What Is It?
An encephalocele is a malformation of the nervous system and surrounding structures similar to spina bifida such as myelomeningocele
. However, unlike the various forms of spina bifida, which affect the spinal cord development, these involve the brain, the other end of the central nervous system.
Normally, the nervous system develops in the embryo from a long tube called the neural tube. The top end of the tube forms the brain and the back end forms the spinal cord. If this tube does not form correctly, a malformation of that part of the nervous system can result. If the tail end of the tube does not form correctly, spina bifida results. If the head end of the tube does not close and form correctly, an encephalocele results.
These malformations can occur at various locations on the head from the far frontal and nasal region to the back of the head. Basically, there is failure of formation of the coverings of the brain so that there is an opening, usually with a large bulge coming out of the head in that region, through a defect in the skull. This bulge typically includes layers of the coverings of the brain but can also include undeveloped brain tissue within the sac. At the most severe end of the spectrum, the entire brain does not develop normally, a condition known as anencephaly. This is not compatible with life.
The exact cause of these malformations is not always known, although they are clearly related to early development in the embryo in utero. Like other dysraphisms like spina bifida, some appear to be associated with nutritional deficiencies such as folate deficiency.
What Types of Symptoms Are Typical?
A child with an encephalocele is born with a defect in the skull which has some degree of a bulging sac coming out of the head. The location of these can vary. Most occur on the midline of the head. The most frontal ones can be entirely into the nasal region and cannot be seen from the outside of the head. Ones that are further forward can be seen as a bulging at the upper nose or forehead. They can also commonly occur at the back of the head where the skull meets the spine.
Although there is usually some brain tissue inside the sac, this is usually undeveloped brain. The degree of brain involvement can vary quite a bit. Some children can have practically normal brain development otherwise while some severe cases can have very substantial brain underdevelopment.
These malformations can occur with other nervous system congenital malformations or conditions. For example, as with spina bifida, hydrocephalus is not uncommon in these patients.
How Is The Diagnosis Typically Made?
Because most are outwardly visible, the diagnosis is made at the time of birth when the bulging sac is noticed. However, further testing, such as CT
scans of the brain, may be done to evaluate the brain within and further define the anatomy of the malformation. These both help to clarify the degree of malformation and to help plan surgical treatment.
What Are Some Common Treatments?
Encephaloceles are typically treated surgically. The aim is both to decrease the cosmetic deformity as well as to help protect the brain and avoid secondary complications such as leakage of cerebrospinal fluid or infection. If the skin over the sac is completely closed, the risk of leakage or infection is not high and the treatment is more aimed at the cosmetic result.
In either case, the sac is generally removed, along with any undeveloped tissue within it. The coverings of the brain are closed tightly to prevent any further herniation or leakage of intracranial contents. Finally, the exterior skin may require reconstruction to achieve a good cosmetic result. While a neurosurgeon generally performs the primary surgery, the cosmetic part is often accomplished with the help of a plastic surgeon. This is particularly true if the malformation involves the nose or face.
The long term prognosis of patients with an encephalocele depends completely on the severity of the defect and the associated brain development. While some are fairly superficial with normal brain development and potential intelligence, others may be severely compromised by the malformation and have chronic disability. Some of the most severe malformations, such as anencephaly where no normal brain develops, are not compatible with life and the infant is stillborn or will die shortly after birth.
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This site is not intended to offer medical advice. Every patient is different, and only your personal physician can help to counsel you about what is best for your situation. What we offer is general reference information about various disorders and treatments for your education.