Prolapsed Intervertbral Disc or Spinal Disc Herniation

An intervertebral disc lies between two adjacent vertebrae. Disc herniation is a condition in which a tear in the annulus fibrosus (Outer firmer ring) of an intervertebral disc  allows the soft, central portion (nucleus pulposus) to bulge out. Due to that adjacent neural structures may get compressed and produce symptoms of radiculopathy.

Following diagram would make it easier to comprehend how a disc bulge can affect nerve roots. On left side is a normal disc and on the right side is a herniated disc.

Lumbar followed by cervical spine are most commonly affected by disc herniation with former being more common than latter. L4-L5 and L5-S1 discs most common to herniate in lumbar spine. In cervical spine C5-C6 and C6-C7 discs are most commonly involved.

Thoracic disc herniation is rare.

Most disc herniations occur in young people. With age nucleus pulposus dries and the risk of herniation is reduced.

It is now being recognized in addition to compression of the nerve root there is release of inflammatory mediator with herniation of disc. This meditor is recognized as tumor necrosis factor-alpha (TNF). This molecule is released  not only by the herniated disc, but also in cases of disc tear, by facet joints, and in spinal stenosis.

Cause

Usually there is a  history of strain on the back which may be in form of lifting heavy weights or sudden movement. In some patients no cause or antecedent event could be elicited.

A preexisting protrusion of the disc might be there before the herniation takes place. A protrusion is one in which fibers of annulus fibrosus are not torn but on increase in internal pressure it bulges out. Following diagram hows stages of disc herniation

Minor back pain and chronic back tiredness is an indicator of general wear and tear that makes one susceptible to herniation on the occurrence of a traumatic event from bending  or a traumatic injury from a fall.

Clinical Presentation

The symptoms and presentation depend on the region involved. In cervical disc herniation the pain may occur in region of the skull, the neck, shoulder girdle, scapula, shoulder, arm, and hand.Lumbar disc can present with the pain in the lower back, buttocks, thigh, and may radiate into the foot and/or toe. The sciatic nerve is the most commonly affected  but he femoral nerve can also be affected.

The severity of symptoms may range from little or no pain to severe and unrelenting back pain that will radiate into the regions of affected nerve roots. It may be accompanied by neural deficits.

These symptoms occur in one side of the body when disc is on lateral aspect which is the most common type. In some cases however the disc is central and may cause involvement of more than one nerve roots on either side of the body. These central discs also present with bladder and bowel involvement ( Urinary incontinence) and  requires urgent removal by surgery.

Diagnosis

Diagnosis is based on the history, symptoms, and physical examination. Straight leg raise test is frequently performed in the physical examination of lumbar disc though the specificity of the test is not that good.

Investigations and Imaging

X-ray

Plain X-rays have limited role in diagnosis of disc herniation as they are unable ot define soft tissues such as discs, muscles, and nerves. But  they are still used to rule out  other diseases like tumors, infections, etc.

MRI

Magnetic resonance imaging is the best investigation to confirm the disc pathologies. It can show the spinal cord, nerve roots, and surrounding areas and is very sensitive investigation to show even slight bulge of the disc.

Following MRI image shows disc herniation between L5 and S1 vertebrae.

Treatment

Contrary to the perception the majority of herniated discs can be managed with non operative treatment.

Follwing treatment modalities may be used in conjunction to treat disc herniation non operatively.

• Physical therapy, which may include ultrasound, massage, conditioning, and exercise programs
• Non-steroidal anti-inflammatory drugs
• Oral steroids
• Epidural steroid injection
• Lumbosacral back support[31]

Operative Treatment

If non operative methods fail, surgery should be considered. However there are certain conditions where surgery is indicated without considering option of non operative treatment

• Significant neurological deficit
• Cauda equina syndrome [Its a medical emergency]

Note: A recent study has found that  1-year outcomes were similar for patients assigned to early surgery and those assigned to conservative treatment with eventual surgery if needed, but the rates of pain relief and of perceived recovery were faster for those assigned to early surgery. Thus patient decision and pain tolerance become important part of surgical decision.

Surgical goals include relief of nerve compression, allowing the nerve to recover, as well as the relief of associated back pain and restoration of normal function.

Surgical options include employed are

For lumbar spine

• Chemonucleolysis
• Intradiscal electrothermal annuloplasty
• Discectomy/Microdiscectomy
• Laminectomy /Hemilaminectomy
• Nucleoplasty
• Disc replacement

For Cervical spine

• Anterior cervical discectomy and fusion (for cervical disc herniation)
• Disc arthroplasty

Stem cells are being investigated for their potential role in treatment of disc herniation.