Hemimegalencephaly

Hemimegalencephaly or unilateral megalencephaly is a rare condition characterized by the enlargement of one-half of the brain. Children with this disorder may have a large, sometimes asymmetrical head. Often they suffer from intractable seizures and mental retardation. The prognosis for those with hemimegalencephaly ranges from poor to highly functioning. In some cases, children with hemimegalencephaly are severely mentally retarded and must undergo a hemispherectomy to stop seizure activity. In others, seizure activity can be controlled by medication; and the affected child develops mentally and physically trailing normal development by one to two years.