The updated guidance on managing acute flaccid myelitis is unlikely to relieve the frustrations of physicians struggling to treat the condition.
After reviewing the extant data on the baffling disorder, the Centers for Disease Control and Prevention found no evidence that corticosteroids, interferon, antivirals, or any other immunologic or biologic therapy is an effective treatment.
All of the treatments mentioned in the guidance have been used anecdotally, and often for cases proven to be associated with enterovirus-related cases. However, there are no well validated studies confirming benefit for any of these approaches, the agency said in its clinical management document.
Acute flaccid myelitis (AFM) has stricken 90 patients in the United States this year and another 252 cases are being investigated, according to new data from the CDC. The number of confirmed cases is triple that seen in 2017. Whether the disease is an infectious or autoimmune process, or something else entirely, remains unknown.
In response to the outbreak – the largest since 2014 – an expert panel of 4 CDC staff physicians reviewed the literature to find what, if any, treatments were effective; another 14 external experts provided input on the recommendations. At this point, nothing can be officially recommended, the agency said.
Corticosteroids
Corticosteroids should not be administered to most patients with AFM. In addition to “a theoretical concern” about the potential adverse effects of these drugs in acute infections, there is some hard evidence that they are associated with worse outcomes in enteroviral neuroinvasive diseases, particularly those caused by EV-71.
This observation, following a 2012 outbreak in Cambodia, led a World Health Organization commission to conclude that corticosteroids were contraindicated in the management of EV-71–associated neuroinvasive disease. This year, there has been an uptick in EV-A71-associated neurologic disease.
The CDC did hedge its advice on corticosteroids a bit in the setting of AFM, however. “There may be theoretical benefit for steroids in the setting of severe cord swelling or long tract signs suggesting white matter involvement, where steroids may salvage tissue that may be harmed due to an ongoing immune/inflammatory response. While AFM is clinically and radiographically defined by the predominance of gray matter damage in the spinal cord, some patients may have some white matter involvement. It is not clear if these different patterns are important relative to therapeutic considerations.”
Nevertheless, the agency does not recommend corticosteroid use for these patients. “The possible benefits of the use of corticosteroids to manage spinal cord edema or white matter involvement in AFM should be balanced with the possible harm due to immunosuppression in the setting of possible viral infection.”
IVIG
While IVIG holds some theoretical benefit for AFM, there are no high-level human data, the guidelines state. The treatment is generally safe and well tolerated, but the few reports of its use in AFM did not show clear benefit. These include two case series. One suggested an acute improvement of neurologic status, but no long-term resolution of deficits. The other indicated neither significant improvement nor deterioration.