Pain and Connective Tissue Properties: Radicular Pain
Radicular or neurogenic pain is produced when the nerve root or dorsal root ganglia are involved in symptom production. This is the product of pressure on nerve roots that are already inflammed or irritated, not on normal nerve roots. Although sudden onset of sciatica does occur, experimentally tension or pressure has only reproduced radicular pain on sensitised, not normal nerve roots.
It is different in quality from somatic pain. Radicular pain is severe and shooting in quality, felt along a narrow strip, and this different in quality from the vague, dull aching associated with somatic-referred pain. All nerve root pain will be felt in the leg, and its always referred pain; oftne the leg pain will be worse than any back pain that may be present. However, all leg pain is not nerve root pain. Radicular pain tends to be distributed in dermatomal patterns, with the L4, L5, and S1 nerve roots most commonly affected. Typically pain from the L4 is felt down the anterior aspect of the thigh and leg, L5 is down the lateral aspect and S1 down the posterior aspect--however, variety exists.
Pain and Connective Tissue Properties: Somatic Pain
Somatic Pain
Somatic structures include the intervertebral disc, posterior longitudinal ligament, SIJ, facet joint capsule, etc. Only pain that originates from cutaneous tissue is felt localised to the area; all pain that stems from deep somatic structures is referred pain to a greater or lesser extent. The deeper the structure the more difficult it is to localise the pain source--therefore, most musculoskeletal pain is referred pain to a varying degree. Referred pain simply reflects the lack of localising information available with nociceptor activity from deep structures. the quality of somatic referred pain is deep and aching in quality, vague, and hard to localise.
