year history of focal-onset seizures. She also reported years-long slowly progressive right-sided weakness that was corroborated on examination. Repeated brain MRIs over 15 years showed multifocal left hemispheric T2 fluid-attenuated inversion recovery-hyperintense lesions with patchy enhancement and microhemorrhages, no diffusion restriction, and a left cerebellar infarct (Figure 1, A-F).