Antinociceptive effect of linear polarized 0.6 to 1.6 microm irradiation of lumbar sympathetic ganglia in chronic constriction injury rats.

Abstract--Linear polarized near-infrared light created with linear polarized near-infrared light therapy equipment (Super Lizer[TM] HA-550, Tokyo Iken Co, Ltd, Tokyo, Japan) has been used for the treatment of various painful disorders in Japan. Irradiation near the stellate ganglion with a Super Lizer (ISGL) is an especially notable therapeutic method used with stellate ganglion block (SGB) or substitutes for SGB. ISGL is a safe, simple, well-tolerated, and effective treatment. We examined the effects of irradiation with a Super Lizer applied to an area near the lumbar sympathetic ganglia on the ligated side in a chronic constriction injury (CCI) model, which is believed to be an animal model of complex regional pain syndrome (CRPS). Rats showing thermal hyperalgesia in a radiant heat test 1 wk postoperatively were used in Experiments 1 and 2: (1) Thermal hyperalgesia of irradiation group (n = 11) was less than that of the control or nonirradiation (n = 11) group at 1, 3, and 8 h after irradiation; however, the effect disappeared 12 h after irradiation. (2) Daily irradiation (n = 16) and 1 wk (n = 14) from 7 days after nerve ligation significantly shortened the interval from thermal hyperalgesia until recovery. Rats showing mechanical hyperalgesia in the von Frey hair test 1 wk postoperatively were used in Experiment 3: 1 wk irradiation beginning 7 days after nerve ligation (n = 9) did not promote the recovery from mechanical hyperalgesia. We speculate that repeated ISGL may be more effective than a single ISGL in alleviating pain in CRPS patients. We cannot explain the discrepancy between the results obtained in Experiments 2 and 3. We believe the results of this study are relevant to the effect of ISGL for patients with upper-limb CRPS: irradiation near the lumbar sympathetic ganglia of the rat is effective for thermal but not mechanical pain in CCI. Key words: chronic constriction injury model, complex regional pain syndrome, control study, ISGL, linear polarized near-infrared light, reflex sympathetic dystrophy, rehabilitation, stellate ganglion block, Super Lizer[TM]. INTRODUCTION Complex regional pain syndrome (CRPS) causes intractable chronic pain. CRPS occurs after minor trauma, such as an injection, a drip infusion, or iatrogenic puncture, as well as after surgery or accidental injury. Among many treatments, stellate ganglion block (SGB) is one of the most effective treatments. However, SGB sometimes causes complications such as infection, nerve injury, bleeding, and pneumothorax [1]. Other serious complications such as shock, respiratory arrest, and death [2] can occur, although they are uncommon. Furthermore, some patients fear the procedure, which may require emergency treatment equipment and techniques, including intubation. Because of such limitations, only trained anesthesiologists usually perform SGB. In Japan, linear polarized near-infrared light created with linear polarized near-infrared light therapy equipment (Super Lizer[TM] HA-550, Tokyo Iken Co, Ltd, Tokyo, Japan) has been used mainly to treat painful disorders. Many open studies and case reports showed that direct irradiation or irradiation near the stellate ganglion with a Super Lizer[TM] (ISGL) was effective for temporomandibular joint pain, frozen shoulder, osteoarthritis, rheumatoid arthritis, thalamic pain, postherpetic neuralgia, etc. [3-8]. Recently, ISGL has often been used with SGB or substitutes for ISGB to treat patients with upper-limb CRPS [9-11]. Only one small, short-term double-blind study demonstrated the efficacy of the ISGL for patients with CRPS [12]. No long-term double-blind studies have demonstrated its efficacy in these patients. Thus, the present study examined the long-term efficacy of irradiation near the lumbar sympathetic ganglia with a chronic constriction injury (CCI) model [13], which is believed to be an animal model of CRPS [14-15]. METHODS Linear Polarized Near-Infrared Light Therapy Equipment The linear polarized near-infrared light therapy equipment [16-17] consists of a power source, light source, light-guiding system, and lens unit. …