Where do arachnoid cysts grow?

Where do arachnoid cysts grow?

Arachnoid cysts usually grow on the brain (intracranial arachnoid cysts). Less commonly, they grow on the spinal cord (spinal arachnoid cysts). Both types develop on a thin membrane that covers and protects the brain and spinal cord. Providers call this membrane the arachnoid membrane because it looks like a spider web.

The cysts can form in several areas of the brain. Most arachnoid cysts grow in the middle fossa region, located in front of the ears. They can also grow in the suprasellar region (behind the eyes) and the posterior fossa (at the base of the skull).

These areas of the brain and spinal cord contain cerebrospinal fluid (CSF). CSF is a clear fluid that cushions the brain and spinal cord. It also delivers nutrients and removes waste from the brain. Arachnoid cysts form when cerebrospinal fluid collects and builds up inside a sac.