Lumbar Discogenic Pain

Question 1

Definition/description

Answer 1

Of all the patients who are dealing with low back pain, it appears that in approximately 28 to 40% of these cases, pain is caused by a discogenic affliction.[1]

Detailed structure of the intervertebral disc (adapted from Bogduk 2005)
Pain can be related to different types of pain which come from muscles, bones, vertebral joints other than the intervertebral disc or other structures in the spine. A degenerated intervertebral disk can release nociceptive molecules and growth factors which result in nerve ingrowth into the disc (level:3A)

Discogenic pain is pain arising from stimulation of pain sensitive afferents within the annulus fibrosus and is a separate condition from disc herniation with associated radiculopathy

Question 2

Clinically relevant anatomy

Answer 2

The intervertebral disc (IVD) is the principal joint between two vertebrae in the vertebral column.
Each IVD is composed of three structures:

1. The nucleus pulposus (NP), a gelatinous inner part;
2. The annulus fibrosus (AF), an outer ring of fibrous tissue that encloses the nucleus pulposus;
3. Two endplates of hyaline cartilage.

The endplates serve as an interface between the disc and the vertebrae, they cover the upper and lower level of the annulus fibrosus and the nucleus pulposus.
The cells in the outer region of the annulus fibrosus are fibroblast-like cells which are disposed parallel to the collagen fibers, while those in the inner annulus fibrosus are chondrocyte-like cells.

The nucleus pulposus mainly consists of hydrophilic proteoglycans; which absorb water and pressurize the disc, it also distributes weight to the annulus fibrosus and vertebral endplates and conserves disc height.

Discogenic pain is attributed to degenerative changes in the intervertebral disc due to aging or a trauma. The healthy disc of an adult has scattered nerves which are mainly restricted to the outer lamellae. Degenerated discs have nerves that go through deeper intradiscal structures till the inner third of the annulus and the nucleus. These nerves contain nociceptive neurotransmitters and initiate production of cytokines, provoking nociceptive information from within the disc.

Question 3

Epidemiology/ Etiology

Answer 3

Discogenic pain is a form of low back pain, caused by chemically or mechanically damaged intervertebral discs.
This damage can find its origin in traumatic events, as well as in deterioration due to aging.

In patients dealing with discogenic low back pain, there were findings of high levels of proinflammatory mediators (cytokines). The production of these proinflammatory mediators occurs in the nucleus pulposus of the disc and is in general viewed as a major cause of the discogenic low back pain

Question 4

Differential diagnosis

Answer 4

• Lumbosacral Disc Injuries
The causative factor of the intervertebral discs of the lumbosacral spine injuries are low back pain (LBP). It is a more frequent source than muscular strain or ligamentous sprain. There is no single injury to the intervertebral disc that has been unequivocally identified as a pain generator.

• Lumbosacral Facet Syndrome
Zygapophyseal -joints are not the single or primary cause of LBP and are often mistaken for discogenic pain. The Z-joint is one of the most common sources of low back pain (LBP).

•Lumbosacral Radiculopathy
However radiculopathy is not the cause of back pain, some of the major causes of acute and chronic low back pain (LBP) are associated with it. The cause of lumbosacral radiculopathy is nerve root impingement and/ or inflammation with neurologic symptoms in the areas that are supplied by the affected nerve root or rots.

• Lumbosacral Spondylolisthesis
Spondylolisthesis is most common in the lower lumbar spine region. Causes are minor overuse trauma, particularly repetitive hyperextension of the lumbar spine. If the pars defect is bilateral, it may allow slippage of the vertebra, typically L5 on S1, resulting in spondylolisthesis.

•Lumbosacral Spondylolysis
Causes of Lumboscaral spondylolyse are mostly mechanical factors, they could trigger or develop lubar spondylolysis. There is also a heredity factor. The most common place is at L5 (85%) and may be observed as high as L2. Lumbosacral spondylolysis (lumbar spondylolysis) is the cause of the most common type of spondylolisthesis.