What’s Up Doc column: Do I need an MRI for low back pain?
Columns share an author’s personal perspective.
Q: I tweaked my back and have been having back pain for the last week. Do I need an MRI?
A: Risk factors for low back pain (LBP, including sciatica, as discussed below) include smoking, obesity, older age, both strenuous and certain sedentary (for example office work with lots of sitting) types of work, others. Trauma, whether minor like “twisting my back” or more severe trauma such as a car accident, fall or another traumatic event, is the most common inciting factor. Risk factors for a more serious underlying condition (as discussed below) causing someone’s LBP include immunocompromised state, being on hemodialysis, having a history of intravenous drug abuse, having certain active infections (such as endocarditis), and others.
Almost 90% of Americans will have at least one episode of LBP in their lives, with 50% having a second episode within six months and three-quarters having a second episode within a year. Many others will have another episode at some later time in their lives.
The most common etiology of LBP is nonspecific muscular-skeletal pain; that is there is no specific identifiable underlying condition or disease. Less than 1% of cases of LBP are due to systemic issues such as cancer, infection, cauda equina syndrome (where part of the cauda equina - the “horse tail” bundle of nerves/nerve roots leaving the spine - is compressed), or other systemic causes.
Only about a third of LBP patients seek medical care, although this is still enough to make low back pain one of the top two reasons people see their healthcare provider. The other two-thirds of LBP patients “ride it out,” typically with a similar resolution of their symptoms as discussed below.
A thorough history and physical exam to help identify the small percentage of people with a risk for more concerning causes of their LBP, such as a history of malignancy, fever or other risk for an infectious cause, focal neurological symptoms, point tenderness or others, is indicated. The very small subset of the patients felt to be at a higher risk of some of these conditions may require an MRI (or some other test, such as a blood test, other imaging tests, etc.), but the overwhelming majority of patients do not require any further testing; so the overwhelming majority of LBP patients do not require an MRI.
A subset of patients with LBP develop sciatica, where there is pressure on the sciatic nerve. Sciatica patients’ symptoms include pain, weakness, numbness and/or other symptoms that radiate down their leg. There are disks (soft, cushioning tissue that acts as a kind of shock absorber) between the spinal vertebrae that enable the spine to be able to bend and twist. The most common cause of sciatica is pressure on the sciatic nerve from a herniated, slipped or bulging disk. However, it should be noted that serial MRI’s show that most people with disk herniation actually have their herniation improve/worsen on and off over time, and about a third of people without back pain or sciatica have some disk herniation; so disk herniation clearly comes and goes in many people and in and of itself is not a necessary or sufficient finding for LBP or sciatica.
Episodes of LBP and/or sciatica overwhelmingly resolve over days to weeks to months; three-quarters of patients have their symptoms resolve over days to weeks, and almost 90% have a resolution within a couple of months.
Since the overwhelming majority of cases of LBP resolve over days to months, the initial treatment aims to help with the acute symptoms. Treatment options include massage therapy, application of heat, acupuncture, spinal manipulation (for example, from a chiropractic or other health care provider trained in this procedure), and/or topical medications or non-steroidal anti-inflammatory drugs (NSAIDs) such as over-the-counter ibuprofen; in some uncommon cases, other medications such as muscle relaxants may be utilized. Certain other treatments, for example, injections, cold application, traction, yoga and others have limited data supporting their effectiveness but may sometimes be recommended in select cases. Surgery may be considered in some selected patients with refractory and severe symptoms, but is usually only considered for certain specific indications and only after aggressive attempts with other treatments have not helped.
After improvement from an acute episode of LBP, physical therapy (PT) and an appropriate exercise regimen can help, specifically to decrease the likelihood of recurrent episodes. The appropriate PT/exercise for each individual should be evaluated by an appropriate healthcare provider.
Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com.