A disc prolapse is the term used when the cause of nerve root entrapment, most usually in either the cervical or lumbar spine, is a herniated disc. As described in the section on spine anatomy, the disc consists of the annulus fibrosis, which is a circumferential structure at the edge of the disc space, and the nucleus pulposus, which is the central material. With a disc prolapse, the annulus tears and the central nucleus ruptures out and a piece of this presses on the nerve root. In the lumbar spine this produces sciatica (leg pain) and in the cervical spine produces brachialgia (arm pain). Often this disc prolapse resolves without the need for surgery but in persistent and severe cases, surgical removal of the disc prolapse has an excellent success rate in relieving the brachialgia or sciatica. The underlying cause of the disc prolapse is degenerate disc disease (spondylosis). This is generally an age-related condition and becomes increasingly common with age but a disc prolapse is frequently seen in patients over the age of 30 and much less commonly seen below this. It is not known why a relatively small percentage of patients with degenerate disc disease have a disc prolapse which is a relatively rare event in the context of the very common underlying degenerate disc disease.