Acute Hypotonia in an Infant

Acute flaccid myelitis (AFM) is increasing in incidence in the United States and presenting to emergency departments (EDs) across the country. This clinical entity presents as acute paralysis, with magnetic resonance imaging changes in the gray matter only in children younger than 21 years of age. The etiology is unknown, although preceding viral illnesses are common. There are no consensus guidelines regarding treatment.

A 4-month-old girl presented with decreased bilateral arm movement. The history consisted of a recent upper respiratory illness and abrupt decline in movement. She was found to have truncal and peripheral hypotonia, while maintaining her airway. Magnetic resonance imaging found gray matter hyperintensity at C2-C6, with no white matter changes. The patient was positive for enterovirus. Intravenous steroids and intravenous immunoglobulin were given, with slight improvement prior to discharge to an inpatient rehabilitation center. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: AFM was largely nonexistent in the United States after implementation of the polio vaccine, but the incidence has recently increased. Pediatric patients are now presenting to EDs with acute hypotonia, and emergency physicians must recognize how to differentiate this emerging diagnosis from other causes of acute flaccid paralysis. The clinical course of AFM does not seem to change acutely, in stark contrast to disease entities like botulism, which can change in hours. Patients with AFM do not need aggressive ED diagnostic evaluation, but rather transfer to a pediatric hospital for further care. Therefore, discerning the etiology of pediatric hypotonia with history and physical examination alone is important.