When should an MRI or computed tomography myelogram be ordered for a patient with low back pain?
Only if your approach will be altered. Patients with a high concern for cancer, infection, or patients who are surgical candidates should have an MRI. Occasionally an MRI or CT of the sacroiliac joints is needed to diagnose early ankylosing spondylitis. A CT myelogram may be necessary if the patient cannot have an MRI (pacemaker, etc). In patients with adequate renal function, an MRI with gadolinium is indicated for patients who have undergone prior lumbar spine surgery to exclude infection or nerve root compression due to scar tissue. An MRI is not needed in a patient whose history and physical examination are consistent with lumbar radiculopathy and is improving with conservative therapy. All imaging procedures must be interpreted in conjunction with the clinical history, physical examination, laboratory results, and electrophysiologic studies.