Herniated discs, also known as slipped or ruptured discs, occur when the soft inner gelatinous nucleus pulposus of an intervertebral disc pushes through a tear in the outer fibrous annulus fibrosis. This can cause pain, numbness, or weakness if the extruded disc material puts pressure on nearby nerves. In some cases, herniated discs can gradually resorb and dissolve over time without the need for surgery.
What is a herniated disc?
The spine is made up of 33 vertebrae stacked on top of each other, separated by discs which act as shock absorbers. Each disc has a tough outer layer called the annulus fibrosis and a soft, jelly-like center called the nucleus pulposus.
A herniated disc occurs when the nucleus pushes out through a weak spot or tear in the annulus. This causes the disc to bulge out beyond its normal space. A herniated disc can occur in any part of the spine, but is most common in the lower back (lumbar spine) and neck (cervical spine).
Types of herniated discs
There are several classifications of herniated discs depending on the location and severity of the rupture:
- Protruding: The nucleus bulges out but the annulus is still intact.
- Extruded: The nucleus breaks through the annulus and leaks out into the spinal canal.
- Sequestered: A fragment of the nucleus breaks off entirely and becomes a separate, loose fragment in the spinal canal.
Symptoms
Symptoms of a herniated disc can include:
- Local or radiating pain in the area supplied by an affected nerve root
- Numbness or tingling in the arms or legs
- Muscle weakness in the arms or legs
- Loss of reflexes
- Cauda equina syndrome – rare severe compression causing loss of bowel/bladder control
However, it’s important to note that herniated discs do not always cause symptoms. Many people have herniations that are detected incidentally on imaging but which do not produce any noticeable problems.
How do herniated discs heal and dissolve over time?
In many cases, herniated discs can gradually resolve without surgery over weeks to months. There are several processes that allow this natural disc resorption to occur:
Retraction of disc material
The extruded disc material can spontaneously retract back into the disc over time, relieving pressure on the nerve roots. However, complete retraction to the disc’s original position is rare.
Dehydration
The nucleus pulposus is approximately 80% water. Once the herniated material breaches the annulus, it is exposed to the biomechanical pressures outside the disc which can cause the tissue to desiccate and dehydrate.
Inflammatory resorption
The body triggers an inflammatory response to break down and dissolve the foreign disc material. Macrophages and cytokines are recruited to phagocytize and enzymatically degrade the herniated tissue.
New matrix formation
Fibroblasts migrate to the site and synthesize scar tissue composed of collagen and proteoglycans around the residual disc material to wall it off.
This fibrotic tissue remodels over time and can lead to thickening and hyalinization, converting the remaining disc tissue into an immobilized mass separated from the spinal nerve.
Factors affecting resorption rate
Several factors influence the rate and extent to which a herniated disc will spontaneously regress:
- Size – Smaller herniations have better rates of resolution
- Location – Extruded fragments fare better than sequestered
- Age – Younger individuals have better resorption
- Smoking – Impedes the resorption process
Larger herniations that cause significant nerve compression are less likely to regress on their own compared to smaller protrusions. However, even large extrusions and sequestrations can gradually dissipate over time.
Does a resolved herniation restore normal spinal anatomy?
Although herniated disc resorption can reduce symptoms, the affected disc is permanently damaged and does not return to normal. The processes involved in resolution lead to scarring and altered biomechanics. Key changes include:
- The annular tear remains even after regression of the herniation
- The desiccated, fibrotic disc tissue lacks the pliability and shock absorption of a healthy disc
- The fibrotic scar tissue reduces disc height
- Segmental stiffness increases due to disc degradation
These factors can accelerate degenerative disc disease at the affected spinal level. Patients who experience a herniation may have recurrent episodes and an elevated risk of developing spinal stenosis later in life.
Can a resolved herniation recur or get worse?
Yes, it is possible for a herniated disc that has regressed to recur or become symptomatic again in the future. This occurs because:
- The annular defect remains as a weak spot vulnerable to re-herniation
- Further degenerative changes can develop in the disc over time
- A new injury or strain can cause re-herniation through the damaged annulus
Patients who have improvement after a herniation should take care to avoid re-injury through activities that strain the back. Proper lifting techniques and core muscle strengthening can help prevent recurrence.
When is surgery necessary for a herniated disc?
Surgery is generally only considered if conservative treatment fails and the herniation continues causing significant neurological symptoms. Surgical options include:
Discectomy
Removes the protruding portion of the disc through an incision in the back. This decompresses the nerve root but does not repair the annular tear.
Microdiscectomy
Uses a smaller incision and microscope to remove disc material. Less invasive with quicker recovery.
Laminectomy
Removes part of the bony lamina to increase space for the nerves. Often done with a discectomy.
Spinal fusion
Joins two or more vertebrae together to eliminate motion and stabilize the spine. Used for recurrent herniations or severe degeneration.
Surgery has associated risks including infection, bleeding, and nerve injury. However, it can provide rapid relief in cases where conservative therapy fails to alleviate neurological symptoms.
Conclusion
The outlook for herniated discs ultimately depends on the severity of nerve compression. Mild disc protrusions often dissolve gradually over several months through dehydration, inflammatory resorption, and scar tissue remodeling. Larger extrusions or fragmentations have a lower rate of spontaneous regression but can still dissipate in some cases. Surgery may be necessary if conservative treatment fails to relieve neurological symptoms. Patients who experience herniated disc resolution can reduce their risk of recurrence by avoiding re-injury and maintaining core and back muscle strength.
