Arachnoid cysts (1453)

Key points below

What is an arachnoid cyst?

The brain and spinal cord are covered and protected by three layers of membranes (meninges). These layers are called the dura mater, the arachnoid and the pia mater.
An arachnoid cyst is a fluid-filled sac found in the arachnoid layer around the brain or the spinal cord.
Sometimes arachnoid cysts develop within the ventricles inside the brain. Ventricles are normal collections of cerebral spinal fluid (CSF) found deep in the brain.
Arachnoid cysts are filled with CSF. This is the same fluid naturally found in and around the brain and spinal cord.
Arachnoid cysts are not tumors.
There are two types of arachnoid cysts:
Primary arachnoid cyst. This type is most common in children. Most often they are present at birth (congenital). The exact cause is unknown.
Secondary arachnoid cyst. These can develop as a result of a head injury or an infection. They are rare and not as common in children.
Most arachnoid cysts are found when a child has a CT scan or MRI for some reason, like a head injury.

Do they cause any problems?

Most arachnoid cysts do not cause any problems.
If the cyst is large it may put pressure on the brain or spinal cord, and cause symptoms.

Arachnoid cysts in the head can cause:headaches

seizures
developmental delays
rapid head growth
dizziness
hydrocephalus
nausea or vomiting

Arachnoid cysts in the spinal cord can cause:

back or leg pain
numbness or tingling of the arms or legs
weakness of the arms or legs
bowel or bladder problems

How are they treated?

If your child has symptoms from the cyst, surgery may be needed to drain the fluid out of the cyst. Your child’s neurosurgeon will recommend 1 of 2 surgeries:

1. Cyst fenestration. Many small holes are made within the cyst. CSF drains from inside of the cyst to the space around the brain or spinal cord.
2. Shunting. A shunt (thin tube) is placed in the cyst wall to drain the CSF into the abdomen. From there it will be absorbed back into the bloodstream.

ALERT

Call your child’s doctor, nurse, or clinic if you have any questions or concerns or if your child has special health care needs that were not covered by this information.