Between each vertebra lies a fibrocartilagenous structure called the intervertebral disc. This disc is present at all levels of the cervical spine except for the first and second vertebra (atlas and axis). The disc is comprised of a series of outer fibrous rings (annulus fibrosis) and a softer center (nucleus pulposus). The walls of the disc are thinnest and weakest posterior laterally where the spinal nerves exit the spinal column. The disc serves as a joint between the vertebra, functions as a cushion and allows movement between the vertebra.
Inflammation, damage or degeneration of a disc may produce loss of neck motion, pain radiating to the arm, numbness and weakness. The cervical fifth and sixth C5-C6 and cervical sixth and seventh C6-C7 levels have the highest rate of disc degeneration and herniation.