Choroid Plexus Cysts

Baby at doctor
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When Tina and Jim Angelman* of Brighton, Massachusetts saw their baby on the ultrasound screen, it was a moment of pure joy. Exclamations of “Is it a boy or a girl?” and “Look at those tiny hands!” filled the room, until Tina noticed the technician huddling closer to his screen. When he left to get the doctor, Tina filled with dread. The doctor’s words fell heavily. “I’m sorry, but I see something that may indicate a problem. Your baby has a choroid plexus cyst.”

At that moment, Tina and Jim’s feelings about their baby and the pregnancy changed. “It’s pretty hard to describe how it feels to go from cloud nine to the worst day of your life in the span of a two-minute conversation. I didn’t know what to think—the radiologist didn’t really give us a clear picture of what was going on, and it all seemed very vague,” says Jim.

A similar scenario played out for Cindy Scoville of Phelps, New York during her 18-week ultrasound. “I was so stressed, worried, sad, and anxious,” she said after the doctor revealed that her son had four choroid plexus cysts.

At least one out of one hundred parents will share this frightening experience during a routine ultrasound. What is a choroid plexus cyst? What does it mean? And what can parents do about it?

What is a Choroid Plexus Cyst?

The choroid plexus is an area of the brain that is not involved thinking or personality. Rather, the choroid plexus makes a fluid that protects and nourishes the brain and spinal cord. When a fluid-filled space is seen in the choroid plexus during an ultrasound, it is called a choroid plexus cyst (CPC). “We don’t know why, but between 1 and 3 percent of all fetuses will manifest a CPC at 16 to 24 weeks of pregnancy,” says Dr. Roy A. Filly, a Professor of Radiology and of Obstetrics, Gynecology and Reproductive Sciences and Chief of the Section of Diagnostic Sonography at University of California, San Francisco. CPCs can be found either on one side of the brain (unilateral) or both sides (bilateral). They can vary in size and shape, from small and round to large and irregular. Some fetuses have more than one.

Regardless of their number, shape or size, choroid plexus cysts are not harmful to the baby. “I am not aware of a single instance where a CPC caused damage to a fetus,” says Dr. Filly.

Dr. Peter Doubilet, a Professor of Radiology at Harvard Medical School, agrees, “That’s one very important fact. CPCs are not harmful, and they nearly always go away by the third trimester of pregnancy.”

If CPCs are found during an ultrasound, the radiologist will scrutinize every organ and body part to look for other abnormalities, such as a malformed heart, head, hands or feet, and stunted growth of the baby. When no other abnormalities are found, the diagnosis is called an “isolated CPC.”

The Significance of an Isolated CPC

If CPCs do not cause any damage, why does anyone worry about them? The problem is really one of association—being at the wrong place at the wrong time. Wrong or right, CPCs have become associated with a severe genetic disease called Trisomy 18. It is well documented that about half of babies with Trisomy 18 show a CPC on ultrasound. But Dr. Bronsteen from the Division of Fetal Imaging at William Beaumont Hospital in Royal Oak, Michigan points out, “Nearly all babies with Trisomy 18 who have a CPC have other abnormalities on the ultrasound, especially in the heart, hand, and foot.” The real question arises when a baby has a CPC with nothing else wrong: the “isolated CPC.”

*Names have been changed by request

This is where the experts cannot precisely agree. “The vast majority of fetuses with [isolated] CPCs are completely normal, but when CPCs are seen, the chance of Trisomy 18 goes up,” says Dr. Doubilet, “This risk is still very small: about 1 in 300.” This means that if 300 fetuses have isolated CPCs, only one of them will have Trisomy 18. “While the risk is small, it is higher than the risk of approximately 1 in 3,000 among all pregnant women,” points out Dr. Doubilet. Other doctors have reservations: “The problem with this research is that it studied a high-risk population instead of the general population of pregnant women,” says Dr. Filly. “I have no instance in 25 years of experience of an isolated CPC indicating Trisomy 18.”

Dr. Bronsteen notes, “You need to ask if the person doing the ultrasound exam has the expertise to look for all the abnormalities that are seen with Trisomy 18. In the dozen years we’ve been tracking it, we did have some babies with an diagnosis of isolated CPC turn out to have Trisomy 18, but in all those cases we did not get a complete look at the baby.” His own research indicates that it is very important for the sonographer to view the baby’s hands before concluding that the CPC is isolated.

This debate among experts can leave parents bewildered. But even if an isolated CPC does mean an increased risk, that risk is still extremely small. The take-home message? If a CPC is found with no other warning signs, the outcome is virtually always positive.

What Parents Can Do

When a baby is diagnosed with a CPC, there are several things that parents can do. After consultation with their doctor, they will usually undergo a Level II ultrasound. This is a detailed ultrasound exam that is targeted to look for fetal abnormalities. It’s important not to rely on the results of a scan performed in a doctor’s office or a scan done by someone who is not a trained expert in detecting abnormalities by ultrasound. Only after this kind of intense scan can the diagnosis of an isolated CPC be truly confirmed.

Once other abnormalities besides the CPC have been ruled out, there are two things parents can do: watch and wait, or have an amniocentesis. An amniocentesis is the only way to know for sure before birth that the baby does not have a genetic disease. But even though an amnio can give a sure answer, it carries its own risk. About one in 250 women will miscarry her baby after an amnio, regardless of whether the baby is healthy or not.

The other option is to watch and wait. Generally the doctor will track the progress of the fetus through several follow up ultrasound examinations. Most CPCs will resolve on their own by the sixth month of pregnancy, and a definitive exam of the baby’s health can be made after the birth.

While no one can make this decision except the parents and their doctor, many experts suggest that the risk of an amnio is not worth it when the only abnormality the baby has is a CPC. “In our practice, we don’t like to do an amnio on somebody whose baby has a very low risk of Trisomy 18 because you wind up losing more normal pregnancies…than you will find Trisomy 18 babies. It doesn’t make sense to have a miscarriage of two or three normal babies to find one with Trisomy 18,” says Dr. Bronsteen. Your doctor can tell you what his or her recommendation is for your unique situation.

The Angelmans discussed the diagnosis with their doctor and opted to have a Level II ultrasound, which showed no other problems. “It was on the back of our minds the whole pregnancy, and it made it hard not to worry. But our son was born healthy and happy,” say Jim and Tina.

After talking with her doctor, Cindy Scoville also decided to have a Level II ultrasound. “At 24 weeks no other abnormalities were found and the sonographer was able to see everything very clearly.” says Cindy. “Our little boy is beautiful, healthy and everything we dreamed of. Another happy ending to the worrisome beginning of dealing with a CPC diagnosis during pregnancy.”

A CPC diagnosis is scary, no doubt about it. But rest assured that the experts agree that the vast majority of these babies are perfectly healthy, and their CPC is just a normal part of growth and development.

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