Rasmussen encephalitis is a relatively rare disorder defined by chronic inflammation of the brain (unilateral cerebral pathology) that results in progressive deterioration of function in one hemisphere, often followed by gradual partial recovery of function associated with reorganization. Etiology is generally unknown with no indications of viral pathogenesis (e.g., cytomegalovirus) or genetic determination. Rasmussen encephalitis is generally identified following the onset of intractable seizures, but it may not be diagnosed until surgery to address seizure frequency. Actual prevalence of the disorder is unknown.
A rare inflammatory disorder, typically involving a single hemisphere of the brain and often resulting in hemiplegia and partial seizures that are difficult to control. The condition is more common in children than in adults.