Tarlov cysts, also referred to as perineural or sacral nerve root cysts, are cerebrospinal-fluid filled sacs that occur as dilatations of nerve root sheaths at the dorsal root ganglion. They commonly occur at the sacral spine especially around S1, S3. However, they can occur at any level of the spine. In fact, approximately 11% of people with the condition have multiple cysts distributed along the cervical, thoracic, and lumbar vertebrae as well.
Tarlov cysts are relatively rare with an annual incidence of approximately 5 % and are more common in women than in men. The etiology and the process of formation of these cysts are not well defined. However, several hypotheses have been postulated, including the obstruction of venous drainage in the perineum due to the deposition of hemosiderin as a result of trauma, congenital origin and hemorrhagic infiltration of spinal tissue following trauma.