Encephalocele Health Article

Definition

An encephalocele is a defect characterized by the herniation of brain tissue and membranes through an opening in the cranium.

Description

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.

Genetic profile

The genetics of neural tube defects, including encephalocele, are not well understood.

Most encephaloceles are sporadic, following a multifactorial pattern (genetic and environmental factors involved) of inheritance. It is known that there is a genetic basis to encephaloceles and other neural tube defects, and it is believed that neural tube defects may be caused by different genetic factors in different subsets of families. Proof that genetic factors contribute to encephaloceles is that it is known to run in families, and it has been seen in association with some chromosome abnormalities. The number of genes and their location is still not known.

Occipital encephaloceles are associated with several single gene syndromes, including Meckle syndrome, dyssegmental dwarfism, Knobloch syndrome, Warburg syndrome, cryptophthalmos, and Voss syndrome. Anterior encephalocele may occur with frontonasal dysplasia. Encephalocele can also be seen in the amniotic band syndrome.

Demographics

The frequency of encephalocele has been reported to be between one in 2,000 to one in 5,000 live births. Anterior encephalocele is more common in Africa, Thailand, and India. Females outnumber males for occipital encephalocele but not other types.

The incidence of all neural tube defects is different in different parts of the world. It is highest in northern Europe, specifically the British Isles and especially South Wales. In the United States, it is higher on the East Coast than the West Coast.

The rate of sporadic neural tube defects in the general population is about one in 1,000. The rate is higher in areas with higher incidence. The chance for a recurrence of a neural tube defect after having an affected child is 2%. After two affected children the risk is 10%. The chance for an affected person to have an affected child is 4%. The chance for a second degree relative to have an affected child is 0.5%. Third degree relatives do not have an increased risk. Recurrence risks are given for neural tube defects as a group. A family with a previous child with anencephaly could have a child with spina bifida or encephalocele (the types do not "breed true" in families).

Care must be taken to be sure that the neural tube defect in the family was sporadic and not associated with a genetic syndrome, which would have a higher risk of recurrence.

Signs and symptoms

Symptoms of encephalocele may include hydrocephalus, spastic quadriplegia (paralysis of all four limbs), developmental delay, mental and growth retardation, uneven gait (ataxia), or seizures.

The size of the cerebral and skull abnormalities associated with encephaloceles are variable. Large encephaloceles are usually associated with microcephaly (abnormally small head). Microcephaly is usually associated with mental retardation.

Occipital encephalocele may be asymptomatic. If the ventricles are involved, hydrocephalus may occur. Anterior encephalocele may progress in size and may be solid, cystic, or both. There may be microcephaly and/or hydrocephaly, ocular hypertelorism (wide-spaced eyes), and cleft palate. There may be problems with vision, breathing, and feeding in patients with anterior encephaloceles. Many patients have mental retardation.