Conference Coverage

Clinical Scoring System May Help Diagnose Acute Flaccid Myelitis

Proposed diagnostic criteria require validation.


 

CHICAGO—Use of the CDC case definition for acute flaccid myelitis may lead to misdiagnosis in patients with other conditions, according to research presented at the 47th Annual Meeting of the Child Neurology Society. A review of 45 reported cases of acute flaccid myelitis found that 12 of the patients had other diseases, such as polyradiculoneuropathy, transverse myelitis, spinal cord ischemia, clinically isolated syndrome, meningitis, and myelopathy due to severe Chiari I malformation, said Matthew Elrick, MD, PhD, Clinical Fellow in Neurology at Johns Hopkins Hospital in Baltimore, and colleagues.

Acute flaccid myelitis is a polio-like illness of acute spinal motor neuron injury following viral infection. Recent outbreaks have been reported, but clinical diagnostic criteria are lacking. Clinical characteristics may help differentiate acute flaccid myelitis from other causes of myelopathy, Dr. Elrick said.

Dr. Elrick and colleagues analyzed cases from two patient cohorts. One cohort included patients who were recruited nationwide based on the CDC case definition of acute flaccid myelitis. The other cohort included patients who were referred to the Johns Hopkins Transverse Myelitis Center and received a diagnosis of acute flaccid myelitis. The researchers reviewed patients’ records and imaging data. An independent neurologist reviewed a subset of cases to confirm inter-rater reliability. Characteristics that differed significantly between patients with and without acute flaccid myelitis were used to build a clinical scoring system.

The CDC case definition includes clinical criteria (ie, an illness with onset of acute flaccid limb weakness), confirmatory laboratory evidence (ie, MRI showing spinal cord lesion largely restricted to gray matter and spanning one or more vertebral segments), and supportive laboratory evidence (ie, CSF with pleocytosis). Clinically compatible cases with confirmatory laboratory evidence are considered confirmed, and clinically compatible cases with supportive laboratory evidence are considered probable.

The investigators based their proposed criteria on the physiologic understanding of acute flaccid myelitis as a disease of the motor neuron with features similar to those of poliomyelitis. They refined the criteria based on features commonly seen in apparent cases (eg, weakness involving the limbs, neck, face, or bulbar muscles and prodromal illness with fever, respiratory symptoms, or gastrointestinal symptoms). In addition, they incorporated rule-out criteria to exclude mimics.

Based on the results of their analysis, they developed a clinical scoring system to aid in the bedside diagnosis of acute flaccid myelitis by considering features such as asymmetric onset, decreased tone, and absence of increased tone.

The proposed criteria and clinical scoring system require validation and may be updated in light of data from recent cases of acute flaccid myelitis, Dr. Elrick said.

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