Tarlov cyst

Tarlov cysts, also known as perineural cysts, are type II innervated meningeal cysts, cerebrospinal-fluid-filled (CSF) sacs most frequently located in the spinal canal of the S1-to-S5 region of the spinal cord (much less often in the cervical, thoracic or lumbar spine), and can be distinguished from other meningeal cysts by their nerve-fiber-filled walls. Tarlov cysts are defined as cysts formed within the nerve-root sheath at the dorsal root ganglion. Since Tarlov cysts are cysts of the spinal meninges, symptomatic Tarlov cysts by definition cause myelopathy. The etiology of these cysts is not well understood; some current theories explaining this phenomenon have not yet been tested or challenged but include increased pressure in CSF, filling of congenital cysts with one-way valves, inflammation in response to trauma and disease. They are named for neurologist Isadore Tarlov, who described them in 1938.