Arachnoid cysts are fluid-filled sacs in the brain or spinal cord. They can be present before birth or result from a head injury. They typically do not cause symptoms or require treatment. Many cysts ...

An arachnoid cyst is most likely to develop in your head, but it can also develop around your spinal cord. It’s called an arachnoid cyst because it occurs in the space between your brain, or spinal ...