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[Acute Flaccid Myelitis]
1Department of Pediatric Neurology, Fukuoka Children's Hospital.
Abstract:
Acute flaccid myelitis (AFM) is a newly defined, rare, but clinically distinct syndrome of acute flaccid paralysis with spinal motor neuron involvement of unknown etiology. Clusters of AFM coincided with a nationwide outbreak of enterovirus D68 (EV-D68) in the United States during autumn to winter of 2014 and in Japan during the autumn of 2015. Although EV-D68 was detected in only 20% of the AFM patients, mainly from respiratory specimens without apparent viral detection from blood and cerebrospinal fluid (CSF) samples, strong temporal associations were noted. Core symptoms of AFM are focal limb weakness and cranial nerve dysfunction with acute onset, although limb paralysis varied in type and severity. Most patients showed extensive longitudinal spinal involvement on magnetic resonance imaging, pleocytosis in CSF, and abnormal motor conduction and/or F-waves in neurophysiological investigations in the acute phase which was within two weeks after onset. Immunomodulation therapy consisting of high-dose intravenous immunoglobulin or pulse methylprednisolone did not improve prognosis. Only about 10% of the patients showed complete recovery of limb weakness, but others had variable residual weakness at follow-up. With no effective treatment identified in the acute stage, studies are required to elucidate the pathophysiology and pathomechanisms of AFM and to develop both preventive measures and novel therapeutic interventions.
Insights
Acute flaccid myelitis (AFM) is a rare neurological condition. While linked to enterovirus D68, its exact cause remains unknown, and current treatments show limited effectiveness.
Area of Science:
- Neurology
- Infectious Diseases
- Virology
Background:
- Acute flaccid myelitis (AFM) is a distinct neurological syndrome characterized by acute flaccid paralysis.
- AFM cases have temporally coincided with enterovirus D68 (EV-D68) outbreaks in the US and Japan.
- The precise etiology of AFM remains largely unknown.
Purpose of the Study:
- To summarize the clinical features, epidemiology, and outcomes of acute flaccid myelitis.
- To explore the association between AFM and enterovirus D68.
- To review current therapeutic approaches and identify needs for future research.
Main Methods:
- Review of clinical data from AFM patients during outbreaks.
- Analysis of viral detection in respiratory and cerebrospinal fluid samples.
- Assessment of neuroimaging, cerebrospinal fluid analysis, and neurophysiological findings.
- Evaluation of patient outcomes following immunomodulation therapy.
Main Results:
- AFM presents with focal limb weakness and cranial nerve dysfunction, often with extensive spinal cord involvement on MRI.
- EV-D68 was detected in a minority of AFM patients, primarily in respiratory samples.
- Immunomodulatory therapies (IVIG, pulse methylprednisolone) did not significantly improve prognosis.
- Complete recovery was rare, with most patients experiencing residual weakness.
Conclusions:
- The link between EV-D68 and AFM is suggested by temporal associations but not definitively proven by viral detection in all cases.
- Current treatments for AFM are largely ineffective in the acute stage.
- Further research into AFM pathophysiology and novel therapeutic strategies is crucial.
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