Rasmussen’s encephalitis (RE) is a very rare, chronic inflammatory neurological disease that usually affects only one hemisphere (half) of the brain. It most often occurs in children under the age of 10 but can also affect adolescents and adults. It has features of an autoimmune disease in which immune system cells enter the brain and cause damage. RE is characterized by frequent and severe seizures, progressive loss of neurological functions including motor skills, speech, and eventual paralysis on one side of the body (hemiparesis), inflammation of the brain (encephalitis), and mental deterioration. Children with RE frequently enter a phase of permanent, but stable, neurological deficits after 8 to 12 months; the disease in adults and adolescents may continue to progress slowly.
Anti-epileptic drugs are frequently helpful but usually do not entirely control seizures. Recent studies have shown some success with treatments that suppress or modulate the immune system, in particular those that use corticosteroids, intravenous immunoglobulin, or tacrolimus. Surgery to control seizures may be recommended, particularly in children where recovery potential is high. Some centers suggest early surgery for RE as a way to treat the seizures and to take advantage of developmental neuroplasticy, where different parts of the brain learn new connections following injury or trauma. Surgical procedures, such as functional hemispherectomy (surgery to remove the part of the hemisphere where the seizures start) and functional hemispherotomy (surgically severing all connections between the right and left halves of the brain), may reduce the frequency of seizures and also improve behavior and cognitive abilities.
The prognosis for individuals with Rasmussen’s encephalitis varies. Despite the advances in medical treatment, none has yet been shown to halt the progress of the disease in the long term. The disorder may lead to severe neurological deficits or it may cause only milder impairments. For some children, surgery -- particularly hemispherectomy or hemispherotomy -- may halt disease progression and stabilize seizures. However, most individuals with Rasmussen’s encephalitis are left with some paralysis, cognitive deficits, and problems with speech. In some very rare cases, the disease can progress to involve the opposite brain hemisphere.
Scientists continue to study the capacity of the human brain for functional neuroplasticity, where brain functions that are affected by damage or disease are handled by other parts of the brain. Other research focuses on finding better ways ot prevent, treat, and ultimately cure progressive neurological disorders such as Rasmussen's encephalitis by understanding the neuro-inflammatory process in RE and ways to stop the brain inflammation. Information from the National Library of Medicine’s MedlinePlus Encephalitis