Monday, October 29, 2018

Acute Flaccid Myelitis: what family physicians should know

- Jennifer Middleton, MD, MPH

Although still quite rare, occurrences of acute flaccid myelitis (AFM), a polio-like condition that results in sudden limb weakness, have been increasing in the United States (US). Most of the affected individuals are children, and a definitive cause is not yet known. Family physicians can aid the Centers for Disease Control and Prevention (CDC)'s investigation by recognizing AFM's presentation and reporting suspected cases to their local health departments.

AFM is not a new condition, but its prevalence in the United States has been increasing, with 386 confirmed cases across 34 states since August of 2014. AFM's prevalence has been higher in the summer months during this time, but cases have been reported year-round. Patients present with sudden loss of strength in one or more limbs, with associated loss of muscle tone and reflexes. Some patients may also have facial drooping or speech changes. Urinary retention has occasionally been noted, and, rarely, some patients even experience respiratory failure. MRI of the spine reveals a gray matter lesion, and cerebrospinal fluid (CSF) typically shows excess white blood cells.

Often, a viral syndrome precedes these neurologic symptoms, but CDC researchers have yet to identify a clear etiology, viral or otherwise. Testing of affected individuals for poliovirus has consistently been negative. The increase in AFM cases does coincide with increased enterovirus D68 activity in the US, but testing in AFM patients has been inconsistent re: accompanying enterovirus infection. With no clearly identified cause, the CDC advises general prevention strategies such as hand washing and mosquito bite avoidance. Treatment for AFM is supportive, with the involvement of neurologists, physical therapists, and occupational therapists.

Physicians should promptly report any patient who presents with sudden flaccid limb weakness, regardless of lab or imaging findings; gathering information from affected individuals will be critical to identifying AFM's etiology. Family physicians can report cases by contacting their local health department and completing this patient summary form, available on the CDC website. For patients with muscle weakness that don't fit the clinical picture of AFM, this AFP article on "Evaluation of the Patient with Muscle Weakness" may be helpful. Since West Nile virus can also cause AFM, this 2016 AFP article on "Emerging Vector-Borne Diseases" may also be of interest.