What are Arachnoid Cysts
Arachnoid cysts are fluid-filled sacs in the space between your brain or spinal cord and one of the membranes that covers the brain or spinal cord (arachnoid membrane).
The cyst is filled with clear fluid (cerebrospinal fluid) that protects and nourishes your brain and spinal cord. Arachnoid cysts are not cancerous.
Arachnoid cysts usually develop in the middle part of your brain. They can also develop near your spinal cord. If a cyst is small and not causing symptoms, you may not need treatment. Your health care provider may check the cyst regularly to see if it grows over time. If your cyst is large enough to cause symptoms, you may need a surgical procedure to drain or remove it.
What are the causes?
The most common cause of an arachnoid cyst is a defect that develops before birth. This is called a primary arachnoid cyst. A secondary arachnoid cyst is less common and may be caused by:
- Head injury.
- Brain infection.
- A tumor that develops after brain surgery.
What increases the risk?
You may be at risk for a primary arachnoid cyst if you:
- Have a family history of brain cysts.
- Have inherited genes that increase your risk.
- Are male.
You may be at risk for a secondary arachnoid cyst if you have had:
- A brain injury.
- A brain infection.
- A brain tumor.
- Brain surgery.
What are the signs or symptoms?
It is possible to have an arachnoid cyst without any symptoms. If you do have symptoms, the type of symptoms will depend on the size and location of your cyst. Signs and symptoms of an arachnoid cyst near your brain may include:
- Nausea and vomiting.
- Headache.
- Seizures.
- Dizziness and loss of balance.
- Problems with hearing or vision.
- Clumsiness.
- Weakness.
Signs and symptoms of an arachnoid cyst near your spinal cord may include:
- Leg weakness and tingling.
- Arm weakness and tingling.
- Curved spine.
- Back pain.
- Arm or leg pain.
- Jerky movements of the arms or legs (spasticity).
How is this diagnosed?
Your health care provider may suspect an arachnoid cyst from your signs and symptoms. You will need to have tests done to confirm the diagnosis. These may include:
- CT scan.
- MRI.
How is this treated?
Surgery is the only treatment for an arachnoid cyst that causes symptoms. This may involve brain or spinal cord surgery to do one of the following:
- Open and drain the cyst.
- Drain the cyst by placing a tube (shunt) into the cyst.
- Remove the cyst completely.
