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  • Writer's picturePietro D'Urso

Arachnoid cysts

Updated: Mar 15, 2021

Arachnoid cysts are fluid filled sacs that form on the arachnoid membrane; that covers the brain and spinal cord. These will most commonly occur at the base of the skull or on the surface of the brain, and in rare cases on the spinal cord.

In a lot of cases arachnoid cysts will be present from birth (congenital) without causing any symptoms (asymptomatic). In other cases, these can be caused by a head trauma, brain surgery or a brain infection.

The symptoms associated with an arachnoid cyst will differ depending on the size and location, however they will most commonly include:

  • Headaches

  • Nausea

  • Vomiting

  • Problems with balance

  • Dizziness

  • Seizures

  • Fatigue

  • Problems with vision

  • Hydrocephalus (build-up of fluid on the brain)

The exact cause of an arachnoid cyst is unknown; however, it is believed to come from an unexplained tear or split in the arachnoid membrane. Research has shown that these can run in families so may be linked to genetics.

These are most commonly found in in male patients. They are also the most common intracranial (within the skull) cysts.

A CT scan or MRI scan will usually be used to make a diagnosis. If the cysts are asymptomatic then they may be found when looking for something else.

If an arachnoid cyst is found, but causing no symptoms, then it will be left. In these cases, you will have regular check-ups to ensure that it is stable and not causing any pressure.

If the arachnoid cyst is causing symptoms then surgery will be required. The type of surgery that is offered will depend on size and location. The images from the MRI scan or CT scan will be used to help make a decision for the best surgical approach.

This article is intended to inform and give insight but not treat, diagnose or replace the advice of a doctor. Always seek medical advice with any questions regarding a medical condition.

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