Cranium Bifidum

Overview

Cranium bifidum is a birth defect in which there is an incomplete closure (a cleft or gap) in the bones of the skull. The term describes a split in the cranium, much as spina bifida describes a split in the spine. It belongs to the broader group of neural tube and cranial defects that arise early in pregnancy.

The significance of cranium bifidum depends on whether tissue protrudes through the gap. In some cases the opening is small and covered by skin, with nothing pushing through (cranium bifidum occultum). In others, the protective membranes around the brain bulge out (a cranial meningocele), or brain tissue itself protrudes (an encephalocele). The outlook and treatment vary widely depending on the type and what tissue is involved.

Features

The features depend on the size and type of the defect:

• A soft bulge or sac on the head, often at the back, top, or front of the skull
• A visible or felt gap in the skull bones
• Skin-covered or, less often, open lesions
• In encephalocele, neurological problems such as developmental delay, weakness, vision problems, or seizures, depending on the brain tissue affected
• Sometimes a buildup of fluid in the brain (hydrocephalus)

A small, hidden defect may cause no symptoms at all and be found only on imaging.

Causes

Cranium bifidum and related defects arise when the structures that should close over the brain and form the skull early in pregnancy do not fully come together. Contributing factors are similar to those for other neural tube defects:

• Incomplete neural tube or skull closure: The underlying mechanism during early fetal development.
• Low folic acid (folate): Inadequate folate around conception increases the risk of neural tube and cranial defects.
• Genetic factors: A family history of neural tube defects raises risk, and some cases are part of genetic syndromes.
• Other factors: Poorly controlled diabetes and certain medications during pregnancy.

In many individual cases, no single cause can be identified.

Risk Factors

• Inadequate folic acid before and during early pregnancy
• A family history of neural tube defects
• A previous pregnancy affected by a neural tube defect
• Poorly controlled maternal diabetes
• Use of certain medications in pregnancy
• Some inherited genetic syndromes

Diagnosis

Cranium bifidum may be found before or after birth:

• Prenatal ultrasound: Can show a skull defect or a bulging sac during pregnancy.
• Maternal blood screening: May raise suspicion of a neural tube defect.
• Physical examination at birth: A visible bulge or skull gap prompts further testing.
• MRI and CT scans: Detailed imaging shows the size of the defect and whether brain tissue is involved.

Treatment

Treatment depends on the type and severity of the defect.

• Surgery: Many cases need an operation to close the skull defect, return protruding tissue when possible, and protect the brain. Timing depends on the child's condition.
• Managing hydrocephalus: If excess fluid builds up in the brain, a shunt may be placed to drain it.
• Supportive therapies: Physical, occupational, and speech therapy help children with developmental or neurological effects.
• Ongoing follow-up: Regular care monitors growth, development, and any complications.

Outcomes range from excellent for small, skin-covered defects to more guarded when significant brain tissue is involved.

Prevention

• Take a daily folic acid supplement before conception and in early pregnancy
• Eat folate-rich foods such as leafy greens, beans, and fortified grains
• Control diabetes before becoming pregnant
• Review medications with a doctor before and during pregnancy
• Seek genetic counseling if you have a personal or family history of neural tube defects

When to See a Doctor

A skull defect found before or at birth is managed by a specialist team. Seek prompt medical attention if a child with a known or suspected cranial defect has:

• A new or enlarging bulge on the head
• Leakage of fluid from the area, fever, or signs of infection
• Seizures, persistent vomiting, or unusual sleepiness
• Delays in development or new neurological symptoms

If you are planning a pregnancy, talk to a doctor about folic acid and any risk factors in advance.

Related Topics

Frequently Asked Questions

References

1. MedlinePlus, U.S. National Library of Medicine. Encephalocele.
2. Centers for Disease Control and Prevention (CDC). Facts about Encephalocele.
3. March of Dimes. Neural tube defects.
4. National Institute of Neurological Disorders and Stroke (NINDS). Encephaloceles.