Encephalocele

What happens

The neural tube, which forms the brain and spinal cord, closes in the first 4 weeks of pregnancy, often before a person knows they are pregnant. If the part at the top does not close completely, or the skull fails to form properly over it, the brain and its coverings (the meninges) can bulge out through the gap.

The sac may contain:

• only meninges and fluid (meningocele), which has a better outlook
• meninges and brain tissue (encephalocele or meningoencephalocele)
• brain tissue and part of the fluid-filled ventricles

It is related to other neural tube defects such as spina bifida and anencephaly.

Types by location

Causes and risk factors

The exact cause is usually unknown. Contributing factors include:

• low folate before and in early pregnancy
• genetic syndromes, such as Meckel-Gruber syndrome, Walker-Warburg syndrome and others
• family history of neural tube defects
• maternal diabetes and obesity
• certain anti-seizure medicines such as valproate in early pregnancy
• high body temperature in early pregnancy (fever or hot tubs)
• environmental and geographic factors

Signs and symptoms

At birth, most encephaloceles are visible as a skin-covered or membrane-covered sac on the head. They range from small to larger than the baby's head. Associated problems depend on how much brain is involved:

• hydrocephalus: build-up of fluid in the brain, in a large proportion of affected babies
• microcephaly: a small head
• seizures
• developmental delay and intellectual disability
• weakness or stiffness of the limbs
• vision problems
• feeding difficulties
• facial differences, such as wide-set eyes, with frontal types

Diagnosis

• Prenatal ultrasound: often during the anatomy scan around 18 to 22 weeks, or earlier
• Maternal serum alpha-fetoprotein (AFP): may be raised, though less reliably than with open spina bifida
• Fetal MRI: shows how much brain tissue is in the sac and any other brain abnormalities
• Genetic testing: amniocentesis or testing after birth for associated syndromes
• After birth: MRI and CT scans plan surgery and check for hydrocephalus

A prenatal diagnosis allows families to meet specialists, plan delivery at a center with pediatric neurosurgery, and discuss options. Cesarean delivery is often recommended for larger sacs.

Treatment

Surgery

Surgery is usually done in the first days to months of life, depending on the size, skin coverage and the baby's condition. The neurosurgeon:

• places the protruding tissue back into the skull if it is functional, or removes non-functioning tissue
• closes the membranes and repairs the skull defect
• for frontal types, works with craniofacial surgeons to correct facial differences

Managing related conditions

• Hydrocephalus: a shunt or endoscopic procedure to drain excess fluid
• Seizures: anti-seizure medicines
• Therapy and support: physical, occupational and speech therapy, early intervention services, vision and feeding support

Outlook

The outlook varies widely:

• small encephaloceles containing mostly membranes, and many frontal types, often have good outcomes with normal or near-normal development
• large occipital encephaloceles with much brain tissue, hydrocephalus or other brain malformations carry a higher risk of developmental disability, and some babies do not survive

Long-term care is provided by a multidisciplinary team including neurosurgery, neurology, developmental pediatrics and therapies.

Prevention

• Folic acid: the CDC and USPSTF recommend that anyone who could become pregnant take 400 micrograms (0.4 mg) of folic acid daily, starting at least 1 month before conception. Those with a previous neural tube defect pregnancy are usually advised to take a higher dose under medical guidance
• control diabetes and weight before pregnancy
• review seizure medicines with a doctor before pregnancy
• avoid overheating and treat fever in early pregnancy

Frequently asked questions

What is an encephalocele?

An encephalocele is a rare birth defect in which brain tissue and its coverings bulge through an opening in the skull, forming a sac. It is a neural tube defect that develops in the first month of pregnancy.

What causes encephalocele?

The cause is often unknown. Low folic acid, genetic syndromes, family history of neural tube defects, maternal diabetes, certain seizure medicines and high fever in early pregnancy can increase the risk.

Can encephalocele be treated?

Yes. Surgery closes the skull defect and either returns the tissue to the skull or removes non-functioning tissue. Related problems such as hydrocephalus and seizures are also treated. Outcomes depend on the size and contents of the sac.

Can encephalocele be prevented?

Not all cases can be prevented, but taking 400 micrograms of folic acid daily from at least a month before pregnancy reduces the risk of neural tube defects. Higher doses may be recommended after a previous affected pregnancy.