Lumbar Disc Herniation




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Disc Herniation Viewing | The Symptoms | The Prevalence | The Confusion | The Research | Treatment Options | Birth of a Herniation | Disc Bulge | Disc Protrusion | Disc Extrusion | Disc Sequestration
(Note: Please go to the Disc Anatomy Page before you read this, so you are up-to-speed with the terminology I am going to use on this page.)

What is a Lumbar Disc Herniation?

disc herniationWhat is a disc herniation? A disc herniation, which can also be referred to as a protrusion, prolapse, rupture, slipped disc, or bulge (a commonly used incorrect term), is an often-painful condition that occurs when the nucleus pulposus (the Jell-O-like center of the disc) tears through its containing annulus fibrosus (annulus) and escapes through the normally smooth elliptical contour of the disc periphery (outer disc).

An analogy commonly used to describe the disc herniation goes like this. The disc is analogous to a car tire: it has a very strong tread (the annulus) which holds in place a highly pressurized inner substance called air (the nucleus). If you run over a nail and pierce the tread, the air escapes and you get a flat tire.

The difference between the tire analogy and disc herniation is that when the air escapes, nothing happens other than the tire goes flat. When the disc herniations occurs, the nucleus material in the center does not simply diffuse harmlessly into the air, but instead compresses the adjacent neural structures (i.e., the anterior dura of the thecal sac, the traversing nerve root, and/or the exiting nerve root) and may result in a pain-producing inflammatory reaction either within the disc itself or adjacent neural structures. *Can you see the massive disc herniation in the above sagittal MRI image? If not, keep reading.

How Do You See the Disc Herniation?

Disc herniations are completely invisible on standard radiographs (x-rays) and are poorly visualized on CT. In order to view them, a special study called an MRI (magnetic resonance imaging) will be ordered by your doctor, which is the gold standard for looking at the disc, as well as other soft tissue structures.

In layman's terms, the MR uses magnetism to re-create an exact picture of the disc within a computer. These many pictures or slices, are reassembled on either film or a DVD disk and then given to the ordering doctor, along with a report from the radiologist, for interpretation.

*I have an entire webpage devoted to MRI and the disc, which you should visit, if you want to learn more. (The MRI Page)

What Are the Symptoms of Disc Herniation?

The answer to this question really depends on the size and location of the disc herniation.

The Contain Disc Herniation

Disc herniations that are still contained by the outer annulus and posterior longitudinal ligament (PLL), typically cause low back pain without dermatomal lower extremity pain (radicular pain, sciatica). The affected person may experience a vague lower extremity pain which typically does not extend downward past the knee, but the major complaint is almost always severe low back pain.

The theorized mechanism for this often severe low back pain is that the annular tear through the posterior disc, which is what has spawned the disc herniation in the first place, has allowed nucleus to directly contact the pain-carrying nerve fiber of the posterior annulus (i.e., the sinuvertebral nerve endings) which in turn has resulted in a horrible pain-producing inflammatory process. Furthermore, since the tire has not ruptured, there is still tremendous pressure within that sensitive posterior region of the disc which irritates things even further. A third pain mechanism is due to the fact a biomechanical shift of the axial load as occurred because of the ruptured nucleus and the new pivot point is over the posterior annulus instead of the center of the disc. This phenomenon also results in increased mechanical irritation of the already inflamed posterior disc.

Another strange irony is the fact that smaller and innocent looking disc herniations (i.e., contained herniations [aka: protrusions, or subligamentous herniations]) are the most refractory (resistant) to treatment. That is, they and respond less favorably to surgery (discectomy) and conservative care, when compared to the larger disc extrusions and sequestrations (50, 51).

How do we know this? By studying the spine research database, which includes a award-winning study by our friend Dr. Carragee of Stanford. In this 2001 study, Eugene Carragee published a paper that indicated patients with a contained disc herniation, which was defined as measuring less than 6 mm, had a success rate of only 24% after discectomy! That was compared to a success rate of 98% for patients with a large herniation (9 mm or more) (10 50).

So how do we treat such a small contained herniation? Derby et al (151) says, unfortunately, that we have yet to discover a good cure and interbody fusion is really the only alternative.

There are what I call experimental treatments such as Nucleoplasty, SED, Disc Biacuplasty, IDET and percutaneous discectomy, that claim success with the small little devils. [149,150] However, with the exception of Disc Biacuplasty, there continues to be scant quality research demonstrating efficacy of these fringe treatments. Read below for more.

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 compressive 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 of whom complaints of back and lower limb pain is certainly not as easy as once believed.

The Non-Contained Disc Herniation

Disc herniations that are no longer contained by the outer annulus and PLL (i.e., non-contained disc herniation, disc extrusion, or sequestration) typically present with radiating lower extremity pain (sciatica, radicular pain) greater than lower back pain.

Although the tire (disc) has now popped which greatly reduces the pressure within the disc (intradiscal pressure) and alleviates at least some of the low back pain, the nuclear material is now free to soak into the adjacent sciatic nerve roots (exiting and traversing lumbar nerve roots) and cause a pain-producing inflammatory process. [70,71] Such an inflammatory process is strongly associated with radicular pain—a burning, stinging, numbing and sometimes electrical-like pain down the lower extremity in a (at least early on) dermatomal pattern.

The Prevalence of Disc Herniations, With or Without Sciatica

The prevalence (frequency of occurrence) of disc herniation in humans has been described by Heliovaara et al (1987) in a massive population study. More specifically, these researchers looked at data from 7,217 randomly selected volunteers over the age of 30, who were all available for interview and examination. Of this randomly chosen group, 5.1% of men and 3.7% of women were found to be suffering from a symptomatic lumbar disc herniation at the time of the evaluation. In other words you could say that approximately 4% of all humans are suffering from symptomatic lumbar disc herniation at any given time. They also concluded 77% of men and 74% of women had suffered a significant bout of back pain at some point during the lifetimes (lifetime prevalence). With regard to radiating lower extremity pain, 35% of all men and 45% of all women reported suffering at some point during our lifetimes; however, true radiculopathy (actual sciatica) was reported in only 5% of men and 4% of women at some point in their lifetime. The former and latter radiculopathy percentages were later confirmed by Manninen et al (20).

With regard to age, the fourth and fifth decades of life are by far the most common time for a person to suffer asymptomatic disc herniation [65].

With regard to herniations size, arguably and ironically, the bigger the herniation the better. That is because – for reasons not completely understood – these bigger herniations respond much better to surgical decompression. This phenomenon has been well researched by Carragee et al. (10, 22) and will be discussed more below. With regard to pain, however, the size of the herniation has nothing to do with it. That is, very small herniations can be just as painful (if not more painful) than giant herniations (23, 24).

The duration of symptoms can also be an ominous predictor of the future.

Figure # 10: This 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 (a remnant HIZ sign is also seen here). 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); this is usually a precursor to disc herniation for it weakens the annulus that contains the pressurized and irritative nuclear material.

The Confusion: Are Disc Herniations Always Painful?

Modern research as demonstrated that the relationship between disc herniation and its often-time associated sciatica are a far more complex and bewildering than previously realized. For example, since the invent of MRI, we have learned that some patients have disc herniation on MRI without suffering low back pain or sciatica. (25, 26)!

Conversely, other patients have terrible back and leg pain yet have no disc herniation or visible disc defect on MRI. (11) (Click here for the false positive rates for MRI.)

As if the preceding paragraphs were notconfusing enough, why some patients completely recovered from a large disc herniation without surgery or even a size reduction of the disc herniation (as visualized on post MRI studies), remains a mystery—resolution of the inflammatory process is the prime suspect.

Other ironies of disc herniation have been discovered. 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. Specifically, small innocent looking disc herniations or bulges were found to cause just as much pain and disability as the more severe looking disc pathology, such as disc extrusions and massive disc herniations. [170]

Therefore, the medical research community certainly does not have the pain-disc herniation relationship down pat.

THE RESEARCH:

It was not until 1934 that the medical research community first figured out that a herniated lumbar disc was a cause of chronic low back pain and sciatica and by surgically removing the fragment of herniated disc, the patients often got better. [42]

However, over the last thirty-years there have been several well-designed medical investigations which have demonstrated that lumbar disc surgery for herniation is no more effective than conservative care (analgesics, exercise, and physical therapy) in the long run, although discectomy does appear to get patients out of pain and back to work faster. [13,73,74]

In a more recent study, (2007) Peul et al published the results of their medical investigation into surgical outcome of sciatica in the prestigious New England Journal of Medicine. Like Weber, they randomized over 200 patients into either a disc surgery group or a conservative care (non-surgical) group and found the same result: the patients 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 the ones who went the non-surgical route [An abstract of the study is here].

Treatment Options: Surgery Versus Conservative Care

One of the horrible complications associated with a herniated lumber disc is sciatica—a terrible burning, stinging, shooting pain that travels from the low back all the way down the lower extremity usually into the foot. The annual incidence of disc herniation-induced sciatica is 5 per 1000 people [8,9].

One of the most surprising discoveries regarding treatment options for disc herniation-induced radiculopathy is that disc surgery (microdiscectomy) and conservative non-surgical treatment work the same with respect to over-all long-term improvement [Weber]. The only advantage of microdiscectomy is that usually gets the injured person out of pain and back to work faster than conservative care alone IF the surgery is done in time (less than one year) and IF they are a proper candidate for the surgery.

The only true indications for surgery are (1) they simply can't stand the pain, (2) they have a progressive worsening of neurological symptom (i.e., worsening of muscle weakness in the upper or lower extremities) and (3) the development of the dangerous cauda equina syndrome. All of the latter three conditions are surgical musts in most cases.

Another important thing to understand is that 10% to 40% of microdiscectomies FAIL and leave the patient suffering what is called "failed back surgery syndrome [104].

Discectomy

According to the medical research, if you must have surgery for disc herniation-related back pain / sciatica, open discectomy (aka: microdiscectomy) may be the way to go (99). However, surgery is indicated only if conservative treatment has 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, intractable pain.

Furthermore, open discectomy works much better for just herniations that are non--contained (i.e., extrusions or sequestrations) (40).

When to have the surgery is also critical in order to increase the chance of success (not so with fusion type surgeries). That is, you certainly don't want to wait any longer than one year before having the surgery for disc-herniation related sciatica (50)--three or four months is about all you should wait. See the Surgery Timing Page for more information.

Open discectomy (i.e., microdiscectomy, open discectomy, laminectomy) is not a panacea and works poorly for small contained disc herniations (100, 101).

MINIMALLY INVASIVE TECHNIQUES:

It all started with a papaya enzyme that was used to dissolve the center of a herniated disc. More specifically, in 1959, Smith (43) reported on a new treatment intervention termed "chemonucleolysis," which used chymopapain (a substance derived from papaya fruit) to digest a portion of the nucleus pulposus in hopes of decompressing a herniated disc from the inside (This technique is now banned in the United States secondary complications).

In the 70s and 80s, Hijikata (44) and Onkin et al (45) respectively, developed the first minimally invasive percutaneous lumbar discectomy. While the first model was manually operated (44) it was soon automated, which was termed the automated percutaneous lumbar discectomy (APLD) (45).

The next procedure invented was based on the principles of APLD and called the DeKompressor system (117-119).

According to Manchikanti et al (33), we now have the forthcoming different approaches to percutaneous disc decompression and all have been shown to reduce intradiscal pressure (which in turn ostensibly diminishes pressure on sensitized sinuvertebral nerve endings in the outer annulus of the disc): #1) chemonucleolysis ( not available in this country anymore); #2) percutaneous nucleotomy; #3) percutaneous discectomy; and laser treatments (34-39).

So if a symptomatic contained disc herniation only has a one in four chance of being cured via traditional micro/open discectomy(10), then how the hell do you treat it? There are a gaggle of minimally invasive techniques that have come to fruition over the years. First we have the percutaneous techniques that all involve poking a small needle into the center of the disc and removing nuclear material. This in turn reduces the intradiscal pressure, which in turn is supposed to suck the herniation back inside the disc.

Percutaneous Laser disc decompression (PLDD): Another version of this pre-cutaneous technique uses a laser to diminish nuclear material, which in turn is supposed to reduce the size of the contained disc herniation. Although some authors have claimed this PLDD the best thing since sliced bread for treating contained herniations; other authors disagree (7, 15) in part because (amazingly--this has been around for 20 years) there has yet to be a randomized controlled trial completed to tell us whether or not this treatment is really efficacious– that is about to change (14). Other authors have published opinions that laser discectomy may be associated with end plate injury and has enjoyed less success than chemonucleolysis in randomized studies [52].

Nucleoplasty:

Percutaneous Disc Decompression using Coblation technology (Nucleoplasty) was approved by the FDA in year 2000 and gained immediate popularity among surgeons (46, 41, 47). in fact, within two short years it was utilized in approximately 8000 patients (16); the official name of the procedure is called Nucleoplasty. This technique uses radiofrequency energy to remove nuclear material and create small channels within the disc (41). The channels within the nucleus are then thermally treated to produce a zone of thermal coagulation. So you could say Nucleoplasty combines coagulation and tissue ablation (it is this ablation process that is the patented coblation technology), which in turn decompress the herniated disc.

Does it work?: During the 12 years since its FDA approval, the efficacy of the procedure remains controversial, notwithstanding the increasing utilization of the procedure. For example, Gibson and Waddell (two extremely respected and world-renowned spinal researchers) stated that all minimally invasive decompression techniques including coblation therapy "should be regarded as research techniques."(40) To make things even bleaker, The Centers for Medicare and Medicaid Services (CMS) issued a non-certification for these intradiscal procedures (48). More specifically, these noncertified, thermal intradiscal procedures are percutaneous or (plasma) disc decompression (PDD) or coblation, along with other intradiscal therapies.

Birth of the Disc Herniation

Lets begin our tutorial with a quick review of the normal disc, and then proceed through each type of herniation.

The Normal Disc:

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 annular tearing, or Internal Disc Disruption.

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 'Disc Bulge' on MRI (only because the MRI can NOT show the condition within the disc), although in reality it is a 'Grade 3 Radial Annular Tear' (you would need CT discography to identify the tear) that has disrupted the posterior annulus and allowed irritating nucleus pulposus material to enter into the outer fibers of the disc. Again, this in of itself (IDD) may cause severe and disabling pain in some unfortunate people; however, the subject of Internal Disc Disruption is not the focus of this page. Also note that the PLL, although bulged, continues to be intact and has not ruptured. As well shall see later, the PLL is the 'key' to differentiating between a disc protrusion and a disc extrusion. Finally, note that the Sinuvertebral nerves are irritated (red) and are sending pain signals on to the brain through the sympathetic nervous system (gray ramus communicans). Also note that this IDD may cause some referred lower leg pain as well (spinal nerve has some orange in it to indicate referred pain.)

DISC PROTRUTION: Posterior Longitudinal Ligament is still Intact.

Figure #3 demonstrates a 4 millimeter disc protrusion 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.

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, 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 sooner the better IF you're NOT improving with conservative care. Another interesting phenomenon about extrusions are the fact that these larger disc lesions have a greater ability to be 'reabsorbed' by the body! This 'shrinkage phenomenon' has been demonstrated time and time again in the literature; in fact, you can expect that in 80% of large disc extrusions, there will be at least a 50% 'shrinkage' of size (5,6). Unfortunately, this doesn't always mean that the pain associated with the extrusion will fade! Some patients recover from disc extrusion yet demonstrate NO change in the size of their extrusion at all, where others fail to recover yet their extrusion has markedly decreased in size! That just goes to prove that we still have a lot to learn about the relationship between disc herniation and pain!

DISC SEQUESTRATION: The Final End-Phase of the Disc Herniation.

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).

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. These T1 MR images demonstrates a large 9mm disc extrusion (red star) as visualized on both the Axial (over-head) and Sagittal (side) views.

 

 

 

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.

 

 

 

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