Does MRI Have Your Patient’s Back?

Abstract & Commentary

By Rahul Gupta, MD, MPH, FACP, Clinical Assistant Professor, West Virginia University School of Medicine, Charleston, WV. Dr. Gupta reports no financial relationships relevant to this field of study.

Synopsis: MRI scan was unable to discriminate between patients with favorable outcome and those with an unfavorable outcome when conducted at 1-year follow-up in patients who were treated for sciatica and disk herniation.

Source: el Barzouhi A, et al. Magnetic resonance imaging in follow-up assessment of sciatica. N Engl J Med 2013;368:999-1007.

Sciatica is a common presenting condition, affecting as many as 40% of adults at some time in their lives. Although herniated disc tends to be a common etiology for this diagnosis, it resolves in most people in up to 8 weeks time. Clinicians commonly order diagnostic scans such as MRI in those cases where either the symptoms do not resolve in a timely manner or seem to have unusual or progressive presentation. With studies demonstrating that up to 76% of people who do not have symptoms will show signs of disk herniation on an MRI, it is difficult to associate MRI findings to clinical symptoms.1 Therefore, it is fair to say that many people have herniated discs, often without any clinical symptoms. In fact, even after successful lumbar disc surgery, more than half of the asymptomatic patients may show persistent disc herniation on follow-up MRI. However, despite these existing data, the fact is that physicians often repeat MRI after treatment just to be sure that “everything is fine.” While these MRIs can cost hundreds to thousands of dollars per scan, there is the issue of contrast-related adverse effects as well as anxiety related to findings of persistent herniation while asymptomatic.

In their study, el Barzouhi and colleagues conducted a multicenter, randomized trial comparing surgery and prolonged conservative care for sciatica and lumbar-disk herniation and included 267 patients with a history of 6-12 weeks of sciatica and disk herniation. The patients were randomly assigned to an early surgery strategy group (n = 131) or to a nonsurgical prolonged conservative care (n = 136) group. Fifteen in the surgery group recovered without surgery, and 54 in the nonsurgery group underwent surgery within the year. All patients underwent MRI at baseline and after 1 year. According to the researchers, the 1-year evaluation period was selected since postoperative fibrosis usually stabilizes by 6 months, with no further changes at 1 year. A 4-point scale to assess disk herniation on MRI was used, ranging from 1 for “definitely present” to 4 for “definitely absent.” A favorable clinical outcome was defined as complete or nearly complete disappearance of symptoms at 1 year. The researchers found that 84% of the patients reported having a favorable outcome at 1 year. Disk herniation was visible in 35% of patients with a favorable outcome and in 33% with an unfavorable outcome (95% confidence interval [CI] for difference in proportion, -18.8 to 12.6; P = 0.70). Nerve root compression was present in 24% of those with a favorable outcome and in 26% of those with an unfavorable outcome. Of patients with disk herniation, 85% reported a favorable outcome compared with 83% with no disk herniation (P = 0.70). After adjustment for randomized treatment, the presence of disk herniation on MRI was not associated with a favorable outcome at 1 year (odds ratio, 0.82; 95% CI, 0.40-1.71; P = 0.60). In other words, having a MRI scan at 1 year after treatment had no discriminatory power to assess the difference between having a favorable outcome or not having a favorable outcome.

Commentary

In most clinical settings, it is not uncommon for the busy clinician to end the patient interview with the words, “but let’s go ahead and order some tests just to be sure.” These “tests” often mean a battery of laboratory and imaging tests. Both the physician and the patient/family “feel” better. There is comfort on both sides that all that can be tested is being tested. This “just in case” scenario is probably repeated tens of thousands of times in clinical settings each day in the United States. However, over the past 2 decades or so, our ability to detect abnormalities by modern-day imaging techniques has grown at a more rapid rate than our ability to understand the relevance and clinical implications of such findings. As a result, often a deluge of further evaluations and interventions is conducted, leading to significant anxiety and suffering of the patient, in addition to unnecessary cost to the health care system. Findings by el Barzouhi and colleagues highlight this issue by demonstrating the absence of clinical correlation between symptoms and anatomical abnormalities visible on MRI done 1 year after treatment for symptomatic lumbar-disc herniation.

This study questions the value of MRI in clinical decision making for patients with persistent or recurrent sciatica after initial treatment. Interestingly, in a study conducted more than 20 years ago, Boden et al performed MRI on individuals who had never suffered from sciatica or low back pain and found a substantial abnormality in about one-third of the study subjects.2 In the subgroup that was ≥ 60 years of age, 57% of the scans had abnormal findings, including herniated nucleus pulposus and spinal stenosis. Since then, we have learned that patients who receive an MRI are more likely to undergo surgery over the subsequent year than those undergoing plain radiography, and yet the outcomes at 1 year are equivalent.3 Once again, good clinical history taking and physical examination can often alleviate the need for repeated MRI scans. Instead of treating the MRI, we cannot go wrong by refocusing on the patient, including explaining limitations of imaging tests such as MRI to our patients so that the results do not lead to further unnecessary testing or anxiety.

References

1. Boos N, et al. 1995 Volvo Award in clinical sciences. The diagnostic accuracy of magnetic resonance imaging, work perception, and psychosocial factors in identifying symptomatic disc herniations. Spine 1995;20:2613-2625.

2. Boden SD, et al. Abnormal magnetic-resonance scans of the lumbar spine in asymptomatic subjects. A prospective investigation. J Bone Joint Surg Am 1990;72:403-408.

3. Jarvik JG, et al. Rapid magnetic resonance imaging vs radiographs for patients with low back pain: A randomized controlled trial. JAMA 2003;289:2810-2818.