Disc Bulges, Herniations, and Degeneration on MRI: What the Research Actually Shows About Injury Causation

Disc Bulges, Herniations, and Degeneration on MRI: What the Research Actually Shows About Injury Causation

A systematic review of 33 studies found that 30% of completely pain-free 20-year-olds already have disc bulges on MRI. Before any accident happened.

The MRI report arrives. It says disc bulge at L4-5, annular fissure at L5-S1, disc degeneration at multiple levels. The treating physician writes that these findings are causally related to the accident. The demand goes up. And everyone in the room proceeds as if the MRI proved something.

It did not. Not by itself.

What the MRI proved is that the patient has a spine, and that their spine looks like the spines of a large percentage of people who feel completely fine. Understanding this distinction is not a minor point of medical nuance. It is the difference between a causation opinion and a guess dressed up in clinical language. This page reviews the research that every California attorney and claims professional should understand before they evaluate any spine injury case.

The Foundation: What Brinjikji and Jarvik Found

In 2015, a research team from the Mayo Clinic, the University of Washington, Kaiser Permanente, and several other institutions published a systematic review in the American Journal of Neuroradiology. They searched MEDLINE and EMBASE for studies that imaged the spines of people with no back pain, no motor or sensory symptoms, and no history of trauma. They found 33 studies covering 3,110 asymptomatic individuals and pooled the data by age decade.

The results were striking enough that they have been cited in thousands of subsequent studies and presentations. Here is what they found across age groups for the most litigated imaging findings:

Source: Brinjikji W, Luetmer PH, Comstock B, et al. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR Am J Neuroradiol. 2015;36(4):811-816.

Read that table again slowly. More than half of completely asymptomatic 30-year-olds have disc degeneration. Thirty percent of asymptomatic 20-year-olds have a disc bulge. By age 50, the majority of pain-free adults have disc degeneration, disc signal loss, disc height loss, and disc bulges. By 80, disc degeneration is present in 96% of people who feel fine.

The authors concluded: imaging findings of degenerative spine disease are present in high proportions of asymptomatic individuals, increasing with age. Many imaging-based degenerative features are likely part of normal aging and unassociated with pain.

What This Means for Litigation

Attorneys on both sides use spine MRIs as anchors in injury arguments. The logic is intuitive: the accident happened, the MRI shows damage, the damage caused the symptoms. The problem is that the MRI cannot tell you whether the findings existed before the accident. In most cases, there is no pre-accident MRI for comparison. And even if there were, the research shows that most of those findings would have been there regardless of any accident.

The Classic Scenario

A 47-year-old plaintiff is rear-ended. She had no prior back treatment on record. Post-accident MRI shows disc degeneration at L3-4, L4-5, and L5-S1, with a disc bulge at L4-5 and an annular fissure at L5-S1. Her treating physician writes that these findings are causally related to the accident and recommends epidural injections and possible surgery.

At age 47, according to Brinjikji, a randomly selected asymptomatic woman would have an approximately 80% chance of disc degeneration, 73% chance of disc signal loss, 60% chance of a disc bulge, and a 23% chance of an annular fissure on MRI. The finding that she has these findings after an accident does not establish that the accident caused them. It establishes that she has a spine that looks like most 47-year-old spines.

The causation question is not what the MRI shows. The causation question is what changed as a result of the accident, and whether the objective clinical picture, the mechanism of injury, the temporal relationship between the accident and symptom onset, and the prior history support a conclusion that the accident caused or significantly aggravated a pre-existing condition.

The Genetic Component: Battie and the Twin Spine Study

If MRI findings of degeneration are so prevalent in asymptomatic individuals, what drives disc degeneration? The dominant view for decades was that occupational factors, posture, and physical loading were the primary causes. The Twin Spine Study, led by Michele Battie at the University of Alberta and involving Finnish twins imaged with MRI, challenged that assumption substantially.

In a series of studies including a 2014 paper in Arthritis and Rheumatology, Battie and colleagues found that lumbar spinal stenosis is 67% heritable when assessed qualitatively on MRI, and the dural sac cross-sectional area is 81% heritable. The genetic correlation between disc bulging and central canal dimensions was extremely high, suggesting that genes influence spinal stenosis largely through their effect on disc degeneration.

Earlier Battie studies on disc degeneration in identical versus fraternal twins found that genetic factors accounted for approximately 74% of the variance in disc degeneration. Occupational physical loading, which everyone assumed was the main driver, contributed relatively little once genetic factors were accounted for.

The implication for litigation: a claimant presenting with lumbar spinal stenosis or multilevel disc degeneration after a workplace or vehicle accident is likely presenting with a condition that was largely determined by their genes before they ever set foot in their workplace or sat in a car. The accident may have produced symptoms, and it may have aggravated a pre-existing condition. What it almost certainly did not do is cause a structurally normal spine to degenerate.

Source: Battie MC, Ortega-Alonso A, Niemelainen R, et al. Lumbar spinal stenosis is a highly genetic condition partly mediated by disc degeneration. Arthritis Rheumatol. 2014;66(12):3505-3510.

The Self-Report Problem: What Patients Tell Their Doctors

A third layer of complexity in spine injury litigation involves the accuracy of the history the claimant provides. In the absence of prior treatment records, attorneys and treating physicians frequently rely on the claimant's report that they had no back problems before the accident.

Research presented by Dr. Diana Kraemer at the 2023 IAIME Annual Scientific Meeting addressed this directly. Examining the accuracy of self-reported history in patients with persistent pain after motor vehicle accidents, studies found:

• Prior axial pain: approximately 50% of subjects were found to have previous axial pain when medical records were audited against self-reported interview, where none had been reported in interview
• Alcohol, substance use, psychological history: approximately 75% did not report alcohol use, illicit drug use, or psychological diagnoses
• The fault attribution effect: for those who perceived the accident was the fault of another, the medically audited rate of prior neck and back pain was more than twice the self-reported rate
• Psychological history under-reporting: in the perceived-fault group, the audited rate of prior psychological problems was more than seven times the self-reported rate

This is not a statement about whether any individual claimant is honest. It reflects a documented pattern in which the context of litigation, particularly when fault is attributed to another party, is associated with systematic under-reporting of prior medical history. The practical implication is that a complete, independent review of all prior medical records is essential to any causation opinion, and that relying on the claimant's history alone is methodologically unsound.

What a Sound Causation Opinion Requires

Taken together, this research points toward a framework for what a sound causation opinion in a spinal injury case requires:

• Pre-existing conditions must be assessed independently of self-report: complete record review including pharmacy records, prior imaging, and prior treating notes is essential
• MRI findings cannot be attributed to the accident without exclusion of age-related degeneration: the examiner must address whether the findings are consistent with normal aging for the claimant's demographic
• Mechanism analysis is required: the biomechanical forces involved must be sufficient to cause the claimed structural injury; the presence of degenerative findings does not establish that those findings are traumatic in origin
• Temporality must be assessed critically: the onset of symptoms relative to the accident matters, but delayed symptom onset after a pre-existing degenerative condition is also consistent with natural history rather than causation
• Genetic and environmental factors must be addressed: multilevel degeneration in a younger claimant is more likely to reflect a genetic predisposition than a single traumatic event

This is what a thorough independent medical evaluation provides: not a rubber stamp on the MRI findings, but a clinical analysis that places the imaging in context. The MRI is the beginning of the causation analysis, not the end of it.

A Note on What This Research Does Not Say

This research does not say that accidents cannot cause spinal injuries. They can. Acute disc herniations occur. Fractures occur. Ligamentous injuries occur. Nerve root compression causing radiculopathy can be caused by trauma. None of that is in dispute.

What the research says is that degenerative findings on MRI are common in people who feel perfectly fine, and that the presence of those findings after an accident does not prove the accident caused them. In a case involving a 55-year-old with multilevel degeneration and no acute findings, the research supports the position that the degeneration preceded the accident. In a case involving a 28-year-old with a single-level acute disc herniation at a level that correlates precisely with the mechanism, a new onset of radiculopathy with an appropriate dermatomal pattern, and no prior back treatment, the analysis is entirely different.

Context is everything. That is precisely why independent medical evaluation exists.

Related pages:

• The Language Trap: How Radiology Reports Mislead Attorneys and Juries
• What Makes a Defensible IME Report
• IME vs. Treating Physician: Understanding the Difference
• Low-Speed Rear-End Collisions and Injury: What the Volunteer Studies Show

Primary sources: Brinjikji W et al., AJNR 2015; Battie MC et al., Arthritis Rheumatol 2014; Kraemer D, IAIME Annual Scientific Meeting 2023.