Ventriculomegaly

What is ventriculomegaly?

Ventriculomegaly is a condition where the fluid-spilled spaces in a fetus’s brain (ventricles) are larger than usual. This happens because cerebrospinal fluid (CSF) becomes trapped in the ventricles, causing them to widen or expand. CSF is a fluid that protects your brain and spinal cord. CSF typically flows or circulates around our brain and spinal cord before getting reabsorbed. In a fetus with ventriculomegaly, the flow and circulation is disrupted, which causes it to build up.

A healthcare provider typically diagnoses ventriculomegaly during a prenatal ultrasound in the second or third trimester. Your provider will order additional testing to determine the extent of the fluid buildup. In most cases, the fetus is born healthy and the ventricles either stop growing or decrease to their usual size.

Another word you may hear when learning about ventriculomegaly is hydrocephalus. Hydrocephalus is when the buildup of CSF causes enlarged ventricles and pressure on a person’s brain. A provider diagnoses hydrocephalus after birth. Ventriculomegaly is the term for enlarged ventricles in a fetus during a pregnancy.

How common is ventriculomegaly?

Ventriculomegaly occurs in 2 out of 1,000 live births in the United States. Most cases of ventriculomegaly are mild and don’t cause complications at birth.

What are the symptoms of ventriculomegaly?

In most cases, there are no symptoms of ventriculomegaly. Your healthcare provider usually discovers the fetus’s ventricles are enlarged during a prenatal ultrasound. Infants born with mild ventriculomegaly usually don’t show symptoms.

If the condition is severe, your baby may show signs of hydrocephalus shortly after birth. Symptoms in infants could include:

• An unusually large head or sudden growth in head size.
• Bulging soft spot (fontanel) on top of your baby’s head.
• Inability to hold their eyes up (downward gaze).
• Extreme tiredness or irritability.
• Vomiting.
• Poor feeding.

What causes ventriculomegaly?

Ventriculomegaly has multiple causes. It’s also possible for there to be no cause. It’s important to note that this condition usually happens by chance and isn’t due to genetics or environmental factors.

The most common reasons a fetus has ventriculomegaly are:

• A blockage or imbalance prevents spinal fluid from moving freely and being absorbed naturally.
• An injury or another problem affects the fetus’s brain development.

Is it genetic?

No, ventriculomegaly isn’t hereditary. This means it happens spontaneously and doesn’t appear to be passed down by biological parents.

What are the risk factors for ventriculomegaly?

Ventriculomegaly usually happens by chance. It can happen on its own or happen alongside pregnancy complications. Some studies show that the following conditions may increase the risk of fetal ventriculomegaly:

• Spina bifida.
• Agenesis of the corpus callosum (ACC).
• Infections in the pregnant person such as syphilis or cytomegalovirus (CMV).
• Chromosomal disorders such as Down syndrome.

What are the complications of ventriculomegaly?

The outcome for fetuses with ventriculomegaly depends on the severity and underlying cause. The outcome is generally better when the ventricles are mildly enlarged and there are no other irregular or abnormal findings on a prenatal ultrasound.

However, a fetus with larger ventricles or a fetus with large ventricles plus other congenital conditions are at higher risk for complications. While rare, infants born with severe ventriculomegaly may have neurological impairments or developmental delays.

Can a baby live with ventriculomegaly?

Yes. Ventriculomegaly is treatable.

How is ventriculomegaly diagnosed?

Healthcare providers generally diagnose this condition during routine fetal anatomy scans at around 18 to 22 weeks of pregnancy. It can also be diagnosed later in pregnancy. During this ultrasound, your provider measures certain parts of the fetus’s brain. An abnormally large measurement may mean the fetus has ventriculomegaly.

Your provider may order additional imaging tests such as fetal magnetic resonance imaging (MRI). This test produces images of the fetus’s brain and allows your provider to see the fetus’s ventricles in greater detail. An MRI is completely safe.

Your provider will likely order more frequent ultrasounds for the remainder of your pregnancy. This allows them to monitor the amount of fluid inside the ventricles of the fetus’s brain.

A procedure called an amniocentesis may be performed in certain situations. This involves your provider inserting a thin needle into the amniotic sac (the fluid-filled bubble around the fetus) and withdrawing some fluid. The fluid can be tested for infection, such as cytomegalovirus.

After birth, your baby will receive additional ultrasounds or MRIs on their brain. This will determine if they have hydrocephalus and if surgical treatment is necessary.

Criteria for diagnosing ventriculomegaly

The severity of fetal ventriculomegaly ranges from mild to severe based on the measurement of the ventricle. In a typical fetal brain, the ventricles are less than 10 millimeters (mm) wide — or about the width of a pea.

• Mild: The ventricles are between 10 mm to 12 mm.
• Moderate: The ventricles are between 13 mm to 15 mm.
• Severe: The ventricles are more than 15 mm wide.

How is ventriculomegaly treated?

Treatment for ventriculomegaly happens after your baby is born. It’s usually only required if your baby shows signs of hydrocephalus.

A healthcare provider will perform an ultrasound or MRI on your baby. If there’s still an unsafe amount of fluid in your baby’s ventricle, they may need brain surgery to decrease the amount of fluid in their ventricles and pressure on their brain.

The most common type of surgery involves placing a shunt in their brain to drain the fluid (ventriculoperitoneal shunt surgery). A shunt is a flexible tube that drains the excess CSF to another area of their body (like their abdomen).

A second type of surgery, called endoscopic third ventriculostomy (ETV) may be necessary in certain situations. This involves a surgeon placing an endoscope in the top of your baby’s head (fontanel). This creates another pathway for CSF to flow in and around their brain.

Can ventriculomegaly go away?

Sometimes, ventriculomegaly gets better without treatment. It can also stay the same or resolve on its own before birth. Your healthcare provider will continue to monitor the size of the fetus’s brain for the remainder of your pregnancy.

Can ventriculomegaly be prevented?

No, there’s nothing you can do to prevent ventriculomegaly.

What can I expect if my baby has ventriculomegaly?

If you receive a diagnosis during pregnancy, your provider will monitor the fetus’s brain closely. After birth, your baby will receive testing to see if their ventricles are enlarged. If there are no signs of enlarged ventricles or pressure on your baby’s brain, they may not need surgery after birth. Most babies with mild cases have no long-term health effects from the condition.

Children born with ventriculomegaly may go on to develop hydrocephalus. Surgical treatment will be necessary in these cases. Your child may need monitoring for several years after surgery to ensure their brain pressure is normal.

Should I worry about ventriculomegaly?

If a fetus has mild ventriculomegaly and no other health conditions, there’s about a 90% chance that there are no long-term effects from ventriculomegaly.

It may be troubling to hear your baby may be born with a medical condition. Be sure to ask your provider any questions you have. Let them ease your worries that your baby will be healthy. They’ll do all they can to support you.

Does ventriculomegaly affect delivery?

Not usually. A vaginal delivery is usually OK as long as the fetus’s head isn’t too large. A C-section may be required if other medical problems are present or if the fetus has a large head. Your provider may recommend delivery in a hospital that can treat babies born with specific needs. This ensures there are specialists available for their care, as well as a neonatal intensive care unit (NICU).

Does ventriculomegaly mean my baby has Down syndrome?

Not necessarily. There are correlations between ventriculomegaly and Down syndrome. A fetus may be at an increased risk of chromosomal disorders like Down syndrome if they have enlarged ventricles. However, ventriculomegaly doesn’t mean your baby will have Down syndrome.

What questions should I ask my provider about ventriculomegaly?

It’s normal to have questions about a ventriculomegaly diagnosis. You may want to ask your healthcare provider the following questions:

• Do I need additional testing?
• Is there anything I need to do differently because of this diagnosis?
• Is there a treatment for ventriculomegaly?
• Will my baby have cognitive or developmental delays?
• Will my baby need surgery after birth?

A note from Cleveland Clinic

Getting a diagnosis of ventriculomegaly during pregnancy may be quite shocking. You may be wondering if your pregnancy is in trouble or if you did something wrong. Rest assured that you didn’t do anything wrong and, in most cases, your baby will be born healthy. Talk to your pregnancy care provider about what the diagnosis means and what care your baby may need at birth. Your provider is there to answer your questions and take any steps necessary to keep your pregnancy and your baby healthy.