Intervertebral discs function as shock absorbers between vertebral bodies. Intervertebral discs have an inner gel-like center called the nucleus pulposus which is surrounded by an outer fibrous disc wall, the anulus fibrosus. When there is a disorder of the disc, the displaced disc material can impinge on neural structures. Intervertebral disc herniations most commonly occur in the lumbar spine, but can also occur in the cervical or thoracic spine.