What is Encephalocele?
Encephalocele is typically a birth defect that affects the neural tube, the part of a fetus that becomes the brain and spinal cord. This defect causes a bag-like structure to form outside the skull, which can contain brain matter, protective tissues called meninges, or a fluid called cerebrospinal fluid (CSF) that cushions the brain and spine. This can sometimes occur due to trauma, tumors, or accidental medical injury.
When the sac contains only meninges and CSF, it’s more precisely called a meningocele. If the sac contains brain tissue, it’s referred to as an encephalocele. However, both of these conditions are often simply called encephaloceles.
The repair surgery for an encephalocele isn’t considered an emergency. The exceptions are cases where the skin covering the sac has an ulcer (a skin sore) or where the sac leaks CSF. In these cases, quick surgery is needed to prevent a brain infection called meningitis. This surgery can be done as early as two months old, but it’s usually postponed until around four months to several years of age. This is due to the small amount of blood in infants. The aim of the surgery is to tightly seal the opening in the skull and reconstruct any bone defects.
What Causes Encephalocele?
Most brain hernias, or encephaloceles, are present from birth. Some might occur later on due to things like tumors, injuries, or medical interventions. A popular theory suggests that these hernias happen when two layers of the early embryo skin, called the surface ectoderm and the neuroectoderm, do not separate properly. This defect tends to happen around the 25th day of embryonic development. If there is an issue at this time, a skin-covered gap might not form properly.
Both genes and environmental conditions can play a role in the development of an encephalocele. Certain infections (such as toxoplasma, rubella, cytomegalovirus, and herpes simplex virus), close family marriages, and past pregnancies with neural tube defects are known to contribute. Moreover, more than 30 different medical conditions, like Meckel-Gruber syndrome, Walker-Warburg syndrome, Fraser syndrome, and others, have been linked with encephaloceles. The link between a mother’s use of a vitamin called folate and the risk of encephalocele isn’t yet fully understood.
Risk Factors and Frequency for Encephalocele
Neural tube defects (NTDs) are conditions present at birth that affect the baby’s spine, spinal cord or brain. Myelomeningocele, meningocele, encephalocele, and anencephaly make up 80% of all NTDs. The type of NTD known as encephaloceles, represent 15% to 20% of all NTDs. For reference, that means around 1 in 10,000 children are born with encephalocele. However, this may not be a completely accurate number, because some pregnancies are terminated after encephalocele is detected in the baby before birth. These conditions typically happen more often in developing countries. The estimated global occurrence of NTDs is about 180 for every 100,000 live births. However, in Ethiopia, it’s much higher – 630 cases per 100,000 children.
- Although more women than men tend to have NTDs, encephalocele is notably more common in females (4.5 to 1).
- Women are more likely to have a type of encephalocele at the back of the head, while men are more likely to have it at the front. Although, some research has found that it could be equally common in the front for both sexes.
When it comes to encephalocele, about 70% to 90% of cases occur at the back of the head. But this seems to vary based on location. For instance, in places like Asia, Africa, and Russia, encephalocele is more common at the front of the head, with about 1 case in every 3,500 to 6,000 live births. However, this is less common in North America and Europe, where there is roughly 1 case in every 35,000 live births. In India, the prevalence seems to vary, with some areas reporting as high as 60% at the back of the head, while others as low as 26%.
Neurological issues are more often found in cases where encephaloceles are at the back of the head. Interestingly, in some studies about ear canal imaging, they found that about 22.2% of people had pit defects in the middle of their cranial fossa, and within that group, 5% had encephalocele.
Signs and Symptoms of Encephalocele
An encephalocele is a medical condition where a part of the brain protrudes through an opening in the skull, forming a noticeable lump on the patient’s head. This lump can either be in the front (anterior) or the back (posterior) of the head and is usually visible, appearing as a skin-covered mass. Depending upon its location, it could be related to the nasal bridge, forehead, inside corner of the eye, or above or below a structure in the skull called the torcula. This protrusion is usually filled with Cerebrospinal Fluid (CSF), which cushions the brain, and the sack it forms can sometimes appear translucent.
Depending on the size of the encephalocele, it can cause a severe deformation of the face and cause the eyes to be spaced further apart than normal. A person with an encephalocele usually has healthy vision but can experience problems like nasal obstruction, snoring, leakage of CSF, or even meningitis if the encephalocele affects the inside of the nose. Large encephaloceles in the posterior part of the head, containing a considerable amount of brain tissue, can cause muscular stiffness or spasms.
The most common symptom of an anterior encephalocele is a blocked nasal passage. Other reported symptoms include CSF leak from the nose and meningitis. Some people might also have widely spaced eyes. Common locations for anterior basal encephaloceles include a thin plate of bone at the roof of the nasal cavity (64% cases), followed by the roof of the ethmoid sinus (31.3% cases) and a part of the sphenoid bone or sella (15.5% cases).
Posterior encephalocele often comes with conditions like hydrocephalus, which is a build-up of CSF in the brain, occurring in 40% to 60% of the cases involving the back of the head. However, encephalocele at the forehead is accompanied by hydrocephalus only in 14% cases. Seizures are also reported in 17% of posterior cases, while they are less common in anterior cases. In some cases, where the encephalocele is in the temporal lobe/middle cranial fossa, sudden leakage of CSF from the ear or nose can be an indication. These cases may also experience repeated episodes of meningitis before a correct diagnosis is established.
Testing for Encephalocele
An ultrasound performed between the 9th and 11th weeks of pregnancy is usually the primary way to detect the presence of a fluid-filled sac through a skull defect. As the pregnancy progresses, by the 13th week, this ultrasound can help distinguish between a meningocele (where there’s no brain tissue popping out of the defect) or an encephalocele (where brain tissue is present in the defect).
Around the same time, around the 10th week, a DNA test can be done to check for any chromosomal abnormalities. However, it’s important to remember that even if this DNA test doesn’t find anything unusual, it’s possible that an ultrasound could still reveal abnormal results in about 3.5% of cases. This is because, in approximately 8% of cases, chromosomal abnormalities might not be detected via this DNA screening.
If more detail is required, a Prenatal Magnetic Resonance Imaging (MRI, a kind of detailed imaging technique) can be employed. This will help reveal the defect more clearly, but it should be noted that it might need the baby to be sedated. After the baby is born, an MRI of the baby’s brain can provide detailed information about the defect, its contents, the brain tissue, and any related anomalies.
A CT scan (a specific type of X-ray) of the head with three-dimensional reconstruction can also help evaluate the skull defect, bone anomalies (abnormalities), and hydrocephalus (a condition that causes the buildup of fluid in the brain). If the defect is located close to the dural sinuses (channels that contain blood returning from the brain), an angiography (a test that uses X-rays to view your body’s blood vessels) might be needed. This can be done using either CT or MRI angiography.
Treatment Options for Encephalocele
Encephalocele, a rare birth defect where brain tissue protrudes out from a defect in the skull, is typically treated with surgery. The main goals of the procedure are to fix the bone defect, eliminate any excess skin, and remove any non-functional brain tissue.
After the surgical removal of an anterior encephalocele (that is, one located at the front of the head) in infants or young children, the facial skeleton will substantially change shape as it continues to grow. In extensive cases, craniofacial reconstruction might be necessary to correct abnormalities in the distance between the eyes and other bone defects.
Most of the time, the surgery is performed using an open approach. However, when an anterior encephalocele is located in the area behind the nose and eyes, an endoscopic approach can be used instead. The endoscopic endonasal surgery wherein a tool called an endoscope is inserted through the nose, is relatively safe. However, in 5 to 9 percent of cases, the encephalocele might reoccur, requiring another surgery.
The timing of the surgery depends on multiple factors including the encephalocele’s size, location, associated complications, and whether there is a layer of skin covering it. If the encephalocele is covered by skin, which acts as a protective layer, the surgery might be delayed for a while. But if the encephalocele is exposed, surgery is usually recommended soon after birth. In cases of basal encephaloceles or those that occur at the base of the skull, early surgery is needed to prevent infections and progressive herniation or bulging of the brain.
For encephaloceles located at the top or base of the skull, it’s important to weigh the surgical risks against potential facial deformities, risks to the airway, and infections. Some doctors recommend delaying surgery until the child is 2 to 3 years old unless there’s an actively leaking fluid or a life-threatening condition. However, others suggest surgery as early as two months if the encephalocele has caused sufficient nasal expansion, thereby reducing the complexity of the procedure.
In all cases, it’s crucial to seal up the defect in the dura, a protective covering of the brain, using either pericranium or the patient’s own dura. The bone defect is closed up using a piece of the patient’s own skull bone, a titanium mesh, or a type of bone-building material. For small defects, a repair may not be necessary. A special type of drainage can be used during and after surgery to prevent leaks of cerebrospinal fluid (CSF), a fluid surrounding the brain and spinal cord. After surgery, CSF leak can happen in some cases but it can be effectively managed with lumbar drainage. The need for a second operation due to CSF leak happens in a small percentage of cases.
What else can Encephalocele be?
These are some conditions that could be confused with each other because they present similarly:
- Nasal glioma
- Cranial dermal sinus tract
- Nasal dermoid cyst
- Nasal epidermoid
- Dacryocystitis
- Dacryocystocele
- Hemangioma
- Nasal polyp
What to expect with Encephalocele
The future health of someone with an encephalocele, a situation where a portion of the brain pushes out through an opening in the skull, depends on several factors. These factors include its location, size, how much brain is inside the sac that protrudes, whether there are channels that carry fluid surrounding the brain and spinal cord (dural sinuses) present in the sac, and if there is a condition where the fluid accumulating in the brain (hydrocephalus).
The prospects are generally better if the encephalocele is located in the forehead region (the frontoethmoidal area) than if it’s in the back or sides of the skull (occipital or parietal areas). The presence of any additional birth defects in the brain also tends to impact the prognosis. In one study, hydrocephalus and other abnormalities inside the skull were the major factors predicting whether a patient might face developmental delays. A poor outcome is also often associated with seizure disorder, an unusually small head (microcephaly), and the presence of brain tissue in the sac.
Before the surgical correction of the defect, hydrocephalus is found in 34% of all patients. After the defect is closed, it develops in 4% of them.
In the long-term, about half of the children with encephaloceles display normal development, 11% have mild impairment, 16% moderate impairment, and 25% severe impairment. Encephaloceles situated at the back of the skull (occipital) generally bring about worse outcomes than those in the front due to increased risks of seizures and hydrocephalus. Approximately half of the patients with occipital encephaloceles struggle with living independently in society.
Other factors that can increase the likelihood of death include a low birth weight, multiple deformities inside the skull, and being of Black race. On a broader scale, the mortality rate has been observed to be between 4%-30%. Most of these deaths tragically occur on the first day of life, but about 71% of the patients survive to their first birthday, and 67% live until they’re 20 years old.
Possible Complications When Diagnosed with Encephalocele
The primary complications one might experience following complex medical procedures are leaks in the cerebrospinal fluid (CSF) and meningitis, an inflammation affecting the membranes around the brain and spinal cord. The rate of complications for endoscopic repairs, which is a modern, less invasive way of doing the procedure using a tube with a mini camera, is approximately 14%. This statistic is notably lower than the over 20% complication rate associated with the older, open surgical procedures.
Common Complications:
- Leak of cerebrospinal fluid (CSF)
- Meningitis (inflammation of the brain and spinal cord membranes)
- Seizures
- Hydrocephalus (buildup of fluid in the brain)
- Recurrence of condition after endoscopic procedure
- Developmental delays
- Developmental impairments
Preventing Encephalocele
An ultrasound is typically done between the 9th and 11th weeks of pregnancy and will show a fluid sac. This helps doctors understand how the baby is growing. Parents are then informed about the progress to help them understand the situation, and in some cases, discuss the option of ending the pregnancy. Genetic counseling could also be helpful for those affected and their families.
To reduce the risk of Neural Tube Defects (NTDs) – abnormal development of the brain, spine or spinal cord – it’s recommended that women who can potentially have children should include folic acid in their diet. This can be achieved either by eating foods fortified with folic acid or by taking supplements of folic acid. But, there’s no clear proof that a lack of folic acid directly leads to encephalocele – a rare type of birth defect where the baby’s brain is forming outside the skull. Regardless, women who can have children are advised to consume 400 mg of folic acid every day.
For kids who experience developmental delays – they don’t reach developmental milestones at the expected times – it’s advised to consider special education and additional services in medical, social, and vocational areas. These services are designed to help fulfill their potentials.