Arachnoid Cysts

Arachnoid cysts are fluid-filled sacs that grow on the brain and spine. They are not tumors, and they are not cancerous. On rare occasions, if they grow too big or press on other structures in the body, they can cause brain damage or movement problems.


  • Most arachnoid cysts appear at birth (primary arachnoid cysts). They usually occur in the womb during the early weeks of pregnancy. Healthcare providers aren’t sure what causes arachnoid cysts to form.

  • Sometimes arachnoid cysts run in families, so providers think genetics may cause them to develop. People who have certain health conditions, such as arachnoiditis or Marfan syndrome, may be more likely to develop arachnoid cysts.

  • Less often, arachnoid cysts grow after some sort of childhood head trauma, such as a brain injury, surgery or infection. When this happens, providers call them secondary arachnoid cysts.


The vast majority of arachnoid cysts produce no symptoms. When they do, symptoms of an arachnoid cyst range from mild to severe. They depend on the location and size of the cyst and whether it’s pressing on nerves, the brain or the spinal cord. When symptoms do occur, they’re more likely to appear before age 20. They include:

  • Headaches.

  • Hydrocephalus (excess cerebrospinal fluid collects in the brain).

  • Nausea and vomiting.

  • Seizures.

  • Vertigo and dizziness.

Other symptoms vary depending on the location of the cyst. They include:

Middle fossa region

Cysts in this area of the brain can cause problems with vision, hearing, movement and balance. They can lead to fatigue and weakness or paralysis, usually on one side of the body. Some children have neurological (nervous system) symptoms

These may include delays in development and changes in behavior.

Suprasellar region

Cysts in this region can cause vision problems. They may also affect the endocrine system, which controls puberty and sexual development. Some people with suprasellar or posterior fossa arachnoid cysts bob their heads uncontrollably

They may move their heads side to side or in a circular motion.

Spinal cord

Spinal arachnoid cysts can lead to numbness and tingling in the feet and hands, muscle spasms, movement problems and paralysis. Back pain and scoliosis are also common. Some people develop urinary tract infections from a spinal cyst.


  • Signs of arachnoid cysts are often similar to symptoms of other conditions.

  • If you or your child has symptoms of an arachnoid cyst, your provider will ask about your health history.

  • They may recommend tests based on your symptoms.

  • Healthcare providers often discover arachnoid cysts when someone seeks treatment for another health concern, such as seizures.

  • Providers use imaging studies, including MRIs and CT scans, to see pictures of the cysts.


Endoscopic procedures

Depending on the location and size of the cyst, your provider may recommend an endoscopic procedure to drain the cyst or open a ‘window’ in it. Endoscopic procedures use a small, thin tube with a camera and tiny tools. These minimally invasive procedures use smaller incisions. This means you need less recovery time than traditional surgery.

Open craniotomy fenestration

During this procedure, your provider removes part of the skull and makes small incisions (cuts) in the cyst. These ‘windows’ allow fluid to drain from the cyst. Your body absorbs the fluid over time. Your provider replaces the skull piece and seals it in place with stitches.


Your provider inserts a cyst operitoneal shunt (also called a CP shunt) into the cyst. A shunt is a device made of catheters (thin tubes) and a valve. Fluid drains through the tubes into your abdomen (belly). Your body absorbs the fluid. The shunt will remain in place so fluid can continue to drain.

Surgical removal

Healthcare providers usually remove spinal arachnoid cysts. Your provider makes an incision near the cyst and removes it. If it’s not possible to remove the cyst because of its location or size, your provider may recommend draining it or placing a shunt in the cyst.

diseases disorders arachnoid-cysts treatments health prevention nervous-system

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