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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 damage. If a cyst grows or causes symptoms, your doctor may drain the fluid from the cyst. Treatment may also include surgery to place a shunt or to remove the covering 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 call line 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.
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Current as of: August 4, 2020
Author: Healthwise Staff
Medical Review:E. Gregory Thompson MD - Internal Medicine & Steven C. Schachter MD - Neurology & Colin Chalk MD, CM, FRCPC - Neurology
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