BACKGROUND Acute disseminated encephalomyelitis (ADEM) is a demyelinating disease that usually presents in pediatric patients, usually following a viral or bacterial infection. The clinical findings in ADEM include acute neurologic decline that typically presents with encephalopathy, with some cases progressing to multiple sclerosis. An atypical case of ADEM is reported that presented in a middle-aged adult. CASE REPORT A 46-year-old Caucasian man, who had recently emigrated to the US from Ukraine, presented with gait abnormalities that began four days after he developed abdominal cramps. Magnetic resonance imaging (MRI) of the brain with contrast, fluid-attenuated inversion recovery (FLAIR), and T2-weighting showed contrast-enhancing, patchy, diffuse lesions in both cerebral hemispheres. Cerebrospinal fluid (CSF) was negative for oligoclonal bands. On hospital admission, the patient was treated with intravenous (IV) methylprednisolone, 500 mg twice daily. He responded well and was discharged from hospital after a week, with resolution of his presenting symptoms and signs. CONCLUSIONS This report is of an atypical presentation of ADEM in a middle-aged patient who presented with spastic paresis. Although there are no set guidelines for the diagnosis of ADEM in adults, this diagnosis should be considered in patients with acute onset of demyelinating lesions in cerebral MRI. As this case has shown, first-line treatment is with high-dose steroids, which can be rapidly effective.