Choroid Plexus Cysts are Harmless
One of the rather common findings in a detailed ultrasound scan in the first half of pregnancy is what is known as ‘Choroid Plexus Cysts’. Up to 2% of all babies will be found to have one or more of these small cysts in the part of the brain known as the Choroid Plexus (hence the name)
The brain and spinal cord is surrounded by fluid (cerebrospinal fluid), the chief function of which is to act as a cushion. The Choroid plexus is the part of the brain that produces this fluid.
Choroid plexus cysts, commonly abbreviated as CPCs in scan reports, are one feature the finding of which can cause real anxiety on the part of prospective parents. They are part of a group of ultrasound scan findings termed as ‘soft markers’. Other soft markers include:
- Nuchal fold thickening
- Single umbilical artery (instead of the normal two)
- ‘Golf balls’ in the heart
- Renal (kidney) pelvis dilatation
- Echogenic bowel
- Short ‘long’ bones (Rhizomelic limbs)
To avoid information overload, which can be counter-productive; we shall restrict ourselves to just the one ‘soft marker’ in this hub and we will cover the other soft markers in separate hubs.
When a detailed ultrasound scan is done, usually at the mid-point of pregnancy (around 20 weeks gestation); the aim is to take a careful detailed look at the baby’s anatomy to see if everything is as it should be. Around 3% of babies will be found to have what are described as major anomalies. There is a whole variety of these. These may or may not be associated with known genetic or chromosomal defects such as Down’s syndrome.
Away from the major congenital anomalies, we come to what are known as ‘soft markers’ as listed above.
Choroid plexus cysts
Choroid plexus cysts (CPC) will usually be found in the first half of pregnancy. They almost invariably disappear and cannot be found in the later stages of pregnancy. Tracking these by doing serial ultrasound scans is therefore of no clinical value.
The significance of CPCs arises from the fact that they have been associated with a serious chromosomal defect called Edward’s syndrome. Edward’s syndrome is also known as Trisomy 18. You may be aware that, for human beings, there are 23 pairs of chromosomes. It so happens that in this defect, the baby ends up with 3 chromosomes on set number 18 hence the name ‘Trisomy 18’. In that respect, this condition is similar to Down’s syndrome but in the latter, the extra chromosome is on set number 21. That is why Down’s syndrome is also known as Trisomy 21. The practical difference, however, is that Edward’s syndrome is a much more serious condition with the majority of babies either stillborn or dying within days or weeks of birth. Unlike babies affected by Down’s syndrome, those with Edward’s syndrome never grow into late childhood, let alone adulthood. The association of choroid plexus cysts with this condition is therefore legitimately terrifying but it shouldn’t be. Here is why:
Choroid Plexus Cysts aren’t Edward’s syndrome
I cannot emphasize the header above strongly enough. Whilst up to one in every fifty babies will be found to have choroid plexus cysts on their prenatal scans, it is only a tiny minority of these who will be affected by Edward’s syndrome. Consider this: Edward’s syndrome occurs in 1 in every 5000 live births. That makes it a hundred times less common than choroid plexus cysts (CPCs). You can therefore see clearly that the overwhelming majority of babies found to have CPCs will, in fact, not be affected by Edward's syndrome.
It is useful also to be aware that babies with Edward’s syndrome will almost always have other, usually major, organ defects that are easily identifiable on a scan. Presence of these increases the possibility of the baby being affected quite significantly. When defects of the heart, kidneys, gut or limbs are found, the mother should be properly counselled and offered a diagnostic test.
If choroid plexus cysts are found in isolation, that is, without any other structural anomalies; the chances of there being a major chromosomal defects such as Edward’s syndrome, are very low and there is no justification to embark upon any invasive procedures.
- Choroid Plexus Cysts are a common finding, seen in up to 2% of all babies on ultrasound scans
accompanied by other soft markers or major organ abnormalities, the possibility
of Edward’s syndrome is increased. This is uncommon.
plexus cysts always disappear in late pregnancy and cannot be found on scans
performed after around 26 weeks. This is regardless of whether the baby is affected by another condition.
- When choroid plexus cysts are found in isolation without any other soft markers and/or organ anomalies, they are almost always innocent and no further action is called for.
The header says 'Choroid Plexus Cysts are harmless'. That is indeed the case in the overwhelming majority.
I will cover
the other ‘soft markers’ in a separate hub but if you can’t wait, there is good
information about the