Intracranial cyst

This leaflet is to help you understand intracranial cysts.

What is an intracranial cyst?

Intracranial cysts are fluid-filled sacs found in the baby’s skull, that although it can press against the brain, these cysts are generally not harmful and do not mean that your baby will have health problems. Only in rare instances are they a serious finding.

What causes intracranial cysts?

The cause is unclear, but they are usually sporadic, meaning they occur randomly. They can be divided into arachnoid cysts and glio-ependymal or neuroepithelial cysts.

Arachnoid cysts develop within the internal layers of the meninges, the membrane that surrounds the brain. They may result from a problem in the development of the meninges, or or from complications such as in-utero bleeding or inflammation.

Glio-ependymal cysts, which contain specific types of brain cells and are found in specific areas of the brain, such as the base or near the back of the brain.

Although some intracranial cysts can grow during pregnancy, most remain stable in size, with only about 20% showing enlargement.

Most intracranial cysts are isolated anomalies, but they can sometimes occur along with ventriculomegaly (enlarged brain cavities), macrocephaly (an enlarged head), dysgenesis of the corpus callosum (abnormal development of the brain's connections) or chromosomal abnormalities.

Should I have more tests done?

You may be referred to a neurosonographer or maternal fetal medicine specialist for detailed ultrasound of the fetal brain and central nervous system, and magnetic resonance imaging (MRI), to confirm that the cyst is isolated or if other anomalies are present, and to differentiate from other possible brain abnormalities. Genetic counseling and testing may also be considered, though the risk of genetic abnormalities is small in the case of isolated intracranial cysts.

What does it mean for my baby after it is born?

Intracranial cysts, even when large, are usually benign lesions associated with a favourable outcome. Most lesions are stable in size, and some may even regress (shrink). Even large lesions that require treatment typically have a good outcome.