An encephalocele is a defect characterized by the herniation of brain tissue and membranes through an opening in the cranium.
Encephlaoceles are classified as neural tube defects, which are a group of disorders occurring due to the failure of closure of the neural tube at about week four of fetal development.
Other neural tube defects include anencephaly and spina bifida. Anencephaly results from failure of closure of the cranial end of the neural tube. This is a lethal condition. Spina bifida results from failure of neural tube closure in the spine. Spina bifida is a variable condition that is usually not lethal, but causes problems with bladder and bowel control and ambulation. It is usually associated with hydrocephalus (water on the brain) which can be treated with a shunt to drain the fluid into the body cavity. Encephalocele is the most rare neural tube defect.
Encephaloceles are classified according to their location. Occipital (arising at the back of the head where the head meets the neck) encephaloceles occur in 75% of cases, parietal encephaloceles in 10%, and anterior encephaloceles (arising from the base of the nose) in 15%. Anterioposterior encephaloceles have a poorer prognosis.