Rasmussen encephalitis is an extremely rare chronic inflammatory neurodegenerative disease affecting a single cerebral hemisphere, causing progressive neurological deterioration and intractable seizures. Imaging plays an important role in diagnosis by demonstrating focal or unihemispheric involvement and excluding other possible causes. Here, we report a case of Rasmussen encephalitis with an update on recent diagnostic criteria and emphasis on differential diagnoses which can be excluded on imaging.