Encephalocele Health Article

Diagnosis

Encephalocele can be diagnosed by ultrasound examination. Ultrasound examination is a screening test, the quality of which is affected by many factors including the machine used, skill of the operator, size and location of the lesion, and position of the fetus.

It is not likely that maternal serum alpha-fetoprotein testing (AFP) or amniocentesis would detect encephalocele. Alpha fetoprotein is a normal serum protein produced by the fetal liver. The AFP normally stays within the fetus, with a small amount present in the amniotic fluid from the fetal urine. When there is an "open" neural tube defect, there is a high amount of AFP in the amniotic fluid and the maternal serum. Although encephalocele is a neural tube defect, AFP testing on maternal blood or amniotic fluid only detects open neural tube defects. Encephaloceles are closed neural tube defects, meaning they are covered by a thick covering. This covering does not allow the AFP to leak into the maternal blood or the amniotic fluid in increased amounts that would be detected by the aforementioned tests. Pregnancies in which an encephalocele is diagnosed should be offered an amniocentesis and amniotic fluid biochemistry to better understand the cause of the abnormality.

CT scan can be used to determine the contents of the encephalocele once the baby is born. Some centers offer fetal MRI to attempt to classify the encephalocele prior to deliver. This is usually done at 22 weeks gestation.

Treatment and management

Nutrition, specifically defeciency of folic acid, has been implicated as causing an increased risk for neural tube defects. All women of childbearing age should take 0.4 mg of folic acid to reduce the risk of birth defects. Women with a previous child with a neural tube defect should take 4.0 mg of folic acid. This amount has been shown to reduce the recurrence risk for neural tube defects by 50%.

Prognosis

Size, location, and contents of the encephalocele determine the outcome for the child. Anterior encephaloceles have a much better prognosis than posterior. Mortality due to occipital encephalocele is reported as about 30% if hydrocephalus is present, and 2% if it is not. For all types of encephalocele with hydrocephalus, the mortality rate is 60%. Most patients with parietal encephalocele have associated brain malformations, and mental retardation occurs in 40%. Massive occipital encephalocele with microcephaly have a mortality rate of nearly 100%. Patients with encephaloceles that contain a single frontal lobe are more likely to have normal intelligence without hydrocephalus. Posterior have a poorer prognosis if they contain large amounts of the contents of the posterior fossa (an area of the brain at the back of the head), especially the brain stem. Complications such as hemorrhage or air embolism (stroke) can occur.

BOOKS

Goodman, Richard M., and Robert J. Gorlin. Encephalocele. New York: Oxford University Press, 1983.

ORGANIZATIONS

Association of Birth Defects in Children. 930 Woodcock Rd., Suite 225, Orlando, FL 32803. (407) 895-0802. <http://www.biethdefects.org>.

March of Dimes Birth Defects Foundation. 1275 Mamaroneck Ave., White Plains, NY 10605. (888) 663-4637. resourcecenter@modimes.org. <http://www.modimes.org>.

WEBSITES

National Institute of Neurological Disorders and Stroke. <http://www.ninds.nih.gov/health_and_medical/disorders/encephaloceles>.

Online Mendelian Inheritance in Man. <http://www.ncbi.nlm.nih.gov/htbin-post/OMIM>.

Amy Vance, MS, CGC