Radiographs, CT Scans, Myelography, MRI, Bone Scan, Electrodiagnostic Tests and Discography
Acute Adult Spine
The use of radiologic diagnostic tests for the spine is determined by the area of concern, clinical history, physical exam, and the information being sought. (60) Plain radiographs of the spine can identify deformity, most fractures, destructive lesions, spondylolisthesis, and spondolytic changes but are less sensitive for soft tissues, and cannot depict discs and nerves.
Computed Tomography (CT) Scans
Flexion/extension films are used to determine stability of the spine. Computed Tomography (CT) scans use x-ray beams to create images of the tissues being examined. CT scans provide excellent information regarding trauma and fractures. CT can provide multi-planar reconstruction, which is valuable in determining vertebral alignment.
Myelography involves the injection of water-soluble contrast agents into the subarachnoid space, to identify any area of obstruction of flow that could indicate compression on neural structures.
Magnetic Resonance Imaging (MRI)
Magnetic Resonance Imaging (MRI) uses a magnetic field to measure re-emission of absorbed radiofrequency. MRI is highly sensitive for traumatic conditions involving bony and soft tissues. MRI allows visualization of disc material and spinal nerve roots to evaluate disc herniations and spinal stenosis. With intravenous contrast, the capability of MRI to detect tumors or infection is enhanced.
Bone scans can identify most tumors, fractures, degenerative changes, and infections by the concentrated uptake of the radioisotope in areas of increased metabolic activity (Figure 12).
Bone Scan of a patient with a T-7 metastatic lesion.
Electrodiagnostic testing can help pinpoint the specific nerve root involved, characterize the dysfunction as acute, chronic, or improving, differentiate intraspinal from peripheral dysfunction, and identify the generalized neuropathy of diabetes or alcoholism.
Discography is a controversial radiologic procedure that involves injection of dye into the nucleus of the disc in order to identify the painful disc level and to determine integrity of the annulus. (61) The procedure is repeated at several levels of the lumbar spine (usually to the highest non-painful disc) and often in non-contiguous levels to 'blind' the patient to the level being tested.
Radiographs are taken to observe the pattern of dye distribution, and judgments can be made about the integrity of the annulus fibrosis. Further, the patient's pain response is assessed with particular attention to whether the patient's daily pain is exactly reproduced during injection, and to what degree. A response of exact (concordant) reproduction of pain is considered diagnostic of painful disc degeneration.
The diagnostic accuracy and utility of this test is debated, because of the reliance on the patient's subjective response, equivocal interpretation of results, and potential risk of complications. However, in the hands of a careful clinician, many practitioners consider it a useful test in the work-up of painful disc degeneration. (62,63)