Top of the page
An arachnoid cyst is a fluid-filled sac that grows between the arachnoid membrane and the brain or spinal cord. The arachnoid is one of the layers of tissue (membranes) that cover the brain and spinal cord.
This type of cyst can form as a baby grows in the uterus. Or the cyst may form later in life from an illness or head injury.
Some arachnoid cysts don't cause any symptoms. If you do have symptoms, they may include:
If the cyst presses on the spinal cord, the symptoms might include:
Treatment may not be needed if there aren't any symptoms. You may have follow-up appointments and regular MRI tests. This is to see if the cyst is growing.
Some cysts are large or are in a place where they cause symptoms. A cyst that puts pressure on the brain or spinal cord may cause permanent injury. Treatment may be a surgery to place a shunt or to remove part or all of the cyst. This may allow the fluid to drain.
Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse advice line (811 in most provinces and territories) if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.
Go to https://www.healthwise.net/patientEd
Enter A170 in the search box to learn more about "Learning About Arachnoid Cysts".
Current as of: December 13, 2021
Author: Healthwise Staff
Medical Review:E. Gregory Thompson MD - Internal Medicine & Steven C. Schachter MD - Neurology & Colin Chalk MD, CM, FRCPC - Neurology
Care instructions adapted under license by your healthcare professional. If you have questions about a medical condition or this instruction, always ask your healthcare professional. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.
©2006-2022 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.