Acute flaccid myelitis and enterovirus D68: lessons from the past and present

Abstract

Acute flaccid myelitis is characterized by the combination of acute flaccid paralysis and a spinal cord lesion largely restricted to the gray matter on magnetic resonance imaging. The term acute flaccid myelitis was introduced in 2014 after the upsurge of pediatric cases in the USA with enterovirus D68 infection. Since then, an increasing number of cases have been reported worldwide. Whereas the terminology is new, the clinical syndrome has been recognized in the past in association with several other neurotropic viruses such as poliovirus.Conclusion: This review presents the current knowledge on acute flaccid myelitis with respect to the clinical presentation and its differential diagnosis with Guillain-Barré syndrome and acute transverse myelitis. We also discuss the association with enterovirus D68 and the presumed pathophysiological mechanism of this infection causing anterior horn cell damage. Sharing clinical knowledge and insights from basic research is needed to make progress in diagnosis, treatment, and prevention of this new polio-like disease. What is Known: • Acute flaccid myelitis (AFM) is a polio-like condition characterized by rapid progressive asymmetric weakness, together with specific findings on MRI • AFM has been related to different viral agents, but recent outbreaks are predominantly associated with enterovirus D68. What is New: • Improving knowledge on AFM must increase early recognition and adequate diagnostic procedures by clinicians. • The increasing incidence of AFM urges cooperation between pediatricians, neurologists, and microbiologists for the development of treatment and preventive options.

Keywords: Acute flaccid myelitis; Acute flaccid paralysis; Enterovirus; Enterovirus D68; Poliomyelitis; Poliovirus.

Fig. 1

MRI of the neuraxis in a 3-year-old boy with EV-D68–associated AFM. a Brain: transverse T2-weighted image showing an area of slight hyperintensity in the dorsal pons (arrow). b and c Spinal cord: sagittal T2-weighted images showing longitudinal slight hyperintensity largely restricted to the central cord, where the gray matter is situated (arrow). d Spinal cord: contrast enhancement of the ventral caudal roots on a sagittal T1-weigthed image (arrow) (republished with permission from [16])

Fig. 2

MRI of the spinal cord in a 3-year-old boy with Guillain-Barré syndrome. a Sagittal contrast-enhanced T1 showing typical enhancing anterior caudal roots. b Subtraction of A with more clear depiction of enhancing caudal root. c Transverse T1 showing more clear enhancement of anterior motor roots

Fig. 3

MRI of the spinal cord in a 15-year-old boy with acute transverse myelitis, eventually diagnosed with relapsing remitting multiple sclerosis. a Sagittal T2 showing focal swelling of the spinal cord at level Th11–12. b Sagittal T1 showing contrast enhancement of the lesion

Fig. 4

MRI of a 13-year-old boy with a provisional diagnosis of acute demyelinating encephalomyelitis. a Sagittal short tau inversion recovery (STIR) with edematous cervicothoracic spinal cord from the level of C4. b Sagittal T1 of the spinal cord showing diffuse areas of slight enhancement. c Enhancement of mainly dorsal roots in a sagittal T1 of the lumbar spine. d and e Transverse T2 at the level of the pons (d) and thalamus (e) showing asymmetric hyperintense areas.