Prolapsed inter-vertebral disc
This is the most common cause of specific back pain.
A prolapsed disc occurs when the annulus is damaged or torn (typically by a twisting movement of the back). The nucleus pulposus is squeezed out, or prolapses and may compress a nerve root in the space between the vertebra and surrounding ligaments typically causing sciatica.
Lumbar discs in the lower back are the ones most likely to be damaged and prolapse. Whether or not sciatica develops, depends upon the position of the prolapse and the size of the spinal canal.
If there is sufficient space for the prolapsed disc to occupy, then back pain alone will occur. However, if the space is too small to accommodate the prolapsing disc, then pressure (or compression) of the nerve root will occur. This will cause leg pain and/or other symptoms in the specific region supplied by the nerve.
Nerve root entrapment
This occurs when there is pressure on a specific nerve root (or roots), entrapping or pinching the nerve. This interferes with the function of the nerve, and is interpreted by the brain as pain or other symptoms (such as tingling or numbness) in the distant area supplied by the nerve.
Depending upon the degree of pressure on the nerve root, weakness of leg muscles, muscle wasting and reduction or loss of reflexes may occur.
Symptoms
The main symptom of a prolapsed disc is pain, although this may not always be the presenting symptom. Pain is usually experienced in the lower lumbar region and in the buttocks and thighs. It may spread up the spine as well.
If the disc prolapse is compressing a nerve root, typically the sciatic nerve, then more distant pain affecting the whole of one leg in the distribution of the sciatic nerve will occur.
This distant experience of pain is known as radiation. Typically, sciatic pain radiates into the buttocks and down the back and outer aspect of the thigh and calf to the foot and toes.
Other symptoms e.g. numbness and tingling (paraesthesia) in the affected leg are also common. In severe cases, bowel and bladder function can be affected.
If the prolapsed disc occurs in the neck, usually between the 6th and 7th cervical vertebra, it results in neck pain. There pain may radiate down the neck along the upper arm and shoulder on the same side and if severe may be associated with numbness and tingling (paraesthesia) and or weakness of the upper limb.
Clinical findings
These will vary depending upon which nerve root in the lumbar spine is compressed.
The following features are commonly present, but may vary in severity:
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Where true nerve root compression is present movements are restricted and painful in some directions, or on the affected side, whilst in other directions they show very little restriction or pain.
Disabling effects
In the acute or initial phase of a prolapsed disc, the onset of back and/or leg pain may render the person temporarily immobile. This severe restriction is usually short lived, lasting from a few days to a maximum of 2 weeks, and the individual should be encouraged to resume activity at the earliest opportunity.
Such a person may experience some difficulty in bending. However, this can usually be overcome by bending at the hips and knees.
As long as hip and knee function are preserved, and a functional range of hip and knee movements are present, any difficulty in bending forwards (flexion) should not prevent a person from dressing independently. The ability to rise from sitting should not be impaired in the majority of cases.
Some difficulty may be experienced with lower garment dressing, especially shoes and socks, but technical aids are available to overcome this if present. Similarly inability to bend the spine would not normally prevent an individual from attending to their toilet needs independently.
Only those who develop severe nerve root compression will have significant restrictions of walking, or ability to care for themselves (e.g. needing assistance with bathing, dressing/undressing lower garments, using stairs, rising from a normal height chair, preparing a main meal and attending to toilet needs). Marked neurological signs and muscle wasting should be present in such cases.
In severe cases with foot drop and significant muscle wasting, an increased risk of falls may be present.
Treatment
The recommended treatment for patients with a prolapsed inter-vertebral disc, including those with nerve root entrapment, is to remain as active as possible. Regular pain relief medication should be taken. Some individuals find the application of heat and cold to the affected area beneficial in the acute phase.
As stated earlier, some people may be confined to bed in the acute stage of a prolapsed disc, but this should not be considered a treatment. A return to activities after 48 hours should be encouraged in the majority of cases, although a few individuals may require bed rest for 1-2 weeks.
If after four to six weeks from onset, there is clear evidence of nerve root involvement with:
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an urgent specialist referral should be sought.
Following specialist investigation, if sciatica can be proven to arise from a prolapsed inter-vertebral disc causing nerve root pressure, surgery may be indicated. (About one percent (1%) of prolapsed disc cases requires surgery)
Advances in surgical techniques such as micro-discectomy mean that in some cases surgery can be performed with only a single night in hospital, or even as a day case.
In cases of disc prolapse in the cervical region, most people recover with treatment. The majority are managed conservatively with interventions such as anti-inflammatory medication and physical therapy. However, surgery is indicated in those cases of deteriorating neurological function, or intractable neck pain.
Amended November 2010
