Some arachnoid cysts are found incidentally, meaning it is discovered on a scan done for another reason (such as after a head injury). Some arachnoid cysts may even be detected on a prenatal ultrasound. If an arachnoid cyst is not causing any symptoms, treatment may not be necessary.
Arachnoid cysts that do cause symptoms, however, need to be evaluated for treatment. The first step is an accurate diagnosis, since the symptoms may be caused by other conditions. A patient with the symptoms of an arachnoid cyst may be sent for a CT scan or magnetic resonance imaging (MRI). A specific type of MRI called diffusion-weighted MRI (dMRI) helps distinguish fluid-filled arachnoid cysts from other types of cysts. The usual treatment for an arachnoid cyst is draining it. This surgical procedure should be done by an experienced pediatric neurosurgeon at a major medical center. (See Surgery for an Arachnoid Cyst.)
Reviewed by: Jeffrey Greenfield, M.D., Ph.D.
Last reviewed/last updated: March 2021