Hemispherectomy or hemispherotomy involves removal or a functional disconnection of most, or all of, one half of the brain typically leaving the basal ganglia and thalamus. It is reserved for people with the most catastrophic epilepsies, such as those due to Rasmussen's encephalitis. If the surgery is performed on very young patients (2–5 years old), then the remaining hemisphere may acquire some motor control of the ipsilateral body due to neuroplasticity; in older patients, paralysis results on the side of the body opposite to the part of the brain that was removed with less prospect for recovery.