Effects of 830 nm continuous wave laser diode irradiation on median nerve function in normal subjects

Abstract

The presence, magnitude, and nature of the effect that low intensity laser irradiation has on nerve function, growth, and repair constitute a contentious area of research. We have addressed one aspect of this controversy by systematically examining the influence of 830 nm laser radiation on median nerve function. In particular, we investigated median nerve motor and sensory distal latencies, action potential amplitudes, action potential areas, and conduction velocities as well as dorsal hand skin temperatures in 33 normal subjects in a double-blinded, randomized controlled study. All subjects received identical treatment: 30 seconds of "irradiation" at 10 points over the course of the right median nerve (five sites on the forearm and five sites distal to the wrist crease) with either an active (1.2 J/point) or inactive (0 J/point) 40 mW 830 nm continuous wave IR laser diode. Latencies, conduction velocities, amplitudes, areas, and skin temperatures were collected bilaterally at a baseline immediately prior to irradiation and at intervals of 1, 5, 10, 15, 20, and 30 minutes following treatment. Analysis of the results reveals that motor and sensory distal latencies were decreased in the treated limbs of the laser-treated group relative to the control group by 3-4% (P < .016 and .046, respectively, rank sum test). No significant differences in these quantities were found between the limbs within either group. Similarly, no alterations of action potential amplitudes, action potential areas, forearm conduction velocities, or skin temperatures were detected within or between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of effect of pulsed low-intensity infrared (820 nm) laser irradiation on nerve conduction in the human superficial radial nerve

“…These latter studies have indicated significant laser-mediated increases in median nerve conduction latencies compared with placebo and that such effects are apparently dose dependent [14] and localised to the site (and ipsilateral side) of irradiation [13]. Furthermore, application of higher radiant exposures with this same model (1.2 J per point; ∼12 J/cm 2 ) has been found by Basford's group to decrease nerve conduction latencies [16]. In contrast to these generally positive findings, assessment of the potential relevance of pulsing by using a modulated output source (820 nm; 40 mW average output) found no significant laser-mediated effects when compared with sham controls [15].…”

Stimulation Effect of Low Level Laser Therapy on Sciatic Nerve Regeneration in Rat

“…[26][27][28] Most reports on the effect of LLLT on PNS injury are in cases of axonotmesis. [13][14][15][18][19][20][21]25,[29][30][31][32] However, promising results have been obtained in severe cases of neurotmesis when LLLT is used in combination with or Gore-Tex tubes. 27 The cutaneous branch consisted of 400 myelinated and 1800 unmyelinated afferent axons.…”

Efeitos local e sistêmico do laser de baixa potência no limiar de dor por pressão em indivíduos saudáveis

“…No entanto, uma possível explicação seria que a irradiação do laser (3 J) inibiu as fibras nervosas aferentes de grande diâmetro, promovendo enfraquecimento do sistema inibitório espinhal 33 . Outra hipótese seria que o laser teria alterado a condução nervosa periférica 21 , porém com este estudo essa hipótese não pôde ser confirmada devido a não mensuração dessa variável.…”

“…O LBP vem sendo usado com o objetivo de promover efeitos analgésicos [4][5][6][7] , modulação da inflamação [8][9][10][11][12][13][14] , efeitos cicatriciais [15][16][17] e vasodilatadores locais 19 , sem os riscos de produção de calor e dano ao tecido irradiado 7,18,19 . A ação analgésica da laserterapia pode ser explicada a partir de algumas hipóteses: modulação dos processos inflamató-rios 3,9,20 , alteração da excitação e condução nervosa dos neurônios periféricos 21,22 , liberação de opioides endógenos 23,24 e aumento na síntese de serotonina 4,25 . Acredita-se também que o LBP pode gerar um efeito sistêmico pelas mudanças metabólicas tanto no local da irradiação como em áreas mais distantes devido ao fato de substâncias serem liberadas na circulação sanguínea 26,27 , como também ocorrer vasodilatação e aumento do fluxo sanguíneo [28][29][30][31] .…”