Evidence for the existence of low-energy laser bioeffects on the nervous system.

The reported effects of low-energy laser irradiation on the nervous system are manifested in alterations in cellular and extracellular biochemical constituents and reactions, as well as in changes in cell division rates. These bioeffects were observed in both in vivo and in vitro experiments. Other observed phenomena relate to the function of the nervous system and consist mainly of induced alteration in electrical conduction, stimulation thresholds, and behavioral effects. Clinical aspects of low-energy laser bioeffects relate mainly to pain mitigation and postponement of the posttraumatic neural degeneration processes. Many of the reported observations were obtained by experiments apparently conducted according to less than rigorous scientific criteria, and some could not be duplicated. On the whole, however, there is little doubt that low-energy laser irradiation exerts some effects on the nervous system under specific conditions of irradiation and tissue exposure via a mechanism which is probably photochemical in nature.