Sciatica is caused by nerve compression somewhere along the sciatic nerve. Determining the specific source of that compression is often a trial and error process involving a series of diagnostic tests. The culprit is usually a herniated disc. One of the most common image tests used to confirm the location of the offending disc is an MRI scan, which is widely considered to be a very reliable diagnostic tool. New research suggests MRI results may not always provide an accurate determination of sciatica due to disc herniation.
Herniated Discs and Sciatica
A herniated disc only becomes problematic, meaning painful, if it’s pressing on a nerve root or a nerve is affected by inflammation. If the nerve that’s being compressed by the disc is the sciatic nerve, the longest single nerve in the human body running from the lower back to the legs, it’s referred to as sciatica. It’s a condition characterized by pain that radiates beyond the source, usually extending to the buttock, hips, thighs, and legs.
When is an MRI Recommended?
When patients aren’t responding to conservative remedies for more than a month or so, sciatica treatment often includes a more detailed attempt at diagnosis with magnetic resonance imaging (MRI). Recent research suggests this particular image test, which offers a detailed look at both soft tissues and bones, may not be effective at identifying every instances of sciatica due to disc herniation.
Sciatica Treatment Patterns
Dutch researchers took a look at a group of patients to determine rates of spontaneous regression, or the disappearance of sciatica symptoms with little or no intervention among patients with different types of lower-back disc herniation. The study included patients with disc extrusion, or a disc that is ruptured or “herniated,” along with specific types of herniation.
Some of the subjects had a disc protrusion or a protruding disc with a smaller amount of protruding disc material at its base extending below or above the disc itself. Others had a disc sequestration, where disc material separates and migrates. Researchers determined that the worse the damage, the better the odds are of experiencing self-healing, or spontaneous resolution of radiating leg pain.
Linking MRI Findings to Nerve Root Pain
Involving nearly 300 patients, the study focused on individuals who had experienced sciatic nerve pain for at least six weeks related to abnormal neurological patterns. MRI findings also had to be linked to the affected nerve root.
The group was further divided by those who only had conservative care and those who opted for surgery following non-surgical treatments that weren’t effective for them. More than half of those in the first group ended up having surgery when followed up a year later.
Higher Recovery Rates with Less-Severe Pain
Subjects with compression that showed up on an MRI scan experienced a higher recovery rate than patients with no compression. Those within this group also reported less-severe leg pain when followed up and self-reported a lower pain score.
A higher recovery rate was also observed in patients with disc extrusion when compared with patients who had a protruding herniation. Those within this group also reported leg pain that wasn’t as severe, although this correlation wasn’t reflected in their RDQ (Roland Morris Disability) score, which assesses pain based on questionnaire answers.
Herniated Disc Size Not a Factor
Size of the herniated disc didn’t appear to be a significant factor in the study. Recovery rates and self-reported assessments of leg pain experienced were similar among all patients and did not appear to affect patient decisions to have subsequent surgery among those in the conservative treatment group. There was an even distribution of larger herniated disc among both groups, including those who chose not to have surgery.
Disc Size Not Correlated to Positive Outcomes
While it would seem logical that patients with a larger herniation who had surgery would experience a better outcome, this wasn’t the case with the subjects studied. Disc herniation size appears to be irrelevant when determining whether or not a patient will respond well to treatment.
Researchers theorized the reason for these findings could be that sciatic be linked to either nerve root compression from the affected disc or inflammation. It was also suggested that possible inflammation-related instances of sciatica are less-likely to heal spontaneously. Based on results of this study and similar prior studies, researchers suggested prognosis for a patient was better for those with clear nerve compression showing up on their MRI scan.
Effectively Diagnosing Sciatica
Image testing remains the standard method of confirming whether or not sciatic nerve pain is from a herniated disc. While new research suggests imaging alone, especially with an MRI scan, may not always result in an accurate diagnosis, a comprehensive diagnostic process can still be beneficial for patients. In addition to image tests, it’s a process that often includes:
Medical history of the patient
A thorough physical exam
Descriptions of when pain occurs, including what activities or movements seem to trigger noticeable discomfort
More than a million patients have MRI scans annually with results showing no conclusive evidence of a sciatic-related herniated disc. New research into magnetic resonance neurography shows that this imaging technique is more effective at diagnosing sciatica for patients who weren’t diagnosed following initial image testing through other methods. While MRIs may not be effective as a sole diagnostic tool for sciatica related to disc herniation, such testing is still useful in overall patient assessment.
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