An intervertebral disc (more commonly just called a disc) refers to the cushion that is between the bones called vertebrae (bones of the spine). To be even more specific, the disc lies in the frontmost part of the spine in between the part of the vertebra call vertebral body.
Figure: Front view of the disc and vertebral body
The disc comprise of an outer ring, called the annulus, and the inner jelly-like substance called the nucleus pulposus. It acts like a shock-absorber and distributes the load when there is pressure on the spine. Physical activities such as weight lifting can increase the pressure on the spine and in the intervertebral disc. You may be surprised to know that daily activities such as prolonged sitting, can also cause an increase in the pressure on the lower part of the spine and in the discs of the lower back (lumbar spine).
A slipped disc is a condition where the cushion (called the intervertebral disc) between the bones of the spine (vertebral body) has slipped out of its usual confines. This can happen with or without a tear in the outer ring (annulus). Another term for a slipped disc is herniated disc or herniated nucleus pulposus, referring to the jelly-like substance inside that has come out.
Slipped discs or herniated discs occur in the neck (cervical slipped disc) or in the low back (lumbar slipped disc). Rarely, it occurs in the middle of the spine (thoracic slipped disc).
Figure: Side view of the disc and vertebral body
A slipped disc or a herniated disc, can cause pain in the area where it has occurred. This can cause neck pain or low back pain. If the disc touches or puts pressure on the nerve, then pain can go down the arms or legs. A herniated disc in the neck can cause pain down the arms while a disc in the lower back can cause pain down the legs. There can be associated tingling, numbness or weakness of the arms or legs which can affect physical activities or even daily activities.
When symptoms suggesting pressure on the nerves occur, medical advice should be sought. Medical advice should also be sought when neck and back pain affects daily activities (such as sleeping), occurs for a prolonged duration, and is not relieved with conservative treatment (non-operative treatment) measures such as painkillers or physical therapy (physiotherapy). Urgent medical advice should be sought if there is any difficulty in urinating or urinary retention (which may mean there is severe pressure on the nerves to the bladder from the herniated disc). If the affected nerves are not decompressed (to be freed) quickly, permanent loss of bladder function may occur.
Herniated discs in the neck can cause a compression of the spinal cord. In addition to pain, tingling or numbness of the arms or legs, patients may experience problems with dexterity (such as buttoning shirts or using chopsticks) as the affected nerves are compressed. Walking may also become unsteady and may be noticeable while performing daily activities. Prolonged pressure on the nerves in the spinal cord can cause damage. Medical advice should be sought if one experiences these symptoms.
An annular tear alone is not the same as a slipped disc. The annulus is the outer ring of the disc. An annular tear, also sometimes referred to as annular fissure, is a tear of the lining of the intervertebral disc. Pain at the area of tear may result in low back pain or neck pain. Conservative treatment (non-operative treatment) of annular tears with medications and physical therapy (physiotherapy) can give good pain relief. A slipped disc or herniated disc occurs when the disc material has slipped out through the tear in the outer ring of the disc ie the annulus.
A slipped disc can be diagnosed accurately via an MRI (magnetic resonance imaging). This is a non-invasive scan and it does not involve any radiation. Clear images of the herniated disc and any pressure on the nerves or spinal cord can be visualised. Whether it be conservative treatment (non-operative treatment) or operative treatment, the MRI is useful to guide the treatment of a slipped disc or herniated disc.
Figure: An MRI showing a slipped disc in the low back (lumbar spine)
Figure: An MRI showing a slipped disc in the neck (cervical spine)
Treatment of a slipped disc is often done successfully using non-operative measures (conservative treatment). Good pain relief from a slipped disc occur when different modalities of treatment are combined. Medications, such as muscle relaxants and anti-inflammatory medications, a short period of rest, followed by early initiation of physical therapy (physiotherapy) can provide excellent pain relief in many patients. Short-term usage of anti-inflammatory medications is usually well tolerated. Caution should be exercised however, when anti-inflammatory medications need to be taken for prolonged periods due to potential side effects. As pain gets better, most patients are able to return to their daily activities and later on gradually resume more strenuous physical activities.
Operative treatment of a slipped disc may be indicated when conservative treatment (non-operative treatment) for a slipped disc has failed. This is because prolonged pressure on the nerves or spinal cord can cause irreversible damage to the nerves or spinal cord. If there is associated weakness of the arms or legs and the MRI shows significant compression (pressure on the nerves or spinal cord) from a slipped disc, surgery sometimes may need to be done early to preserve the remaining nerve or spinal cord function and potentiate recovery.
Surgical treatment of a slipped disc involves removing the offending herniated disc material and create a space for the affected nerve(s) or spinal cord such that they can recover. Surgical treatments of a slipped disc can often be done as a minimally-invasive procedure using a small incision (cut). The advantage of a minimally invasive decompression (to free the nerve) and discectomy (removal of the herniated disc affecting the nerve) is decreased post-operative pain and faster recovery. Minimally invasive decompression and discectomy may even be done as a day surgery procedure. Physical therapy (physiotherapy) may be required post-operatively.
In some cases, an injection (epidural steroid) may be done at the place of the offending slipped disc, to decrease the associated inflammation to give good pain relief.
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