Metabolic and Toxic Myelopathies

OBJECTIVE

This article reviews the clinical presentation, diagnostic evaluation, and treatment of metabolic and toxic myelopathies resulting from nutritional deficiencies, environmental and dietary toxins, drugs of abuse, systemic medical illnesses, and oncologic treatments.

LATEST DEVELOPMENTS

Increased use of bariatric surgery for obesity has led to higher incidences of deficiencies in nutrients such as vitamin B12 and copper, which can cause subacute combined degeneration. Myelopathies secondary to dietary toxins including konzo and lathyrism are likely to become more prevalent in the setting of climate change leading to drought and flooding. Although modern advances in radiation therapy techniques have reduced the incidence of radiation myelopathy, patients with cancer are living longer due to improved treatments and may require reirradiation that can increase the risk of this condition. Immune checkpoint inhibitors are increasingly used for the treatment of cancer and are associated with a wide variety of immune-mediated neurologic syndromes including myelitis.

ESSENTIAL POINTS

Metabolic and toxic causes should be considered in the diagnosis of myelopathy in patients with particular clinical syndromes, risk factors, and neuroimaging findings. Some of these conditions may be reversible if identified and treated early, requiring careful history, examination, and laboratory and radiologic evaluation for prompt diagnosis.

Consensus Competencies for Postgraduate Fellowship Training in Global Neurology

BACKGROUND AND OBJECTIVES

Use a modified Delphi approach to develop competencies for neurologists completing ≥1 year of advanced global neurology training.

METHODS

An expert panel of 19 United States-based neurologists involved in global health was recruited from the American Academy of Neurology Global Health Section and the American Neurological Association International Outreach Committee. An extensive list of global health competencies was generated from review of global health curricula and adapted for global neurology training. Using a modified Delphi method, United States-based neurologists participated in 3 rounds of voting on a survey with potential competencies rated on a 4-point Likert scale. A final group discussion was held to reach consensus. Proposed competencies were then subjected to a formal review from a group of 7 neurologists from low- and middle-income countries (LMICs) with experience working with neurology trainees from high-income countries (HICs) who commented on potential gaps, feasibility, and local implementation challenges of the proposed competencies. This feedback was used to modify and finalize competencies.

RESULTS

Three rounds of surveys, a conference call with United States-based experts, and a semistructured questionnaire and focus group discussion with LMIC experts were used to discuss and reach consensus on the final competencies. This resulted in a competency framework consisting of 47 competencies across 8 domains: (1) cultural context, social determinants of health and access to care; (2) clinical and teaching skills and neurologic medical knowledge; (3) team-based practice; (4) developing global neurology partnerships; (5) ethics; (6) approach to clinical care; (7) community neurologic health; (8) health care systems and multinational health care organizations.

DISCUSSION

These proposed competencies can serve as a foundation on which future global neurology training programs can be built and trainees evaluated. It may also serve as a model for global health training programs in other medical specialties as well as a framework to expand the number of neurologists from HICs trained in global neurology.

Clinical Features and Diagnosis of Intramedullary Spinal Cord Abscess in Adults: A Systematic Review

BACKGROUND AND OBJECTIVES

Intramedullary spinal cord abscess (ISCA) was described 200 years ago but remains poorly understood and is often mistaken for immune-mediated or neoplastic processes. We present a systematic review of ISCA in adults, describing the clinical presentation, diagnostic features, treatment strategies, and outcomes.

METHODS

Database searches for intramedullary abscess were performed on April 15, 2019, and repeated on February 9, 2022, using PubMed and EMBASE with 2 unpublished cases also included. Publications were independently reviewed for inclusion by 2 authors followed by adjudication. Data were abstracted using an online form and then analyzed for predictors of disability.

RESULTS

A total of 202 cases were included (median age 45 years [interquartile range 31-58]; 70% male). Thirty-one percent of those affected had no identified predisposing condition. The most common symptom was weakness (97%), and the median symptom duration before presentation was 10 days (interquartile range 5-42). An MRI showed restricted diffusion in 100% of 8 cases where performed and enhancement in 99% of 153 cases where performed. The most common organisms were Mycobacterium tuberculosis (29%), Streptococcus sp. (13%), and Staphylococcus sp. (10%). All patients received antimicrobial therapy; surgical drainage was performed in 65%. At follow-up (median 6 months), 12% had died, 69% were ambulatory, and 77% had improved compared with clinical nadir. Of those who underwent operative intervention, surgery within 24 hours of diagnosis was associated with an increased likelihood of being ambulatory at follow-up compared with surgery after 24 hours (odds ratio 4.44; 95% CI 1.26-15.61; p = 0.020).

DISCUSSION

ISCA is important to consider in any patient presenting with acute-to-subacute, progressive myelopathy. Immunocompromise and typical signs of infection (e.g., fever) are often absent. Diffusion restriction and gadolinium enhancement on MRI seem to be sensitive. Antimicrobial therapy with surgical drainage is the most common therapeutic approach, but morbidity remains substantial. If performed, urgent surgery may be more beneficial.

The case of a 49-year-old man with involuntary toe movements

A 49-year-old man presented with 3 years of leg pain and involuntary toe movements. He described the pain as mild burning, radiating from the left foot upward to the leg. On examination, there were involuntary continuous flexion-extension movements of his left toes (video). Strength, sensation, and reflexes were normal. Lumbosacral MRI demonstrated diffuse degenerative disc disease with multi-level mild-to-moderate foraminal stenosis. Nerve conduction studies were normal. EMG showed neurogenic potentials and active denervation changes in the left anterior tibial and soleus muscles consistent with radiculopathy. The diagnosis of painful legs and moving toes is discussed.

Historical Perspectives on the Neurologic Manifestations of Viral Pandemics

Neurologic symptoms have been reported in over 30% of hospitalized patients with coronavirus disease 2019 (COVID-19), but the pathogenesis of these symptoms remains under investigation. Here, we place the neurologic complications of COVID-19 within the context of three historical viral pandemics that have been associated with neurologic diseases: (1) the 1918 influenza pandemic, subsequent spread of encephalitis lethargica, and lessons for the study of COVID-19-related neuroinflammation; (2) the controversial link between the 1976 influenza vaccination campaign and Guillain-Barré Syndrome and its implications for the post- and parainfectious complications of COVID-19 and COVID-19 vaccination; and (3) potential applications of scientific techniques developed in the wake of the human immunodeficiency virus pandemic to the study of postacute sequelae of COVID-19.

A 47-Year-Old Man Presenting With Seizures and Prior Stroke

A 47-year-old man presented to his local hospital in Peru after a generalized tonic-clonic seizure. His family reported a history of prior stroke of unclear etiology. This case report discusses the approach to a first seizure (including in tropical regions like Peru), the relationship between stroke and seizures, the approach to stroke in the young, and how to diagnose rare diseases in resource-limited settings.

Engaging teaching strategies in neurology: the flipped classroom and simulation training

Just as neurology continues to expand its diagnostic and therapeutic modalities, so too does neurology education continue to expand in its pedagogical modalities. In this article, we describe two educational techniques-the flipped classroom and simulation-that we have incorporated in our teaching of neurology to students and doctors in training, with some practical tips for their successful implementation.

Clinical Problem-Solving: 72-Year-Old Woman With Multifocal Strokes and an Intracardiac Mass

We present the case of a 72-year-old female with multifocal strokes found to have multiple, mobile intracardiac masses. We discuss the differential diagnosis and evaluation of intracardiac masses, and the challenges in management of the ultimately diagnosed etiology of stroke in this patient.

Beyond electives: Rethinking training in global neurology

Global health electives in neurology residencies provide opportunities for high-income country trainees, but have limited benefits-and may create burdens-for lower-income country hosts. Current suspension of global health electives for U.S. neurology residents due to the COVID-19 pandemic provides an opportunity to reflect on ways to reimagine global health education during this period and beyond. The framework proposed in this article underscores the need for equitable, bidirectional international partnerships and highlights global health educational innovations developed during the pandemic.

Approach to Neurologic Infections

PURPOSE OF REVIEW

This article provides an overview of the clinical approach to the diagnosis of neurologic infections, focusing on the symptoms, signs, imaging features, and laboratory findings of the major categories of neuroinfectious diseases.

RECENT FINDINGS

The increased use of immunosuppressive and immunomodulatory therapy to treat autoimmune diseases has led to an increase in opportunistic neurologic infections. The description of numerous causes of autoimmune antibody-mediated encephalitis over the past decade has expanded the differential diagnosis of encephalitis beyond infection. The emergence of metagenomic next-generation sequencing has led to diagnoses of rare or unexpected causes of neurologic infections and has the potential to enhance diagnostic precision in neuroinfectious diseases.

SUMMARY

Infections of the nervous system can affect any level of the neuraxis and present over any time course. Neurologic infections may present atypically with respect to clinical, radiologic, and CSF analysis features in immunocompromised patients or older adults. A thorough evaluation including systemic features, past medical history, travel, exposures, detailed examination, neuroimaging, and CSF analysis is often necessary to make a definitive diagnosis. It is important to be aware of the test characteristics and limitations of microbiological tests on CSF for neurologic infections to avoid being misled by false positives or false negatives.

Meningitis

PURPOSE OF REVIEW

This article reviews the diagnosis and treatment of infectious meningitis, including updates on newer molecular diagnostic techniques for microbiological diagnosis.

RECENT FINDINGS

New polymerase chain reaction (PCR)-based molecular diagnostic techniques have improved the timeliness of microbiological diagnosis in meningitis, but clinicians must be aware of the limitations of such tests. Next-generation sequencing can now be applied to CSF, allowing for diagnosis of infections not identifiable by conventional means.

SUMMARY

Infectious meningitis can be caused by a broad range of organisms. The clinician must be aware of the test characteristics of new molecular techniques for microbiological diagnosis as well as traditional techniques to tailor antimicrobial therapy appropriately in patients with meningitis.

Clinical-Radiologic Dissociation in Post-traumatic Syringomyelia

Post-traumatic syringomyelia develops years to decades after spinal trauma in up to 28% of patients. We report a case of a man who developed extensive syringomyelia 14 years after spinal trauma, but had only minimal symptoms. Presumed pathophysiology of this condition and options for surgical management are briefly reviewed.

Metabolic and Toxic Myelopathies

Metabolic and toxic causes of myelopathy form a heterogeneous group of disorders. In this review, we discuss the causes of metabolic and toxic myelopathies with respect to clinical presentation, pathophysiology, diagnostic testing, treatment, and prognosis. This review is organized by temporal course (hyperacute, acute, subacute, and chronic) and etiology (e.g., nutritional deficiency, toxic exposure). Broadly, the myelopathies associated with dietary toxins (neurolathyrism, konzo) and decompression sickness present suddenly (hyperacute). The myelopathies associated with heroin use and electrical injury present over hours to days (acutely). Most nutritional deficiencies (cobalamin, folate, copper) and toxic substances (nitrous oxide, zinc, organophosphates, clioquinol) cause a myelopathy of subacute onset. Vitamin E deficiency and hepatic myelopathy cause a chronic myelopathy. Radiation- and intrathecal chemotherapy-induced myelopathy can cause a transient and/or a progressive syndrome. For many metabolic and toxic causes of myelopathy, clinical deficits may stabilize or improve with rapid identification and treatment. Familiarity with these disorders is therefore essential.

Antiepileptic Drug Management in Hospitalized Epilepsy Patients With Nil Per Os Diets: A Retrospective Review

Background and Purpose

Antiepileptic drug (AED) management in patients with epilepsy who cannot take their usual oral medications is a common neurologic dilemma in the hospital setting. Strategies to maintain seizure control in patients with nil per os (NPO, nothing by mouth) diet orders include continuation of oral AEDs despite NPO nutrition orders, administration of intravenous AED(s), or temporary administration of benzodiazepines. The frequency with which these strategies are used and their effectiveness in preventing in-hospital seizures is unknown.

Methods

We conducted a retrospective cohort study to determine AED management strategies and seizure frequency in hospitalized epilepsy patients with NPO diet status admitted to an academic medical center between 2001 and 2016. Clinical documentation was reviewed. Antiepileptic drug selection (medication and route of administration) and presence or absence of seizures were recorded.

Results

We identified 199 admissions during which epilepsy patients had NPO diet orders. Antiepileptic drug management strategies included continuation of oral medications (50.3% of admissions), intravenous AED monotherapy (22.1%), intravenous AED polytherapy (12.6%), benzodiazepines (1.0%), holding AEDs (4.5%), or a combination (9.5%). Seizures occurred during 14 admissions. Treatment with AED polytherapy prior to admission and changing the patient's AED regimen during admission were associated with increased odds of seizures during admission (P = .0028; P = .0114).

Conclusions

These results suggest that patients' home oral AED regimens should be continued when possible in order to minimize the frequency of seizures during hospitalizations.

The Many Faces of Neurocysticercosis

Neurocysticercosis (NCC) is the most common parasitic disease of the central nervous system, and one of the most common causes of epilepsy worldwide. The radiologic appearance of neurocysticercosis varies depending on the stage of the disease, and the stage of the disease determines the appropriate treatment. In this article, we review key neuroimaging characteristics of the stages of NCC (vesicular, colloidal, granular, and calcified) and treatment principles for these different stages of the disease.

Neurology Training Worldwide

Neurology training is essential for providing neurologic care globally. Large disparities in availability of neurology training exist between higher- and lower-income countries. This review explores the worldwide distribution of neurology training programs and trainees, the characteristics of training programs in different parts of the world, and initiatives aimed at increasing access to neurology training in under-resourced regions.

Paraneoplastic Neuromyelitis Optica Spectrum Disorder as Presentation of Esophageal Adenocarcinoma

Neuromyelitis optica spectrum disorders are a group of relapsing, inflammatory, demyelinating neurologic syndromes involving the central nervous system associated with antibodies against aquaporin-4. Although most commonly an idiopathic autoimmune condition, neuromyelitis optica may occur as a paraneoplastic syndrome in rare instances. We report a case of transverse myelitis caused by paraneoplastic neuromyelitis optica as the presenting clinical syndrome in a patient with esophageal adenocarcinoma.

Glioblastoma arising within sites of encephalomalacia from cerebrovascular insult: two cases and a review of the literature

Glioblastoma is the most common primary parenchymal brain malignancy, with median survival of less than one year. While there are likely multiple predisposing genetic and environmental factors in glioblastoma formation, chronic inflammation resulting from non-traumatic vascular brain injury is one proposed risk factor for oncogenesis. Here, we report two instances of glioblastoma arising within areas of encephalomalacia caused by remote vascular insults (one following aneurysmal subarachnoid hemorrhage and one following ischemic infarction), review the literature associating glioblastoma with prior brain injury, and discuss potential mechanisms for malignant transformation in injured brain tissue.

Head CT findings at a public hospital in rural Haiti

BACKGROUND

Neuroimaging is often unavailable in low-income countries, creating challenges for precise diagnosis of neurologic disease in individual patients, and impeding acquisition of precise neuroepidemiologic data for program and policy development.

METHODS

We analyzed reports from 3614 head CTs performed between July 2013 and January 2016 at Hôpital Universitaire de Mirebalais, a public academic hospital in rural Haiti, extracting patients' age, study indication, and radiologic findings.

RESULTS

The most common indications for head CT were headache (27%), trauma (19.9%), abnormal neurological exam (12.2%), and stroke (11.3%). The most common categories of neurologic abnormalities were traumatic (31%), vascular (25.8%), and infectious (12%). Of 291 strokes, 64% were ischemic (median age at diagnosis 60.8years, SD 17.4) and 36% were hemorrhagic (median age 52.0, SD 15.5). In patients undergoing head CT for seizures or epilepsy, 17.5% had evidence of neurocysticercosis. In patients with head trauma, 42.6% had intracranial hemorrhage or fracture. Atrophy was noted on 10% of CTs (median age 57.1; SD 23.8), and was characterized as out of proportion to age in 2% (median age 34.1, SD 15.3).

CONCLUSIONS

Median age of stroke patients in this rural low-income population is lower than in high-income countries and proportion of stroke due to intracerebral hemorrhage is higher. Neurocysticercosis is present in nearly one fifth of patients with seizures/epilepsy. These findings can inform policies and programs for prevention and treatment of neurologic disease in low-income settings.

What to do when patients with epilepsy cannot take their usual oral medications

When people with epilepsy are hospitalised for medical or surgical conditions, they may be unable to take their home antiepileptic drugs (AEDs). Such 'nil by mouth' people with epilepsy require alternative AED regimens to prevent breakthrough seizures. Here, we describe several strategies for maintaining seizure control in patients with epilepsy who have medical or surgical contraindications to their home oral regimens. These strategies include using non-pill oral formulations, using an intravenous formulation of the patient's home AED(s), using a benzodiazepine bridge and/or using alternative intravenous AED(s) when there are no intravenous formulations.

Availability, accessibility, and affordability of neurodiagnostic tests in 37 countries

OBJECTIVE

To determine the availability, accessibility, and affordability of EEG, EMG, CSF analysis, head CT, and brain MRI for neurologic disorders across countries.

METHODS

An online, 60-question survey was distributed to neurology practitioners in 2014 to assess the presence, wait time, and cost of each test in private and public health sectors. Data were stratified by World Bank country income group. Affordability was calculated with reference to the World Health Organization's definition of catastrophic health expenditure as health-related out-of-pocket expenditure of >40% of disposable household income, and assessment of providers' perceptions of affordability to the patient.

RESULTS

Availability of EEG and EMG is correlated with higher World Bank income group (correlation coefficient 0.38, test for trend p = 0.046; 0.376, p = 0.043); CSF, CT, and MRI did not show statistically significant associations with income groups. Patients in public systems wait longer for neurodiagnostic tests, especially MRI, EEG, and urgent CT (p < 0.0001). The mean cost per test, across all tests, was lower in the public vs private sector (US $55.25 vs $214.62, p < 0.001). Each drop in World Bank income group is associated with a 29% decrease in the estimated share of the population who can afford a given test (95% confidence interval -33.4, 25.2; p < 0.001). In most low-income countries surveyed, only the top 10% or 20% of the population was able to afford tests below catastrophic levels. In surveyed lower-middle-income countries, >40% of the population, on average, could not afford neurodiagnostic tests.

CONCLUSIONS

Neurodiagnostic tests are least affordable in the lowest income settings. Closing this "diagnostic gap" for countries with the lowest incomes is essential.