Disc herniation can occur in any disc in the spine, but the two most common forms are the cervical disc herniation and the lumbar disc herniation. The latter is the most common, causing lower 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 lower 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. At the same time osteoarthritic degeneration makes its inroads.

Intervertebral disc

Intervertebral discs (or intervertebral fibrocartilage) lie between adjacent vertebrae in the spine. Each disc forms a cartilaginous joint to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together.

Discs consist of an outer annulus fibrosus, which surrounds the inner nucleus pulposus. The annulus fibrosus consists of several layers of fibrocartilage. The strong annular fibers contain the nucleus pulposus and distribute pressure evenly across the disc. The nucleus pulposus contains loose fibers suspended in a mucoprotein gel the consistency of jelly. The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's daily activities and keeping the two vertebrae separated. The disc can be likened to a doughnut: whereby the annulus fibrosis is similar to the dough and the nucleus pulposis is the jelly. If one presses down on the front of the doughnut the jelly moves posteriorly or to the back. When one develops a prolapsed disc the jelly/ nucleus pulposis is forced out of the doughnut/ disc and may put pressure on the nerve located near the disc. This will give one the symptoms of sciatica.

There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas. The atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment). The axis acts as a post around which the atlas can rotate, allowing the neck to swivel. There are a total of twenty-three discs in the spine, which are identified by specifying the particular vertebrae they separate. For example, the disc between the fifth and sixth cervical vertabrae is designated "C5-6".

Medical conditions related to the intervertebral disc

As people age, the nucleus pulposus begins to dehydrate, which limits its ability to absorb shock. The annulus fibrosus gets weaker with age and begins to tear. While this may not cause pain in some people, in others one or both of these may cause chronic pain.

Pain due to the inability of the dehydrating nucleus pulposus to absorb shock is called axial pain or disc space pain. One generally refers to the gradual dehydration of the nucleus pulposus as degenerative disc disease.

When the annulus fibrosus tears due to an injury or the aging process, the nucleus pulposus can begin to extrude through the tear. This is called disc herniation. Near the posterior side of each disc, all along the spine, major spinal nerves extend out to different organs, tissues, extremities etc. It is very common for the herniated disc to press against these nerves (pinched nerve) causing radiating pain, numbness, tingling, and diminished strength and/or range of motion. In addition, the contact of the inner nuclear gel, which contains inflammatory proteins, with a nerve can also cause significant pain. Nerve-related pain is called radicular pain.

Herniated discs go by many names and these can mean different things to different medical professionals. A slipped disc, ruptured disc, or a bulging disc can all refer to the same medical condition. Protrusions of the disc into the adjacent vertebra are known as Schmorl's nodes.


Spinal disc herniation

A spinal disc herniation is a pathological condition in which a tear in the outer, fibrous ring (annulus fibrosus) of an intervertebral disc allows the soft, central portion (nucleus pulposus) to be extruded (herniated) to the outside of the disc.

It is normally a further development of a previously existing disc protrusion, a condition in which the outermost layers of the annulus fibrosus are still intact, but can bulge when the disc is under pressure.

Terminology

Some of the terms commonly used to describe the condition include herniated disc, prolapsed disc, ruptured disc, and the misleading expression "slipped disc." Other terms that are closely related include disc protrusion, bulging disc, pinched nerve, sciatica, disc disease, disc degeneration, degenerative disc disease, and black disc.

The popular term "slipped disc" is quite misleading, as an intervertebral disc, being tightly sandwiched between two vertebrae, cannot actually "slip," "slide," 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."

The spelling "disc" is based on the Latin root discus. Most English language publications use the spelling "disc" more often than "disk." Nomina Anatomica designates the structures as "disci intervertebrales" [plural form] and Terminologia Anatomica as "discus intervertebralis/Intervertebral disc".


Cervical disc herniation

Cervical disc herniations occur in the neck, most often between the sixth and seventh cervical vertebral bodies. Symptoms can affect the back of the skull, the neck, shoulder girdle, scapula, shoulder, arm, and hand. The nerves of the cervical plexus and brachial plexus can be affected. [3]


Thoracic disc herniation

Thoracic discs are very stable and herniations in this region are quite rare. Herniation of the uppermost thoracic discs can mimic cervical disc herniations, while herniation of the other discs can mimic lumbar herniations. 


Lumbar disc herniation

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, 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. [5]


Causes

Causes of a disc herniation can include general wear and tear on the disc over time, repetitive movements, stress on the disc that occurs while twisting and lifting, or other injuries.


Symptoms

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 or back pain that will radiate into the regions served by an affected nerve root when it is irritated or impinged by the herniated material. Other symptoms may include sensory changes such as numbness, tingling, muscular weakness or paralysis, and affection of reflexes. 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.

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. It has been estimated that as many as 50% of the population have focal herniated discs in their cervical region that do not cause noticeable symptoms. [6]

Typically, symptoms are experienced only on one side of the body. If the prolapse is very large and presses on the spinal cord or the cauda equina in the lumbar region, affection of both sides of the body may occur, often with serious consequences.


Diagnosis

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 evaluate the efficacy of potential treatment options. These tests may include the following:

		X-ray: Although traditional plain X-rays are limited in their ability to image soft tissues such as discs, muscles, and nerves, they are still used to confirm or exclude other possibilities such as tumors, infections, fractures, etc.. In spite of these limitations, X-ray can still play a relatively inexpensive role in confirming the suspicion of the presence of a herniated disc. If a suspicion is thus strengthened, other methods may be used to provide final confirmation.
		Computed tomography scan (CT or CAT scan): A diagnostic image created after a computer reads x-rays. It can show the shape and size of the spinal canal, its contents, and the structures around it, including soft tissues.

		Magnetic resonance imaging (MRI): A diagnostic test that produces three-dimensional images of body structures using powerful magnets and computer technology. It can show the spinal cord, nerve roots, and surrounding areas, as well as enlargement, degeneration, and tumors. It shows soft tissues even better than CAT scans. MRI Scan of lumbar disc herniation between fourth and fifth lumbar vertebral bodies.
		Myelogram: An x-ray of the spinal canal following injection of a contrast material into the surrounding cerebrospinal fluid spaces. By revealing displacement of the contrast material, it can show the presence of structures that can cause pressure on the spinal cord or nerves, such as herniated discs, tumors, or bone spurs. Because it involves the injection of foreign substances, scans are now preferred when available, although myelograms still provide excellent outlines of space-occupying lesions.
		Electromyogram and Nerve conduction studies (EMG/NCS): These tests measure the electrical impulse along nerve roots, peripheral nerves, and muscle tissue. This will indicate whether there is ongoing nerve damage, if the nerves are in a state of healing from a past injury, or whether there is another site of nerve compression.

Treatment

The majority of herniated discs will heal themselves in about six weeks and do not require surgery. Your doctor may prescribe bed rest (usually for no more than two days), or advise you to maintain a low, painless activity level for a short period. If your doctor recommends physical therapy, this may include pelvic traction, gentle massage, ice and heat therapy, ultrasound, electrical muscle stimulation, and stretching exercises. [7] Pain medications are often prescribed to alleviate the acute pain and allow the patient to begin exercising and stretching.

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.

There are a variety of non-surgical care alternatives to treat the pain, including:

		Physical therapy
		Osteopathic/chiropractic manipulations
		Massage therapy
		Non-steroidal anti-inflammatory drugs (NSAIDs)
		Oral steroids (e.g. prednisone or methyprednisolone)
		Epidural (cortisone) injection
		Intravenous sedation, analgesia-assisted traction therapy (IVSAAT)

If pain is severe and continuous, or if there are neurological deficits, surgery may be recommended. Surgical options include:

		Microdiscectomy
		Lumbar fusion
		Disc arthroplasty
		Dynamic stabilization

Surgical goals include relief of nerve compression, allowing the nerve to recover, as well as the relief of associated back pain and restoration of normal function.

Future treatments may include stem cell therapy. Doctors Victor Y. L. Leung, Danny Chan and Kenneth M. C. Cheung have reported in the European Spine Journal that "substantial progress has been made in the field of stem cell regeneration of the intervertebral disc. Autogenic mesenchymal stem cells in animal models can arrest intervertebral disc degeneration or even partially regenerate it and the effect is suggested to be dependent on the severity of the degeneration." 


Back pain

Back pain (also known as "dorsopathy") is pain felt in the human back that may come from the muscles, nerves, bones, joints or other structures in the spine. The pain may be constant or intermittent, stay in one place or refer or radiate to other areas. It may be a dull ache, or a sharp or piercing or burning sensation. The pain may be felt in the neck (and might radiate into the arm and hand), in the upper back, or in the low back, (and might radiate into the leg or foot), and may include symptoms other than pain, such as weakness, numbness or tingling.

Back pain is one of humanity's most frequent complaints. In the U.S., acute low back pain (also called lumbago) is the fifth most common reason for all physician visits. About nine out of ten adults experience back pain at some point in their life, and five out of ten working adults have back pain every year .

The spine is a complex interconnecting network of nerves, joints, muscles, tendons and ligaments, and all are capable of producing pain. Large nerves that originate in the spine and go to the legs and arms can make pain radiate to the extremities.


While it is rare, back pain can be a sign of a serious medical problem:

		Typical warning signs of a potentially life-threatening problem are bowel and/or bladder incontinence or progressive weakness in the legs. Patients with these symptoms should seek immediate medical care.
		Severe back pain (such as pain that is bad enough to interrupt sleep) that occurrs with other signs of severe illness (e.g. fever, unexplained weight loss) may also indicate a serious underlying medical condition, such as cancer.
		Back pain that occurs after a trauma, such as a car accident or fall, should also be promptly evaluated by a medical professional to check for a fracture or other injury.
		Back pain in individuals with medical conditions that put them at high risk for a spinal fracture, such as osteoporosis or multiple myeloma, also warrants prompt medical attention.
		In general, however, back pain does not usually require immediate medical intervention. The vast majority of episodes of back pain are self-limiting and non-progressive. Most back pain syndromes are due to inflammation, especially in the acute phase, which typically lasts for two weeks to three months.

Underlying causes

Muscle strains (pulled muscles) are commonly identified as the cause of back pain but in fact muscle imbalances are by far the most common cause of low back pain, and pain from such an injury will often hang around for as long as the muscle imbalances persist. The muscle imbalances cause a mechanical problem with the skeleton which leads to pressure building up at certain points along the spine.

When low back pain lasts more than three months, or if there is more leg pain than back pain, a more specific diagnosis can usually be made. There are several common causes of low back pain and leg pain: for adults under age 50, these include spinal disc herniation and degenerative disc disease; in adults over age 50, common causes also include osteoarthritis (degenerative joint disease) and spinal stenosis. Non-anatomical factors can also contribute to or cause back pain, such as stress, repressed anger, or depression (mood).

Back pain is frequently experienced when no underlying anatomical problem is apparent. Some believe this pain to be caused by tension myositis syndrome.

Treatment

The management goals when treating back pain are to achieve maximal reduction in pain intensity as rapidly as possible; to restore the individual's ability to function in everyday activities; to help the patient cope with residual pain; to assess for side effects of therapy; and to facilitate the patient's passage through the legal and socioeconomic impediments to recovery.

Not all treatments work for all conditions or for all individuals with the same condition, and many find that they need to try several treatment options to determine what works best for them. Only a minority (most estimates are 1% - 10%) require surgery.

		Cold compression therapy is useful for a strained back or chronic back pain as it reduces pain and inflammation, especially after strenuous exercise such as golf, gardening, or lifting.
		Heat Therapy is useful for back spasms or other conditions, often used in conjunction with a pain reliever or muscle relaxer.
		Generally, some form of consistent stretching and exercise is believed to be an essential component of most back treatment programs. Bed rest is rarely recommended, and when necessary is usually limited to one or two days. Strengthening the core body muscles, such as the stomach and low back muscles, is a typical part of any back therapy.
		Injections, such as epidural steroid injections or facet joint injections.
		Medications, such as muscle relaxants, narcotics, non-steroidal anti-inflammatory drugs (NSAIDs/NSAIAs) or paracetamol (acetaminophen).
		Manipulation, as provided by an appropriately trained and qualified physical therapist, osteopath, physiatrist, or a chiropractor.
		Education, and attitude adjustment to focus on psychological or emotional causes (e.g. TMS).

In addition, most people will benefit from assessing any ergonomic or postural factors that may contribute to their back pain, such as improper lifting technique, poor posture, or poor support from their bed or office chair, etc.


Surgery

There are a number of different types of spine surgery to treat a variety of back conditions. Some of the more common forms are:

		Artificial disc replacement, a relatively new form of surgery in the U.S. but has been in use in Europe for decades, primarily used to treat low back pain from a degenerated disc.
		Discectomy/microdiscectomy, usually used to treat pain (especially pain that radiates down the arm or leg) from spinal disc herniations.
		Kyphoplasty and Vertebroplasty, minimally invasive procedures designed to treat pain from osteoporotic compression fractures and sometimes other forms of fracture, such as a fracture caused by certain types of cancer.
		Spinal cord stimulation, where an electrical device is used to interrupt the pain signals being sent to the brain.
		Spinal fusion, usually to treat chronic, severe pain from degenerative disc disease, spondylolisthesis, or deformity, such as from scoliosis.