Acute Flaccid Myelitis: More Likely Missed Than Diagnosed

Richard Mark Kirkner

October 27, 2020

Acute flaccid myelitis (AFM), a polio-like neuroinfectious disorder, is misdiagnosed in the majority of cases, and that can result in loss of valuable time to admit patients and begin treatment to get ahead of the virus that may cause the disease.

At the 2020 CNS-ICNA Conjoint Meeting, held virtually this year, Leslie H. Hayes, MD, of Boston Children's Hospital presented findings of a retrospective case series from 13 institutions in the United States and Canada that determined 78% of patients eventually found to have AFM were initially misdiagnosed.

About 62% were given an alternate diagnosis or multiple diagnoses, and 60% did not get a referral for further care or evaluation. The study included 175 children aged 18 years and younger when symptoms first appeared from 2014 to 2018 and who met the Centers for Disease Control and Prevention case definition of AFM.

"As it becomes more evident that AFM outbreaks are driven by enterovirus infections, treatments targeting the viral infection are likely to be most effective very early in the course of disease, necessitating a precise and early diagnosis," Hayes said. "Thus awareness is needed to help recognize the signs of symptoms of AFM, particularly among frontline clinicians."

One reason for misdiagnosis is that AFM has features that overlap with other neuroinflammatory disorders, she said. "In many cases the patients are misdiagnosed as having benign or self-limiting processes that would not prompt the same monitoring and level of care."

Numbness and prodromal illnesses were associated with misdiagnosis, she said, but otherwise most presenting symptoms were similar between the misdiagnosed and correctly diagnosed patients.

Neurologic disorders with similar features to AFM that the study identified were Guillain-Barré syndrome, spinal cord pathologies such as transverse myelitis, brain pathologies including acute disseminating encephalomyelitis, acute inclusion body encephalitis and stroke, and other neuroinflammatory conditions.

"There were also many patients diagnosed as having processes that in many cases would not prompt inpatient admission, would not involve neurology consultation, and would not be treated in a similar fashion to AFM," Hayes said.

Those diagnoses included plexopathy, neuritis, Bell's palsy, meningoencephalitis, nonspecific infectious illness or parainfectious autoimmune disease, or musculoskeletal problems including toxic or transient synovitis, myositis, fracture or sprain, or torticollis.

"We identified preceding illness and numbness as two features associated with misdiagnosis," Hayes said.

"We evaluated illness severity by evaluating the need for invasive and noninvasive ventilation and found that, while not statistically significant, misdiagnosed patients had a trend toward higher need for such respiratory support," she noted. Specifically, 31.6% of misdiagnosed patients required noninvasive ventilation versus 15.8% of promptly diagnosed patients (P = .06).

Hayes characterized the rates of ICU admissions between the two groups as not statistically significant: 52.5% and 36.8% for the misdiagnosed and promptly diagnosed groups, respectively (P = .1).

Both groups of patients received intravenous immunoglobulin in similar rates (77.9% and 81.6%, respectively, = .63), but the misdiagnosed patients were much more likely to receive steroids, 68.2% versus 44.7% (P = .008). That's likely because steroids are the standard treatment for the neuroinflammatory disorders that they were misdiagnosed with, Hayes said.

Timely diagnosis and treatment was more of an issue for the misdiagnosed patients; their diagnosis was made on average 5 days after the onset of symptoms versus 3 days (P < .001). "We found that time to treatment, particularly time to IVIg, was significantly longer in the misdiagnosed group," Hayes said, at 5 versus 2 days (P < .001).

Hayes has no relevant financial relationships to disclose.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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