What is megalencephalic leukoencephalopathy with subcortical cysts?
Megalencephalic leukoencephalopathy with subcortical cysts is a progressive condition that affects brain development and function. Individuals with this condition typically have an enlarged brain (megalencephaly) that is evident at birth or within the first year of life. Megalencephaly progressively increases the size of the head. Affected people also have leukoencephalopathy, an abnormality of the brain’s white matter. White matter consists of nerve fibers covered by a fatty substance called myelin. Myelin insulates nerve fibers and promotes the rapid transmission of nerve impulses. In megalencephalic leukoencephalopathy with subcortical cysts, the myelin is swollen and stippled with fluid-filled pockets (vacuoles). Over time, the swelling decreases and the myelin begins to waste away (atrophy). Individuals affected with this condition may develop subcortical cysts below an area of the brain called the cerebral cortex. These cysts can grow in size and number. People with megalencephal
