Internal Disc Disruption
Disc Disruption is a pathological process only understood
over the last half of a century. Physical examination of these patients only
tends to reveal pain and guarding, without clear objective signs. Often patients
suffering from this condition were thought to be psychologically impaired
and were used as examples of psychogenic pain disorders, hypochondriasis,
factitious disorders and malingering. Nothing could be further from the truth
and even today the idea of Internal Disc Disruptions has its detractors, especially
in medical legal cases.
1946 medical practitioners believed that the only painful disorders of the
intervertebral discs themselves were those of herniation of the nucleus pulposis,
with impingement of a nerve root. The argument was that the intervertebral
discs lacked innervation and injury to the discs themselves could not be painful.
When discograms were developed in the late 1940's, the idea was to replace
myelography as a means of diagnosing herniations. Discographers injected radio-opaque
dye into the nucleus pulposis of lumbar discs and found that they could trace
the contour of the herniation from the inside of the disc, rather than view
the impression the disc made, as was possible with oil based mylelograms.
The advantage of discograms was thought to be one of replacing the relatively
high side effect risk with myelography, while providing a more direct structural
view of the herniation. To the surprise of early discographers, it was often
determined that pain occurred in non-herniated discs, which showed a disrupted
pattern of the nucleus pulposis outside of its boundaries, but contained within
the walls of the disc. Contrary papers were published with reports of massive
false positive test results, and these remained the cornerstone of discrediting
discograms. Interestingly, they never addressed the issue of internally disrupted
discs, and instead focussed upon pain provocation without frank herniation.
The controversy raged into the 1980's, when anatomists were able to show clear
innervation of the external 1/3 of the intervertebral disc anulus fibrosis,
with a rich supply of nerves feeding three separate pain pathways into the
dorsal horn of the spinal cord.
of pain are both inflammatory and mechanical. The nucleus pulposis of the
intervertebral disc is kept isolated from the body's immune system. When the
disc is disrupted this isolation is broken and the proteoglycans in the nucleus
cause the body to mount an inflammatory response to seal off what it sees
as a foreign invader. When the nuclear material reaches the outer third of
the anulus the inflammatory response causes pain to be transmitted from the
pain nerves in this area. The mechanical problem occurs when the functional
capabilities of the disc anulus are lost. The anulus fibrosis is made up of
tough connective tissue that must withstand the incredible forces of compression
and rotation found in the spine. Much of the disc is weakened by a marauding
nucleus pulposis destroying collagen fibers. The mechanical forces translate
to the remaining fibers and overwhelm the disc's ability to function normally.
The excessive strain transmitted to the highly innervated outer 1/3 of the
disc wall results in a mechanical signal of pain, with normal disc compression