Corticosteroid injections by epidural or root blocks are commonly used to treat leg and back pain and may indicate that in some cases there may be an inflammatory contribution to the pain. In disc material removed from humans during operation has been found heightened levels of inflammatory chemicals which could be affected by steroid use. These inflammatory chemicals may increase degeneration of discs and sensitise the fibres of the outer disc walls. Some chemicals may also sensitise the discs by elevating reactivity of sensory nerves, inhibit the creation of new proteoglycans which hold water in the discs and may contribute to disc degeneration.
The lumbar spinal motion segments have nerve structures supplying them which can be come hypersensitised to incoming stimuli, creating pain from what would have formerly been normal sensations. Sciatic leg pain is known as nerve root or radicular pain and can be caused by irritation, inflammation or compression of the spinal nerves as they exit the spinal cord. Why nerve root pain occurs has not been established but candidates are an impoverishment of blood supply, inflammatory reactions, axon dysfunction from compression and biochemical agents. The compression that occurs may have greater effects on spinal nerve roots than other nerves and result in more significant internal nerve swelling.
The nerve may suffer from excessive inflow of fluid secondary to compression, which results in internal nerve swelling from the increased pressure. This can slow the flow through capillaries and allow fibrosis to develop in the nerve. Nutrition to the spinal nerve roots comes via the cerebrospinal fluid to the tune of about 60% and nerve fibrosis interferes with this, making the nerve more responsive and perhaps more likely to suffer compression symptoms due to the increased reactivity of the nerves. Blocking or reducing the blood supply can cause pain in these nerves, unlike the more usual loss of motor and sensory functions in compression of peripheral nerves.
Development of nerve roots signs and symptoms is more likely if the nerve suffers compression which comes on quickly rather than slowly which may indicate why many older people, who have compromised nerve exits, do not complain of symptoms. In experimental research work significant inflammation has been noted when disc material is placed in the epidural space of dogs and nerves may suffer damage in contact with disc material. Injection of TNF, tumour necrosis factor, into a nerve mimics the changes which occur in nerve root syndromes. Another contributory cause which has been proposed is an inflammatory reaction of an auto-immune cause but this idea has yet to be substantiated.
The spinal facet joints are formed from a joint process of a vertebra above and one below and are synovial joints like many other bodily joints. These joints respond to damage and injury like the rest of our joints and exhibit stiffness, pain, movement loss, muscle spasm and finally degenerative changes. The facet joints develop degenerative changes secondary to the changes which occur in the disc segments themselves. The facet joint capsules, well innervated fibrous bags, have been shown experimentally by injection to be able to refer pain into the legs, thoracic spine and arms, depending on their location. Established sources of pain, facet joints are known to be involved in large proportions of neck, lumbar and thoracic pain.
The sacro-iliac joint between the pelvis and the sacrum is a large synovial joint known to refer painful and other symptoms to the groin, the leg, low back and buttock. In patients with chronic low back pain, experimental testing has shown involvement of the sacroiliac joint in their pain problems in from two to thirty percent of cases. Pain receptors exist in muscular tissue also and respond to stretching and pressure as well as other inputs. If muscles are overburdened either repetitively or in a strain at one point they will respond by shortening, increasing their tension and being painful.
In posturally abnormal or injured muscles a pain syndrome (myofascial pain syndrome) can occur whereby the muscle becomes tight, painful and exhibits trigger points. Palpation of muscle tissue can identify trigger points as firm and tender nodular areas which refer pain out into nearby defined regions. - 14130
The lumbar spinal motion segments have nerve structures supplying them which can be come hypersensitised to incoming stimuli, creating pain from what would have formerly been normal sensations. Sciatic leg pain is known as nerve root or radicular pain and can be caused by irritation, inflammation or compression of the spinal nerves as they exit the spinal cord. Why nerve root pain occurs has not been established but candidates are an impoverishment of blood supply, inflammatory reactions, axon dysfunction from compression and biochemical agents. The compression that occurs may have greater effects on spinal nerve roots than other nerves and result in more significant internal nerve swelling.
The nerve may suffer from excessive inflow of fluid secondary to compression, which results in internal nerve swelling from the increased pressure. This can slow the flow through capillaries and allow fibrosis to develop in the nerve. Nutrition to the spinal nerve roots comes via the cerebrospinal fluid to the tune of about 60% and nerve fibrosis interferes with this, making the nerve more responsive and perhaps more likely to suffer compression symptoms due to the increased reactivity of the nerves. Blocking or reducing the blood supply can cause pain in these nerves, unlike the more usual loss of motor and sensory functions in compression of peripheral nerves.
Development of nerve roots signs and symptoms is more likely if the nerve suffers compression which comes on quickly rather than slowly which may indicate why many older people, who have compromised nerve exits, do not complain of symptoms. In experimental research work significant inflammation has been noted when disc material is placed in the epidural space of dogs and nerves may suffer damage in contact with disc material. Injection of TNF, tumour necrosis factor, into a nerve mimics the changes which occur in nerve root syndromes. Another contributory cause which has been proposed is an inflammatory reaction of an auto-immune cause but this idea has yet to be substantiated.
The spinal facet joints are formed from a joint process of a vertebra above and one below and are synovial joints like many other bodily joints. These joints respond to damage and injury like the rest of our joints and exhibit stiffness, pain, movement loss, muscle spasm and finally degenerative changes. The facet joints develop degenerative changes secondary to the changes which occur in the disc segments themselves. The facet joint capsules, well innervated fibrous bags, have been shown experimentally by injection to be able to refer pain into the legs, thoracic spine and arms, depending on their location. Established sources of pain, facet joints are known to be involved in large proportions of neck, lumbar and thoracic pain.
The sacro-iliac joint between the pelvis and the sacrum is a large synovial joint known to refer painful and other symptoms to the groin, the leg, low back and buttock. In patients with chronic low back pain, experimental testing has shown involvement of the sacroiliac joint in their pain problems in from two to thirty percent of cases. Pain receptors exist in muscular tissue also and respond to stretching and pressure as well as other inputs. If muscles are overburdened either repetitively or in a strain at one point they will respond by shortening, increasing their tension and being painful.
In posturally abnormal or injured muscles a pain syndrome (myofascial pain syndrome) can occur whereby the muscle becomes tight, painful and exhibits trigger points. Palpation of muscle tissue can identify trigger points as firm and tender nodular areas which refer pain out into nearby defined regions. - 14130
About the Author:
Jonathan Blood Smyth is the Superintendent of Physiotherapy at an NHS hospital in the South-West of the UK. He writes articles about back pain, neck pain, and injury management. If you are looking for physiotherapists in Manchester visit his website.
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