Introduction
A choroid plexus cyst refers to the build-up of fluid in the choroid plexus of an unborn baby. It appears as a tiny bubble of fluid during an ultrasound examination. It appears like a blister and is not considered a brain abnormality. In most cases, the cyst resolves without treatment and does not cause any consequences. A choroid plexus cyst is usually diagnosed during the second trimester and can occur in two percent of pregnancies.
What Is a Choroid Plexus?
The choroid plexus refers to a complex network of blood vessels and cells that are present in the ventricles (fluid-filled chambers) of the brain. The major function of the choroid plexus is to secrete cerebrospinal fluid. It also regulates the production of cerebrospinal fluid and its composition. The choroid plexus also serves as a barrier in the brain and separates the blood from the cerebrospinal fluid. In addition, the choroid plexus secretes various growth factors essential for brain development and protects against harmful microorganisms and toxins.
What Is a Choroid Plexus Cyst?
A cyst is an abnormal, noncancerous growth filled with a liquid or semisolid substance. A choroid plexus cyst is a small fluid build-up in the choroid plexus of the brain in an unborn baby. Choroid plexus cysts are usually detected during an ultrasound examination. These cysts are not abnormal, and they resolve without any treatment. Though these cysts are not associated with any abnormalities, they can cause chromosomal abnormalities such as trisomy 18 (a condition that causes developmental delays) in some cases. This can result in stillbirth, severe mental retardation, and developmental abnormalities.
What Are the Causes Associated With a Choroid Plexus Cyst?
A choroid plexus cyst develops when fluid gets trapped in the cellular layers of the choroid plexus. A choroid plexus cyst can be single or multiple. It resembles a blister that forms on the skin. The choroid plexus begins to develop at six weeks of gestation. A choroid plexus cyst may be visible on an ultrasound during 25 weeks of gestation. A small choroid plexus cyst usually disappears within 28 weeks of gestation. However, large choroid plexus cysts can cause hydrocephalus (a condition in which cerebrospinal fluid accumulates within the brain).
What Are the Complications Associated With a Choroid Plexus Cyst?
A choroid plexus cyst does not affect the area of the brain involved in thinking or reasoning and does not have any impact on intelligence or cognitive development. Though a choroid plexus cyst is a normal variant and does not cause any intellectual disabilities or health disorders, it can cause chromosomal abnormalities like trisomy 18, which is also referred to as Edwards syndrome. It is a condition in which three copies of chromosome 18 are present instead of two. Babies with trisomy 18 do not survive birth because of organ disabilities. Babies born with this condition have birth defects, including abnormalities in the heart and head, small mouths, clenched fists, and difficulties in feeding and breathing. Trisomy 18 also causes severe mental disabilities. However, only a small percentage of babies with choroid plexus cysts will have trisomy 18.
How Is a Choroid Plexus Cyst Diagnosed?
A choroid plexus cyst is usually diagnosed during routine ultrasound examinations. If a fetus presents with trisomy 18 along with a choroid plexus cyst, the fetus may have other abnormalities. Therefore, the following tests are recommended to determine if any other congenital disorders are present.
Alpha-Fetoprotein (AFP) Test - AFP test is a screening test that helps determine the levels of alpha-fetoprotein. This test is a usual blood test that is performed during 15 to 20 weeks of pregnancy. Alpha-fetoprotein is produced in the baby’s liver and is present in the amniotic fluid (a fluid that surrounds the baby in the womb). Excessive or too little alpha-fetoprotein may indicate the following conditions:
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Neural tube defects such as spina bifida (a congenital abnormality brought on by improper formation of the spine and spinal cord).
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Down syndrome (a genetic abnormality that results in developmental and intellectual abnormalities).
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Chromosomal abnormalities.
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Abnormalities in the abdominal wall of the fetus.
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Miscalculations in the due date.
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Possibility of twin pregnancies.
Level II Ultrasound - A level II ultrasound scan is also called an anatomy scan or anomaly scan. It is recommended between 18 and 22 weeks of pregnancy. Level II ultrasound provides a detailed view of the baby’s body, including the brain, heart, and other organs. It also helps examine the umbilical cord and amniotic fluid levels. If anatomical abnormalities, such as a small mouth and clenched fists, are present, it indicates the presence of trisomy 18.
Amniocentesis - An amniocentesis is a procedure that uses an ultrasound-guided needle to withdraw amniotic fluid and is tested for birth defects and genetic abnormalities. It is performed to detect congenital abnormalities in babies with a choroid plexus cyst along with trisomy 18.
How Is a Choroid Plexus Cyst Treated?
A choroid plexus cyst usually resolves without any treatment within 28 weeks of gestation. Even if it does not resolve, a healthy baby born with a choroid plexus cyst will develop normally. Surgical removal of the cyst is required in rare cases if the cyst is diagnosed to be a cancerous tumor called choroid plexus carcinoma.
What to Expect With a Choroid Plexus Cyst?
Choroid plexus cysts can be seen in one to two percent of normal fetuses. However, a small percentage of fetuses have an associated chromosomal disorder called trisomy 18. Choroid plexus cysts usually resolve on their own, but multiple cysts require intervention. It does not cause any abnormalities in the brain if associated abnormalities are not present. Also, studies have shown that children with choroid plexus cysts that resolved did not show any cognitive impairments or developmental disabilities.
Conclusion
A choroid plexus cyst is a tiny bubble of fluid in the choroid plexus of the brain. It is usually detected during an ultrasound scan performed during the second trimester of pregnancy. However, it resolves on its own within 28 weeks of pregnancy and does not require treatment. But, it may cause congenital abnormalities, if it is associated with trisomy 18, a chromosomal disorder. However, if any associated abnormalities are not present, the fetuses are normal and do not show cognitive impairments or other disabilities.
