Rasmussen's syndrome is associated with slowly progressive neurologic deterioration and seizures in children. Seizures are often the first problem to appear. Simple partial motor seizures are the most common type, but in one-fifth of these children, the first seizure is an episode of partial or tonic-clonic status epilepticus.
Mild weakness of an arm or leg is the most common initial symptom besides seizures. The weakness and other neurological problems often begin 1 to 3 years after the seizures start. Progressive weakness on one side (hemiparesis) and mental retardation are common, and language disorder (aphasia) often occurs if the disorder affects the side of the brain that controls most language functions, which is usually the left side.
Rasmussen's syndrome usually begins between 14 months and 14 years of age.
Recent studies suggest that the cause of Rasmussen's syndrome is an autoimmune disorder (antibodies are produced against the body's own tissues) directed against receptors on the brain cells. The process may be triggered by a viral infection. A blood test can be helpful in making the diagnosis.
Treatment of this disease with seizure medicines is disappointing. Steroids may be effective, but additional studies are needed. Immunologic therapies (gamma globulin, plasmapheresis) may be helpful in some cases.
In children with severe weakness and loss of touch and vision on the side of the body opposite the involved hemisphere of the brain, a surgical procedure called a functional hemispherectomy may be successful.
Rasmussen's syndrome is rarely fatal, but its effects are devastating. The seizures are typically relentless and weakness and mental impairment often follow. CT and MRI scans of the brain show evidence of a slow loss (atrophy) of brain substance.
Despite the drastic nature of hemispherectomy, where half of the brain is removed, the surgery can be highly effective in stopping the seizures and preventing mental impairment. Children adjust to hemispherectomy remarkably well. After the surgery, most can walk and run, although with a limp. Hand function on the side opposite to the surgery is often significantly impaired and fine motor skills are not possible. Even when the language hemisphere is removed, children typically regain a considerable amount of language skills.