Choroid Plexus Cysts
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Choroid Plexus Cysts are sometimes found in the fetal brain during the second trimester ultrasound. They can be worrisome to new parents, but much of the worry is relieved when more information is provided.
 What Are They?
The area of the brain that makes the spinal fluid that surrounds the brain and spinal cord is called the choroid plexus. There is one on each side of the brain. The choroid plexus is not part of the brain involved in the thinking process. Occasionally (in about 1% of pregnancies), a cyst will form within this area of a growing infant’s brain. This is called a choroid plexus cyst (CPC), and can usually be detected by ultrasound. These cysts can form on just one side of the fetal brain (unilateral) or both sides of the brain (bilateral).
 What Does It Mean?
CPC’s are found in approximately 1% of fetuses during routine ultrasounds and are thought to be a natural phenomenon in brain development. If the baby does not exhibit any other signs of genetic abnormality in the ultrasound, such as clenched fists, malformed organs, or nuchal (neck) thickness, etc. it is likely that the CPC is what they call "isolated" and is unrelated to any other condition. The majority of cysts, when not accompanied by additional markers, resolve on their own, and result in healthy babies. A choroid plexus cyst does have a very weak association with fetal chromosomal abnormalities, most strongly Trisomy 18 (Edward’s Syndrome).
 What Can Be Done?
When a CPC is identified by ultrasound, additional testing is an option. An ultrasound that shows more detail (Level II Ultrasound) can be used to look for both major birth defects and minor findings associated with Trisomy 18. Depending on the information found in previous ultrasounds, this is usually recommended as the first step.
Amniocentesis, to test for chromosomal abnormalities in the baby, is also an option. Because these cysts often resolve on their own, many unnecessary amniocenteses would be done if they were performed in all of these cases. Amniocenteses do carry a risk of miscarriage of .5-1% so it is important to think carefully before making the decision to have one performed. There are additional ways to determine the level of risk associated with genetic disorders including maternal age, and the results of a triple screen test, if one was performed. A visit with a genetic counselor would help determine the risk of a chromosomal abnormality by taking all of the factors into consideration. In most cases, if the Level II ultrasound revealed no additional markers, and the determined risk was low, the amniocentesis would not be advisable. In the vast majority of cases, the cyst will disappear by the 32nd week of gestation, and have no affect whatsoever on the fetus.
 How Worried Should We Be?
The main thing to remember is that if your ultrasound shows a CPC, there is a slight increase in odds that your baby may have a genetic disorder such as Trisomy 18, but the immense majority of babies with CPC’s and no other markers for abnormalities are born perfectly healthy and with no adverse effects. It is reason for concern, but the odds are in your favor. The fetal brain may create these cysts as a normal part of development, and it is most likely it will go away on its own. CPC's have no impact on a person’s health or development. They are almost always temporary.