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General Info. | Treatment Options |The Tutorial | Disc Bulge | Disc Protrusion | Disc Extrusion | Disc Sequestration
In layman's terms, a disc herniation occurs when the inside of the intervertebral disc (nucleus pulposus) tears its way through the posterior outer portion of the disc (annulus fibrosus) and invades the space where the delicate neural structures reside (i.e., the anterior epidural space). The presents of this nuclear material in the anterior epidural space may irritate these neural structures, which in turn may cause the patient to suffer severe back and/or leg pain. In this tutorial we will explore just how a disc herniation occurs and discuss some of the more common classification of herniation. The term 'Disc Herniation' (or 'disc prolapse' as they use in Europe) is a broad and general term that includes three specific types of disc lesions, which are classified based on the degree of disc disruption and posterior longitudinal ligament (PLL). The three main classifications of disc herniation are Protrusion (aka: contained herniation or sub-ligamentous herniation), Extrusion (aka: non-contained herniation, or trans-ligamentous herniation) and Sequestration (aka: free fragment). These terms will be discussed more below. Figure # 10, which is a sagittal (from the side view) T2 Weighted MRI lumbar image, demonstrates two types of disc herniation: the L5/S1 disc has suffered a 9mm disc extrusion (red arrow) that is not contained by the PLL. The L4/5 disc has suffered a smaller 4mm disc protrusion (green arrow) that is contained by the PLL. The L3/4 (blue arrow) is completely normal and has no disc material projecting posteriorly into the epidural space. Also note that the L3/4 disc is white in color, which indicates it is non-degenerated (i.e., full of water and healthy proteoglycan). The two herniated discs (L4/5 & L5/S1) are "black" on this MRI image, which indicates disc desiccation (lack of water and proteoglycan) and is termed "degenerative disc disease" (DDD), which is usually a precursor to disc herniation for it weakens the annulus which contains the pressurized nuclear material. General Information and Confusion: In 1934 the syndrome of "disc herniation" was born when Mixter and Barr first proclaimed that a posterior rupture of the intervertebral disc that allowed nuclear material to escape and compressed the adjacent spinal nerve root(s) was a common cause of back and leg pain - sciatica (125). For nearly 70 years this assertion has held true without much challenge(170). However, modern research as demonstrated that the relationship between disc herniation and its often associated sciatica are a far more complex and bewildering phenomenon than once realized. For example, since the invent of MRI, we have learned that some patients have disc herniation on MRI, yet have no pain at. And, visa versa, some patients have terrible back and leg pain, yet have no disc herniation! (Click here for the false positive rates for MRI.) Moreover, when post MRI is performed on some patients that once suffered disc herniation induced back and leg pain, the herniation is still there, yet the patient is gone. Conversely, some patients who fail to recover from back and leg pain, demonstrate a disappearance of the once prominent disc herniation. Other ironies of disc herniation have been discovered as well. For example, we have learned from the work of Karppinen et al. that the size and severity of disc herniation do NOT correlate with the degree of patient pain, disability, or suffering (170). That is, small disc herniations and even disc bulges may causes just as much pain and disability as massive disc herniations and even extrusion. Another strange irony is the fact that smaller, less complete, and innocent looking disc herniations (i.e., contained herniations, protrusions and/or disc bulges) are usually more difficult to treat and respond less favorably to decompressive surgery (discectomy) than do the larger and more advanced disc extrusions and sequestrations. (50) Moreover, symptomatic contained herniations have a poorer prognosis for recovery than do the larger more complete disc extrusions and sequestrations do. (50) And, to further cloud the water, we now know that sciatica (a horrible burning lower limb pain associated with disc herniation) is not always causes by the direct pressure from a herniated disc. That is, it can be caused from nuclear material "leaking" from the back of the disc onto the adjacent nerve roots, i.e., chemical radiculopathy(3,4) and/or from chemical and pressure irritation of the posterior intradiscal nerve fiber, i.e., the sinuvertebral nerves, which is called discogenic sciatica (1,2). So, diagnosing a patient with complaints of back and lower limb pain is certainly not as easy as once believed. TREATMENT OPTIONS: SURGERY VERSUS CONSERVATIVE CARE Based on nearly thirty years of medical research, I can comfortably conclude the forthcoming with respect to treatment options for disc herniation induced back and lower limb pain: for patients who do not have the danger signs of compressive disc herniation--i.e., loss of bowl and/or bladder control (cauda equina syndrome); progressive worsening of their neurological state (atrophying muscles, progressive muscle weakness [foot drop]); and/or a worsening of their pain--conservative, non-operative care, will work just as well as having back surgery. In 1982, Weber--who won the prestigious Volvo Award for this work--was the first to suggested that back surgery for disc herniation induced back and leg pain was no more effective than letting old man time and mother nature (i.e., having conservative care [i.e., physical therapy, exercise and physical therapy]) work their magic. That is, he experimentally demonstrated that in the long run, patient who had back surgery got no better than those who didn't. The surgery group, however, did get better faster and were doing better at the one year mark; however, by three years, there were no differences between the surgery group and the non-surgery group. [Weber Study] Other investigators have confirms these findings. Recently (2007) Peul et al published the results of their medical investigation into surgical outcome of sciatica in the prestigious New England Journal of Medicine. They also randomized over 200 patients into either a disc surgery group or a conservative care (non-surgical) group. Again, as with the Weber study, the patient who had surgery got rid of their leg pain faster; however, at the one year follow-up, the surgical patients were no better off than that of the non-surgical patients. [An abstract of the study is here] DISCECTOMY: Treatment for severely symptomatic disc herniation-associate sciatica is best accomplished with traditional open discectomy or micro discectomy (99), BUT ONLY IF conservative measures have failed and/or if you have the danger signs associated with disc herniation: loss of bowl and/or bladder control (cauda equina syndrome); progressive worsening of the neurological state (root-related atrophying muscles, progressive muscle weakness [foot drop]); absent reflexes and/or a worsening of pain. Surgery timing, for disc herniation-related sciatica, is also critical. That is, you certainly don't want to wait any longer than one year before having the surgery (50). See the Surgery Timing Page for more information. ENDOSCOPIC & LASER: With regard to the non-invasive techniques, such as endoscopic discectomy, laser discectomy, etc. I'm not a believer and I do not recommend them. With regard to Laser discectomy, neither does a 2007 meta-analysis (a study of all the research ever done on Laser discectomy) by Goupille et al (26) who state, "this treatment cannot be considered validated for disc herniation-associated radiculopathy resistant to medical treatment." Until the inventors and proponents of these procedures step-up to the plate and published some high quality medical investigations (like what Peul et al just did) to prove their efficacy (effectiveness), then I'm not a believer. I can only think the reason the inventors of these techniques haven't done so is because they are afraid that the studies will show their techniques are no better than traditional discectomy or even worse. SO, STEP AND SUBMIT YOUR RANDOMIZED CONTROLLED TRAILS! PUT YOUR RESEARCH WHERE YOUR MOUTHS ARE! THE TUTORIAL: THE BIRTH OF A DISC HERNIATION Lets begin our tutorial with a quick review of the normal disc, and then proceed through each type of herniation. (For a full review of disc anatomy and physiology, please visit my 'Disc Anatomy Page'.) Figure #1: The 'Nucleus Pulposus' (pink #1), which is a water-rich gel-like mass of proteoglycan material, has the duty to support the tremendous 'Axial-Load' (weight) of the body. This nucleus is 'corralled' by the stronger 'Annulus Fibrosus' (green #2). The annulus is made out of concentric rings of a cartilage-like material called 'lamellae' (#9). It is this specially arranged collagen that gives the annulus the tremendous strength needed to hold that nucleus in place. Key Concept: The nucleus pulposus, because of the tremendous axial load upon it, is constantly trying to escape from the confines of the center of the disc. If it does manage to escape (tear) through the PLL (#7), the appearance on MRI is called a disc extrusion. The 'Posterior Longitudinal Ligament' (PLL #7) shields the delicate posterior neural structures and acts as a last line of defense against the potentially irritating nucleus pulposus. Note the posterior disc is 'concave' in shape, as outlined by the PLL. (It will not stay concaved for much longer!) The 'posterior neural structures', which are very sensitive to pressure and chemical irritation, include the following: 'Spinal Nerve Roots' (L4, L5, S1), 'Dura Mater or the Thecal Sac ' (red star), and the 'Dorsal Root Ganglion' (DRG). To learn about the anatomy and physiology of the disc go to: [Disc Anatomy]. And finally we have the Sinuvertebral Nerve (# SN). The Sinuvertebral nerve innervates (connects to) the outer 1/3 of the annulus fibrosus. These tiny nerve ending have the ability to carry PAIN messages to the brain and are thought to be on of the causes of discogenic pain. (Read my IDD page, for more information on discogenic pain.) Oh, one more thing; the epidural space (#8) contains the traversing nerve roots (L5) that are often the favorite target of the compressive disc herniation. THE DISC BULGE: The First Step Toward Disc Herniation: In order for a disc to herniate, its structural components must first 'weaken'. This weakening occurs as a result of Disc Degeneration. Disc degeneration occurs naturally, to some degree, in all disc, but in some people the process become especially severe and damaging. The 'bottom-line' of the degeneration process is that the annulus becomes dried (desiccation) and brittle, hence allowing for the development of Disc Bulging and full thickness posterior anular tearing, or Internal Disc Disruption.
DISC PROTRUTION: Posterior Longitudinal Ligament is still Intact. Figure #3 demonstrates a 4 millimeter disc protrusion The type of presentation in Figure #2. would be 'officially' classified as a 'Disc Herniation' or, more explicitly, a Disc Protrusion (aka: contained herniation or subligamentous disc herniation). Although disc protrusions are seen in about 30% of the normal non-symptomatic population, nerve root compression is not, and if much more indicative of a 'problem. This patient may well be suffering right sided radicular pain (sciatica) and/or lower back pain as a result of compression/irritation of the traversing nerve root and/or irritation of the sinuvertebral nerves in the posterior of the disc. THE DISC EXTRUSION: The Posterior Longitudinal Ligament has ruptured. Figure #4. demonstrates a more serious progression of our pathologically degenerated disc: An 8 millimeter Disc Extrusion (aka: non-contained herniation, transligamentous herniation) is now present. The PLL (blue) has finally been defeated and has completely ruptured,
DISC SEQUESTRATION: The Final End-Phase of the Disc Herniation.
Sequestration (aka: sequester, free-fragment) may be excruciatingly painful (back and leg pain - sciatica) and, if centrally located, may occasionally cause the patient to lose control of their bowl and bladder function, i.e., Cauda Equina Syndrome, which is considered a 'Medical Emergency'! As with the disc extrusion, the sequestration may also undergo a reduction in size from a combination of an immune attack {macrophage attack} and dehydration, although frequently the patient will need immediate decompressive surgery to beat this monster! MRI DISC HERNATIONS: Some real pictures. Figure #6. demonstrates a large 9mm disc extrusion (red star) as visualized on both the Axial (over-head) and Sagittal Note that this extrusion has completely blotted out (can't see) the right traversing S1 nerve roots (left side of image) and has pinched it against the lamina (tiny green arrow). Note the thecal sac is moderately to severely compressed by this large herniation, as noted on both the axial and sagittal images (between blue arrow and red star). This young man (24 years) has avoid surgery and is doing fairly well, although his days of heavy work are probably over for good.
References: 3) Marshall LL, et al. “Chemical irritation of nerve root in disc prolapse.” Lancet 1973; 2:320 4) Marshall LL, et al. “Chemical Radiculitis: A clinical, physiological and immunological study. Clin Orthop 129:61-67, 1977 5) Saal JA, Saal JS, Richard JH. The natural history of lumbar intervertebral disc extrusion treated nonoperatively. Spine 6) Eiichi Takada and Masaya Takahashi et al. "Natural history of lumbar disc hernia with radicular leg pain: Spontaneous MRI changes of the herniated mass and correlation with clinical outcome. "Journal of Orthopaedic Surgery 2001, 9(1): 1–7 7) Goupille et al. "Percutaneous Laser Disc Decompression for the treatment of Lumbar disc herniation." Semin Arthritis Rheum. 2007 Mar 13; (Epub ahead of print). 50) Ng LC, Sell P. 'Predictive value of the duration of sciatica for lumbar discectomy. A prospective cohort study.'J Bone Joint Surg Br. 2004 May;86(4):546-9 " Patients with an uncontained herniated disc had a shorter duration of symptoms and a better functional outcome than those with a contained herniation." 99) Toyone T, Tanaka T, et al. 'Low-back pain following surgery for lumbar disc herniation. A prospective study.' J Bone Joint Surg Am. 2004 May;86-A(5):893-6 "Excision of a herniated disc for relief of sciatica provided rapid relief of sciatica and low-back pain. The findings of the present small study suggest that lumbar disc herniation might be a possible cause of low-back pain." 125) Mixter WJ, Barr JS. “Rupture of the intervertebral disc with involvement of the spinal canal.” N Engl J Med 1934; 211:210-5 290) Kortelainen P, et al. “Symptoms and signs of sciatic and their relation to the location of the lumbar disc herniation.” Spine – 1985; 10:88-92 Copyright © 2002 – 2005 by Dr. Douglas M. Gillard DC |
Figure #2 demonstrates the 'pre-cursor' to a disc herniation. This type of disc lesion - that bulges into the anterior epidural space without any area of focal-ness or out-pouching - would be called a '
and represents a worsening of our disc bulge. The posterior of the disc is 'focally' or 'eccentrically' pushing backwards into the anterior epidural space and has contacted, and even somewhat compressed, the traversing nerve root (white star) and right front corner of the thecal sac. Note that the PLL (blue) still has NOT be disrupted and is still "containing" the near-herniated nuclear material. 
hence allowing for further migration of the the nucleus pulposus into the anterior epidural space. Note the marked displacement of the traversing nerve root (white star) AND the exiting nerve root (green star) (which has now turned completely red with inflammation and venous congestion - the precursors for Radiculopathy). This Disc Extrusion is NOT typically seen in the asymptomatic person and is often an indication for surgical decompression; the 
Figure #5. represents the end-of-the-line for the cycle of disc herniation. Now we can see that a big 'chunk' or 'fragment' of nuclear material has detached itself from the main body of the extrusion is and loose in the epidural space. Note the resulting severe compression of the traversing nerve root (white star), the exiting nerve root (green star) and the lateral aspect of the Thecal Sac (blue star). 
(side) views.