Scanners can be used to examine and evaluate the brain in cases of head trauma, as well as when medical professionals have suspicions about specific disorders. These scans frequently reveal arachnoid cysts (AC), which are tiny sacs filled with fluid that are embedded in a membrane that serves to protect the brain and spinal cord. ACs are not thought to cause symptoms, but some patients have reported having headaches or seizures, and some have developmental delays or other vague neurological symptoms. Treating these cysts is very challenging, however, because although ACs are the most common intracranial brain cyst type, we still don’t know why they occur or why some are harmful while others are harmless.