Metabolic and Toxic Myelopathies

Multiple Sclerosis and Other Acquired Demyelinating Diseases of the Central Nervous System

Acquired demyelinating diseases of the central nervous system (CNS) comprise inflammatory conditions, including multiple sclerosis (MS) and related diseases, as well as noninflammatory conditions caused by toxic, metabolic, infectious, traumatic, and neurodegenerative insults. Here, we review the spectrum of diseases producing acquired CNS demyelination before focusing on the prototypical example of MS, exploring the pathologic mechanisms leading to myelin injury in relapsing and progressive MS and summarizing the mechanisms and modulators of remyelination. We highlight the complex interplay between the immune system, oligodendrocytes and oligodendrocyte progenitor cells (OPCs), and other CNS glia cells such as microglia and astrocytes in the pathogenesis and clinical course of MS. Finally, we review emerging therapeutic strategies that exploit our growing understanding of disease mechanisms to limit progression and promote remyelination.

Nitrous Oxide-Induced Vitamin B12 Deficiency and Myelopathy in Whippets Abusers: A Report of Two Cases

Whippets abuse, prevalent among recreational drug users, poses significant health risks, particularly through the inactivation of vitamin B12 by nitrous oxide (N2O). This deficiency can lead to myelopathy, resulting in serious neurological complications. We present two female patients, aged 22 and 35, with a history of regular whippet use over the past three years, who exhibited clinical symptoms of myelopathy, including motor weakness, rigidity, sensory changes, and gait abnormalities. The 35-year-old patient showed weakness and swelling in her legs; magnetic resonance imaging (MRI) revealed no acute findings, but lab results indicated a critically low serum vitamin B12 level (102 pg/mL), elevated homocysteine (44 µmol/L), and high methylmalonic acid (29,054 nmol/L). She improved with vitamin B12, vitamin D supplementation, and physical and occupational therapy. The 22-year-old patient reported progressive stiffness and tingling, with MRI revealing T2 hyperintensities in the brain and longitudinal T2 hyperintensities in the posterior spinal cord; her vitamin B12 level was 180 pg/mL, and she responded positively to supplementation and physical therapy. These cases underscore the risk of nitrous oxide-induced myelopathy associated with vitamin B12 deficiency among whippet users. Early recognition and intervention are essential to prevent irreversible neurological damage, and routine screening for vitamin B12 deficiency in this population is recommended. Further research is needed to explore the long-term implications of N2O abuse.

Longitudinally Extensive Transverse Myelitis in a Patient With Systemic Lupus Erythematosus: A Case Report and Literature Review

Longitudinally extensive transverse myelitis (LETM) is a rare but severe neurological complication of systemic lupus erythematosus (SLE). The existing literature contains only limited information about this condition. We present a case of a 38-year-old female with SLE who presented with quadriparesis. Magnetic resonance imaging (MRI) of the brain and spinal cord showed T2-weighted high signal intensity involving the brainstem, bilateral middle and inferior cerebellar peduncles, and C1-C7 spinal cord segments. Early intervention with high-dose methylprednisolone and cyclophosphamide was initiated, resulting in partial clinical recovery. A comprehensive literature review highlights the importance of early diagnosis and treatment, discusses the potential etiologies, and explores the prognostic factors influencing patient outcomes. This case report underscores the need for a high level of clinical suspicion and prompt therapeutic intervention to improve prognosis in SLE patients presenting with LETM.

Clinical Approach to Myelopathy Diagnosis

OBJECTIVE

This article describes an integrative strategy to evaluate patients with suspected myelopathy, provides advice on diagnostic approach, and outlines the framework for the etiologic diagnosis of myelopathies.

LATEST DEVELOPMENTS

Advances in diagnostic neuroimaging techniques of the spinal cord and improved understanding of the immune pathogenic mechanisms associated with spinal cord disorders have expanded the knowledge of inflammatory and noninflammatory myelopathies. The discovery of biomarkers of disease, such as anti-aquaporin 4 and anti-myelin oligodendrocyte glycoprotein antibodies involved in myelitis and other immune-related mechanisms, the emergence and identification of infectious disorders that target the spinal cord, and better recognition of myelopathies associated with vascular pathologies have expanded our knowledge about the broad clinical spectrum of myelopathies.

ESSENTIAL POINTS

Myelopathies include a group of inflammatory and noninflammatory disorders of the spinal cord that exhibit a wide variety of motor, sensory, gait, and sensory disturbances and produce major neurologic disability. Both inflammatory and noninflammatory myelopathies comprise a broad spectrum of pathophysiologic mechanisms and etiologic factors that lead to specific clinical features and presentations. Knowledge of the clinical variety of myelopathies and understanding of strategies for the precise diagnosis, identification of etiologic factors, and implementation of therapies can help improve outcomes.

Update in autoimmune and paraneoplastic myelopathies: Newly described antigen targets and antibody testing

Myelopathy is an increasingly recognized presentation of many antibody-mediated neuroinflammatory disorders. While specific features of certain autoimmune myelopathies such as aquaporin-4 antibody associated neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein associated disorder (MOGAD) are well-characterized, other less commonly seen antibody-associated myelopathies are not as well-defined. These include but are not limited to, Hu/ANNA1, anti-glial fibrillary acidic protein (GFAP), anti-CV2/collapsin response mediator protein (CRMP5), and amphiphysin. Here, we review the mentioned more common antibody mediated myelopathies as well those that as less common, followed by a review of differentials that may mimic these disorders.

Clinical Presentation of Subacute Combined Degeneration in a Patient With Chronic B12 Deficiency

BACKGROUND

Subacute combined degeneration (SCD) is a rare complication of chronic vitamin B12 deficiency that presents with a variety of neurologic findings, including decreased sensation in the extremities, increased falls, and visual changes. Treatment of SCD involves prompt replacement of vitamin B12 and addressing the underlying conditions that cause the deficiency. Given the prevalence of B12 deficiency in the older adult population, clinicians should remain alert to its possibility in patients who present with progressive neuropathy.

CASE PRESENTATION

This report presents a case of a patient with progressive SCD secondary to chronic B12 deficiency despite monthly intramuscular B12 injections.

CONCLUSIONS

Appropriate B12 replacement is aggressive and involves intramuscular B12 1000 mcg every other day for 2 to 3 weeks, followed by additional IM administration every 2 months before transitioning to oral therapy. Failure to adequately replenish B12 can lead to progression or lack of resolution of SCD symptoms.