1-4 Cases of Encephalocele per 10,000 Live Births

Encephalocele, sometimes known by the Latin name cranium bifidum, is a neural tube defect characterized by sac-like protrusions of the brain and the membranes that cover it through openings in the skull. These defects are caused by failure of the neural tube to close completely during fetal development. The neural plate appears on the 17th day of gestation as a thickening of the embryonic ectoderm over the notochord. This neuroectoderm gives rise to the central nervous system. On day 18, the neural plate invaginates along the midline, forming the neural groove with the neural folds on either side. By the end of the third gestational week, the neural folds fuse forming the neural tube. The cranial end of the neural tube closes by 24 days and the caudal by 25-26 days. Then, the neural tube is covered dorsally by mesenchyme that forms the vertebral ardhes and skull. Closure of the vertebral arches is completed at 11 weeks of gestation. Defective closure of the neural tube results in neural tube defects (NTDs) which are classified as anterior (anencephaly, encephalocele) and posterior (spina bifida). There have been studies and evidence linking NTD’s to folic acid deficiency.

The severity of encephalocele varies, depending on the location. Currently, the only effective treatments are reparative surgeries following birth.  There are 1-4 cases of encephalocele per 10,000 live births. The development of an encephalocele reduces the chance of live birth to 21%, and only half of these live births survive. Approximately 75% of survivors have a mental deficit. Encephalocele recurs in 3% of patients after surgical repair, whereas the recurrence rate is higher in Meckel-Gruber syndrome* (25%). The absence of brain tissue in the herniated sac is the single most favorable prognostic feature for survival.

The location of the encephalocele greatly impacts the prognosis. Those located in the front, have a 100 percent survival rate, while those located in the back have a 55 percent survival rate. In the United States the most common type of encephalocele is in the back, while in Southeast Asia a frontal type is more common. Approximately 13 to 44 percent of these babies have a chromosomal abnormality…


Photo courtesy of Dimitri Agamanolis, M.D., staff pathologist at Akron Children’s Hospital, and professor of pathology (neuropathology) at Northeastern Ohio Universities College of Medicine (NEOUCOM).


Prenatal Diagnosis of an Encephalocele:

Most encephaloceles are diagnosed on routine ultrasound. The alpha-fetoprotein levels are not typically elevated with this defect because the defect is covered by skin. Once an encephalocele is diagnosed, a thorough examination of the baby is recommended to look for other anomalies. Recently, some research suggests the fetal MRI may give a more detailed picture of the central nervous system. Ultrasound imaging can be limited by the mother’s body habitus, the surrounding amniotic fluid, and the position of the fetus. MRI is a non-invasive diagnostic test that produces better images of soft tissue, and bone or dense tissue does not interfere with the image as it can with ultrasound. The best assessment is done when the fetus is still, which is the challenge of fetal MRI. Your obstetrician will most likely refer you to a specialist that handles high-risk pregnancies. These doctors are called perinatologists.


Birth Defect Research for Children, Inc.


March of Dimes Foundation

Craniofacial Procedure to Treat Encephalocele @ Children’s Hospital Boston

View the full program by visiting:

*Special note on Meckel-Gruber syndrome:

Meckel-Gruber syndrome (MKS) (OMIM 24900) is a lethal, rare, autosomal recessive condition mapped to chromosomes 17q21-24, 11q13, and 8q24. This mapping suggests genetic heterogeneity in MKS. The triad of occipital encephalocele, large polycystic kidneys, and postaxial polydactyly characterizes MKS. Associated abnormalities include oral clefting, genital anomalies, CNS malformations, and liver fibrosis. Pulmonary hypoplasia is the leading cause of death. Improvements in ultrasonography have enabled prenatal diagnosis as early as 10 weeks’ gestation.

Worldwide, the incidence of MKS is 1 per 13,250-140,000 live births. Individuals of Finnish descent have a higher incidence (1 per 9000 live births).



Photo courtesy of Leeds Institute of Molecular Medicine

Pedigrees of two consanguineous families with Meckel-Gruber syndrome, with haplotypes on chromosome 8q22 shown as vertical bars. The disease-associated haplotype is shown in black.

~ by marbleroad on April 22, 2009.

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