A choroid plexus ultrasound is a medical imaging technique that uses sound waves to create pictures of the choroid plexus, a specialized network of cells and blood vessels located within the brain’s fluid-filled ventricles. This article explains what a choroid plexus ultrasound involves, why it might be performed, how its findings are interpreted, and what to expect during the procedure.
Understanding Choroid Plexus Ultrasound
The choroid plexus produces cerebrospinal fluid (CSF), which is a clear fluid that surrounds and protects the brain and spinal cord, cushioning them from trauma and helping to remove waste products. Ultrasound technology uses high-frequency sound waves, which are inaudible to humans, to generate real-time images of internal body structures. These sound waves bounce off tissues and organs, and the echoes are then converted into visual images on a monitor.
A choroid plexus ultrasound is typically performed in two main scenarios. During pregnancy, it is a part of a routine fetal anatomy scan, usually conducted in the second trimester, around 14 to 22 weeks of gestation. For newborns and infants, the scan is performed using transfontanelle ultrasound, where the transducer is placed over the soft spots (fontanelles) on the baby’s head. This method helps to assess the brain’s ventricles and the choroid plexus within them.
Reasons for the Ultrasound
One common reason for a choroid plexus ultrasound is its inclusion in routine prenatal screening, specifically as part of the fetal anatomy scan. This scan allows healthcare providers to examine the developing brain and identify structures like the choroid plexus. The choroid plexus is typically visible by the ninth week of gestation and fills most of the lateral ventricles by 12 weeks.
Sometimes, the ultrasound may reveal choroid plexus cysts (CPCs), which are small, fluid-filled sacs within the choroid plexus. These cysts are relatively common, occurring in about 1% to 2% of pregnancies, or roughly 1 in 50 to 100 fetuses. While often benign and not harmful to the baby, disappearing in most cases by 26 to 28 weeks of gestation, they can occasionally be associated with certain chromosomal conditions, such as Trisomy 18 (Edwards syndrome). Trisomy 18 is a serious condition that affects fetal development, often leading to severe health issues and is present in less than 1 in 3,000 newborns.
However, an isolated CPC, meaning it is the only finding on an otherwise normal comprehensive ultrasound, has a very low association with Trisomy 18, with a chance well under 1%. Beyond prenatal screening, choroid plexus ultrasound is also used to evaluate newborns or infants, especially if there are neurological concerns. It can help assess for conditions like hydrocephalus, which is an abnormal accumulation of cerebrospinal fluid in the brain’s ventricles, or other brain anomalies. The scan offers a non-invasive way to visualize the infant brain’s structures through the open fontanelles.
Interpreting Ultrasound Findings
On an ultrasound, a normal choroid plexus appears as an echogenic, or bright, structure within the brain’s ventricles. In early pregnancy, it might appear butterfly-shaped, filling much of the ventricles, and later becomes more tear-drop shaped. When choroid plexus cysts are present, they appear as sonolucent, or dark, fluid collections within this echogenic tissue. These cysts can vary in size, from a few millimeters to 1-2 centimeters, and may be present in one or both ventricles.
The significance of choroid plexus cysts depends on whether they are isolated findings or if other anomalies are detected. An isolated choroid plexus cyst, without any other unusual findings on a thorough ultrasound, is usually considered a normal variation and typically resolves on its own. In such cases, the likelihood of a serious chromosomal condition like Trisomy 18 is very low, often cited as less than 1%. However, if choroid plexus cysts are found alongside other structural abnormalities or “soft markers” for chromosomal conditions, further evaluation, such as genetic counseling or additional testing like amniocentesis, might be recommended to assess the overall risk. Parents receive detailed explanations of these findings and potential next steps, with reassurance that many findings are benign and do not signify serious problems.
Preparing for the Ultrasound and Safety
Preparing for a choroid plexus ultrasound typically requires no specific actions beforehand. Patients generally do not need to fast or alter their medication schedule. For a fetal ultrasound, the patient will lie comfortably on an examination table, and a water-soluble gel will be applied to the abdomen. Similarly, for an infant, gel is applied to the scalp over the fontanelles.
During the procedure, a technician or sonographer moves a handheld device called a transducer over the gelled area. The transducer sends and receives sound waves, creating images that are displayed on a monitor. The scan itself is generally quick, typically lasting 20 to 30 minutes, and is usually painless, though some pressure from the transducer might be felt.
Ultrasound imaging is widely considered safe for both expectant mothers and fetuses, as well as for infants, because it uses sound waves instead of ionizing radiation, which is found in X-rays.