Años publicados: 1992, 2000, 2012, 2023
NORD gratefully acknowledges Mackenzie Kelleher and Allie Wu, NORD Editorial Interns from the University of Notre Dame and Gregory G. Heuer, MD, PhD, Children’s Hospital of Philadelphia, Division of Neurosurgery, University of Pennsylvania, Department of Neurosurgery, for assistance in the preparation of this report.
Encephaloceles are rare neurological birth defects characterized by sac-like protrusions of brain tissue, the membranes that cover the brain (meninges) and the clear, watery fluid within the tissues that surround the brain (cerebrospinal fluid) through openings in the skull. Encephaloceles are usually congenital (present from birth) and result from the incomplete closing of the neural tube, a structure during fetal development that folds and normally becomes the brain and spinal cord. In some cases, encephaloceles may be acquired from trauma, tumors or injury caused by medical treatment. Surgery is usually necessary to treat encephaloceles.
The exact cause of encephaloceles is unknown, but the disorder most likely results from the combination of several environmental and genetic factors (multifactorial).
The signs of an encephalocele depend on the location of the lesion. Some are present as a skin-covered mass near the midline in the head that is filled brain tissue and cerebrospinal fluid. Some encephaloceles protrude into spaces such as the nasal sinuses or the base of the skull and may not have external signs.
The symptoms of an encephalocele can vary from one individual to another depending upon many different factors including size, amount of brain tissue protruding from the skull and location and type of tissue that is in the lesion. Encephaloceles that protrude from the skull are usually present at the back of the head, occipital or suboccipital, or near the front of the head. The symptoms of the encephalocele are usually not directly a result of the lesion itself, but the changes that accompany the lesion in the underlying brain because of the loss of brain tissue or effects on the underlying brain structure and development. Patients with encephaloceles can develop seizures, microcephaly (smaller than normal head circumference) and developmental delay. The tissue that is in the encephalocele typically becomes scarred and is no longer functional. If there is an abnormal connection to the outside, such as can occur with anterior encephaloceles between the eyes or in the nasal cavity, lesions can present with nasal obstruction, leakage of cerebrospinal fluid from the nose (cerebrospinal fluid rhinorrhea) or even infection (meningitis). Because encephaloceles protrude through the skull, depending on where the protrusion is and the gap in the skull in that location, the lesion can lead to significant skull defects, facial differences or abnormally large distance between the eyes (hypertelorism).
Encephaloceles can result in developmental delays, intellectual disability, learning disabilities and growth delays. Vision impairment, inflammation of the membranes that cover the brain and spinal cord (meningitis, and uncoordinated voluntary movements (ataxia) are also observed. Hydrocephalus, a condition in which excess cerebrospinal fluid in the skull causes pressure on the brain, may occur as well. Hydrocephalus occurs in 60-90% of patients with posterior encephaloceles. Affected individuals may also experience motor abnormalities due to effects on the underlying brain responsible for controlling movement or to increased muscle tone and stiffness (spastic paraplegia).
It is important to note that not all affected individuals have all the symptoms discussed above and some children may have normal intelligence, while others experience intellectual disability. The effects are thought to be due to the amount and type of brain tissue that is involved and how the development of the brain tissue not in the encephalocele was affected. In some patients, particularly those that involve the brain stem, these lesions can be life threatening due to effects on breathing and the heart. Parents should talk to their child’s physician and medical team about their specific case, associated symptoms and overall prognosis.
The exact underlying cause of encephalocele is unknown but is likely linked to both genetic and environmental factors. Most cases occur sporadically because of neural tube defects. The neural tube typically folds and closes early during pregnancy (third or fourth week) to complete the formation of the brain and spinal cord. A neural tube defect occurs when the neural tube does not close completely, which can occur anywhere along the head, neck or spine. The lack of proper closing of the neural tube can lead to a herniation (movement of brain tissue, blood, and cerebrospinal fluid from its normal position in the brain) process which appears as a pedunculated (having a stalk-like base) or sessile (attached directly to its base without a stalk) cystic lesion protruding through a defect in the cranial vault referred as encephalocele.
Frontonasal encephaloceles, usually located between the baby’s nose and forehead, result from abnormal development of the foramen cecum (a small notch where the frontal crest of the frontal bone ends). Occipital encephaloceles are associated with changes (variants or mutations) the CEP290 (centrosomal protein 290) gene.
Most researchers believe that multiple factors are required to develop a neural tube defect that leads to encephalocele. There is a genetic component to the disease, as encephaloceles are more common in individuals who have a family history of neural tube defects such as spina bifida or anencephaly. In such cases, individuals might have a genetic predisposition to developing a neural tube defect and may develop an encephalocele. A person who is genetically predisposed to certain disorders may carry a gene (or genes) for the disease, which may not be expressed unless it is “activated” under certain circumstances, such as exposure to particular environmental factors. TORCH infections (toxoplasma, rubella, cytomegalovirus, herpes simplex virus) have also been implicated in several cases.
Additional environmental factors that lead to lower survival rates for infants with encephalocele include preterm (early) birth, low birth weight, presenting multiple birth defects and being black or African American. Lack of nutrition or medical problems in the mother such as diabetes have also been implicated in the development of encephalocele. There is some evidence that exposure to toxic chemicals including certain medicines or aflatoxins can increase the risk of having a baby with an encephalocele. On occasion, encephaloceles can be acquired from trauma, tumors or other injuries.
Encephalocele may occur as part of more than 30 different syndromes, including Meckel-Gruber syndrome, Van Voss-Cherries syndrome, Fraser syndrome, Roberts syndrome, Knobloch’s syndrome and Walker-Warburg syndrome. Amniotic band syndrome can also be associated with encephalocele.
The Centers for Disease Control and Prevention (CDC) estimates that approximately 375 babies are born each year in the United States with an encephalocele. That would be approximately 1 in 10,000 babies each year. About 70% of encephaloceles are in females and 90% involve the midline. Additionally, females are more likely to have an encephalocele in the back (occipital area) of the skull, while males are more likely to have one in the front of the skull. In Western populations, encephaloceles are more common in the back of the skull. In Southeast Asia, they are more common in the front of the skull. Anterior encephaloceles are more common in Asia, Africa and Russia, with 1 case in 3,500 to 6,000 births.
Most encephaloceles are diagnosed on a routine prenatal ultrasound or seen right away when a baby is born. In some, small encephaloceles may initially go unnoticed but an individual will present symptoms that lead to diagnosis.
An ultrasound exam is a routine examination in which reflected sound waves are used to create an image of the developing fetus. An encephalocele may appear as a cyst on an ultrasound examination. If an encephalocele is diagnosed prenatally, further tests may be recommended to detect whether additional abnormalities are present. Such tests can include prenatal magnetic resonance imaging (fetal MRI).
A postnatal brain MRI is the preferred method of study because it shows the defect, its contents, the brain tissue and other anomalies. A computed tomographic (CT) scan with three-dimensional reconstruction is used to evaluate the skull defect, bone abnormalities and hydrocephalus. If the defect is close to a group of blood channels that drain blood from the cranial cavity (dural sinus), a CT or MRI angiography (a type of MRI that looks specifically at the body’s blood vessels) can be used.
Surgery is usually necessary for children with encephalocele. Surgery is usually performed sometime between birth and 4 months of age depending upon the size, location and associated complications or whether a layer of skin covers the encephalocele. If a layer of skin is present and acts as a protective cover, surgery can be delayed for a few months. If no layer of skin protects an encephalocele, surgery might be recommended shortly after birth. Sometimes, low blood reserve in small children is considered and surgery is delayed until ages 2-3 if there is no life-threatening condition.
Surgery is not done to put the protruding contents of an encephalocele back into the skull. The surgery is performed to prevent further herniation of the tissue and promote healing. The goal of the surgery is to remove the herniated tissue and repair the layers that did not close completely, including the coverings to the brain (the dura), sometimes the skull, and the skin and soft tissues. Closure of the hole in the skull is usually performed in a delayed fashion when the child is older. Endoscopic surgeries are increasingly common for anterior (frontal) encephalocele due to a lower risk.
Additional treatment is based on the specific symptoms present in each individual. Craniofacial abnormalities or additional abnormalities of the skull are treated surgically. Hydrocephalus may be treated by surgically implanting a ventriculoperitoneal (VP) shunt that allows excess cerebrospinal fluid to be drained.
Services that may be beneficial to the patient may include special remedial education, and other medical, social, and/or vocational services.
Genetic counseling is recommended for affected individuals and their families.
Studies have shown that adding folic acid (a form of B vitamin) to the diet of people who might become pregnant can lower the risk of some neural tube defects, but this has been studied most extensively in patients with neural tube defects that affect the spine and not as much in the brain. The CDC and other health agencies have advocated that females of childbearing age should have 400 micrograms of folic acid daily. Folic acid can be found in leafy green vegetables, nuts, beans and citrus fruits. Folic acid is also included in prenatal vitamins.
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Nationwide Children’s Hospital. Encephalocele. Available at:
https://www.nationwidechildrens.org/conditions/encephalocele Accessed Sept 6, 6023.
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Centers for Disease Control and Prevention. Facts About Encephalocele. Last Reviewed: June 28, 2023. Available at: https://www.cdc.gov/ncbddd/birthdefects/Encephalocele.html Accessed Sept 6, 2023.
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Accessed Sept 6, 2023.
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