The clinical correlation with MRI is always a source of further questions – so enjoy.
NOT ALL LUMBAR DISC HERNIATIONS CAUSE PAIN: Over the last 20 years there was a ‘craze’ of MRI and CT studies done on asymptomatic people from all walks of life. It was discovered that a significant number of these ‘pain-free’ people had disc bulges, and disc protrusions (aka: contained herniations) on MRI and CT despite the fact that they had no lower back pain at all! (1-8)
The hypothesis that these asymptomatic people, because of the presents of an asymptomatic disc herniation on MRI, would soon develop symptomatic low back pain and/or sciatica was shot down in flames in 2001 by Borenstein G,
Wiesel SW, et al. More explicitly, these false positive herniation people were
followed for 7 years to see if they would become symptomatic: they didn't (7). Boden SD
In 1995 Fraser et al. conducted a follow-up MRI study on a group of symptomatic disc herniation patients who were randomized to receive either chymopapain injection, or placebo (saline) injection into the herniated disc. Ultimately, 1/3 of the patients ended up having laminectomy, 1/3 had the chymopapain, and 1/3 had the placebo. Surprisingly, about 37% of each group still had the disc herniation at 10 year follow-up; however, there was no relationship between the presents of persistent disc herniation and the degree of patient satisfaction! In other words, some of the patients who were feeling great still had the herniation! (26)
More recently, in 2005 Masui et al. published an investigation into the clinical outcome of 27 patients who were treated conservatively (non-surgically) for symptomatic lumbar disc herniation. Follow-up MRI studies were completed at 2 and 7 years. At 7 years, there was progressive disc degeneration in all patients; however, there was no predictive correlation between MRI findings and the continuation of pain. The authors concluded, "Clinical outcome did not depend on the size of herniation or the grade of degeneration of the intervertebral disc in the minimum 7-year follow-up." (27)
Let's review some of the more scientific investigations in MRI False Positives:
Boden et al. 1990: In a very often quoted study, Boden et al. performed MRI on 67 patients that had never had lower back pain before. They found that 20% of these asymptomatic people under the age 60 had MRI evidence of disc herniation. On the group that was over 60 years old, 37% had confirmed disc herniations and 21% had spinal stenosis despite having no pain. Unfortunately, these investigators failed to differentiate between a protrusion (aka: contained herniation) and an extrusion (non-contained herniation). Also of interest was the fact that 35% of these asymptomatic people between the ages of 20 and 39 had degenerative disc disease with or without a disc bulge (2)
Jenson & Modic et al. 1994: In a bigger and better designed study that was published 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 which demonstrates that MRI is quite accurate for detecting disc extrusions. Out of all 98 volunteers, 64% had an abnormal disc on MRI (bulge, protrusion, and/or extrusion). Also of interest, were the following findings in these asymptomatic subjects: disruption of the outer fibers of the anulus, 14%; degenerative disease of the facet joints, 8%; spondylolysis, 7%, spondylolisthesis, 7%; and central stenosis 7%. (1)
Weishaupt & Boos et al. 1998: In 1998, Weishaupt and Boos et al. randomly collected a group of 60 people (hospital works and non-spinal patients) that had never had back pain before. Twenty people were in their 20's, twenty people were in their 30's, and the final twenty people were in their 40's; this brought the average age of the study to 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.
Boos et al. 1995 Volvo Award Winner:
In 1995, Dr. Norbert Boos won yet another prestigious Volvo Award for his work with 'high-risk' asymptomatic volunteers and MRI false-positives. These investigators took a group of 46 ‘high-risk’ asymptomatic people and scanned their lumbar spine with MRI. All of these volunteers had job duties that are known to be 'high-risk' for the development of symptomatic disc herniation, debilitation, and surgery. These jobs duties included frequent bending, frequent twisting, frequent heavy lifting, frequent contact with vibration, and sedimentary work.
The results indicated that 76% of these asymptomatic, high-risk people had at least one disc herniation (protrusion or extrusion) on MRI; however, noteworthy is the fact that only 13% of these disc herniations were the more severe type of herniation, the extrusion, and no disc sequestrations were found in the asymptomatic group. With respect to nerve root compression by the disc herniation, 17% of the asymptomatic people had minor root “compromise” (defined as contact or deviation of the root) while only 4% had 'major compromise' (defined as compression of the root).
With respect to confirmed Degenerative Disc Disease (DDD) on MRI, 85% of the asymptomatic group had confirmed disc degeneration (aka: DDD) at at least one level, i.e., Grade 3, 4, or 5 type as defined by Pearce et al. This study demonstrates that disc herniation alone does not equate to back and/or leg pain. Seventy-six percent of these high-risk, asymptomatic patients demonstrated disc protrusion or even extrusion (13%) on MRI, yet had no back or leg pain! Obviously, there are other factors that contribute to the phenomenon of sciatica.
CERVICAL MRI: Correlates better with symptomatic disc herniation than lumbar MRI.
Unlike lumbar MRIs, cervical MRIs rarely demonstrate false positives for disc herniation. More explicitly, in 2004 Giuliano et al. performed Cervical MRIs on 100 asymptomatic (people with no neck pain) volunteers and 100 symptomatic (pain-suffering) patients that were in the subacute phase post rear-end motor vehicle accident. The results indicated only 2% (2/100) of the asymptomatic volunteers demonstrated a false-positive disc herniation on MRI; on the other hand, 28% of the symptomatic whiplash patients demonstrated disc herniation on MRI. (517)
DEGENERTIVE DISC DISEASE:
Boden et al. (25) noted a 51% incidence of lumbar disc degeneration in asymptomatic 40-59 year old people. Jarvik et al. (20) noted a 49% incidence of lumbar disc degeneration in asymptomatic 45- to 55-year-olds.
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) Boden SD et al. “Abnormal magnetic resonance scans of the lumbar spine in asymptomatic subjects: A prospective investigation.” J Bone Joint Surg Am 1990; 72A:403-408
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
4) Boos N, et al. “1995 Volvo Award in clinical science: The diagnostic accuracy of MRI, work perception, and psychosocial factors in identifying symptomatic disc herniations.” Spine – 1995; 20:2613-2625
5) Powell MC, et al. “Prevalence of lumbar disc degeneration observed by magnetic resonance in symptomless women.” Lancer – 1986; 2:1366-7
6) Boos N, et al. “Natural history of individuals with asymptomatic disc abnormalities in MRI: Predictors of low back pain-related medical consultation and work incapacity.” Spine 2000; 25:1484
7) Borenstein G,
, 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 Boden SD
8) Wiesel SW, et al. “A study of computer-associated tomography:
The incidence of positive CAT scans in asymptomatic group of patients.” Spine
11) Wood KB, et al. 'Magnetic resonance imaging of the thoracic spine. Evaluation of asymptomatic individual s.' J Bone Joint Surg Am. 1995 Nov;77(11):1631-8
20) Jarvik JJ, et al. "The longitudinal assessment of imaging and disability of the back (LAIDBack) Study." Spine 2001;26: 1158-66.
25) Boden SD, et al. "Abnormal Magnetic-Resonance Scans of the Lumbar Spine in Asymptomatci Subjects." J Bone Joint Surg [AM] 1990; 72:403-408
27) Masui T, et al. 'Natural History of Patients with Lumbar Disc Herniation Observed by Magnetic Resonance Imaging for Minimum 7 Years.' J Spinal Disord Tech. 2005 Apr;18(2):121-126. "Clinical outcome did not depend on the size of herniation or the grade of degeneration of the intervertebral disc in the minimum 7-year follow-up."
517) Giuliano V, et al. 'The use of flexion and extension MR in the evaluation of cervical spine trauma: initial experience in 100 trauma patients compared with 100 normal subjects.' Emerg Radiol. 2002 Nov;9(5):249-53.