Background: Acute flaccid myelitis (AFM) is a condition which causes acute paralysis in pediatric patients. Although awareness of AFM is increasing, the pathophysiology and full spectrum of clinical, biochemical, and radiographic features remain to be fully elucidated. Methods: We report a 5 year-old, previously healthy, male patient who presented with acute right upper extremity weakness following a two day history of fever, cough, and fatigue. The patient underwent extensive inflammatory and infectious workup in addition to MRI imaging of the brain, spinal cord, and bilateral brachial plexuses. Results: Infectious and inflammatory workup did not identify a causative agent. The patient was seen to have bilateral asymmetric (R>L) thickening and enhancement of the anterior horn cells of his cervical (C3-C7) spine, consistent with the spinal grey matter lesions previously described in patients with AFM. Enhancement of the corresponding anterior nerve rootlets and bilateral brachial plexuses was also seen. Conclusions: Patients with acute flaccid myelitis may demonstrate grey matter enhancement extending beyond the spinal cord to the peripheral nerves and plexuses, a radiographic finding which has not previously been published.