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Causes, Symptoms of Lumbar Disc Herniation /Spinal disc herniation also is 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 annulus fibrosis, 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.
Lumbar Disc Herniation /Spinal disc herniation also is a common condition that frequently affects the spine in young and middle-aged patients.1,5,11 The lumbar intervertebral disc is a complex structure composed of collagen, proteoglycans, and sparse fibro chondrocyte cells that serve to dissipate forces exerted on the spine. As part of the normal aging process, the disc fibro chondrocytes can undergo senescence, and proteoglycan production diminishes. This leads to a loss of hydration and disc collapse, which increases strain on the fibers of the annulus fibrosus surrounding the disc. Tears and fissures in the annulus can result, facilitating a herniation of disc material, should sufficient forces be placed on the disc. Alternatively, a large biomechanical force placed on a healthy, normal disc may lead to extrusion of disc material in the setting of catastrophic failure of the annular fibers.5
Anatomy of Spinal Disc Herniation
Herniated = from “a hernia,” a part of the body that bulges out through an abnormal opening
Disc = the disk-shaped cushions between the bones of the spine
The vertebral column (also called the spinal column orbackbone) is made up of 33 bones known as vertebra (plural, vertebrae). Each vertebra is separated from the adjacent vertebrae by intervertebral discs, a spongy but strong connective tissue. The intervertebral discs, along with ligaments and facet joints, connect the individual vertebrae to help maintain the spine’s normal alignment and curvature while also permitting movement.
The image at left shows the entire spinal column from beside and from the front. The bones of the spinal column are orange in color, and the intervertebral discs are white.
In the center of the spinal colum,n there is an open channel called the spinal canal. The spinal cord and spinal nerves are located in the spinal canal, where they are surrounded by spinal fluid and protected by the strong spinal column. On each side of the spine, small openings between adjacent vertebrae called foramina (singular, foramen) allow nerve roots to enter and exit the spinal canal.
The spine is divided into the following distinct regions:
- Cervical spine – consists of seven vertebrae in the neck. These vertebrae are small and allow for the mobile nature of the neck.
- Thoracic spine – consists of 12 vertebrae in the upper and mid-back. These are larger and stronger than the cervical vertebrae. Each thoracic vertebra is attached to a rib on either side. This provides significant stiffness and strength to the thoracic portion of the spine.
- Lumbar spine – usually consists of five vertebrae in the lower back, but may vary between four and six. These vertebrae are the largest because they withstand the greatest amount of force in the spine. The lumbar spine is also more mobile than the thoracic spine. Because of these factors, the lumbar spine is the most frequently affected by degenerative conditions, spinal stenosis, and herniated discs.
- Sacrococcygeal – the very lowest portion of the spine. The sacrococcygeal region consists of one single bone, made of fused vertebrae in the sacrum (five vertebrae) and coccyx (four vertebrae). It attaches to the pelvis on either side. In a small number of people, there may be a disc between the first and second sacral vertebrae. Alternatively, the fifth vertebra in the lumbar (lower) spine may occasionally be fused to the sacrum, leaving only 4 lumbar vertebrae.
- A herniated disc occurs when the fibrous outer portion of the disc ruptures or tears, and the jelly-like core squeezes out. When the herniated disc compresses a nearby nerve, as in the image below, the result can be a pinched nerve. A pinched nerve may cause pain, numbness, tingling or weakness in the arms or legs. The substance that makes up the disc’s jelly-like core can also inflame and irritate the nerve, causing additional pain.
A bulging disc occurs when the outer wall of the disc weakens but doesn’t rupture, and “bulges” outward. A herniated disc may actually begin as a bulging disc whose outer wall is then ruptured by a great amount of pressure.
Disc herniation can occur in the cervical, thoracic, or lumbar spine. The location of the pain depends on the location of the herniated disc. If the herniation occurs in the neck, for example, it can cause pain that radiates into the shoulder and arm; if it occurs in the lower back, the pain produced can radiate down into the hip and leg. Depending on the location, it can damage the spinal cord.
Symptoms of Spinal Disc Herniation
A cervical herniated disc may put pressure on a cervical spinal nerve and can cause symptoms like pain, pins and needles, numbness or weakness in the neck, shoulders, or arms. A large disc herniation in the cervical spine may compress the spinal cord within the spinal canal and cause numbness, stiffness, and weakness in the legs and possibly some difficulty with bowel and bladder control.
A thoracic herniated disc may cause pain in the mid back around the level of the disc herniation. If the disc herniation compresses a thoracic spinal nerve as it travels through the foramen, then pain or numbness may travel around the rib cage from the back to the front of the chest or upper abdomen. A large disc herniation in the thoracic spine may compress the spinal cord within the spinal canal and cause numbness, stiffness and weakness in the legs and possibly some difficulty with bowel and bladder control.
A lumbar herniated disc may cause the following symptoms:
- Intermittent or continuous back pain (this may be made worse by movement, coughing, sneezing, or standing for long periods of time)
- Spasm of the back muscles
- Sciatica — pain that starts near the back or buttock and travels down the leg to the calf or into the foot.
- Muscle weakness in the legs
- Numbness in the leg or foot
- Decreased reflexes at the knee or ankle
- Changes in bladder or bowel function
- Difficulty walking
The symptoms of disc disease may resemble other conditions or medical problems. Always consult a doctor for a diagnosis.
Causes and Risk Factors
Herniated discs can often be the result of degenerative disc disease. As people age, the intervertebral discs lose their water content and ability to cushion the vertebrae. As a result, the discs are not as flexible. Furthermore, the fibrous outer portion of the disc is more likely to rupture or tear.
Acute disc herniations can occur in young, healthy people as a result of an injury or tear to the outer layer of the disc (called the annulus fibrosis) that allows the central, jelly-like portion of the disc (called the nucleus pulposis) to herniate into the spinal canal or foramen.
Tests and Diagnosis of Spinal Disc Herniation
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.
- Projection radiography (X-ray imaging) – 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. However, visual confirmation of a disc herniation can be difficult with a CT.
- Magnetic resonance imaging (MRI) without contrast – 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 better than CAT scans. An MRI performed with a high magnetic field strength usually provides the most conclusive evidence for the diagnosis of a disc herniation. T2-weighted images allow for clear visualization of protruded disc material in the spinal canal.
- 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 myelography involves the injection of foreign substances, MRI scans are now preferred for most patients. Myelograms still provide excellent outlines of space-occupying lesions, especially when combined with CT scanning (CT myelography).
- 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. EMG/NCS studies are typically used to pinpoint the sources of nerve dysfunction distal to the spine.
- Computerized tomography (CT) scan – a series of X-rays, assembled by a computer into 3-dimensional images of the body’s structures
- Myelography – a procedure that involves injecting a liquid dye into the spinal column followed by a series of X-rays and a computerized tomography (CT) scan. This procedure may provide useful images that reveal the indentations of the spinal fluid sac caused by bulging or herniated discs, or bone spurs that might be pressing on the spinal cord or nerves.
- Electromyography (EMG) – tests the electrical activity of a nerve root to help determine the cause of pain.
- The presence and severity of myelopathy can be evaluated by means of transcranial magnetic stimulation (TMS), a neurophysiological method that allows the measurement of the time required for a neural impulse to cross the pyramidal tracts, starting from the cerebral cortex and ending at the anterior horn cells of the cervical, thoracic or lumbar spinal cord. This measurement is called Central Conduction Time (CCT). TMS can aid physicians to:
- determine whether myelopathy exists
- identify the level of the spinal cord where myelopathy is located. This is especially useful in cases where more that two lesions may be responsible for the clinical symptoms and signs, such as in patients with two or more cervical disc hernias
- follow-up the progression of myelopathy in time, for example before and after cervical spine surgery
- TMS can also help in the differential diagnosis of different causes of pyramidal tract damage.
Since a herniated disc may cause similar symptoms to other degenerative spinal conditions, a surgeon may order a variety of diagnostic procedures to rule out other possible conditions.
Treatment of Spinal Disc Herniation