Pain, neurogenic inflammation and symmetry in medical practice

Symmetry is a cardinal feature of certain painful and ineammatory diseases, including rheumatoid arthritis and psoriasis. This symmetry does not occur by chance, but it is as yet unexplained. It has been hypothesized by this group and others that mechanisms of neurogenic ineammation could explain both this symmetrical distribution and the chronicity of these diseases. A recent review has demonstrated contralateral responses in the nervous system to unilateral neurological insults. These responses were topographically precise and stimulus speciec in nature. This article details similar responses that have been observed to ineammatory stimuli in animal models. The role of pro-ineammatory neuropeptides, such as substance P, in these pathways is discussed. The hypothesis could be tested in both animals and humans.