A fatal demyelinating illness in a young woman 10 weeks post partum

Myelin in the Central Nervous System: Structure, Function, and Pathology

Oligodendrocytes generate multiple layers of myelin membrane around axons of the central nervous system to enable fast and efficient nerve conduction. Until recently, saltatory nerve conduction was considered the only purpose of myelin, but it is now clear that myelin has more functions. In fact, myelinating oligodendrocytes are embedded in a vast network of interconnected glial and neuronal cells, and increasing evidence supports an active role of oligodendrocytes within this assembly, for example, by providing metabolic support to neurons, by regulating ion and water homeostasis, and by adapting to activity-dependent neuronal signals. The molecular complexity governing these interactions requires an in-depth molecular understanding of how oligodendrocytes and axons interact and how they generate, maintain, and remodel their myelin sheaths. This review deals with the biology of myelin, the expanded relationship of myelin with its underlying axons and the neighboring cells, and its disturbances in various diseases such as multiple sclerosis, acute disseminated encephalomyelitis, and neuromyelitis optica spectrum disorders. Furthermore, we will highlight how specific interactions between astrocytes, oligodendrocytes, and microglia contribute to demyelination in hereditary white matter pathologies.

An Adult Case of Anti-Myelin Oligodendrocyte Glycoprotein (MOG) Antibody-associated Multiphasic Acute Disseminated Encephalomyelitis at 33-year Intervals

Acute disseminated encephalomyelitis (ADEM) followed by optic neuritis (ON) has been reported as a distinct phenotype associated with anti-myelin oligodendrocyte protein (MOG) antibody. We herein report the case of a 37-year-old woman who was diagnosed with ADEM at 4 years old of age and who subsequently developed ON followed by recurrent ADEM 33 years after the initial onset. A serum analysis showed anti-MOG antibody positivity. This phenotype has only previously been reported in pediatric cases. Neurologists thus need to be aware that the phenotype may occur in adult patients, in whom it may be assumed to be atypical multiple sclerosis.

Missing links in multiple sclerosis etiology. A working connecting hypothesis

The etiology of multiple sclerosis is still elusive despite an extended patchwork of mechanistic events has been accumulated. In this article, are tentatively identified from scattered literature sources new factors that may link well known characteristic of MS such as the central alteration of BBR selectivity, its association with EBV status and its biased distribution of the globe more comprehensively. The hypothesis proposes that the concomitant important rise in some heterophilic antibodies (anti Neu5Gc) which activate BBB endothelial cells and in the frequency of anti EBV committed T cells and of memory B infected cells with EBV contemporary to EBV infection play a major role in MS etiology. In addition, the hypothesis proposes new possible explanations for the elevated risk of MS in specific geographical area.

Marburg's disease: a diagnostic dilemma

This report describes the clinical, radiological and autopsy findings of a young male suffering from acute, monophasic demyelinating disease presenting with acute onset of altered sensorium and a short past history of progressive multiple neurological deficits. The radiological findings revealed acute infarcts in the territory of anterior cerebral artery. The antemortem diagnosis centred on an infective (tubercular) aetiology leading to demyelination based on presence of tubercle bacilli in bronchoalveolar lavage (BAL) fluid. The autopsy revealed multiple subacute and acute plaques showing demyelination, giant astrocytes, numerous macrophages and little perivascular inflammation, thereby confirming the diagnosis of Marburg's type of multiple sclerosis. Marburg's type is a fulminant demyelinating disorder characterised by a severe, rapidly evolving clinical course. Death occurs due to brain stem involvement or severe widespread cerebral lesions.

Perivenous demyelination: association with clinically defined acute disseminated encephalomyelitis and comparison with pathologically confirmed multiple sclerosis

Distinction between acute disseminated encephalomyelitis and acute multiple sclerosis is often clinically difficult. Perivenous demyelination is the pathological hallmark of acute disseminated encephalomyelitis, whereas confluent demyelination is the hallmark of acute multiple sclerosis. We investigated whether perivenous demyelination versus confluent demyelination distinguishes acute disseminated encephalomyelitis from multiple sclerosis. Patients with perivenous demyelination (n = 13; median age 43 years, range 5-67) on brain biopsy and/or autopsy, ascertained retrospectively, were compared with a cohort with confluent demyelination only (n = 91; 84% multiple sclerosis, 16% isolated syndrome at follow-up; median age 39 years, range 10-69). Clinical presentation, course and the International Paediatric Multiple Sclerosis Study Group clinical criteria for acute disseminated encephalomyelitis were assessed in both cohorts. Among the perivenous demyelination cohort, 10 patients had only perivenous demyelination and three also had confluent demyelination. All but one patient with perivenous demyelination only had a monophasic course, whereas two of three with both types had a relapsing course. The perivenous demyelination cohort was more likely than the confluent demyelination cohort to present with encephalopathy (P < 0.001), depressed level of consciousness (P < 0.001), headache (P < 0.001), meningismus (P = 0.04), cerebrospinal fluid pleocytosis (P = 0.04) or multifocal enhancing magnetic resonance imaging lesions (P < 0.001). A distinct pattern of cortical microglial activation and aggregation without associated cortical demyelination was found among six perivenous demyelination patients, all of whom had encephalopathy and four of whom had depressed level of consciousness. This pattern of cortical pathology was not observed in the confluent demyelination cohort, even in one patient with depressed level of consciousness. Clinical criteria were 80% sensitive and 91% specific for pathologically defined acute disseminated encephalomyelitis (perivenous demyelination), but misdiagnosed acute disseminated encephalomyelitis among 9% of patients with confluent demyelination and multiple sclerosis diagnosis at last follow-up. Perivenous demyelination is associated with meningoencephalopathic presentations and a monophasic course. Depressed level of consciousness is a more specific clinical criterion for pathologically confirmed acute disseminated encephalomyelitis than encephalopathy, which over-diagnosed acute disseminated encephalomyelitis among multiple sclerosis patients. A distinct pattern of cortical microglial activation without cortical demyelination may be the pathological correlate of depressed level of consciousness in acute disseminated encephalomyelitis. Although pathological evidence of perivenous demyelination may be superior to clinical criteria for diagnosing acute disseminated encephalomyelitis, the co-occurrence of perivenous and confluent demyelination in some individuals suggests pathogenic overlap between acute disseminated encephalomyelitis and multiple sclerosis and misclassification even with biopsy.

An autopsy case of acute multiple sclerosis (Marburg's type) during pregnancy

We report a case of a 9-month pregnant woman who presented acute psychiatric and neurological symptoms with extensive involvement of the white matter on MRI and no oligoclonal bands on CSF examination. Despite high doses of intravenous steroids, plasmapheresis and immunosuppressive drugs, a fatal outcome (coma) was noted 8 months later. Neuropathological examination confirmed the diagnosis of Marburg's type of multiple sclerosis showing sharp-edged lesions of demyelination, giant astrocytes, numerous macrophages and little perivascular inflammation. We discuss the definition and limits of the Marburg entity with reference to acute disseminated encephalomyelitis, impact of pregnancy, unusual MRI features, neuropathology and treatment.

Vasculitis and rheumatologic diseases may play role in the pathogenesis of acute disseminated encephalomyelitis (ADEM)

Acute disseminated encephalomyelitis (ADEM) is defined as a multifocal, monophasic, demyelinating, and inflammatory disease involving the central nervous system. It typically begins within 6 weeks of an antigenic challenge such as infection or immunization. Perivenous inflammation, edema and demyelination are the pathological hallmarks of ADEM. Reactivity of T-cells against myelin components such as myelin basic protein has been found in children with ADEM. The triggers for immune responses in ADEM are not known, but the two most widely accepted hypotheses are molecular mimicry and self-sensitization secondary to CNS infection. Inflammatory cytokines including tumor necrosis factor alpha (TNFalpha), interleukin 2 (IL2) and interferon gamma (INFgamma) are thought to be important in lesion formation in ADEM. Due to the active role of inflammatory cytokines in the pathogenesis of ADEM, any disease contributing to systemic formation of inflammatory cytokines can potentially be an etiologic factor for the initiation of ADEM. In vasculitis and rheumatologic diseases the number of T-cells, T helper type 1 cytokines and other inflammatory cytokines such as TNFalpha increase substantially. We present this hypothesis that in such setting of inflammation, adhesion molecules are up-regulated on the brain capillary endothelium by cytokines and other inflammatory mediators, altering the permeability of the brain blood barrier and so allowing for inflammatory cell migration. The migratory cells attack the basic myelin protein and the final result is the demyelination seen in ADEM. So we propose that vasculitis and rheumatologic diseases may play role in the pathogenesis of ADEM.