|Spinal disc herniation|
|Synonyms||Slipped disc, herniated nucleus pulposus|
|A spinal disc herniation demonstrated via MRI.|
Spinal disc herniation, also known as a slipped disc, is a medical condition affecting the spine in which a tear in the outer, fibrous ring of an intervertebral disc allows the soft, central portion to bulge out beyond the damaged outer rings.
Disc herniation is usually due to age-related degeneration of the outer ring, known as the anulus fibrosus, although trauma, lifting injuries, or straining have been implicated as well. Tears are almost always postero-lateral (on the back of the sides) owing to the presence of the posterior longitudinal ligament in the spinal canal. This tear in the disc ring may result in the release of chemicals causing inflammation, which may directly cause severe pain even in the absence of nerve root compression.
Disc herniations are normally a further development of a previously existing disc protrusion, a condition in which the outermost layers of the anulus fibrosus are still intact, but can bulge when the disc is under pressure. In contrast to a herniation, none of the central portion escapes beyond the outer layers. Most minor herniations heal within several weeks. Anti-inflammatory treatments for pain associated with disc herniation, protrusion, bulge, or disc tear are generally effective. Severe herniations may not heal of their own accord and may require surgery. The condition may be referred to as a slipped disc, but this term is not accurate as the spinal discs are firmly attached between the vertebrae and cannot "slip" out of place.
Symptoms of a herniated disc can vary depending on the location of the herniation and the types of soft tissue that become involved. They can range from little or no pain if the disc is the only tissue injured, to severe and unrelenting neck pain or low back pain that will radiate into the regions served by affected nerve roots that are irritated or impinged by the herniated material. Often, herniated discs are not diagnosed immediately, as the patients come with undefined pains in the thighs, knees, or feet.
Other symptoms may include sensory changes such as numbness, tingling, paresthesia, and motor changes such as muscular weakness, paralysis, and affection of reflexes. If the herniated disc is in the lumbar region, the patient may also experience sciatica due to irritation of one of the nerve roots of the sciatic nerve. Unlike a pulsating pain or pain that comes and goes, which can be caused by muscle spasm, pain from a herniated disc is usually continuous or at least is continuous in a specific position of the body.
It is possible to have a herniated disc without any pain or noticeable symptoms, depending on its location. If the extruded nucleus pulposus material doesn't press on soft tissues or nerves, it may not cause any symptoms. A small-sample study examining the cervical spine in symptom-free volunteers has found focal disc protrusions in 50% of participants, which suggests that a considerable part of the population can have focal herniated discs in their cervical region that do not cause noticeable symptoms.
A prolapsed disc in the lumbar spine can cause radiating nerve pain. This type of pain is usually felt in the lower extremities or groin area. Radiating nerve pain caused by a prolapsed disc can also cause bowel and bladder incontinence.
Typically, symptoms are experienced only on one side of the body. If the prolapse is very large and presses on the nerves within the spinal column or the cauda equina, both sides of the body may be affected, often with serious consequences. Compression of the cauda equina can cause permanent nerve damage or paralysis. The nerve damage can result in loss of bowel and bladder control as well as sexual dysfunction. This disorder is called cauda equina syndrome. Other complications include chronic pain.
Most authors favour degeneration of the intervertebral disc as the major cause of spinal disc herniation and cite trauma as a low cause. Disc degeneration occurs both with degenerative disc disease and aging. With degeneration, the contents of the disc, the nucleus pulposus and anulus fibrosus, are exposed to altered loads. Specifically, the nucleus becomes fibrous and stiff and less able to bear load. The load is transferred to the anulus, which, if it fails to bear the increased load, can lead to the development of fissures. If the fissures reach the periphery of the anulus, the nuclear material can pass through as a disc herniation.
Disc herniations can result from general wear and tear, such as constant sitting or squatting, driving, or a sedentary lifestyle. However, herniations can also result from the lifting of heavy loads. Professional athletes, especially those playing contact sports such as American football, are prone to disc herniations as well. Within athletic contexts, herniation is often the result of sudden blunt impacts against, or abrupt bending or torsional movements of, the lower back. When the spine is straight, such as in standing or lying down, internal pressure is equalized on all parts of the discs. While sitting or bending to lift, internal pressure on a disc can move from 17 psi (lying down) to over 300 psi (lifting with a rounded back).. Herniation of the contents of the disc into the spinal canal often occurs when the anterior side (stomach side) of the disc is compressed while sitting or bending forward, and the contents (nucleus pulposus) get pressed against the tightly stretched and thinned membrane (anulus fibrosus) on the posterior side (back side) of the disc. The combination of membrane thinning from stretching and increased internal pressure (200 to 300 psi) results in the rupture of the confining membrane. The jelly-like contents of the disc then move into the spinal canal, pressing against the spinal nerves, which may produce intense and potentially disabling pain and other symptoms.
Several genes are also associated with intervertebral disc degeneration. Probable candidate genes like type I collagen (sp1 site), type IX collagen, vitamin D receptor, aggrecan, asporin, MMP3, interleukin-1, and interleukin-6 polymorphisms have been implicated in disc degeneration. Mutation in genes coding for proteins involved in the regulation of the extracellular matrix, such as MMP2 and THBS2, has been demonstrated to contribute to lumbar disc herniation.
Although many minor disc herniations heal on their own with conservative treatment, occasionally disc herniations require surgery for correction. A primary focus of surgery is to remove pressure or reduce mechanical compression on a neural element-- either the spinal cord, or a nerve root. But it is increasingly recognized that back pain, rather than being solely due to compression, may also be due to chemical inflammation. There is evidence that points to a specific inflammatory mediator of this pain. This inflammatory molecule, called tumor necrosis factor alpha (TNF), is released not only by the herniated disc, but also in cases of disc tear (annular tear), by facet joints, and in spinal stenosis. In addition to causing pain and inflammation, TNFs may also contribute to disc degeneration.
The majority of spinal disc herniation cases occur in the lumbar region (95% in L4-L5 or L5-S1). The second most common site is the cervical region (C5-C6, C6-C7). The thoracic region accounts for only 0.15% to 4.0% of cases. Herniations usually occur posterolaterally, where the anulus fibrosus is relatively thin and is not reinforced by the posterior or anterior longitudinal ligament. In the cervical spinal cord, a symptomatic posterolateral herniation between two vertebrae will impinge on the nerve which exits the spinal canal between those two vertebrae on that side. So, for example, a right posterolateral herniation of the disc between vertebrae C5 and C6 will impinge on the right C6 spinal nerve. The rest of the spinal cord, however, is oriented differently, so a symptomatic posterolateral herniation between two vertebrae will actually impinge on the nerve exiting at the next intervertebral foramen down. So, for example, a herniation of the disc between the L5 and S1 vertebrae will impinge on the S1 spinal nerve, which exits between the S1 and S2 vertebrae.
Cervical disc herniations occur in the neck, most often between the fifth and sixth (C5/6) and the sixth and seventh (C6/7) cervical vertebral bodies, particularly in younger population; as an upword shifting of disc disease especially related to central disc location and associated compressive myelopathy with increasing age was observed. Symptoms can affect the back of the skull, the neck, shoulder girdle, scapula, arm, and hand. The nerves of the cervical plexus and brachial plexus can be affected. Usually, a posterolateral disc hernia will affect the nerve root exiting at the level of the disk. Nerve roots are numbered according to the vertebral body below them (except the C8 nerve root). Thus, a C5/6 disc hernia normally affects the C6 nerve root.
Lumbar disc herniations occur in the lower back, most often between the fourth and fifth lumbar vertebral bodies or between the fifth and the sacrum. Symptoms can affect the lower back, buttocks, thigh, anal/genital region (via the perineal nerve), and may radiate into the foot and/or toe. The sciatic nerve is the most commonly affected nerve, causing symptoms of sciatica. The femoral nerve can also be affected and cause the patient to experience a numb, tingling feeling throughout one or both legs and even feet or even a burning feeling in the hips and legs. A hernia in the lumbar region often compresses the nerve root exiting at the level below the disk. Thus, a herniation of the L4/5 disc compresses the L5 nerve root.
Intradural disc herniation is a rare form of disc herniation with an incidence of 0.2-2.2%. Preoperative imaging can be helpful, but intraoperative findings are required to confirm.
Diagnosis is made by a practitioner based on the history, symptoms, and physical examination. At some point in the evaluation, tests may be performed to confirm or rule out other causes of symptoms such as spondylolisthesis, degeneration, tumors, metastases and space-occupying lesions, as well as to evaluate the efficacy of potential treatment options.
Some of the terms commonly used to describe the condition include herniated disc, prolapsed disc, ruptured disc, and slipped disc. Other phenomena that are closely related include disc protrusion, radiculopathy (pinched nerve), sciatica, disc disease, disc degeneration, degenerative disc disease, and black disc.
The popular term slipped disc is a misnomer, as the intervertebral discs are tightly sandwiched between two vertebrae to which they are attached, and cannot actually "slip", or even get out of place. The disc is actually grown together with the adjacent vertebrae and can be squeezed, stretched and twisted, all in small degrees. It can also be torn, ripped, herniated, and degenerated, but it cannot "slip". Some authors consider that the term "slipped disc" is harmful, as it leads to an incorrect idea of what has occurred and thus of the likely outcome. However, during growth, one vertebral body can slip relative to an adjacent vertebral body, a deformity called spondylolisthesis.
Normal situation and spinal disc herniation in cervical vertebrae
Nucleus herniating through tear in anulus (with MRI)
The straight leg raise may be positive, as this finding has low specificity; however, it has high sensitivity. Thus the finding of a negative SLR sign is important in helping to "rule out" the possibility of a lower lumbar disc herniation. A variation is to lift the leg while the patient is sitting. However, this reduces the sensitivity of the test.
Example of a herniated disc at the L5-S1 in the lumbar spine
Because there are various causes for back injuries, prevention must be comprehensive. Back injuries are predominant in manual labor so the majority low back pain prevention methods have been applied primarily toward biomechanics Prevention must come from multiple sources such as education, proper body mechanics, and physical fitness.
Education should emphasize not lifting beyond one's capabilities and giving the body a rest after strenuous effort. Over time, poor posture can cause the IVD to tear or become damaged. Striving to maintain proper posture and body alignment will aid in preventing disc degradation.
Exercises that enhance back strength may also be used to prevent back injuries. Back exercises include the prone press-ups, upper back extension, transverse abdominus bracing, and floor bridges. If pain is present in the back, it can mean that the stabilization muscles of the back are weak and a person needs to train the trunk musculature. Other preventative measures are to lose weight and to not work oneself past fatigue. Signs of fatigue include shaking, poor coordination, muscle burning, and loss of the transverse abdominal brace. Heavy lifting should be done with the legs performing the work, and not the back.
Swimming is a common tool used in strength training. The usage of lumbarsacral support belts may restrict movement at the spine and support the back during lifting.
In the majority of cases, spinal disc herniation doesn't require surgery. A study on sciatica, which can be caused by spinal disc herniation, found that "after 12 weeks, 73% of people showed reasonable to major improvement without surgery." The study, however, did not determine the number of individuals in the group that had sciatica caused by disc herniation.
Non-surgical methods of treatment are usually attempted first, leaving surgery as the last resort. Pain medications are often prescribed as the first attempt to alleviate the acute pain and allow the patient to begin exercising and stretching. There are a variety of other non-surgical methods used in attempts to relieve the condition after it has occurred, often in combination with pain killers. They are either considered indicated, contraindicated, relatively contraindicated, or inconclusive based on the safety profile of their risk-benefit ratio and on whether they may or may not help:
A review of non-surgical spinal decompression found shortcomings in most published studies and concluded that there was only "very limited evidence in the scientific literature to support the effectiveness of non-surgical spinal decompression therapy." Its use and marketing have been very controversial.
Surgery may be useful in those with a herniated disc that is causing significant pain radiating into the leg, significant leg weakness, bladder problems, or loss of bowel control.Discectomy (the partial removal of a disc that is causing leg pain) can provide pain relief sooner than nonsurgical treatments.
Invasive microdiscectomy with a one inch skin opening has not been shown to result in a significantly different outcome than larger open discectomy with respect to pain. It might however have less risk of infection.
Failed back syndrome is a significant, potentially disabling result that can arise following invasive spine surgery to correct disc herniation. Smaller spine procedures that do not remove bone (such as Endoscopic Transforaminal Lumbar Discectomy) can not cause post laminectomy/laminotomy syndrome, (AKA post bone removal syndrome), since no bone (lamina) is removed.
The presence of cauda equina syndrome (in which there is incontinence, weakness, and genital numbness) is considered a medical emergency requiring immediate attention and possibly surgical decompression. Regarding the role of surgery for failed medical therapy in people without a significant neurological deficit, a Cochrane review concluded that "limited evidence is now available to support some aspects of surgical practice".
Disc herniation can occur in any disc in the spine, but the two most common forms are lumbar disc herniation and cervical disc herniation. The former is the most common, causing low back pain (lumbago) and often leg pain as well, in which case it is commonly referred to as sciatica. Lumbar disc herniation occurs 15 times more often than cervical (neck) disc herniation, and it is one of the most common causes of low back pain. The cervical discs are affected 8% of the time and the upper-to-mid-back (thoracic) discs only 1-2% of the time.
The following locations have no discs and are therefore exempt from the risk of disc herniation: the upper two cervical intervertebral spaces, the sacrum, and the coccyx. Most disc herniations occur when a person is in their thirties or forties when the nucleus pulposus is still a gelatin-like substance. With age the nucleus pulposus changes ("dries out") and the risk of herniation is greatly reduced. After age 50 or 60, osteoarthritic degeneration (spondylosis) or spinal stenosis are more likely causes of low back pain or leg pain.
A spinal disc herniation is known in Latin as prolapsus disci intervertebralis.