MRI Findings Not Helpful in Determining Herniated Disc-Related Sciatica Treatment

Standards of care dictate that an MRI is indicated for patients who have herniated disc-related sciatica, often described as severe lower back and leg pain, which does not respond to conservative care after 6 weeks. Compressive etiologies and particularly the severity of the compressive lesion are thought to guide the physician’s choice toward either surgery, or a continued conservative regimen including possible epidural steroid injections.

Abdelilah el Barzouhi, MD, PhD and colleagues called this practice into question in a recent issue of the Journal of Neurosurgery: Spine. What they found was that “MRI has no value in the decision making between early surgery and prolonged conservative care.”

For those patients suffering from their first bout of sciatica, the prognosis is good. In fact, 60%-80% will have a spontaneous resolution of the leg pain after the initial 6-8 week period. According to the authors, “A recent systematic review, which evaluated the probability of spontaneous regression among different types of lumbar herniated discs, found a rate of spontaneous regression of 96% for disc sequestration, 70% for disc extrusion, and 41% for disc protrusion.” Seemingly the worse the lesion, the better the prognosis, and this is what the researchers found.

The Sciatica Trial
The study included 283 patients with severe first occurrence sciatic symptoms persisting between 6-12 weeks. To be eligible for the sciatica trial, patients needed to have a dermatomal pattern of pain distribution, neurological abnormalities, and compressive MRI findings that all correlated to the same nerve root. Patients were randomized to either early surgery (n=141) or prolonged conservative care (n=142) for 6 months followed by surgery for those not improved or earlier surgery for those who needed it due to pain. In the conservative care group, 55 had surgical intervention by 1-year follow-up.

Results
The patients who had nerve root compression on MRI tended to have a higher, although nonsignificant rate of recovery than those without compression (HR: 1.34, P=.10). They also had less severe leg pain during the 1-year follow-up (P<.001), a more favorable Roland Disability Questionnaire (RDQ) score (P=.01), and a lower visual analog (VAS) back pain score (P=.02).

The patients who had a disc extrusion compared to protrusion tended to have a higher although non-significant rate of recovery (HR: 1.15, P=.10). They also had less severe leg pain (P=.006), a lower VAS back pain score (P=.02), but not a more favorable RDQ score (P=.07).

The size of the disc herniation was not associated with either rate of recovery or leg pain, nor did it affect the decision to have surgery in the conservative group. The authors commented, “In a subanalysis involving only patients who were randomized to conservative care, we compared the disc herniation size between those who crossed over to surgery (n=55) and those who did not (n=87). Large disc herniations (≥ 50% of the spinal canal) were nearly equally distributed between those who did and those who did not undergo surgery (24% vs 21%, P =0.65).”

Possibly even more surprising was the fact that larger herniations were not associated with better outcomes in the surgery group. “From a clinical viewpoint, we expected a larger-size disc herniation at baseline to be associated with a better outcome in the surgically treated cohort during follow-up than in the conservatively treated patients. However, the presence of large disc herniations (present in 21% of our included patients) showed no prognostic value, irrespective of surgical or prolonged conservative treatment.”

One explanation for these findings is that the etiology of sciatica could be both compressive and non-compressive (inflammatory). The authors reasoned “a noncompressive (possibly inflammatory) cause of sciatica may be more difficult to resolve spontaneously. The present study in 283 patients with sciatica, as well as 2 earlier studies, support this theory and found a better prognosis for patients with clear nerve root compression on MRI.”

Complications were minimal, occurring in only 1.6% of surgical cases and all resolved spontaneously.

Conclusions
The authors discussed MRI with some caveats. “The marked increase in rates of lumbar spine surgery has partly been linked to the increased availability of advanced diagnostic imaging techniques. Moreover, spine imaging may have an adverse effect; ie, telling patients they have an imaging abnormality can lead to unintended harm related to disease labeling.”

The authors concluded that MRI doesn’t help to guide the sciatic patient to surgery or conservative care, but “may be informative to predict the patient’s prognosis in sciatica.”