Degenerative Disc Disease

Overview

Degenerative disc disease (DDD) of the cervical (neck region) spine indicates that the intervertebral disc has undergone degenerative, wear-and-tear (arthritic) changes, which may or may not lead to significant neck pain and spinal problems. The discs of the spine are joints, and just like all joints in the human body, the discs undergo arthritic changes during the course of life. In 1990, Boden conducted a research study in normal people without neck pain. Magnetic resonance imaging (MRI) tests showed 20% of the people tested over 45 years-old have a disc bulge or degenerative disease, and nearly 60% of people over 65 years-old had degenerative disc disease. Despite being so prevalent, the vast majority of people never develop significant chronic neck pain as a result of this condition. The concept of a lumbar discogenic injury and degeneration causing back pain can also be applied to the cervical spine. As the intervertebral disc becomes dehydrated, it will have a decreased height and lose its viscolelastic properties as a cushion. The cervical spine will become less lordotic, and osteophytes (bone spurs) will form and may encroach upon the neurologic structures in the spinal canal. These degenerative changes may occur alone, or in combination with other cervical disorders such as a herniated disc or cervical spinal stenosis.

Causes

There are a number of specific causes of degenerative disc disease, ranging from an initial injury to the annulus (outer ring of the disc), facet joint injury, fractures, infections or rheumatologic etiologies (causes). Many of these conditions affect the biomechanics and/or biologic characteristics and ultimately lead to a derangement of the normal cartilage and its ability to function. However, the precise cause of DDD is unknown in most cases, yet is assumed to be the result of normal aging in most of these cases.

Symptoms

As previously discussed, the majority of people with degenerative disc disease do not have significant debilitating symptoms. The patients that do have pain generally have a predominance of neck pain in the region of the disc disease. Unless there is another associated condition, patients usually do not have significant radicular (arm) pain symptoms or neurologic abnormalities such as weakness, numbness, or bowel/bladder dysfunction.

Physical Findings

The physical findings for cervical degenerative disc disease are nonspecific. Patients may have cervical tenderness if the pain is severe. Often, the neck range-of-motion is decreased, but the neurologic examination is normal. Special tests such as the Spurling's test and Hoffman's sign are usually negative.

Imaging Studies

X-rays may show that a disc height is diminished, thus confirming the diagnosis of DDD. An MRI is generally recommended so as to identify if there is an associated disc herniation or spinal stenosis, which would impact the treatment regimen. An MRI will also clarify the severity of degenerative disc disease.

Laboratory Tests

There are no laboratory tests used to diagnose degenerative disc disease. Occasionally, specific tests are ordered to rule out infection or other medical/rheumatologic conditions.

Special Tests

A discogram is a test that is performed to help identify which degenerated disc, if any, is causing a patient's neck pain. A doctor performs this procedure by injecting radiopaque dye, under pressure, into the discs of the cervical spine. The procedure is performed using fluoroscopy, a special x-ray machine that allows x-ray images to be viewed instantly on a television monitor.

Diagnosis

The diagnosis of degenerative disc disease is ultimately confirmed if moderate or severe disc height loss is observed on a cervical x-ray. Otherwise, an MRI test would be required to identify this condition if there is only mild DDD. The doctor must then evaluate the location and quality of the neck pain to determine if the degenerated disc is actually generating the patient's pain.

Treatment

The treatment for degenerative disc disease is primarily conservative. The majority of patients with significant pain generally improve with time, as well as non-operative treatments such as oral medications, physical therapy, and other modalities. A short period of immobilization with a soft cervical collar (neck brace) may also be helpful. Epidural steroid injections and facet joint injections are usually not efficacious unless there are other associated spinal conditions such as spinal stenosis, herniated disc, etc. Patients that fail all conservative treatments and still have disabling degenerative disc disease pain are considered candidates for surgery. Although cervical surgery is often reserved for patients with associated radiculopathy or myelopathy, numerous authors report 70-95% good or excellent results when performed primarily for neck pain. Discography may be utilized prior to surgery to identify the specific disc(s) that is generating a patient's pain, especially if multiple discs are degenerated. However, some authors argue that discography is not a very reliable or valid test, and is not always necessary or useful. The surgery for isolated degenerative disc disease is anterior cervical fusion or artificial disc replacement (disc arthroplasty). A complete disc excision with decompression and plating is generally performed, although an anterior corpectomy with strut graft placement may also be required if a patient has concomitant spinal stenosis.

Selected Bibliography

Boden S, McCowin P, et al: Abnormal magnetic resonance scans of the cervical spine in asymptomatic subjects. J Bone Joint Surg Am 1990;72:1178.

Bovim G, Schrader H, Sand T: Neck pain un the general population. Spine 1994;19:1307.

Brodke DS, Zdeblick TA. Modified Smith-Robinson procedure for anterior cervical discectomy and fusion. Spine 1992;17:S427.

Busch G. Anterior fusion for cervical spondylosis. J Neurol 1978;219:117.

Clements DH, O'Leary PF. Anterior cervical discectomy and fusion. Spine 1990; 15: 1023.

Garvey T, Transfeldt E, Malcolm J, et al: Outcome of anterior cervical discectomy and fusion as perceived by patients treated for dominant axial-mechanical cervical spine pain. Spine 2002;27:1887.

Gore DR, Sepic SB. Anterior cervical fusion for degenerated or protruded discs. A review of 146 patients. Spine 1984;9:667.

Palit M, schofferman J, et al: Anterior discectomy and fusion for the management of neck pain. Spine 1999;24:2224.

White AA, Southwick WO, Deponte RJ, et al. Relief of pain by anterior cervical-spine fusion for spondylosis: A report of 65 patients. J Bone Joint Surg Am 1973;55:525.