Disc Herniation: Symptoms, Causes, Pathophysiology, Diagnosis, Prevention, Treatment and Research

Also known as a slipped disc, it is a medical condition that affects the spine.

In this condition, a tear in the outer fibrous annulus of an intervertebral disc allows the soft, central portion to protrude beyond the damaged outer rings.

Signs and symptoms of a herniated disc

The symptoms of a herniated disc may vary depending on the location of the hernia and the types of soft tissue that are involved.

They can vary from little or no pain if the disc is the only injured tissue, to severe and unrelenting pain in the neck or back pain that will radiate to the affected regions by the affected nerve roots that are irritated or affected by the herniated material.

Frequently, herniated discs are not immediately diagnosed, as patients have undefined pains in the thighs, knees or feet.

Other symptoms may include sensory changes such as numbness, tingling, paresthesias, and motor changes such as muscle weakness, paralysis, and reflex affect.

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 throbbing pain or pain that comes and goes, which can be caused by a muscle spasm, the pain of a herniated disc is usually continuous or at least continuous in a specific position of the body.

It is possible to have a herniated disc without pain or noticeable symptoms, depending on your location. If the extruded nucleus pulposus material does not exert pressure on the soft tissues or nerves, it may not cause any symptoms.

A small sample study that examined the cervical spine in volunteers without symptoms found focal disc protrusions in 50% of the participants, suggesting that a considerable part of the population may have focal herniated discs in the cervical region that do not cause symptoms obvious.

A disc prolapsed in the lumbar spine can cause radiating nerve pain. This type of pain is usually felt in the lower extremities or in the groin area. Irradiated nerve pain caused by a prolapsed disc can also cause bowel and bladder incontinence.

Usually, symptoms are experienced only on one side of the body. If the prolapse is very large and presses the nerves inside the spine or the ponytail, both sides of the body can be affected, often with serious consequences.

Compression of the horsetail can cause permanent nerve damage or paralysis. Damage to the nerves can cause loss of bowel and bladder control, as well as sexual dysfunction. This disorder is called horsetail syndrome . Other complications include chronic pain.

Causes

Most authors favor the degeneration of the intervertebral disc as the main cause of spinal disc herniation and cite the trauma as a low cause.

Disc degeneration occurs with both degenerative disc disease and aging. With degeneration, the contents of the disc, the nucleus pulposus and the annulus fibrosis are exposed to altered loads.

Specifically, the core becomes fibrous and rigid and less able to withstand the load. The load is transferred to the anulus, which, if it does not support the higher load, can lead to the development of fissures. If the fissures reach the periphery of the ring, the nuclear material can pass through a herniated disc.

Herniated discs can be the result of general wear and tear, such as sitting or squatting constantly, driving or having a sedentary lifestyle. However, hernias can also be the result of lifting heavy loads.

Professional athletes, especially those who practice contact sports such as football, are also prone to herniated discs.

Within the athletic contexts, the hernia is often the result of abrupt sudden impacts against, or abrupt flexion or twisting movements of the lower back. When the spine is straight, such as stopping or lying down, the internal pressure is equalized in all parts of the discs.

While seated or bent to lift, the internal pressure on a disc can move from 17 psi (lying down) to more than 300 psi (lifting with a rounded back).

Herniation of the disc contents in the spinal canal often occurs when the anterior (side of the stomach) side of the disc is compressed while seated or bent forward, and the contents (nucleus pulposus) are pressed against the tightly stretched and thinned membrane (fibrous anulus) on the back side (back side) of the disk.

The combination of thinning of the membrane by stretching and increased internal pressure (200 to 300 psi) results in rupture of the confining membrane.

The gelatinous content of the disc then moves to the spinal canal, pressing against the spinal nerves, which can produce intense and potentially disabling pain and other symptoms.

Several genes are also associated with the degeneration of the intervertebral disc. Probable candidate genes such as:

  • Collagen type I (site sp1).
  • Collagen type IX.
  • Vitamin D receptor.
  • Agrecano.
  • Asporina.
  • MMP3.
  • Interleukin-1
  • Interleukin-6 polymorphisms.

They have been implicated in disc degeneration. It has been shown that mutation in genes that encode proteins involved in the regulation of the extracellular matrix, such as MMP2 and THBS2, contributes to lumbar disc herniation.

Pathophysiology of a herniated disk

Although many minor herniated discs heal on their own with conservative treatment, occasionally herniated discs require surgery to correct them.

The main objective of the surgery is to eliminate the pressure or reduce the mechanical compression of a neuronal element, either the spinal cord or a nerve root.

But it is increasingly recognized that back pain, instead of just compression, may also be due to chemical inflammation. There is evidence pointing 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 rupture of the disc (ring tear), facet joints and in the spinal stenosis.

In addition to causing pain and inflammation, tumor necrosis alpha can also contribute to disc degeneration.

Most cases of spinal disc herniation 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 represents only 0.15% to 4.0% of cases.

Hernias usually occur posterolaterally, where the fibrous annulus is relatively thin and is not reinforced by the posterior or anterior longitudinal ligament.

In the cervical spinal cord, a symptomatic posterolateral hernia between two vertebrae will affect the nerve that leaves the spinal canal between those two vertebrae on that side. Then, for example, a right posterolateral hernia of the disc between vertebrae C5 and C6 will affect the right C6 spinal nerve.

The rest of the spinal cord, however, is oriented differently, so a symptomatic posterolateral hernia between two vertebrae will actually affect the nerve that comes out in the next intervertebral foramen.

Then, for example, a herniated disc between the vertebrae L5 and S1 will affect the spinal nerve S1, which exits between the vertebrae S1 and S2.

Cervical disc herniation

Cervical disc hernias occur in the neck, most frequently between the fifth and sixth (C5 / 6) and the sixth and seventh (C6 / 7) cervical vertebral bodies.

Symptoms can affect the back of the skull, neck, shoulder girdle, scapula, arm and hand. The nerves of the cervical plexus and the brachial plexus may be affected.

Usually, a posterolateral disc hernia will affect the nerve root that comes out at disc level.

The nerve roots are numbered according to the vertebral body below them (except the C8 nerve root). Therefore, a C5 / 6 herniated disc usually affects the C6 nerve root.

Lumbar disc herniation

Lumbar disc hernias occur in the lower part of the back, most often between the fourth and fifth lumbar vertebral bodies or between the fifth and the sacrum.

The symptoms can affect the lower back, the buttocks, the thigh, the anal / genital region (through the perineal nerve) and can radiate to the foot and / or feet. The sciatic nerve is the most commonly affected nerve, and causes symptoms of sciatica.

The femoral nerve can also be affected and cause the patient to experience a tingling sensation and numbness in one or both legs and even in the feet or even a burning sensation in the hips and legs.

A hernia in the lower back often compresses the nerve root that comes out below the disc. Therefore, a herniated disc L4 / 5 compresses the nerve root L5.

Intradural disc hernia

Intradural disc herniation is a rare form of herniated disc with an incidence of 0.2-2.2%. The preoperative images may be useful, but intraoperative findings are required to confirm.

Diagnosis

The diagnosis is made by a professional based on history, symptoms and physical examination.

At some point during the evaluation, tests may be performed to confirm or rule out other causes of symptoms such as spondylolisthesis, degeneration, tumors, metastasis and space-occupying lesions, as well as to evaluate the efficacy of possible treatment options.

Terminology

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 “sliding disc” is a misnomer, since the intervertebral discs are closely interspersed between the two vertebrae to which they are attached, and can not “slip”, or even slip 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 break, tear, herniate and degenerate, but can not “slide”.

Some authors consider that the term “sliding disc” is harmful, since it leads to an incorrect idea of ​​what has happened and, therefore, of the probable result.

However, during growth, a vertebral body may slip in relation to an adjacent vertebral body, a deformity called spondylolisthesis .

Physical exam

The straight leg increase can be positive, since this finding has low specificity; however, it has high sensitivity.

Therefore, the finding of a negative sign of a straight leg lift is important to help “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.

Images

Projection X-ray (X-ray images) : Although traditional plain radiographs have a limited ability to obtain images of soft tissues such as discs, muscles and nerves, they are still used to confirm or exclude other possibilities such as tumors, infections or fractures, etc.

Despite these limitations, X-rays can still play a relatively inexpensive role in confirming the suspicion of the presence of a herniated disc. If a suspicion is reinforced, other methods can be used to provide final confirmation.

Computed tomography or computed tomography 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 surrounding structures, including soft tissues. However, visual confirmation of a herniated disc can be difficult with a CT scan.

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 better the soft tissues that the scanners of computerized axial tomography.

An MRI performed with a high magnetic field strength usually provides the most conclusive evidence for the diagnosis of a herniated disc. T2-weighted images allow a clear visualization of the protruding disc material in the spinal canal.

Myelogram : an x-ray of the spinal canal after the injection of a contrast material into the spaces of the surrounding spinal fluid.

By revealing the 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 myelography involves the injection of foreign substances, magnetic resonance imaging scans are now preferred for most patients.

Myelograms still provide an excellent description of space-occupying lesions, especially when combined with computed tomography (computed tomography myelography).

Electromyography and nerve conduction studies (EMG / NCS) : These tests measure the electrical impulse along nerve roots, peripheral nerves, and muscle tissue.

This will indicate if nerve damage is in progress, if the nerves are in a healing state of a previous injury, or if there is another site of nerve compression.

Electromyography and nerve conduction studies are usually used to identify sources of nerve dysfunction distal to the spine.

The presence and severity of myelopathy can be evaluated by transcranial magnetic stimulation (TMS), a neurophysiological method that allows measuring the time required for a neural impulse to cross the pyramidal tracts, beginning with the cerebral cortex and ending in the anterior part with corneal cells. of the cervical, thoracic or lumbar spinal cord.

This measurement is called central driving time (TCC). Transcranial magnetic stimulation can help doctors:

  • Identify the level of the spinal cord where the myelopathy is located. This is especially useful in cases where more than two lesions may be responsible for clinical signs and symptoms, such as in patients with two or more cervical disc hernias.
  • Track the progression of myelopathy in time, for example, before and after cervical spine surgery.
  • Transcranial magnetic stimulation can also help in the differential diagnosis of different causes of pyramidal tract damage.

Differential diagnosis

  • Mechanical pain
  • Discogenic pain
  • Miofascial pain.
  • Spondylosis or spondylolisthesis.
  • Spinal stenosis
  • Abscess.
  • Hematoma.
  • Discitis u osteomielitis.
  • Massive injury
  • Myocardial infarction.
  • Aortic dissection.

Prevention

Because there are several causes of back injuries, prevention must be comprehensive. Back injuries are predominant in manual work, so most methods of prevention of low back pain have been applied mainly to biomechanics.

Prevention must come from multiple sources, such as education, proper body mechanics and physical condition.

Education

Education should emphasize not lifting beyond one’s own abilities and letting the body rest after a strenuous effort. Over time, poor posture can cause the intervertebral disc to break or be damaged.

Striving to maintain correct posture and body alignment will help prevent disc degradation.

Exercise

Exercises that improve back strength can also be used to prevent back injuries.

Back exercises include push-ups, extension of the upper back, transverse abdominal supports, and floor bridges.

If there is pain in the back, it may mean that the stabilizing muscles of the back are weak and a person needs to train the trunk musculature. Other preventive measures are losing weight and not working beyond fatigue.

Signs of fatigue include tremors, lack of coordination, muscle burns, and loss of the transverse abdominal brace. Heavy lifting should be done with the legs doing the work, and not the back.

Swimming is a common tool used in strength training. The use of lumbarsacral support belts can restrict movement in the spine and support the back during lifting.

Treatment for herniated disc

In most cases, the spinal disc hernia does not require surgery. A study on sciatica, which may be caused by a spinal disc herniation, found that “after 12 weeks, 73% of people showed a reasonable improvement to older without surgery.”

The study, however, did not determine the number of individuals in the group who had sciatica caused by a herniated disc.

The initial treatment usually consists of non-steroidal anti-inflammatory drugs, but the long-term use of non-steroidal anti-inflammatory drugs for people with persistent back pain is complicated by possible cardiovascular and gastrointestinal toxicity.

Epidural corticosteroid injections provide a mild and questionable short-term improvement in those with sciatica, but they are not long-term benefits.

Complications occur in 0 to 17% of cases when they are performed on the neck, and most are minor. In 2014, the US Food and Drug Administration UU

He suggested that “the injection of corticosteroids into the epidural space of the spine can cause rare but serious adverse events, which include loss of vision, stroke, paralysis and death.”

And that “the effectiveness and safety of the epidural administration of corticosteroids have not been established, and the administration of food and medication has not approved corticosteroids for this use.”

Lumbar disc herniation

Non-surgical treatment methods are usually tried first, leaving surgery as a last resort.

Pain medications are often prescribed as the first attempt to relieve acute pain and allow the patient to begin exercising and stretching.

There are a variety of other non-surgical methods that are used in attempts to alleviate the condition after it has occurred, often in combination with analgesics.

They are considered indicated, contraindicated, relatively contraindicated or inconclusive depending on the safety profile of their risk-benefit relationship and whether or not they can help:

Indicated
  • Education in proper body mechanics.
  • Physiotherapy, to address mechanical factors, and may include modalities to temporarily relieve pain (ie, traction, electrical stimulation, massage).
  • Non-steroidal anti-inflammatory drugs.
  • Weight control.

Spinal manipulation : evidence of moderate quality suggests that spinal manipulation is more effective than placebo for the treatment of acute lumbar disc herniation (less than 3 months) and acute sciatica.

The same study also found evidence of “low to very low” for its usefulness in the treatment of chronic lumbar symptoms (more than 3 months) and “The quality of the evidence for … limb symptoms related to the cervical spine of any duration is low or very low “.

A 2006 review of published research indicated that spinal manipulation is likely to be safe when used by appropriately trained professionals, and research currently suggests that spinal manipulation is safe for the treatment of disc-related pain.

Contraindicated

Spinal manipulation is contraindicated for herniated discs when there are progressive neurological deficits, such as horsetail syndrome.

A review of non-surgical spinal decompression found deficiencies in most of the 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 commercialization have been very controversial.

Surgery

Surgery may be useful in people with a herniated disc that is causing significant pain radiating down the leg, significant weakness of the leg, bladder problems or loss of bowel control.

Discectomy (the partial removal of a disc that causes pain in the legs) can provide pain relief before non-surgical treatments. Discectomy has better results in one year, but not in four to ten years.

The less invasive microdiscectomy has not been shown to result in a significantly different outcome from regular discectomy with respect to pain. However, you may have less risk of infection.

The presence of horsetail syndrome (in which there is incontinence, weakness and genital numbness) is considered a medical emergency that requires immediate attention and possibly surgical decompression.

Regarding the role of surgery for failed medical treatment in people without a significant neurological deficit, a Cochrane review concluded that “limited evidence is now available to support some aspects of surgical practice.”

Epidemiology

The herniated disc can occur in any disc of the spine, but the two most common forms are lumbar herniated disc and cervical herniated disc.

The first is the most common and causes back pain ( lumbago ) and, often, pain in the legs, in which case it is commonly known as sciatica.

Lumbar disc herniation occurs 15 times more often than cervical disc herniation (neck), and is one of the most common causes of low back pain.

The cervical discs are affected 8% of the time and the upper and middle (thoracic) discs only 1-2% of the time.

The following locations do not have discs and, therefore, are free of the risk of disc herniation: the two upper cervical intervertebral spaces, the sacrum and the coccyx.

Most disc hernias occur when a person is in their thirties or when the nucleus pulposus is still a substance similar to gelatin.

With age, the nucleus pulposus changes (dries) and the risk of herniation is greatly reduced. After 50 or 60 years, osteoarthritic degeneration (spondylosis) or spinal stenosis are more likely causes of lower back pain or pain in the legs.

  • 8% men and 2.5% women over 35 experience sciatica during their lives.
  • Of all people, between 60% and 80% experience back pain during their life.
  • In 14%, the pain lasts more than 2 weeks.
  • In general, men have a slightly higher incidence than women.

Etymology

A spinal disc hernia is known in Latin as prolapsus disci intervertebralis.

Investigation

Future treatments may include stem cell therapy. It is the use of stem cells to treat or prevent a disease or condition.

Bone marrow transplantation is the most widely used stem cell therapy, but some therapies derived from umbilical cord blood are also in use.

Research is being carried out to develop various sources of stem cells and to apply stem cell treatments for neurodegenerative diseases and conditions such as diabetes, heart disease and other conditions.

Stem cell therapy has become controversial after developments such as the ability of scientists to isolate and grow embryonic stem cells, create stem cells using nuclear transfer of somatic cells and their use of techniques to create induced pluripotent stem cells.

This controversy is often related to the politics of abortion and human cloning. In addition, efforts to market treatments based on the transplantation of stored umbilical cord blood have been controversial.