Encephalocele: what it is, causes, surgery and outlook

GOSH describes an encephalocele as a rare congenital (present at birth) type of neural tube defect in which part of the skull has not formed properly, so a portion of brain tissue and associated structures are outside the skull. The protruding sac may be covered with skin or with a thin membrane.

GOSH explains the naming. If just the covering of the brain (the meninges) is outside the skull, it tends to be called a meningocele. If both brain tissue and meninges are outside, it can be called an encephalomeningocele. It can affect any area of the skull: the middle of the back of the head, the middle of the top of the head, or the nose and forehead region. A swelling in the nose and forehead region tends to be called a "midfacial cleft" and is explained separately by GOSH.

GOSH explains that in early development the brain and spinal cord start as a tube-like structure, the neural tube, which is open at either end. The openings close within the first weeks of pregnancy and the tube goes on to form the brain and spinal cord. If it fails to close properly the result is a group of problems called neural tube defects.

GOSH says we do not really understand what causes neural tube defects in general, but folic acid can reduce the risk of them happening in future pregnancies. In most cases an encephalocele develops sporadically, "out of the blue", and is not passed from parent to child. It can, however, be a feature of syndromes such as Dandy-Walker syndrome or Chiari malformation, which may have a genetic component, and a family history of neural tube defects increases the risk of having a child with an encephalocele.

GOSH says racial background seems to affect where it occurs: in Western babies a posterior encephalocele (back of the head) is more common, whereas in Eastern babies an anterior encephalocele (front of the head) is more common. Females are more likely to have a posterior encephalocele and males an anterior one.

The location, type and amount of brain tissue outside the skull all shape the treatment plan and outlook. GOSH says anterior encephaloceles are less likely to contain brain tissue, so tend to produce fewer symptoms, and that very large encephaloceles may be incompatible with life, so affected babies may not survive the pregnancy.

The sac or lump is the visible sign. GOSH says the symptoms are very variable, and that many children have no symptoms other than the lump itself. When symptoms occur they can include the following.

• Hydrocephalus: cerebrospinal fluid (CSF) builds up in the cavities of the brain and increases pressure on the brain; GOSH says brain tissue outside the skull reduces CSF flow.

• Developmental delay: reaching milestones such as sitting, crawling or walking later than other children, and sometimes being smaller than children of the same age.

• Learning disabilities that continue throughout life.

• Seizures (fits or convulsions).

• Visual impairment.

GOSH says that if the encephalocele is large it may be seen on routine prenatal ultrasound, which may allow planning of a caesarean section if vaginal birth could be risky. Otherwise, in most cases an encephalocele is visible at birth and easily diagnosed. Very small ones, especially in the nose and forehead area, may not be so visible.

Once suspected, the diagnosis is usually confirmed with imaging, such as MRI, which lets doctors see exactly how much of the skull is affected and whether the sac contains meninges, brain tissue or both. Because an encephalocele can be associated with other problems, doctors examine the child closely to check.

GOSH says encephaloceles always require correction with an operation under general anaesthetic. Timing varies. If the sac is covered only by a thin membrane, surgery soon after birth is needed to prevent infection and damage or drying of the exposed tissue. If it is covered with skin, surgery can be delayed for a month or two to allow the baby to grow and develop.

The surgeon makes an incision near the encephalocele, cuts through the tough covering of the brain (the dura) and removes a portion of skull bone so that the meninges and/or brain tissue can be repositioned inside the skull. If hydrocephalus is present, a shunt is inserted to drain excess CSF into the abdomen. The dura is then repaired and the skull bone replaced, either with the removed portion or a patch of artificial material if there is not enough bone, and the incision is closed.

GOSH says close monitoring is needed in the first few hours after the operation to ensure CSF is not leaking and any shunt is working, with regular neurological observations at least for the first night. Many parents of children with no symptoms other than the lump choose surgery for cosmetic reasons and because of worry about injuries later in life, such as playing sport.

GOSH says the outlook is variable, depending on the location and the amount of meninges and brain tissue outside the skull, on any other problems present, and on whether the encephalocele is part of a syndrome. For a proportion of children the outlook is good, with few long-term effects on functions such as breathing, vision and hearing.

Children with learning disabilities benefit from support in education and day-to-day life, although a degree of independence may be possible. The majority of children with no learning disabilities grow up to lead a normal life, working and raising a family. Your child's neurosurgery team can give a more specific picture once they have the scan results.

The NHS says folate helps reduce the risk of birth defects called neural tube defects, such as spina bifida. It recommends a 400 microgram folic acid supplement daily for anyone pregnant, trying for a baby or who could get pregnant, until 12 weeks of pregnancy, taken before getting pregnant. It says some women have an increased risk of a pregnancy affected by a neural tube defect and are advised to take a higher dose of 5mg each day until 12 weeks, which is unlikely to cause harm as it is short term, but to speak to a doctor first.

GOSH says an adequate intake of folic acid can dramatically reduce the risk of an encephalocele in future pregnancies, and that it can arrange a consultation with a genetic specialist for families with concerns. It also notes that a previous baby with a neural tube defect raises the chance for a future baby, so ask your doctor about the dose that is right for you before you conceive.

Families are looked after by a specialist team who will explain what to watch for. GOSH describes the risk of CSF leaking and of a shunt not working after surgery. If you are worried about a leak, a change in the lump, or your baby seems drowsy, feverish, unusually irritable or is having fits, contact your specialist team or NHS 111 straight away, and call 999 if a child is very unwell, floppy or hard to wake. Your specialist team should tell you who to call out of hours.

On the NHS, an encephalocele found on a scan during pregnancy is referred to a fetal medicine and paediatric neurosurgery team, which will plan the birth and early surgery. If it is found at birth, the baby is transferred to a specialist paediatric neurosurgical centre. Surgery and follow-up are provided by NHS specialist children's units.

Private care for an encephalocele would need to be in a unit with paediatric neurosurgical, intensive care and neurodevelopmental support. Ask which team would manage an emergency, and keep the NHS team informed.