Intervertebral Disc Prolapse
Relevant Anatomy
The intervertebral disc is a fibrocartilaginous structure (a secondary cartilaginous joint – a symphysis) situated between adjacent vertebral bodies.
Each intervertebral disc has 2 main components:
- Nucleus pulposus (the inner core): a gel-like centre made primarily of water that absorbs compressive forces and distributes mechanical load
- Annulus fibrosus (the outer ring): a tough fibrocartilaginous ring with alternating layers (lamellae) that surrounds the nucleus pulposus to provide structural stability
Terms and Types of Intervertebral Disc Prolapse
Intervertebral disc herniation (or disc prolapse) is an umbrella term describing displacement of intervertebral disc material beyond its normal anatomical boundaries.
It includes the following specific patterns / terms:
| Pattern / term | Description |
|---|---|
| Disc bulge | Broad and often symmetrical extension of the intervertebral disc beyond the vertebral body margins
The annulus fibrosus remains intact, and the nucleus pulposus remains contained within the annulus fibrosus |
| Disc protrusion | The nucleus pulposus is focally displaced into a weakened or torn annulus fibrosus
The nucleus pulposus remains contained by the outer annular fibres |
| Disc extrusion | The nucleus pulposus breaches the outer annulus fibrosus, it is no longer contained by the annular fibres |
| Disc sequestration | An extruded fragment of nucleus pulposus becomes completely separated from the intervertebral disc, it exists as a free fragment within the spinal canal |
Pathophysiology
Intervertebral disc herniation usually develops after degeneration and weakening of the annulus fibrosus.
- With ageing, the intervertebral disc gradually loses water and proteoglycan content (this reduces disc elasticity and shock-absorbing capacity, causing the disc to become less flexible and lose height)
- With ageing, repetitive loading, or sudden increases in pressure within the disc, fissures may form in the annulus fibrosus
- This allows the nucleus pulposus to move outwards, into the annulus fibrosus fissures
Symptoms arise through two main mechanisms:
- Mechanical compression of a spinal nerve root or spinal cord or cauda equina
- Chemical inflammation caused by inflammatory mediators released from the herniated disc material
Natural progression of intervertebral disc herniation: normal disc → disc bulge → disc protrusion → disc extrusion → disc sequestration
Clinical Manifestation
Many cases of intervertebral disc prolapse are asymptomatic. Clinical manifestations depend on the location, size and degree of neural compression / chemical inflammation:
| Disc effect | Clinical manifestation |
|---|---|
| Cervical nerve root compression | Cervical Radiculopathy |
| Lumbar nerve root compression | Sciatica and Lumbosacral Radiculopathy |
| Large central lumbar disc prolapse | Cauda equina syndrome |
Intervertebral disc prolapse may also cause mechanical low back pain through annular injury and inflammation.
It is important to note that intervertebral disc prolapse cannot be confirmed clinically without appropriate neuroimaging.
Patients do not usually present with “disc prolapse” itself. Instead, they present with clinical symptoms like low back pain and sciatica.
Investigation and Diagnosis
MRI spine is the investigation of choice for confirming intervertebral disc prolapse and assessing the extent of disc herniation, degree of neural compression, and nerve roots affected.
However, MRI is not routinely performed in patients with uncomplicated low back pain or sciatica solely to confirm or exclude an intervertebral disc prolapse.
This is because degenerative disc abnormalities are common in asymptomatic individuals, and MRI findings do not necessarily correlate with symptoms and may not influence treatment.
NICE: DO NOT routinely offer imaging (including lumbar X-rays and MRI) in a non-specialist setting, assuming there are no red flags suggesting a serious condition (e.g. cauda equina syndrome). Only consider imaging in a specialist setting if the result is likely to change management.
See the Mechanical Low Back Pain (LBP) and Sciatica and Lumbosacral Radiculopathy articles for more information.
Management
Management is guided by the patient’s clinical presentation, rather than the MRI finding alone. An incidental disc bulge or prolapse without symptoms does not require treatment.
Most symptomatic cases presenting as uncomplicated mechanical low back pain or sciatica are managed conservatively (see the Mechanical Low Back Pain (LBP) and Sciatica and Lumbosacral Radiculopathy articles, respectively)
Management options:
| Conservative management |
|
| Interventional management |
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| Operative management |
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