I've noticed for some time that a diagnosis of disc herniation has been stamped on many people suffering from low back pain. While this may indeed be the cause of some back pain cases it is important to understand the prevalence of disc herniation’s in a population. I was curious over the past few weeks of the actual number of people that have herniated discs and yet remain asymptomatic. Here are a couple of studies that can help us put this seemingly definitive diagnosis into some perspective.
In the prestigious New England Journal of Medicine in 1994, Jenson et al. found that 52% of the 98 asymptomatic patients in their study demonstrated a disc bulge on MRI; 27% demonstrated a disc protrusion. Only 1% of the patients had a full blown disc extrusion. Out of all 98 volunteers, 64% had an abnormal disc on MRI (bulge, protrusion, and/or extrusion).
In a study in 1989 found that in a group of asymptomatic patients, 31% have an abnormality (not just disc herniation). That’s a pretty large number. One in every 3 people walking around with no complaints at all has something abnormal going on in their spine. A study in 2001 decided to follow up with these individuals and see if those abnormalities simply hadn’t become symptomatic yet. The idea being that if these abnormalities are present they would inevitably become symptomatic. However, when all patients of the previous study were surveyed only 21 had developed low back pain and 12 of them didn’t have a finding in the original study. Less than half of the patients with a spinal abnormality went on to develop low back pain.
In 1998, Weishaupt and Boos et al. randomly collected a group of 60 people that had never had back pain before. The average age of the study was 35 years old (a very young group). Each patient was put through an MRI and the results were interpreted by two different radiologists.
Here's what they found: 24% of the group had a 'disc bulge'; 40% had confirmed disc protrusion; 18% had disc extrusion - which is a severe form of disc herniation; and 0% had disc sequestration. With respect of nerve root compression, 23% had nerve root contact without displacement, 5% had actual displacement of the nerve root (disc disc herniation) without severe physical compression, and 2% demonstrated full-blown nerve root compression.3
There’s a lot more to read on the subject so please ask if you have any questions.
1) Jensen MC, et al. “MRI imaging of the lumbar spine in people without back pain.” N Engl J Med – 1994; 331:369-373
2) Borenstein G, Boden SD, Wiesel SW, et al. “The value of magnetic resonance imaging of the lumbar spine to predict low-back pain in asymptomatic individuals: A 7-year follow-up study. J Bone Joint [am] 2001; 83:320-34
3) Weishaupt D et al. “MRI of the lumbar spine: Prevalence of intervertebral disc extrusion and sequestration, nerve root compression and plate abnormalities, and osteoarthritis of the fact joints in Asymptomatic Volunteers.” Radiology – 1998; 209:661-666