Arachnoid Cysts

Arachnoid cysts are fluid-filled sacs that develop when one of three membranes (coverings) that protect your central nervous system tear. They usually occur in your skull, next to your temporal lobe, which is the middle part of your brain, near your temple. Sometimes they grow in your spinal canal. The torn membrane fills with fluid from your brain or spinal cord, creating a cyst.



Most arachnoid cysts are present at birth and are called primary arachnoid cysts. Head trauma, meningitis and brain surgery can cause what are called secondary arachnoid cysts.

Arachnoid cysts don’t always cause symptoms. Depending on your cyst’s location and size, you may have:

  • Balance problems
  • Headaches
  • Hearing and visual disturbances
  • Hydrocephalus (fluid building up in your skull)
  • Nausea and vomiting
  • Seizures
  • Tingling or numbness in your legs or arms if the cyst is in your spinal canal


First, you'll meet with your doctor for a physical exam. You'll talk about your symptoms and any concerns. Then, you’ll have a neurological exam and tests, which may include:

  • Imaging tests such as an MRI or CT to identify the type of cyst you have and pinpoint its location. Children with arachnoid cysts may have an ultrasound.

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Treatment Options

Dr. Amin Kassam, Aurora’s Vice President of Neurosciences, explains the Expanded Endonasal Approach.

If your cyst is small and isn’t causing any problems, you may not need treatment. Your doctor may simply monitor your condition. 

If you have a larger arachnoid cyst, treatment is usually your best option. If they’re not treated, large brain cysts can put pressure on your brain and spine and ultimately damage your nerves.

One option may be surgery. Aurora Health Care specializes in minimally invasive surgery techniques, such as the Expanded Endonasal Approach (EEA), which allows for a shorter hospital stay, quicker healing time and fewer scars.

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