Herniated Disk

Definition

Disk herniation is a rupture of fibrocartilagenous material (annulus fibrosis) that surrounds the intervertebral disk. This rupture involves the release of the disk's center portion containing a gelatinous substance called the nucleus pulposus. Pressure from the vertebrae above and below may cause the nucleus pulposus to be forced outward, placing pressure on a spinal nerve and causing considerable pain and damage to the nerve. This condition most frequently occurs in the lumbar region and is also commonly called herniated nucleus pulposus, prolapsed disk, ruptured intervertebral disk, or slipped disk.

Description

The spinal column is made up of 26 vertebrae that are joined together and permit forward and backward bending, side bending, and rotation of the spine. Five distinct regions comprise the spinal column, including the cervical (neck) region, thoracic (chest) region, lumbar (low back) region, sacral and coccygeal (tail-bone) region. The cervical region consists of seven vertebrae, the thoracic region includes 12 vertebrae, and the lumbar region contains five vertebrae. The sacrum is composed of five fused vertebrae, which are connected to four fused vertebrae forming the coccyx. Intervertebral disks lie between each adjacent vertebra.

Each disk is composed of a gelatinous material in the center, called the nucleus pulposus, surrounded by rings of a fiberous tissue (annulus fibrosus). In disk herniation, an intervertebral disk's central portion herniates or slips through the surrounding annulus fibrosus into the spinal canal, putting pressure on a nerve root. Disk herniation most commonly affects the lumbar region between the fifth lumbar vertebra and the first sacral vertebra. However, disk herniation can also occur in the cervical spine. The incidence of cervical disk herniation is most common between the fifth and sixth cervical vertebrae. The second most common area for cervical disk herniation occurs between the sixth and seventh cervical vertebrae. Disk herniation is less common in the thoracic region.

Predisposing factors associated with disk herniation include age, gender, and work environment. The peak age for occurrence of disk herniation is between 20-45 years of age. Studies have shown that males are more commonly affected than females in lumbar disk herniation by a 3:2 ratio. Prolonged exposure to a bent-forward work posture is correlated with an increased incidence of disk herniation.

There are four classifications of disk pathology:

A protrusion may occur where a disk bulges without rupturing the annulus fibrosis.
The disk may prolapse where the nucleus pulposus migrates to the outermost fibers of the annulus fibrosis.
There may be a disk extrusion, which is the case if the annulus fibrosis perforates and material of the nucleus moves into the epidural space.
The sequestrated disk may occur as fragments from the annulus fibrosis and nucleus pulposus are outside the disk proper.

Causes and symptoms

Any direct, forceful, and vertical pressure on the lumbar disks can cause the disk to push its fluid contents into the vertebral body. Herniated nucleus pulposus may occur suddenly from lifting, twisting, or direct injury, or it can occur gradually from degenerative changes with episodes of intensifying symptoms. The annulus may also become weakened over time, allowing stretching or tearing and leading to a disk herniation. Depending on the location of the herniation, the herniated material can also press directly on nerve roots or on the spinal cord, causing a shock-like pain (sciatica) down the legs, weakness, numbness, or problems with bowels, bladder, or sexual function.

Diagnosis

Several radiographic tests are useful for confirming a diagnosis of disk herniation and locating the source of pain. These tests also help the surgeon indicate the extent of the surgery needed to fully decompress the nerve. X rays show structural changes of the lumbar spine. Myelography is a special x ray of the spine in which a dye or air is injected into the patient's spinal canal. The patient lies strapped to a table as the table tilts in various directions and spot x rays are taken. X rays showing a narrowed dye column in the intervertebral disk area indicate possible disk herniation.

Computed tomography scan (CT or CAT scans) exhibit the details of pathology necessary to obtain consistently good surgical results. Magnetic resonance imaging (MRI) analysis of the disks can accurately detect the early stages of disk aging and degeneration. Electomyograms (EMGs) measure the electrical activity of the muscle contractions and possibly show evidence of nerve damage. An EMG is a powerful tool for assessing muscle fatigue associated with muscle impairment with low back pain.

Treatment

Drugs

Unless serious neurologic symptoms occur, herniated disks can initially be treated with pain medication and up to 48 hours of bed rest. There is no proven benefit from resting more than 48 hours. Patients are then encouraged to gradually increase their activity. Pain medications, including antiinflammatories, muscle relaxers, or in severe cases, narcotics, may be continued if needed.

Epidural steroid injections have been used to decrease pain by injecting an antiinflammatory drug,

A herniated disk refers to the rupture of fibrocartilagenous material, called the annulus fibrosis, that surrounds the intervertebral disk. When this occurs, pressure from the vertebrae above and below may force the disk's center portion, a gel-like substance, outward, placing additional pressure on the spinal nerve and causing pain and damage to the nerve.

(Illustration by Electronic Illustrators Group.)

usually a corticosteroid, around the nerve root to reduce inflammation and edema (swelling). This partly relieves the pressure on the nerve root as well as resolves the inflammation.

Physical therapy

Physical therapists are skilled in treating acute back pain caused by the disk herniation. The physical therapist can provide noninvasive therapies, such as ultrasound or diathermy to project heat deep into the tissues of the back or administer manual therapy, if mobility of the spine is impaired. They may help improve posture and develop an exercise program for recovery and long-term protection. Appropriate exercise can help take pressure off inflamed nerve structures, while improving overall posture and flexibility. Traction can be used to try to decrease pressure on the disk. A lumbar support can be helpful for a herniated disk at this level as a temporary measure to reduce pain and improve posture.

Surgery

Surgery is often appropriate for conditions that do not improve with the usual treatment. In this event, a strong, flexible spine is important for a quick recovery after surgery. There are several surgical approaches to treating a herniated disk, including the classic discectomy, microdiscectomy, or percutanteous discectomy. The basic differences among these procedures are the size of the incision, how the disk is reached surgically, and how much of the disk is removed.

Discectomy is the surgical removal of the portion of the disk that is putting pressure on a nerve causing the back pain. In the classic disectomy, the surgeon first enters through the skin and then removes a bony portion of the vertebra called the lamina, hence the term laminectomy. The surgeon removes the disk material that is pressing on a nerve. Rarely is the entire lamina or disk entirely removed. Often, only one side is removed and the surgical procedure is termed hemi-laminectomy.

In microdiscectomy, through the use of an operating microscope, the surgeon removes the offending bone or disk tissue until the nerve is free from compression or stretch. This procedure is possible using local anesthesia. Microsurgery techniques vary and have several advantages over the standard discectomy, such as a smaller incision, less trauma to the musculature and nerves, and easier identification of structures by viewing into the disk space through microscope magnification.

Percutaneous disk excision is performed on an outpatient basis, is less expensive than other surgical procedures, and does not require a general anesthesia. The purpose of percutaneous disk excision is to reduce the volume of the affected disk indirectly by partial removal of the nucleus pulposus, leaving all the structures important to stability practically unaffected. In this procedure, large incisions are avoided by inserting devices that have cutting and suction capability. Suction is applied and the disk is sliced and aspirated.

Arthroscopic microdiscectomy is similar to percutaneous discectomy, however it incorporates modified arthroscopic instruments, including scopes and suction devices. A suction irrigation of saline solution is established through two entry sites. A video discoscope is introduced from one site and the deflecting instruments from the opposite side. In this way, the surgeon is able to search and extract the nuclear fragments under direct visualization.

Laser disk decompression is performed using similar means as percutaneous excision and arthroscopic microdiscectomy, however laser energy is used to remove the disk tissue. Here, laser energy is percutanteously introduced through a needle to vaporize a small volume of nucleus pulposus, thereby dropping the pressure of the disk and decompressing the involved neural tissues. One disadvantage of this procedure is the high initial cost of the laser equipment. It is important to realize that only a very small percentage of people with herniated lumbar disks go on to require surgery. Further, surgery should be followed by appropriate rehabilitation to decrease the chance of reinjury.

Chemonucleolysis

Chemonucleolysis is an alternative to surgical excision. Chymopapain, a purified enzyme derived from the papaya plant, is injected percutaneously into the disk space to reduce the size of the herniated disks. It hydrolyses proteins, thereby decreasing water-binding capacity, when injected into the nucleus pulposus inner disk material. The reduction in size of the disk relieves pressure on the nerve root.

Spinal fusion

Spinal fusion is the process by which bone grafts harvested from the iliac crest (thick border of the ilium located on the pelvis) are placed between the intervertebral bodies after the disk material is removed. This approach is used when there is a need to reestablish the normal bony relationship between the vertebrae. A total discectomy may be needed in some cases because lumbar spinal fusion can help prevent recurrent lumbar disk herniation at a particular level.

Alternative treatment

Acupuncture involves the use of fine needles inserted along the pathway of the pain to move energy locally and relieve the pain. An acupuncturist determines the location of the nerves affected by the herniated disk and positions the needles appropriately. Massage therapists may also provide short-term relief from a herniated disk. Following manual examination and x-ray diagnosis, chiropractic treatment usually includes manipulation to correct muscle and joint malfunctions, while care is taken not to place an additional strain on the injured disk. If a full trial of conservative therapy fails, or if neurologic problems (weakness, bowel or bladder problems, and sensory loss) develop, the next step is usually evaluation by an orthopedic surgeon.

Key terms

Annulus fibrosis — The outer portion of the intervertebral disk made primarily of fibrocartilage rings.

Epidural space — The space immediately surrounding the outermost membrane of the spinal cord.

Excision — The process of excising, removing, or amputating.

Fibrocartilage — Cartilage that consists of dense fibers.

Nucleus pulposus — The center portion of the intervertebral disk that is made up of a gelatinous substance.

Percutaneous — Performed through the skin.

Prognosis

Only 5-10% of patients with unrelenting sciatica and neurological involvement, leading to chronic pain of the lumbar spine, need to have a surgical procedure performed. This strongly suggests that many patients with herniated disks at the lumbar level respond well to conservative treatment. For those patients who do require surgery for lumbar disk herniation, the reviewed procedures of nerve root decompression caused by disk herniation is favorable. Results of studies varied from 60-90% success rates. Disk surgery has progressively evolved in the direction of decreasing invasiveness. Each surgical procedure is not without possible complications, which can lead to chronic low back pain and restricted lifestyle.

Prevention

Proper exercises to strengthen the lower back and abdominal muscles are key in preventing excess stress and compressive forces on lumbar disks. Good posture will help prevent problems on cervical, thoracic, and lumbar disks. A good flexibility program is critical for prevention of muscle and spasm that can cause an increase in compressive forces on disks at any level. Proper lifting of heavy objects is important for all muscles and levels of the individual disks. Good posture in sitting, standing, and lying down is helpful for the spine. Losing weight, if needed, can prevent weakness and unnecessary stress on the disks caused by obesity. Choosing proper footwear may also be helpful to reduce the impact forces to the lumbar disks while walking on hard surfaces. Wearing special back support devices may be helpful if heavy lifting is required with combinations of twisting.

Resources

Other

"Back Pain." Healthtouch Online Page. http://www.healthtouch.com.

herniated disk

[her´ne-āt″ed]

protrusion of all or part of the nucleus pulposus through the weakened or torn outer ring (anulus fibrosus) of an intervertebral disk; it occurs most often in the lower back and occasionally in the neck or upper portion of the spinal column. Called also disk herniation, herniation of intervertebral disk or of nucleus pulposus, ruptured disk, and, popularly, “slipped disk.”

Causes and Symptoms. Between each pair of vertebrae lies a pad of cartilage and fiber (the anulus fibrosus) that encloses a soft, mucoid central portion (the nucleus pulposus). The pads act as cushions between the vertebrae, absorbing ordinary shocks and strains, and shifting position to accommodate various movements of the spine. If the nucleus pulposus herniates through a weakened outer ring, it can impinge on spinal nerve roots as they exit from the spinal canal, or on the spinal cord itself, causing severe pain. Herniation may be caused by injury or by sudden straining with the spine in an unnatural position. It may also come on gradually as a result of a progressive deterioration of the disks.

Symptoms depend upon the location and the extent to which the disk material has been pushed out. Most cases involve the disks between the fourth and fifth lumbar vertebrae or between the fifth lumbar vertebra and the sacrum. There is severe pain in the lower back and difficulty in walking. The sciatic nerve, which originates in the lower part of the spinal cord, is affected, with resulting pain at the back of the thigh and lower leg. A cough, sneeze, or strain will send the pain along the course of the sciatic nerve to the calf or ankle. When the disks of the cervical vertebrae are affected, severe pain in the back of the neck radiates down the arms to the fingers. Neck movements are restricted, and any neck motion, such as coughing, sneezing, or straining, will accentuate the pain.

Diagnosis and Treatment. Careful examination is necessary to distinguish this condition from other disturbances of the spine. This may include laboratory tests, x-ray examinations, myelography, magnetic resonance imaging (MRI), and CT scans. The x-rays or MRI may reveal pathologic changes in the spine and narrowing of the space between the vertebrae.

Treatment varies according to the seriousness of the condition. Conservative treatment for a herniated disk in the lower back consists of bed rest with leg- and back-strengthening exercises, as well as muscle relaxants and analgesics to relieve pain. Pelvic traction may be applied. In chronic cases the wearing of a surgical support may be helpful. Care must be taken to avoid aggravating the condition by excessive physical effort. Herniated disks in the neck are treated in a similar manner with bed rest, analgesics, anti-inflammatory agents, and traction. A collar may be worn to immobilize the neck when the patient is out of bed. If the response to these measures is inadequate or if the condition becomes disabling, surgery may be necessary to relieve the pressure on the injured disk. microdiskectomy is a newer surgical technique that is minimally invasive. Another treatment is chemonucleolysis, in which an enzyme that causes shrinkage in the size of the disk is injected into the herniated nucleus pulposus.

Patient Care. The patient receiving conservative treatment for a herniated disk must always have the spine in good alignment so as to avoid pressure on the adjacent nerves. In addition to using a firm mattress and bed boards, the patient should be instructed in the proper method of turning himself or herself by “log-rolling.” To accomplish this the patient crosses arms over chest, flexes the knee opposite the side being turned onto, and then rolls over “in one piece,” being sure that the spine is not bent forward or twisted. Training in good posture and body mechanics, especially during lifting or stooping, are important in preventing recurrence of acute episodes.

Transverse section showing normal intervertebral disk and ruptured intervertebral disk with herniation of the nucleus pulposus (herniated disk).

herniated disk

The protrusion of a degenerated or fragmented intervertebral disk into the intervertebral foramen, compressing the nerve root.

herniated disk

Herniated intervertebral disk, herniated nucleus pulposus, prolapsed intervertebral disk, slipped disk Neurology The herniation of an intervertebral disk, most commonly, lumbar; the term herniation in this context describes a spectrum of disk defects

Herniation disk types, used for MRI exams

Bulge–circumferential symmetric extension of the disk beyond interspace

Protrusion–focal or asymmetric extension of the disk beyond interspace

Extrusion–more extreme extension of the disk beyond interspace Note: Bulges and protrusions on MRI examination are common findings in normal subjects, and appear to be coincidental findings–NEJM 1994; 331:69oa

Patient discussion about herniated disk

Q. I have a low back pain that radiates to my leg when i pick up stuff. Is it a disc herniation? I am a 43 years old bank teller. During the past 5 months I've suffered from a low back pain. The pain is not very strong, but it gets much worse while doing physical activity. When i walk or lift heavy things the pain is even stronger, and it radiates to my left leg. Can it be signs for disc herniation?

A. It's possible that you have a nerve impingement from a disc herniation, but not necessarily so. What you need to know is that even if you have a herniated disc, the question is what would the recommended treatment be?
90% or more of herniated discs resolve without surgical treatment within 6 months. MRI imaging is generally only indicated if one is considering surgery; in other words, your pain and neurological status is such that surgery is clinically indicated. Then, an MRI may be helpful for the surgeon. If surgery is not indicated based on clinical/symptoms, then it probably is unwise to get an MRI. They often show abnormalities that are simply 'red herrings' and often prompt people to proceed with surgery that really is not needed. Beware!

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