Correspondence

Magnetic Resonance Imaging of the Lumbar Spine

N Engl J Med 1994; 331:1525-1526December 1, 1994

Article

To the Editor:

Jensen et al. (July 14 issue)1 found that 64 percent of a group of 98 people without back pain had lumbar-spine disk abnormalities (bulges, protrusions, or extrusions). This result may be a substantial overestimate. How did the authors ensure that their study participants were truly free of symptoms? Participants were recruited from a particular hospital; presumably they were patients or employees and were likely to have a greater awareness of magnetic resonance imaging (MRI) than people in general. Given the high cost of MRI, it is conceivable that a substantial number of people with a history of back pain would volunteer for a free examination, just as in the early days of testing for antibody to the human immunodeficiency virus a substantial number of blood donors came forward in order to find out whether they were infected with the virus.

Only “about 20 patients” were excluded from the study by Jensen et al., and 98 people were enrolled. The exclusion rate -- about 17 percent -- does not seem consistent with the 80 percent lifetime prevalence of low back pain cited by the authors, even when the mean age of the study group, 42.3 years, is considered.

Robert S. Zucker, M.D., M.P.H.
4510 Sussex Dr., Columbus, OH 43220

1 References

1. 1

   Jensen MC, Brandt-Zawadzki MN, Obuchowski N, Modic MT, Malkasian D, Ross JS. Magnetic resonance imaging of the lumbar spine in people without back pain. N Engl J Med 1994;331:69-73
   Full Text | Web of Science | Medline

To the Editor:

I wonder about the very high percentage of people without back pain among the applicants to the study. The authors do not mention giving any financial reward to the participants, as volunteers undergoing a study, which is the custom in the United States. Is it possible that the applicants, probably knowing that they would get some money if they participated, forgot their earlier back pain? Did the authors also study the medical records of the applicants?

Ger H. Ritsema, M.D.
St. Clara Hospital, 3078 HT Rotterdam, the Netherlands

To the Editor:

What is the association between the anatomical findings on MRI and the many self-limited episodes of acute low back pain that may or may not come to medical attention? Jensen et al. begin their report by citing the statistic that 31 million Americans have low back pain at any given time. Physicians often diagnose acute self-limited episodes as back “strain” or “muscle spasm.” How many of these episodes actually represent a rupture of the annulus with disk protrusion or severe facet impingement? This possibility comes to mind because the MRI abnormalities are common and acute, and self-limited back pain is also common. A number of people in this study could have forgotten about several days of backache in previous years. Longitudinal studies that compare base-line MRI and repeated imaging after episodes of back strain with MRI in a control group would be needed to determine whether the common abnormalities noted on MRI are associated with self-limited clinical episodes of acute back strain.

Paul J. Drinka, M.D.
Wisconsin Veterans Home, King, WI 54946-0620

To the Editor:

No attempt was made to report the relation of disk abnormalities to either exiting nerve roots or the thecal sac. As is widely recognized, it is not necessarily the exact nature or size of the disk abnormality that is most important but, rather, what the abnormality is doing to the sensitive neural elements.

David M. Lefkowitz, M.D.
Creighton University Medical Center, Omaha, NE 68131

To the Editor:

The editorial by Deyo (July 14 issue)1 advocates caution in the early use of imaging in patients with back pain or sciatica, rather than caution in ascribing clinical importance to what are now recognized as normal anatomical variations in the lumbar spine. If the purpose of this editorial is to promote proper interpretation of MRI scans and appreciation of normal variations, then it serves a useful purpose. However, opposition to the use of this diagnostic procedure should not preclude its proper application. Lumbar MRI is properly used to detect the presence of anatomical abnormalities that do cause symptoms.

Mistaken use of a technique is not a reason to forgo its application in patients who will benefit from a timely diagnosis. Early use of diagnostic studies to confirm normal findings or detect abnormalities, which can be remediated, is often the best medical care.

E. James Potchen, M.D.
Michigan State University, East Lansing, MI 48824

1 References

1. 1

   Deyo RA. Magnetic resonance imaging of the lumbar spine -- terrific test or tar baby? N Engl J Med 1994;331:115-116
   Full Text | Web of Science | Medline

Author/Editor Response

The authors reply:

To the Editor: It is impossible to be completely sure that our study group was truly free of symptoms, given the vagaries of human honesty, memory, but a number of steps were taken to minimize the potential for including symptomatic patients. Recruitment was through fliers that indicated that participants must be free of symptoms. During an interview, each participant was told that he or she would not receive any information about the results of the study (to eliminate people who wanted free, potentially useful information). The relatively low exclusion rate (approximately 17 percent) is consistent with the 80 percent lifetime prevalence of low back pain when one considers that the participants were selected to be asymptomatic.

The people who were excluded were those who misunderstood the flier, were dishonest, or suddenly “remembered” previous symptoms. Although medical records were not reviewed, a history of any back problems was carefully elicited. No participant had undergone prior imaging studies of the back. Our results are also similar to those of previous studies. As Dr. Drinka suggests, longitudinal studies with base-line MRI and repeated imaging after episodes of back strain would be quite helpful.

We did not attempt to report the relation of disk abnormalities to the underlying neural structures. We studied people without symptoms and focused on anatomical abnormalities.

We agree with Dr. Potchen that the optimal diagnostic procedure should not be forsaken simply because inappropriate use of the information occurs. A negative study has value. Determining base-line morphologic alterations in a group of people is also quite important in determining appropriate management strategies. MRI is an informational tool and not a therapeutic technique.

Michael Brant-Zawadzki, M.D.
Maureen C. Jensen, M.D.
Hoag Memorial Hospital, Newport Beach, CA 92658-8912

Author/Editor Response

Dr. Potchen and I would probably agree that not every person with low back pain requires an MRI scan. Since at least two thirds of adults will have back pain at some time in their lives and since most episodes are self-limited, this would be wasteful. We would probably also agree that for the patient with classic radicular symptoms who has not had a response to several weeks of conservative therapy, MRI is a highly appropriate test. The ambiguity arises in cases of patients with low back pain in the absence of sciatica, in whom the presence of anatomical abnormalities is most difficult to interpret. This difficulty is due to the poor association between symptoms and anatomical abnormalities (in many structures, not just the intervertebral disk), as documented in several studies.

We can rarely be certain whether an anatomical abnormality causes the symptoms or what the therapeutic implications of the finding may be. Research in this area should have a high priority. We should be clear with our patients and ourselves that this is research, requiring that we obtain the consent of patients, make cautious use of the findings, and carefully record and analyze in a preplanned manner the associations among anatomical findings, symptoms, the response to therapy, and the subsequent clinical course.

Richard A. Deyo, M.D., M.P.H.
University of Washington, Seattle, WA 98195

Citing Articles (1)

Citing Articles

1. 1

   Leonardo Kapural, Nagy Mekhail, James Bena, Robert McLain, John Tetzlaff, Miranda Kapural, Mena Mekhail, Samuel Polk. (2007) Value of the Magnetic Resonance Imaging in Patients With Painful Lumbar Spinal Stenosis (LSS) Undergoing Lumbar Epidural Steroid Injections. The Clinical Journal of Pain 23:7, 571-575
   CrossRef