There are a number of important factors to take into consideration for an MRI scan, including limitations with interpretation of findings and the timing of when an MRI scan should be performed.
Evaluating MRI Scan Results
First, the difficulty with the results of an MRI scan, as with many other diagnostic studies, is that the "abnormality" that shows up on the MRI scan may not actually be the cause of back pain. Numerous clinical studies have shown that approximately 30% of individuals in their thirties and forties have a lumbar disc herniation on their MRI scan, although they do not have any back pain.
Therefore, an MRI scan cannot be interpreted on its own. Everything seen on an MRI needs to be well-correlated to the individual patient’s situation, including:
- Symptoms (such as the duration, location, and severity of pain)
- Any neurological deficits on their physical examination
Another important consideration with MRI scans is the timing of when the scan is done. The only time an MRI scan is needed immediately is when a patient has either:
- Bowel or bladder incontinence
- Progressive weakness in the legs due to nerve damage.
Fortunately, both of the above situations are rare.
When to Have an MRI Scan to Diagnose Back Problems
When patients have predominantly leg pain and a lumbar disc herniation is suspected, MRI scans are usually recommended early in a patient’s course of pain. This is because surgery for a lumbar disc herniation generally carries few unwanted side effects (morbidity) and leads to an early return to normal function for the patient.
When patients have primarily lower back pain, generally the only surgical treatment available is a lumbar spinal fusion. This type of spine surgery does carry a reasonable amount of unwanted aftereffects (morbidity) and a longer healing time. Therefore, physicians often recommend waiting 3 to 6 months (after the onset of low back pain) before having an MRI scan done in order to see if the pain will get better with conservative (nonsurgical) treatments.
As a very general rule, if the results of the MRI scan are not going to affect a patient’s further back pain treatment—and patient will continue with non-surgical treatments such as chiropractic treatments, physical therapy and medications—waiting to obtain an MRI scan in most situations is a reasonable option.