Discs are named based upon their adjacent vertebrae. For instance, the L4-L5 disc is the disc that lies between the fourth lumbar and fifth lumbar vertebrae. They are up to 3/8 in. thick and 1 and 5/8 in. wide in the lumbar spine, but are smaller in the cervical and thoracic regions [1]. The disc is composed of an outer layer, the annulus fibrosis, and an inner region, the nucleus pulposus. The annulus fibrosis is a leather-like outer covering of the disc. The nucleus pulposus is the gelatin like material within the disc which aids in cushioning and distributing forces placed on the spine. If a tear occurs in the annulus fibrosis and nucleus pulposus protrudes through the tear, a herniation of the disc occurs.

The cervical spine is composed of seven vertebrae, and eight paired cervical nerves exit at each level. The cervical spinal cord occupies the spinal canal just behind the vertebrae and discs. Herniated discs in this region can cause compression of not only the nerve roots, but also of the spinal cord itself. Symptoms of herniated cervical discs can cause cervical radiculopathy, from compression of nerve roots, or myelopathy, from compression of the spinal cord.