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Disc disease is a fairly common cause of chronic back and neck pain in the United States, and is estimated to contribute to as many as 10% of low back pain cases. Possible causes of disc pathology can include acute injury in which a disc is torn, causing loss of disc material which may leave its joint space and aggravate nearby nerves causing pain, or degenerative ‘wear-and-tear’ as a disc loses fluid and strength with time and advancing age, which allows adjacent vertebrae to come into contact with one another and rub. An acute or degenerative cause can result in a loss of disc stability allows it to bulge, like a squeezed water-balloon, outside of its disc space which can cause compression of nearby nerves and subsequently, pain. These conditions most commonly occur in inter-vertebral discs located in the cervical (neck) portion of the spine, or in the lumbar (lower back) portion of the spine.
Discography is a provocative test for concordant pain, or pain which corresponds to a patient’s usual, experienced pain (Williams & Park, 2007). During discography, a needle is inserted into selected inter-vertebral discs and injected with fluid in an effort to reproduce a patient’s typical chronic pain. By eliciting pain, physicians are able to confirm a tested disc as the source of pain and proceed to appropriate therapy.
Discography originated in the 1940’s as an experimental, clinical method for evaluation of disc disease in cervical (neck) and lumbar (lower back) regions of the spine. Ever since, discography has had a limited, but very important role in the diagnosis of disc-related pain, particularly when conventional diagnostic imaging methods such as MRI or CT scan fail to identify any abnormalities (Williams & Park, 2007).
The spine consists of a column of bones, known as vertebrae, which are stacked atop one another from the pelvis to the base of the skull, protecting the spinal cord (Nidus Information Systems, 2010). There are 33 of these vertebrae divided into five regions: (1) cervical, which are found in the neck closest to the skull (identified as C1-C7), (2) thoracic, found along the upper back (identified as T1-T12), (3) lumbar, found along the lower back (identified as L1-L5), (4) sacral, which are contiguous with the pelvis or hip (identified as S1-S5), and (5) coccygeal, which are fused as the tailbone.
Each of these vertebrae are separated by cartilaginous, inter-vertebral discs composed of a tough, fibrous outer layer and filled with a soft, gelatinous inner layer. These discs support the vertebrae and allow them to shift across one another, facilitating movement of the spine. The fibrous outer layer is called the annulus fibrosus, and the gelatinous inner layer is called the nucleus pulposus. Disc disease can occur due to acute trauma or injury to the discs or as they thin and lose fluid due to natural, age-related degeneration over time.
Discography can be used at many different spinal levels (Williams & Park, 2007). Thoracic discography is useful in the evaluation of upper back, upper abdominal and chest pain, cervical discography is useful for identifying disc-related pain in the neck and upper extremities, and lumbar discography is useful for the evaluation of disc-related pain in the lower back.
The details of a discography procedure are dependent upon the approach used, and the location of targeted discs; for example, the approach for lumbar discs differs from the approach used to reach cervical or thoracic discs. Regardless of approach, however, the procedure begins by positioning the patient on a procedure table for the best access to the targeted disc, and sterilizing the site of discography injection to prevent infection. For thoracic and lumbar discography, the discs are generally accessed from the back, while for cervical discography, access may occur through the front of a patients neck to avoid critical structures (Williams & Park, 2007). For patients who may be pre-disposed to infection, antibiotics may be prophylactically administered to reduce the risk of infectious complication. The patient is then sedated and a local anesthetic is applied to the injection site to reduce discomfort for the remainder of the procedure.
Under fluoroscopic guidance, a real-time x-ray technology that allows interventional pain specialists to safely and effectively guide needle placement, a needle is directed into the discs to be assessed. Once placed, contrast dye is injected into the disc and disc pressure can be recorded. Any pain experienced by the patient is logged and compared to the patient’s typical experience of pain. A positive test is one in which a disc reproduces the patient’s pain, while testing of other discs does not. For a positive provocation test, physicians will need to inject adjacent discs and ensure that they are pain-free as a test control (Williams & Park, 2007).
The discography procedure should not be performed on patients experiencing compression of the spinal cord, or that have bleeding disorders or known allergies to the contrast dye used in the procedure (Williams & Park, 2007).
Discography is valuable for planning surgical treatments of disc-related pain, testing the integrity discs, especially when a known abnormality in adjacent tissues exists, and identifying pain-inducing discs from other, normal discs (Williams & Park, 2007). It is also valuable ruling out internal disc disruption and suspected herniation, as well as determining the appropriate spinal level to which subsequent treatment is targeted.
The risk of complications from discography is very low, however potential problems following the procedure can include discitis, or infection and inflammation of injected discs, nerve root injury, inadvertent puncture of surrounding tissues, central nervous system infection, bleeding and allergic reactions (Williams & Park, 2007). Specific to cervical discography, infectious abscesses can also develop, and injury to the esophagus, carotid artery, jugular veins and spinal cord can occur. Specific to thoracic discography, lung puncture and subsequent collapse can occur.
A well-controlled 1990 study by Walsh et al., found that discography had a 0% false positive rate as a diagnostic tool, and should thus be considered a highly reliable test (Williams & Park, 2007). A systematic review of lumbar discography found strong evidence for the diagnostic accuracy of lumbar discography, such that for well-selected patients, the benefits outweigh the risks (Wolfer, et al., 2008). Another systematic review reached the same conclusion for cervical discography (Manchikanti, et al., 2009).
References/ Journal Articles
- Discography – PainDoctor.com
- Manchikanti, L., et al. (2009). Systematic Review of Cervical Discography as a Diagnostic Test for Chronic Spinal Pain. Pain Physician, 305-321.
- Nidus Information Systems. (2010). Herniated Disk. Retrieved April 15, 2012, from MD Consult: http://www.mdconsult.com.ezproxy2.library.arizona.edu/das/patient/body/234155712-5/1108605568/10041/35144.html
- Williams, K., & Park, A. (2007). Injection Studies. Retrieved April 30, 2012, from MD Consult. Canale & Beaty: Campbell’s Operative Orthopaedics, 11th ed.: http://www.mdconsult.com.ezproxy2.library.arizona.edu/books/page.do?eid=4-u1.0-B978-0-323-03329-9..50042-8–cesec38&isbn=978-0-323-03329-9&sid=1304454019&uniqId=332403380-3#4-u1.0-B978-0-323-03329-9..50042-8–cesec47
- Wolfer, L., et al. (2008). Systematic Review of Lumbar Provocation Discography in Asymptomatic Subjects with a Meta-analysis of False-positive Rates. Pain Physician , 513-538.