Acute flaccid myelitis in childhood: a retrospective cohort study

Background and purpose Clusters of acute limb weakness in paediatric patients have been linked to outbreaks of non‐polio enteroviruses, termed acute flaccid myelitis (AFM). Outside these clusters, in countries where polio is not endemic, this poliomyelitic‐like illness is rare in childhood and its natural history is not well defined. We describe presenting features, investigation findings and long‐term outcome of a series of children with AFM. Methods This was a retrospective cohort study. Results Eight children (six females) aged 3 months to 8 years (median age 5 years) met case criteria. Initial symptoms were pain (n = 7) followed by limb weakness with hypotonia (n = 8). Flaccid paralysis occurred in only three patients. Two had cranial nerve dysfunction. Magnetic resonance imaging of the spinal cord demonstrated grey matter involvement particularly affecting the anterior cord, with longitudinally extensive changes in three children. Cerebrospinal fluid examination showed pleocytosis in six children with raised cerebrospinal fluid protein in five. Nerve conduction and electromyography findings were consistent with a motor neuronopathy. Residual deficits were common, with moderate to severe weakness seen in five patients. Median follow‐up was 28 months (range 17–108 months, 30.4 patient years in total). Conclusions Acute flaccid myelitis is an uncommon condition in childhood with a high rate of significant long‐term morbidity. AFM should be considered in children presenting with acute limb pain and weakness.