Encephalocele is a rare birth anomaly, a variant of neural tube defect (NTD). The process of embryologic development of brain and head fails to form and fuse bone tissue and results into the brain tissue herniation from the skull. The most common location of encephalocele is in the midline occipital area.
The presentation of encephalocele varies, depending on the defect location and size. Occipital form usually has midline involvement. Fronto-ethmoidal form manifests as a protruding visible mass along the nose. The root for the majority of fronto-ethmoidal encephaloceles is located at the foramen caecum. Foramen caecum is a small orifice formed by the closure of the frontal and ethmoidal bones. Basal encephaloceles are located internally and do not usually manifest as visible structures, though there may be a lump or bump in the oropharynx or nasopharynx of the patient.
Every newborn with an open NTD should be thoroughly examined and every defects must be documented as the baseline for future comparison. Particular attention should be given to neurological exam: reflexes (sucking and crying), upper and lower extremities motor and sensory functions, urinary stream and anal sphincter control. Motor functions should be assessed by evaluation of muscle bulk, spontaneous and stimulated movements and muscle tone on palpation. Usually patients with encephalocele have slightly higher level of sensory dysfunction than that of motor. Hip and foot deformities should be compared and evaluated. If there is segmental disparity in more than 1 level, an underlying neurological deficit should be suspected. Head circumference measurement is also diagnostically important.
- Respiratory Distress
A preterm neonate presenting with respiratory distress after birth was found to have a clival encephalocele, which is a variant of a basal encephalocele, and hypoplasia of the cerebellum. [ncbi.nlm.nih.gov]
Severe respiratory distress such as that seen in our patient is associated with pharyngeal airway obstruction. [pediatrics.aappublications.org]
Face, Head & Neck
- Facial Mass
This rare clinical presentation of encephaloceles should be taken into consideration during the evaluation of the lateral facial masses in the infancy period, and possible intracranial connection should be ruled out before surgery to avoid complications [ncbi.nlm.nih.gov]
Case of the Week: June 9-June 16, 2006 Child with facial mass. (Click for a larger image.) Case Details Frontal mass contains brain tissue in continuity with the frontal lobe. [pedsradiology.com]
The diagnosis is usually made prenatally. The most important diagnostic modality is fetal ultrasound, which is used for screening. The earliest reported case was diagnosed at 13 weeks of gestation. The diagnosis is based on a visualization of cranial defect with varying levels of brain protrusion. It is of uttermost importance to perform a thorough search for other abnormalities if encephalocele is diagnosed, as there are high levels of associations.
Other prenatal studies are rarely used to diagnose encephalocele. Maternal serum alpha-fetoprotein levels are increased in only 3% of mothers as the majority of encephaloceles are covered with skin. Although the CT scan is informative, it can pose great harm to fetal development due to radiation exposure.
Imaging studies, however, are quite useful after the birth. MRI is the study of choice for visualizing neural tissue defects, allowing to detect both encephalocele and associated anomalies. MRI is also a useful tool for evaluating fluid or CSF-filled cavities and identify possible hydrocephalus, Chiari malformation, holoprosencephaly, Dandy-Walker complex, aqueduct stenosis and agenesis of the corpus callosum. CT imaging may also be useful, particularly for its excellent depiction of bony structures, especially with coronal, sagittal, or 3-dimensional (3D) reconstruction. CT scans, however, are much less capable of visualizing soft tissues, important for encephalocele diagnosis. Together with the risks of exposure of young children to radiation limit the use of CT imaging, making the MRI of superior value.
Angiography can be used prior to the surgical treatment to determine the involvement intracranial and extracranial vasculature in the formation of encephalocele. It is especially helpful to evaluate the possibility of displacement of dural sinuses into the sac. However, MRI usually is also capable of depicting the dural sinuses anatomy, making cerebral angiography rarely performed study.
- Posterior Fossa Cysts
The authors present an extremely rare case of a laterally oriented, pathologically proven encephalocele associated with a posterior fossa cyst and cerebellar migrational defect in an infant. [ncbi.nlm.nih.gov]
CT may also depict associated cerebral anomalies such as hydrocephalus, posterior fossa cysts, and others ( 16, 21, 28 ). [ispn.guide]
Surgery is the treatment of choice for patients with encephalocele. Depending on the associated complications, size and location of the lesion surgery can either be delayed for up to 4 months or performed shortly after birth. The surgery can be postponed only if there is a protective level of skin covering the encephalocele.
The repair strategy for encephalocele is similar to that of hernias in general surgery. The procedure includes dissection of the sac, isolation of the neck, neck closure and reinforcement of dural defect. The content of the sack is often comprised of non-viable gliosed heterotrophic tissue and should be removed. The remaining dural defect should be closed and reinforced with graft if necessary. Ideally, it is done with bone grafts (split cranium, split rib, or acrylic). It may be necesary to perform a secondary reconstruction of bony structures later in life for cosmetic reasons.
General management of newborns with open NTDs includes coverage of defect with sterile wet saline dressing. The patient should be kept warm and positioned prone to reduce pressure on the encephalocele . If associated hydrocephalus is present, it should be treated with shunting prior to the management of encephalocele.
The main prognostic factors are the location and size of the lesion as well as presence of other congenital abnormalities and the involvement of brain tissue within the sac of the lesion. Most encephaloceles are successfully corrected by surgery as even the large ones have mostly heterotrophic nervous tissue inside, the removal of which does not affect the functional status of nervous system. The anterior defects are reported to have better long-term prognosis with more than half of the patients preserving normal intelligence quotient (IQ). The occipital form, however, is of much greater severity with high mortality rate and increased probability of mental and physical retardation.
Associated anomalies pose a huge impact on the outcome. Microcephaly is linked with a much poorer prognosis as well as mental retardation and physical defects. Hydrocephalus is quite common in association with encephalocele and may pose serious harm, however, can be minimized by treatment.
The precise etiology of encephalocele remains unknown with most cases occurring sporadically. However, it is presumed to result from combination of multiple factors, both genetic and environmental .
Encephaloceles are associated with other NTDs reported in family history, such as spina bifida and anencephaly, which may point to the genetic predisposition. Female predominance, ethnicity linkage and the increased incidence in offsprings of consanguineous marriages as well as association with chromosomal abnormalities (trisomy 13, 18, 21) may also suggest genetic basis for encephalocele development. However, concordance between monozygotic twins is low, suggesting genetic factors to only predispose to the environmental influence.
NTDs are associated with maternal deficit of folic acid and zinc  . Supplementation of women of childbearing age with folate successfully prevents NTDs. Recent studies suggest other possible maternal causes: diabetes, zinc deficiency, alcohol abuse, intrauterine hyperthermia and valproate use, exposure to toxins and infections. Possible environmental factors involved are geographic location, season of conception and socioeconomic status.
Overall incidence of encephalocele is reported to be from 1 per 300 to 1 per 10000 live births   and accounts for 8-19% of all dysraphisms , which is, however, less common than analogous spinal defect (myelomeningocele). NTDs are one of the most common birth defects . Of newborns born with encephalocele, 20% are alive and only half of them survive. Approximately 40% of encephaloceles are reported in newborns with chromosomal abnormalities.
The most common locations of the defect are frontoethmoidal (50%) and occipital (37.5%) regions. Occipital encephaloceles are more common in females, with approximately 70% of them occurring in girls. Anterior defects are more often in males and the frontobasal type shows no sex predominance. Newborns with encephalocele have a high incidence of hydrocephalus in the range of approximately 50%.
The process of neural tube formation is comprised of two steps: primary neurulation and secondary neurulation .
Primary neurulation: First, neural folds elevate and reach each other bilaterally, forming the neural tube. The foremost closing occurs at the caudal rhombencephalon or cranial spinal cord, starting with ectoderm fusion, followed by the neuroectoderm. Cranial neuropore closes at the time of fourth gestational week. The last region to close is the commissural plate. The level of caudal neuropore closure is between T11 and S2. Separation of cutaneous ectoderm from neuroderm occurs at the same time, parallel to this process. The ectoderm forms the overlying skin. The posterior vertebral arches are formed by the migration of lateral mesoderm in between the 2 ectodermal layers. The defects in primary neurulation are believed to result in open NTDs.
Secondary neurulation: Referred to as canalization , this process involves further differentiation of caudal regions after the primary neurulation. The filum terminale and conus medullaris form from a cell mass of a medial eminence. The conus then becomes more rostral in spite of differential growth of vertebral column and spinal cord. The defects in secondary neurulation are thought to result into closed NTDs.
The failure of embryological development is of unknown etiology and formation of encephalocele cannot be prevented. Preventive measures are therefore focused on the appropriate diagnosis and treatment for the avoidance of possible complications. A Caesarian delivery may be performed in lieu of natural birth as it is less traumatic for the fetal head.
Encephalocele is a rare birth anomaly, characterized by defect in skull formation, leaving an open orifice in the bony tissue from which the brain tissue herniates. The content of protrusion may either be only the brain tissue, or contain cerebrospinal fluid (CSF) and membranes covering the brain (meninges). The defect is usually covered by skin or thin membrane, thus resembling a small sack. Encephalocele may be located on any part of the head, however, the occipital region is the most common location. Encephaloceles are usually significant in size and directly visible, though in rare cases the defect can be small or internal and remain unnoticed upon birth.
Encephalocele is a variant of neural tube defect (NTD). NTDs are a result of failure of normal nervous system embryological development process, which consists of 2 distinct steps: primary neurulation and secondary neurulation. During the development, neural tube folds and closes to form the brain and spinal cord. NTDs occur when the tube fails to close completely, which can develop on any level along the head, neck and spine, but most commonly happens at the site of anterior and posterior neuropores as they are last to close  . The open defect leads to protrusion of nervous tissue, either on a stalk (pedunculated) or sessile (attached directly). Encephaloceles result from a bony defect in skull structure, which is a direct consequence of failure of the surface ectoderm to separate from neuroectoderm.
The herniation may contain only brain tissue (encephalocele), brain tissue with meninges (meningoencephalocele) or only meninges (meningocele). The sac may also contain tissues from both brain and spinal cord, in which case is referred to as encephalomyeloceles.
The most common location for encephalocele in the United States and Western Europe is the occipital region (75%) with the most defects involving the midline (90%). Encephaloceles have a high association with other congenital abnormalities with approximately half of the patients having various birth defects. Hydrocephalus is also a common comorbidity.
Most of the encephaloceles are diagnosed prenatally via fetal ultrasound through which the structural defect is visualized. The diagnosis can be made as early as 13 weeks of gestation. Imaging studies such as MRI or CT may be used after birth for more detailed assessment of encephalocele before the surgical intervention.
Surgical removal of the sac and reconstruction of bony tissues is the treatment of choice. Depending on the associated complications, size of the lesion, location and wether it is covered by skin, surgery can be delayed for up to 4 months or performed shortly after birth. Prognosis varies depending on the defect location and brain tissue involvement with anterior variants having the most positive outcomes.
Encephalocele is a defect in the newborn's skull, which forms when the natural fetal development of brain goes wrong. It is caused by failure of embryo's cells to come together and form a closed skull covering the fetal brain. The result is an opening in the skull from which the brain may herniate. It is usually covered by thin skin, resembling a form of a sac. The opening most commonly locates in the middle of the back of the head (midline occipital area), however, may occur at any part of the head. Encephaloceles on the front of the skull are more likely to result in better outcomes as they usually have less brain tissue involved inside the sac.
It is unknown what causes encephaloceles to occur, however, the cause is believed to be a combination of multiple factors such as genetic predisposition, exposure to toxins, infections and alcohol and deficits in maternal nutrition. Folic acid is particularly important for the normal development of the nervous tissue as its deficits have been linked with an increase in neural tissue anomalies.
The rate of encephalocele occurrence is approximately 1 in 5000 live births. There is association with stillbirths before 20 weeks of gestation. Of those born with encephalocele only 20% are alive and only half of them survive. The defect is much more common in females, with 70% of encephaloceles occurring in girls, however, the frontal form is more common in boys.
Treatment consists of the surgery to remove the sac and herniated neural tissue and reconstruct the open bony defect. Concomitant hydrocephalus may be treated with shunting procedure. The outcome depends on the involvement of the brain tissue inside the sac and presence of other abnormalities. Antibiotic prophylaxis before and after the surgery will be given to the child for prevention of meningitis. Multi-stage reconstructive surgery may be required later in life for cosmetic reasons.
Approximately half of the surviving babies will have some degree of brain deficits, resulting in movement and learning problems. The extent of damage depends on the part of the brain involved and the size of the defect. Children will require extensive follow-up management with multidisciplinary approach of a team of neurologist, neurosurgeon and pediatrician. Rehabilitation programs may be helpful for families with affected child to achieve progress in development.
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