Disorders affecting intervertebral discs include:

• Disc herniation (prolapsed intervertebral disc)
• Degenerative disc disease
• Infection (discitis)

Spinal disc problems can lead to symptoms of back pain and/or sciatica. There are many other causes of back pain and/or sciatica but they do not primarily originate from the intervertebral discs. A comprehensive differential diagnosis for back pain and/or sciatica can be found in the related articles Examination of the Spine and Low Back Pain and Sciatica.

This article focuses on thoracic, lumbar and sacral disc problems. Cervical disc problems are discussed in the article Cervical Disc Protrusions and Lesions.

Back pain with/without sciatica is extremely common. Most may be classified as 'simple' back pain where serious underlying pathology is unlikely. However, the clinician must always be aware of "reg flag" warning signs which may merit investigations or even emergency admission. These are also discussed in this article.

Anatomy¹

• The spinal cord is shorter than spinal canal.
• The cord ends between the L1 and L2 vertebrae in adults and between L2 and L3 in children.
• Below the termination of the cord the nerve roots form the cauda equina which has a horse-tail like appearance.
• The cauda equina contains the nerve roots L1-5 and S1-5.
• Spinal pathology below L1 of the vertebral column produces mostly lower motor neurone signs.
• The intervertebral discs lie between adjacent vertebrae. They consist of a peripheral fibrocartilagenous part called the annulus fibrosus and a central semifluid/gelatinous part, the nucleus pulposus.

Assessment of a patient presenting with back pain and/or sciatica

This is described in detail in the articles on spinal examination and sciatica and low back pain.

When to refer someone with low back pain/sciatica^2,3

• If red flags suggest a serious condition:
  • Refer with appropriate urgency.
• If there is progressive, persistent, or severe neurological deficit:
  • Refer for neurosurgical or orthopaedic assessment (preferably to be seen within 1 week).
• If pain or disability remain problematic for more than a week or two:
  • Consider early referral for physiotherapy or other physical therapy.
• If, after 6 weeks, sciatica is still disabling and distressing:
  • Refer for neurosurgical or orthopaedic assessment (preferably to be seen within 3 weeks).
• If pain or disability continue to be a problem despite appropriate pharmacotherapy and physical therapy:
  • Consider referral to a multidisciplinary back pain service or a chronic pain clinic.

Prolapsed intervertebral disc

Pathophysiology³

• The nucleus pulposus of the disc is usually contained by the annulus fibrosus.
• If the nucleus herniates, it can irritate and/or compress the adjacent nerve root causing symptoms of sciatica.³
• The term sciatica is used for the pain, tingling, and numbness that arise due to nerve root entrapment in the lumbosacral spine. The symptoms may be felt in one or more of the lumbar nerve roots.
• About 90% of cases of sciatica are caused by a herniated intervertebral disc. This most commonly occurs at the L5/S1 level.³ Other causes are discussed in the dedicated article on sciatica.
• Traumatic disc herniation can occur. Disc herniation can also occur secondary to degenerative disc disease.
• A herniated nucleus pulposus is most common in those of less than 40 years old whilst degeneration of discs tends to affect those over 40 with the prevalence increasing with advancing age.
• Disc lesions of the lumbar spine are more common than the cervical spine and disc lesions of the thoracic spine are rare (the rib cage has a stabilising effect).

Presentation

• Lumbosacral disc herniation
  • If there is nerve entrapment in the lumbosacral spine, this leads to symptoms of sciatica which include:³
    • Unilateral leg pain that radiates below the knee to the foot/toes.
    • The leg pain is more severe than the back pain.
    • Numbness, paraesthesia, weakness and/or loss of tendon reflexes may be present and are found in the same distribution and are only in one nerve root distribution.
    • There is a positive straight leg raising test (there is greater leg pain and/or more nerve compression symptoms on raising the leg).
    • Pain is usually relieved by lying down and exacerbated by long walks and prolonged sitting.⁴
    • The functional distribution of the lumbar nerve roots and the sciatic nerve are detailed in the sciatica article.
    • Large herniations can compress the cauda equina leading to symptoms/signs of saddle anaesthesia, urinary retention and incontinence as described above.
  • Symptoms tend to at least partially resolve in 66% of people with a disc herniation after 6 months. This is because the herniated portion tends to regress over time.⁵
  • However, nerve root compression can lead to permanent nerve damage with sensory and motor deficit.³
• Thoracic disc herniation⁶
  • Disc lesions in the thoracic spine can lead to either nerve root irritation or cord compression.
  • Thoracic spine lesions can present with symptoms similar to lumbar disc lesions.
  • In nerve root irritation, there may be shooting pain down the legs.
  • There may be pain, paraesthesia or dysaesthesia in a dermatomal distribution.
  • A thoracoabdominal sensory examination can help to determine the level of the lesion: nipple is innervated by T4; xiphoid by T7, umbilicus by T10; inguinal region by T12.
  • Testing of the abdominal and cremasteric reflexes can help to identify myelopathy and cord compression.
  • Cord compression:
    • This is a neurosurgical emergency.
    • Cord compression in the thoracic spine can produce paraplegia.
    • There may be clonus or a positive Babinski reflex.
    • There may be bladder/bowel dysfunction.
    • Herniation of T2-5 can mimic cervical disc disease.

Investigation

• No investigation may be needed if symptoms settle within 6 weeks.
• MRI is very sensitive in showing disc herniations.⁴
• CT myelography may also be used.
• Plain X-rays are sometimes useful as they can show misalignments, instabilities and congenital anomalies well.⁴

Management³

• Analgesia:
  • Simple analgesics as first line (paracetamol/NSAID). These may be used in combination.
  • A weak opioid such as codeine or tramadol may be added if pain is still present.
  • Consider a benzodiazepine (e.g. diazepam) if there is muscle spasm.
  • Consider a trial of a tricyclic antidepressant or gabapentin if there is persistent sciatica.
  • If stronger analgesia is needed, refer to a pain clinic/specialist service.
• Encouragement to keep active: swimming is a good exercise.
• Heat and massage may relieve muscle spasm.
• Avoidance of activities that may aggravate pain: e.g. lifting, prolonged sitting.
• Physiotherapy
• Surgery: pain due to a herniated lumbosacral disc may settle within 6 weeks. If it does not, or there are red flag signs such as cauda equina syndrome, referral to an orthopaedic or neurosurgeon should be considered. Where surgery is required, less invasive procedures are to be recommended. Laser lumbar discectomy has been reviewed by NICE.⁷ They have suggested that evidence on its safety and efficacy are lacking and that it should only be undertaken if there are appropriate arrangements for audit and/or research

Prevention

• Regular exercise.
• Weight loss if overweight.
• Safe lifting techniques.
• Correct sitting position and posture.

Degenerative disc disease

• The exact cause of this is not known. Some suggest that it is a natural part of ageing, however, disc degeneration can also occur in young people. The cause is likely to be multifactorial including genetic, environmental, traumatic, inflammatory, infectious and other factors.⁸
• Annular tears, internal disc disruption and resorption, disc space narrowing, disc fibrosis and osteophyte formation can all occur.⁸
• Degenerative disc disease may lead to disc herniation.

Discitis⁹

Pathophysiology

• Discitis is inflammation of the vertebral disc space. It is usually associated with infection and can coexist with vertebral osteomyelitis.
• It most commonly affects the lumbar spine. The thoracic spine is least commonly affected with the cervical spine between the two.
• There is usually haematogenous spread of infection from other parts of the body. The urinary tract, lungs and soft-tissues are common primary sites for infection. It may be difficult to find a primary site.
• Staphylococcus aureus is the most common pathogen.
• Discitis can occur in children but most commonly affects males in their 50s.
• Risk factors include any cause of immunosuppression (including diabetes) and intravenous drug use.
• Discitis may rarely follow surgery involving the disc space.

Presentation

• An insidious onset is common.
• There may be neck or back pain with localised tenderness. Pain is worse on movement. Mobility may be restricted.
• There may be associated fever and weight loss.
• Neurological deficit may be present. This is more likely in the cervical spine.

Investigations

• ESR and CRP are raised. They can be used to monitor response to treatment.
• White blood cell count may be normal.
• Blood, sputum, urine and any other appropriate cultures should be taken to look for the source of infection.
• X-ray of the spine may show disc space narrowing, endplate irregularities and annulus calcification. Osteomyelitis changes may be seen including decreased bone density and bone destruction. However, X-ray may be normal initially.
• Nuclear medicine scans may be helpful.
• CT and MRI scanning show changes earlier than plain X-ray. MRI is the most sensitive and specific.
• CT-guided or open biopsy of the infected disc space area can provide histological confirmation of discitis and allow culture. Surgical debridement may be carried out at the same time.

Management

• Antibiotics are needed. These should be adjusted if/when culture results are available. Parenteral treatment is usually used and may be needed for 6-8 weeks. ESR can be used to monitor response.
• Bed rest is advised. Two weeks are suggested.
• Immobilisation with a brace is advised when bed rest is discontinued. This may be needed for 3-6 months.
• Analgesia should be prescribed as required.
• Surgical treatment may be needed if there is neurological deficit, spinal deformity or lack of response to antibiotic treatment.

Prognosis

• Antibiotic treatment with/without surgery is usually successful in treating the condition.
• 15% of people have permanent neurological deficits.
• Complications can include spread of infection into the epidural space or paraspinal soft tissues.
• Mortality is reported as 2-12%.

Document references

1. Eck JC, Hodges SD, Humphreys SC; Cauda Equina Syndrome. eMedicine. Last Updated May 23, 2007.
2. Back pain - low (without radiculopathy), Clinical Knowledge Summaries (November 2009)
3. Sciatica (lumbar radiculopathy), Clinical Knowledge Summaries (November 2009)
4. Sahrakar K, Melicharek M; Lumbar Disc Disease. eMedicine. Last Updated Oct 23, 2008.
5. Jordan J, Konstantinou K, Shawyer MT, Weinstein J; Herniated lumbar disc. BMJ Clinical Evidence. BMJ Publishing Ltd. 2007.
6. Hannani K; Thoracic Disc Injuries. eMedicine. Last Updated Dec 21, 2007.
7. Laser lumbar discectomy, NICE (2003)
8. Patel RK, Slipman CW; Lumbar Degenerative Disk Disease. eMedicine. Last Updated Jan 18, 2007.
9. Jallo G, Marcovici A; Diskitis. eMedicine. Last Updated Feb 9, 2007.

Internet and further reading

• European guidelines for the management of acute nonspecific low back pain in primary care, COST B13 Working Group (2004)
• European guidelines for the management of chronic non-specific low back pain, COST B13 Working Group (2004)
• European guidelines for prevention in low back pain, COST B13 Working Group (2004)

Acknowledgements