Children's Hospital Colorado
Colorado Fetal Care Center

Arachnoid Cysts

We see more, treat more and heal more kids than any other hospital in the region.

U.S. News & World Report ranked in all 10 specialties badge

Would you like to learn more about us?
Colorado Fetal Care Center
Do you have questions about this condition?
Call

What is an arachnoid cyst?

There are two types of arachnoid cysts: congenital and acquired. Congenital arachnoid cysts are the result of abnormal development of a brain structure called leptomeninges. Acquired congenital arachnoid cysts are the result of bleeding, trauma or infection.

An arachnoid cyst is usually a single or simple cyst rather than a collection of multiple cysts. It can be round, oval or crescent moon-shaped. These cysts usually do not grow quickly, remaining stable during pregnancy. Arachnoid cysts tend to account for only 1% of neonatal intracranial masses and mostly affect the left side of the brain. The precise of arachnoid cysts is unknown.

How are arachnoid cysts diagnosed?

Most cases of arachnoid cysts are detected after 20 weeks of pregnancy during ultrasound. On ultrasound, an arachnoid cyst may look like a clear, round, oval or crescent moon-shaped mass in the back of the brain. When an arachnoid cyst is detected within the fetal brain, the patient will be given a complete anatomic sonographic fetal diagnosis to rule out other abnormalities.

Sometimes, a prenatal MRI may be necessary, as well. If other abnormalities are present, amniocentesis may be recommended to look for a chromosomal or genetic abnormality. If the arachnoid cyst is the result of a chromosomal abnormality, genetic counseling may also become part of the mother and baby's treatment plan.

Based on the measurement of cerebrospinal fluid in the brain, as well as the size of a baby's ventricles, an arachnoid cyst may be suspected. If the volume of fluid is high, a baby with a cyst may also be diagnosed with hydrocephalus.

Next steps

Compassionate care, wherever you are

We’re here when you need us. Telehealth appointments are available across every specialty, so you can get the high-quality care we’ve always offered from the comfort, privacy and convenience of home.

See if telehealth is right for you

 

Get to know our pediatric experts.

Michael Zaretsky, MD

Michael Zaretsky, MD

Maternal-Fetal Medicine, Ob/Gyn Obstetrics & Gynecology

Why?

Amanda Schmitt, MD

Amanda Schmitt, MD

Ob/Gyn Obstetrics & Gynecology

Why?

Emily Bucholz, MD

Emily Bucholz, MD

Cardiology - Pediatric, Pediatrics

Why?

Nicholas Behrendt, MD

Nicholas Behrendt, MD

Maternal-Fetal Medicine, Ob/Gyn Obstetrics & Gynecology

Why?