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Neural tube defect in which the brain protrudes out of the skull From Wikipedia, the free encyclopedia
Encephalocele 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. Encephaloceles cause a groove down the middle of the skull, or between the forehead and nose, or on the back side of the skull. The severity of encephalocele varies, depending on its location.[1]
| Encephalocele | |
|---|---|
| Other names | Cranium bifidum |
| |
| Illustration of a child with encephalocele | |
| Specialty | Medical genetics  |
| Usual onset | congenital |
| Treatment | Surgery |
Encephaloceles are often accompanied by craniofacial abnormalities or other brain malformations. Symptoms may include neurologic problems, hydrocephalus (cerebrospinal fluid accumulated in the brain), spastic quadriplegia (paralysis of the limbs), microcephaly (an abnormally small head), ataxia (uncoordinated muscle movement), developmental delay, vision problems, mental and growth retardation, and seizures.[citation needed]
Since its earliest cited case in the 16th century, many generations of scientists have attempted to explain the cause.[2] Little has been revealed in the centuries to follow. Although the exact cause is unknown, encephaloceles are caused by failure of the neural tube to close completely during fetal development. Both environmental and genetic factors have been seen to contribute to the cause of encephaloceles.[3] Some studies have revealed a higher occurrence in female embryos, suggesting a genetic cause.[4] Research has indicated that teratogens (substances known to cause birth defects), trypan blue (a stain used to color dead tissues or cells blue), and arsenic may damage the developing fetus and cause encephaloceles. [citation needed]
Proper levels of folic acid have been shown to help prevent such defects when taken before pregnancy, and early in pregnancy.[citation needed]
Occipital encephaloceles are frequently accompanied by hydrocephalus, as seen in 60-90% of patients.[5]
Usually encephaloceles are noticeable deformities and are diagnosed immediately after birth, but a small encephalocele in the nasal or forehead region can go undetected. Various physical and mental developmental delays can indicate the presence of encephaloceles.[citation needed]
Encephaloceles of the face are generally classified as nasofrontal, nasoethmoidal, or naso-orbital, however, there can be some overlap in the type of encephalocele. They can also appear along any part of the cranial vault, as they result from abnormal closure of cranial bones; the most common location for encephaloceles is the occipital region. If the bulging portion contains only cerebrospinal fluid and the overlying membrane, it may be called a meningocele. If brain tissue is present, it may be referred to as a meningoencephalocele.[6] When the head size or occipitofrontal circumference is smaller than the herniating sac, then it is termed as giant encephalocele.[7]
Separation of the neural and surface ectoderm causes apoptosis in the midline. A disturbance in this separation process at the final closure due to the lack of apoptosis is considered to be a critical aspect of nasofrontal and nasoethmoidal encephalocele.[8]
It is recommended that women take a multivitamin with 400 micrograms of folic acid daily to reduce the likelihood of any type of neural tube defects before and during the first 28 days after conception.[9]
Currently, the only effective treatment for encephaloceles is reparative surgery, generally performed during infancy. The extent to which it can be corrected depends on the location and size of the encephaloceles; however, large protrusions can be removed without causing major disability. Surgery repositions the bulging area back into the skull, removes the protrusions, and corrects the deformities, typically relieving pressure that can delay normal brain development. Occasionally, shunts are placed to drain excess cerebrospinal fluid from the brain.[citation needed]
The goals of treatment include:
Recovery is difficult to predict prior to surgery, and depends on the type of brain tissue involved and location of the encephaloceles. If surgery is successful, and developmental delays have not occurred, a patient can develop normally. Where neurologic and developmental damage has occurred, the specialists will focus on minimizing both mental and physical disabilities.[citation needed]
In general, when the bulging material consists of primarily cerebrospinal fluid, a complete recovery can occur. When a large amount of brain tissue is present in the encephaloceles, there is a higher chance of perioperative complication.[citation needed]
Encephaloceles occur rarely, at a rate of one per 5,000 live births worldwide. Encephaloceles of the back of the head are more common in Europe and North America, while encephaloceles on the front of the head more frequently occur in Southeast Asia, Africa, Malaysia, and Russia. Ethnic, genetic, and environmental factors, as well as parental age, can all affect the likelihood of encephaloceles. The condition can occur in families with a family history of spina bifida.[11]
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