Acute disseminated encephalomyelitis

To be, or not to be… Guillain-Barré Syndrome

Guillain-Barré Syndrome (GBS) is currently the most frequent cause of acute flaccid paralysis on a global scale, being an autoimmune disorder wherein demyelination of the peripheral nerves occurs. Its main clinical features are a symmetrical ascending muscle weakness with reduced osteotendinous reflexes and variable sensory involvement. GBS most commonly occurs after an infection, especially viral (including COVID-19), but may also transpire after immunization with certain vaccines or in the development of specific malignancies. Immunoglobulins, plasmapheresis, and glucocorticoids represent the principal treatment modalities, however patients with severe disease progression may require supportive therapy in an intensive care unit. Due to its symptomology, which overlaps with numerous neurological and infectious illnesses, the diagnosis of GBS may often be misattributed to pathologies that are essentially different from this syndrome. Moreover, many of these require specific treatment methods distinct to those recommended for GBS, in lack of which the prognosis of the patient is drastically affected. Such diseases include exposure to toxins either environmental or foodborne, central nervous system infections, metabolic or serum ion alterations, demyelinating pathologies, or even conditions amenable to neurosurgical intervention. This extensive narrative review aims to systematically and comprehensively tackle the most notable and challenging differential diagnoses of GBS, emphasizing on the clinical discrepancies between the diseases, the appropriate paraclinical investigations, and suitable management indications.

Tumefactive Acute Disseminated Encephalomyelitis

Tumefactive demyelination is a phenomenon involving the radiographic resemblance of an acute demyelinating process in the central nervous system to neoplasia. Although this has been described and characterized for multiple sclerosis, it has been reported in a few cases in patients with acute disseminated encephalomyelitis (ADEM) within the past decade. While it may be challenging to establish a diagnosis of tumefactive ADEM according to clinical and radiological data alone, a thorough review of the clinical history and following the patient over time can be supportive of the same. The principal diagnostic confounds include neoplastic disease and a first attack of multiple sclerosis. A definitive diagnosis can be made by biopsy, which reveals perivenular demyelination and mononuclear cell infiltration in ADEM, in contrast to confluent plaque-like areas of demyelination in patients with multiple sclerosis. Histopathologic evidence of neoplastic disease includes characteristic features, including nuclear atypia and polymorphism, cellular hyperproliferation, mitoses, necrosis, endothelial proliferation, rosettes, and/or pseudorosettes. ADEM responds excellently to treatment with corticosteroids and is monophasic, with recurrence occurring infrequently. We review the literature on tumefactive ADEM and discuss the clinical manifestations, imaging characteristics, and histopathologic findings used to distinguish it from other conditions.

Acute disseminated encephalomyelitis (ADEM) associated with mosquito-borne diseases: Chikungunya virus X yellow fever immunization

Acute disseminated encephalomyelitis (ADEM) is a demyelinating autoimmune neuropathic condition characterized by extensive bilateral and confluent lesions in the cerebral white matter and cerebellum. The basal ganglia and gray matter may also be involved. In most cases, the symptoms are preceded by viral infection or vaccination. In this report, we present a case of ADEM associated with optic neuritis presenting alongside two potential triggering factors: chikungunya virus infection and yellow fever immunization.

Multiphasic disseminated encephalomyelitis associated with herpes virus infection in a patient with TLR3 deficiency

We report a case of a 14-year-old girl that presented headache, amaurosis, drowsiness, fever, vomiting and diffuse reduction of muscle strength. She had been diagnosed with ADEM one year before and had a previous diagnosis of Toll-Like 3 receptor deficiency. Cerebrospinal fluid analysis revealed pleocytosis (28/mm³, 12/mm³ red blood cells, 70% lymphocytes cells, 2% monocytes cells, 28% neutrophils), normal total protein (38 pg/mL) and normal glucose level (53/mm³). Studies for CSF oligoclonal bands and serum anti-MOG were negative but polymerase chain reaction (PCR) testing was positive for herpes virus 1. In the first ADEM episode, PCR for herpes virus was also positive. Magnetic resonance imaging (MRI) of the brain revealed disseminated hyperintense lesions on T2-weighted and FLAIR images in the white matter of frontal, parietal and temporal lobes, corresponding to extensive asymmetric areas of demyelination that produced mass effect and gadolinium enhancement. Electroencephalography demonstrated irregular diffuse and generalized slow-wave activity with predominance in frontal region. The diagnosis of multiphasic disseminated encephalomyelitis (MDEM) triggered by herpes simplex virus was made. Herpes virus is a neurotropic virus that can cause a wide variety of neurological infection-triggered autoimmune disorders and that is particularly damaging to the central nervous system in situations of impaired immune system. TLR3 is expressed in astrocytes and dendritic cells of the central nervous system and is essential for natural immunity to herpes simplex. TLR3-deficient patients have already been described with herpes simplex encephalitis. TLR3 deficiency may predispose and explain autoimmune and demyelinating manifestations induced by herpes virus. The association of multiphasic disseminated encephalomyelitis triggered by herpes virus in a patient with TLR3 deficiency has not been previously reported in the literature.

Encephalitis in US Children

Encephalitis is an uncommon but severe disease characterized by neurologic dysfunction with central nervous system inflammation. Children with encephalitis should receive supportive care and empiric therapies for common and treatable causes while prioritizing diagnostic evaluation for common, treatable, and high-risk conditions. Even with an extensive diagnostic workup, an infectious cause is identified in less than half of cases, suggesting a role for postinfectious or noninfectious processes.

Meningeal inflammation and demyelination in a patient clinically diagnosed with acute disseminated encephalomyelitis

Acute disseminated encephalomyelitis (ADEM) and multiple sclerosis (MS) are both CNS inflammatory demyelinating diseases with overlapping clinical features. A case is reported of a 51-year-old female who presented with headache, progressive aphasia and hemiparesis without preceding infection or vaccination. Brain MRI revealed multiple, often confluent, subcortical white matter lesions without enhancement, affecting predominantly the left cerebral hemisphere. CSF examination failed to reveal oligoclonal bands. Brain biopsy revealed both pathological features of ADEM and findings are consistent with the early stage of MS, including meningeal B and T lymphocytic infiltration, perivenular demyelination, subpial demyelination and discrete confluent plaque-like foci of demyelination. Steroid treatment resulted in remarkable clinical and radiological improvement and there has been no recurrence in six years of follow-up. This case highlights the difficulties in differentiating between ADEM and the first attack of MS and further suggests that ADEM and the early stage of MS, and its tumefactive variant, may have a common underlying pathologic mechanism, which may have a therapeutic implication in treating these diseases.

Enhancing the utility of a prM/E-expressing chimeric vaccine for Japanese encephalitis by addition of the JEV NS1 gene

Recently, we demonstrated that a single-cycle West Nile virus (WNV) named RepliVAX WN could be used to produce a chimeric Japanese encephalitis (JE) vaccine (RepliVAX JE) by replacing the WNV prM/E genes with those of JEV. Here, we tested if replacement of WNV NS1 gene in RepliVAX JE with that of JEV (producing TripliVAX JE) could produce a superior vaccine. TripliVAX JE elicited higher anti-E immunity and displayed better efficacy in mice than RepliVAX JE. Furthermore, TripliVAX JE displayed reduced immune interference caused by pre-existing anti-NS1 immunity. Thus, we propose prM/E/NS1 chimerization as a new strategy for flavivirus vaccine development.

Combating Japanese encephalitis: Vero-cell derived inactivated vaccines and the situation in Japan

Japanese encephalitis (JE) is a major public health threat in Asia, because of its high mortality and high incidence of psychoneurological sequelae in survivors. It is caused by JE virus (JEV) infection, transmitted by vector mosquitoes. The disease is vaccine preventable and has been well controlled in some countries. Since no specific antivirals have been approved, prevention with vaccine is important in this disease. This article provides a general overview of JE and JEV, but special focus has been put on recently developed Vero cell-derived formalin-inactivated JE vaccines, and the situation in Japan relating to these vaccines. In Japan, where JE has been well controlled, the strong governmental recommendation of the mouse brain-derived vaccine for routine immunization was suspended in 2005, owing to a patient suffering severe postvaccination events. In 2010, the recommendation was reinstated, targeting a limited population utilizing a Vero cell-derived vaccine.