Laboratory studies are nonspecific. Analysis of cerebral spinal fluid often demonstrates a lymphocytic pleocytosis, normal glucose, normal or slightly elevated protein, and absence of identifiable viral, bacterial, or fungal pathogens.^4,9,13

An MRI of the spinal cord is critical for diagnosis. The MRI may be normal on an initial presentation, but eventually an area of central gray matter lesions with edema of both the anterior and posterior segments of the spinal cord will develop. Lesions frequently occur over a span of several spinal cord levels and are most commonly located in the cervical spinal cord. Cortical lesions may also be noted.^1,5,9 The classic appearance of the MRI has been described as similar to poliovirus infection.^1,5

AFM can be difficult to diagnose, especially initially, because it shares many of the same signs and symptoms as other neurologic diseases, such as transverse myelitis and Guillain-Barré syndrome. The official elements for an AFM case definition, as defined by the Council of State and Territorial Epidemiologists, are provided in Table 1.14 However, clinicians are being asked to report all cases of weakness or paralysis meeting the clinical case presentation, regardless of MRI or laboratory results.⁵

(click for larger image) Table 1: Acute Flaccid Myelitis Case Definition
Source: Counsel of State and Territorial Epidemiologists

AFM Management

The onset of weakness may be abrupt and rapidly progress to respiratory failure. When these patients are evaluated in the emergency department or sent for MRI, the clinician should anticipate and be prepared for rapid deterioration. Hospital admission and appropriate consultation are indicated based on the condition of the patient and local institutional protocols. Patients with any indication of rapid progression or respiratory compromise should be admitted to the intensive care unit. The CDC expert panel on AFM discourages the use of steroids or other immunosuppressant agents as these may actually increase mortality.⁵ Further specific recommendations on AFM management may be found at the CDC’s AFM website, www.cdc.gov/acute-flaccid-myelitis.

AFM should be reported to the clinician’s state department of health and the CDC. These organizations can provide guidance on obtaining epidemiologic data and specimen collection to help identify the cause of AFM.⁵