are fluid-filled sacs that most often affect nerve roots in the sacrum, the group of bones at the base of the spine. These cysts can compress nerve roots, causing lower back pain, sciatica (shock-like or burning pain in the lower back, buttocks, and down one leg to below the knee), urinary incontinence, headaches, sexual dysfunction, constipation, and some loss of feeling or control of movement in the leg and/or foot. Pressure on the nerves next to the cysts can also cause pain and deterioration of the surrounding bone. Tarlov cysts may become symptomatic following shock, trauma, or exertion that causes the buildup of cerebrospinal fluid. Current information indicates that women are more commonly diagnosed with Tarlov cysts. The reason for this is unknown. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.