What is a Herniated Disc?

A herniated, or slipped, disc is a generalized term referring to displacement of any part (fluid, cartilage or bone) of an inter-vertebral disc outside the borders of its joint, or disc space1.The borders of this space are defined by the surrounding vertebral bones. Such herniations can be focal (a small displacement) or broad-based (a large displacement), and are often subcategorized under other names such as protruding, extruding, bulging and more. The use of the term ‘slipped’ can be misleading, however, as the disc doesn’t necessarily shift or move3.

herniated discRisk factors for herniation include:

  • Male gender2
  • Middle – older age2
  • Pre-existing/congenital defects of the spine2, 9
  • Strenuous physical activity; repeated heavy lifting, twisting or bending2, 9
  • Family history of herniation9
  • Cigarette smoking9
  • Poor nutrition9
  • Overweight/obesity9
  • Pregnancy/childbirth9
  • Sedentary lifestyle9

Although some patients may not notice when a disc has herniated, many will experience local pain or pain as a consequence of the disc displacement pressing against a nerve or nerve root; a condition known as a radiculopathy8. A radiculopathy can cause mild to severe pain in the back, neck, lower and upper extremities, as well numbness and/or weakness in some circumstances. This pain can be very diverse, ranging from a dull ache to a stabbing or pulsing sensation, and typically occurs on one side of the body2. Additionally, pain will usually manifest mildly and progressively get worse- particularly at night and/or after long periods of standing or sitting. Pain, numbness or weakness will generally subside over time, but may require medical intervention.

Pathophysiology

The spine consists of a column of bones, known as vertebrae, which are stacked atop one another from the pelvis to the base of the skull, protecting the spinal cord2. Each of these vertebrae are separated by cartilaginous, inter-vertebral discs composed of a tough, fibrous outer layer and filled with a soft, gelatinous inner layer. These discs support the vertebrae and allow them to shift across one another, facilitating movement of the spine. The fibrous outer layer is called the annulus fibrosus, and the gelatinous inner layer is called the nucleus pulposus. Disc herniation occurs when the nucleus pulposus pushes out through a weakening or tear in the annulus fibrosus5.

The lumbar spine, adjacent to the lower back, is the most common location of disc herniation2, 9. Less than 10% of herniations occur in the cervical spine (neck), and even fewer occur in the thoracic spine (upper back). Pain associated with a lumbar disc herniation will typically involve the lower back and/or legs. Pain associated with a cervical disc herniation will involve the neck and/or arms and shoulders.

Some common causes of herniation include:

  • Degenerative changes from aging, dehydration of the nucleus and/or tears of the annulus9
  • Repetitive micro trauma of the discs from strain and activity (heavy lifting, twisting) 9, 13
  • Major trauma or injury to the disc9, 13

Potential symptoms of herniation include9:

  • Cervical
    • pain in neck or shoulder
    • radiating pain through arm or chest
    • numbness in hands/fingers
    • motor weakness in hands/fingers headache
    • vertigo or dizziness
    • hearing or vision disturbance
  • Lumbar
    • pain in back or legs, exacerbated by exertion
    • radiating pain into lower extremities
    • numbness in legs/feet
    • motor weakness in legs/feet
    • groin or rectal pain and/or numbness
    • incontinence (bowel/bladder)

Diagnosis

Diagnosis of a herniated disc is made via a full history and physical examination by a physician, and can be supported by an array of diagnostic tests. An experienced physician can conduct a neurological examination to assess spinal curvature, muscle reflex and strength, and sensation2. Diagnostic tests are usually reserved only for when pain is unresponsive to conservative treatment and persists longer than 4-6 weeks5.

Tests that may be ordered by a physician may include:

  • X-Ray: a spinal x-ray can be used to rule out other possible causes of pain5, 6, 13
  • MRI/CT: magnetic resonance imaging (MRI) or computed tomography (CT) scans can allow nerve compression to be visualized5, 6, 13
  • Electrical and nerve conduction tests can be done to isolate effected nerve roots5, 6, 13
  • Myelography, or imaging of the spinal cord (and nerve roots), can be performed by injecting contrast material and imaging to determine size and location of a disc herniation 5, 6, 13
  • Discography, or imaging of the disc itself, can be performed by injecting contrast material into a disc and performing a CT scan to determine abnormalities and assess pain 6, 7, 13

In some cases, a lumbar herniated disc can cause a condition known as Cauda Equina syndrome if it compresses a certain group of nerve roots (the lumbar plexus) in the lower spine. Cauda Equina can cause additional symptoms such as urinary or bowel incontinence, new weakness, impotence, and/or numbness in the groin area9. This syndrome is considered a surgical emergency, requiring immediate decompression of affected nerve roots.

Treatment

The best method for treating a herniation is to prevent it from occurring in the first place! Some tips for preventing a herniated disc include:

  • weight management through proper diet13
  • maintaining strong, flexible muscles (walking and swimming work well)13
  • practice good posture and proper lifting techniques (with legs, not back) 2
  • a back brace may be useful periodically for spinal support2

Prevention aside, most patients with a herniated disc recover without surgery; one study suggested that as many as 95% of patients with lumbar herniation enjoyed full recovery in a few weeks2, 4. These patients generally improve with conservative treatment:

  • Conservative
    • Over the counter anti-inflammatory/pain relievers2, 9, 13 such as aspirin, ibuprofen and naproxen (NSAIDS) can be used for long term pain management and swelling reduction
    • Lifestyle changes; balanced diet and moderate exercise can eliminate strain from weight issues2, 9
    • Prescription pain relievers2, 9, 13 such as opioids or narcotics can be prescribed for short term use in the event of significant pain
    • Muscle relaxants9, 13 can be used if back spasms occur with pain
    • Hot/cold packs13 can be used to reduce swelling (cold) and increase blood perfusion (heat) to affected tissues
    • Traction13 involves the tensing of bones and muscles in such a manner as to open the inter-vertebral disc space, relieving pressure; this is typically managed by a therapist
    • Neck/back massage13 can relax muscles and reduce strain
    • Physical Therapy2, 9, 13 can help strengthen and stabilize muscles and joints, assist with practicing correct posture, and offer instruction for proper lifting techniques

Most people with herniated discs will not require additional intervention; however injections and/or surgery may be indicated when conservative treatment fails and pain persists2, 5, 13.

  • Injections
    • Steroids2, 9, 13 can be injected directly into the affected area to control pain for longer periods of time by reducing inflammation around the nerves
    • Oxygen-ozone10 is much more common outside of America and can be injected into an affected disc to reduce volume and alleviate compression. Studies have shown therapeutic success in up to 70% of patients with oxygen-ozone, and up to 78% when combined with steroidal injections
  • Surgical Intervention
    • Open Discectomy5 is the most common surgical treatment, particularly for lumbar herniations, and has been used and improved for the past 60 years. Part of the damaged disc is surgically removed to alleviate pressure and pain
    • Micro-discectomy3, 5 simply incorporates the use of magnification via a surgical micro-scope to remove part of the lamina to visualize the disc and nerve tissue during surgery; the result is a smaller incision and less bone removal
    • Fusion9 of adjacent vertebral bones is sometimes recommended to prevent recurrent herniations
    • Other minimally invasive techniques5 are being attempted in the hopes preserving more tissue and producing less trauma.

In some cases, the herniated discs may spontaneously regress, or get better. A recent large study estimated that between 35-63% of patients will show diminished volume of lumbar herniations within 2 months of occurrence, possibly as the result of natural disc dehydration or the immune system clearing out the herniation as it would any other foreign body, such as a bacteria or virus12.

Post-treatment, it may take time before patients are able to resume normal activities; it is important for these patients to avoid certain strenuous activities to prevent recurrence2.

Current Research

Spine surgery is a very active field in terms of improving the way in which surgeries are performed5. Discectomies, which have for years been open and invasive, are now often being performed through smaller incisions (arthroscopically) with reduced anesthesia. Arthroscopic discectomies have yet to replace open discectomies as to “gold standard” for herniated disc treatment, however.

In lieu of disc discectomy and fusion, which ultimately reduces mobility, artificial disc replacement surgery is a technique in development for the treatment of radiculopathies. Because this is an emerging technique, few studies exist regarding the long-term outcomes and durability of artificial discs, however one recent study of 115 patients suggested that artificial disc replacement was viewed as more favorable than conventional surgical methods14.

Finally, some studies have investigated the regeneration of inter-vertebral disc cells for transplantation and the removal of nucleus pulposus (nucleoplasty) to reduce disc size; however outcomes have been poor to date11.

References

1 Fardon, D.; Milette, P. Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology. Spine. Vol 26, E93-E113. 2001.

2 Nidus Information Services 2010: Herniated Disk. Patient Handouts page. MD Consult Web site, Core Collection. Available at http://www.mdconsult.com.ezproxy2.library.arizona.edu/das/patient/body/234155712-5/1108605568/10041/35144.html. Accessed January 24, 2011.

3 eOrthopod 2009. What’s the difference between herniated disc and slipped disc? Available at http://www.eorthopod.com/content/whats-the-difference-between-herniated-disc-and-slipped-disc-i-want

4 Ferri’s Netter Patient Advisor 2010: Managing your slipped disc. Patient Handouts page. MD Consult Web site, Core Collection. Available at http://www.mdconsult.com.ezproxy2.library.arizona.edu/das/patient/body/234418695-7/1108603559/10084/39132.html. Accessed January 27, 2011.

5 North American Spine Society 2009: Lumbar (open) Microscopic Disectomy. Patient Handouts page. Available at http://www.knowyourback.org/Pages/Treatments/SurgicalOptions/LumbarDiscectomy.aspx. Accessed January 27, 2011.

6 Milette, P. Classification, diagnostic imaging, and imaging characterization of a lumbar herniated disc. Radiologic Clinics of North America. Vol 36, 2000.

7 North American Spine Society 2006: Lumbar (open) Microscopic Disectomy. Patient Handouts page. Available at www.spine.org/Documents/discography_2006.pdf. Accessed January 27, 2011.

8 Robinson, J.; Kothari, M. Clinical features and diagnosis of cervical radiculopathy. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2010.

9 Rihn, J.; et al. Herniated intervertebral disc. First Consult, MD Consult Web site. Available at: http://www.mdconsult.com.ezproxy2.library.arizona.edu/das/pdxmd/body/234418695-2/1108889771?type=med&eid=9-u1.0-_1_mt_1014932. Posted July 29, 2010. Accessed January 27, 2011.

10 Andreula, C.; et al. Minimally Invasive Oxygen-Ozone Therapy for Lumbar Disc Herniation. American Journal of Neuroradiology. Vol 24, 996-1000. 2003.

11 Hegewald, A.; et al. Adequacy of herniated disc tissue as a cell source for nucleus pulposus regeneration. Laboratory investigation. Journal of Neurosurgery, Spine. DOI: 10.3171, 2010.

12 Chang, C.; et al. Spontaneous Regression of Lumbar Herniated Disc. J Chin Med Assoc. Vol 72, 650-653. 2009.

13 Clinical Reference Systems 2010: Herniated Disk. Patient Handouts page. MD Consult Web site, Core Collection. Available at http://www.mdconsult.com.ezproxy2.library.arizona.edu/das/patient/body/234418695-2/1109885219/10068/37519.html. Accessed January 27, 2011.

14 Robinson, J.; Kothari, M. Treatment of cervical radiculopathy. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2010.