The recently publicised preliminary findings[1] of abnormal nerve growth into intervertebral discs has direct impact on Personal Injury claims for low back and neck pain.
English and French researchers looked at the depth of penetration of nerves into samples of painful discs removed at surgery and compared them with similar samples of painless discs from the same patients and from people free from back symptoms who had died. In painless discs the nerves were limited to the outer two-thirds of the anulus fibrosus, but of painful discs they penetrated into the inner third of the anulus in nearly half, and into the central nucleus pulposus in nearly a quarter.
More dramatically, the pain-detecting Substance P was present in the nerve fibres of pain sufferers, absent from those of controls.
| PRACTICE
POINT Injury to an Intervertebral Disc is usually a process, rarely an event |
As detailed in Medical Litigation News Volume 2, Issue 4, asymptomatic bulging of discs is increasingly common with age [2], [3], [4] and should be viewed as a phase in the process of Degenerative Disc Disease. Tempting as it may be to attribute such newly-discovered bulging to a recent injury, this belies medical science.
This is not to say that persistent back or neck pain may not appear for the first time after significant injury and be causally related. When and why Degenerating Discs become painful has hitherto been a mystery.
| PRACTICE
POINT Previous general practitioner records are usually more valuable evidence of post-traumatic causation of low back and neck pain than diagnostic imaging |
Common as it is, the cause of most back pain is unknown. As previously reported [5], injecting xray dye (discography) does not reliably distinguish between painful and painless discs.
If the preliminary findings on abnormal nerve growth are confirmed, our understanding of the causes of back and neck pain will have advanced. Radically different therapies may follow.
| PRACTICE
POINT The faulty model of "post-traumatic bulge" may soon be replaced by "abnormal nerve supply" |
From the medicolegal perspective, the newly painful intervertebral disc can be viewed as a "thin skill" or "crumbling skull". Absent evidence of malingering (Medical Litigation News Volume 1, Issue 5 and Volume 2, Issue 9), the useful question then changes from Did the injury cause the disc bulge, to How soon would the back or neck have become persistently painful without the injury?
As degeneration of the intervertebral disc proceeds, encroachment on the intervertebral canal may develop. Central protrusion or bulging of the disc itself may compromise the available space for the spinal cord, and degenerative wear and tear on the facet joints may cause bony overgrowths to intrude on the spinal canal.
Of asymptomatic subjects over age 70 years, not only do more than one-third have disc protrusions on Magnetic Resonance Imaging (MRI), but a fifth have spinal stenosis [6].
Even in younger people, a combination of a relatively narrow spinal canal and varying degrees of degenerative disc disease may so compromise the available space for the spinal cord that pain and neurological symptoms caused by spinal stenosis may appear de novo caused by exacerbation after a relatively back or neck injury ("thin skull").
Copyright © 2008 Electronic Handbook of Legal Medicine