Between each vertebra of the spine, there is a fibrocartilagenous structure called the intervertebral disc. This disc is at all levels of the cervical spine except for the first and second vertebra (atlas and axis). The intervertebral disc is comprised of a series of outer fibrous rings (annulus fibrosis) and a soft 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 vertebrae, functions as a cushion and allows movement between the vertebrae.
Loss of neck motion, pain radiating to the arm, numbness and weakness may be caused by inflammation, damage or degeneration of a disc. Discs that tend to suffer the highest rate of degeneration and herniation are the cervical fifth and sixth (C5-C6) and the cervical sixth and seventh (C6-C7).
When the outer walls (annulus) of the disc become weak the nucleus polposus can push the walls out creating a bulge. Bulging discs are common and may be asymptomatic. They can occur as part of the aging process. If the bulge does put pressure on the nerves and surrounding soft tissue it can become symptomatic.