Acute electrophysiological effect of pulsed gallium-arsenide low-energy laser irradiation on isolated frog sciatic nerve

Peripheral nerve injury and myelination: Potential therapeutic strategies

Traumatic peripheral nerve injury represents a major clinical and public health problem that often leads to significant functional impairment and permanent disability. Despite modern diagnostic procedures and advanced microsurgical techniques, functional recovery after peripheral nerve repair is often unsatisfactory. Therefore, there is an unmet need for new therapeutic or adjunctive strategies to promote the functional recovery in nerve injury patients. In contrast to the central nervous system, Schwann cells in the peripheral nervous system play a pivotal role in several aspects of nerve repair such as degeneration, remyelination, and axonal growth. Several non-surgical approaches, including pharmacological, electrical, cell-based, and laser therapies, have been employed to promote myelination and enhance functional recovery after peripheral nerve injury. This review will succinctly discuss the potential therapeutic strategies in the context of myelination following peripheral neurotrauma.

Effect of low-level laser therapy (685 nm, 3 J/cm(2)) on functional recovery of the sciatic nerve in rats following crushing lesion

Previous studies have shown that low-level laser therapy (LLLT) promotes posttraumatic nerve regeneration. The objective of the present study was to assess the efficacy of 685-nm LLLT at the dosage of 3 J/cm(2) in the functional recovery of the sciatic nerve in rats following crushing injury. The left sciatic nerves of 20 male Wistar rats were subjected to controlled crush injury by a hemostatic tweezers, and the rats were randomly allocated into two experimental groups as follows: control group and laser group. Laser irradiation (685 nm wavelength; 15 mW, CW, 3 J/cm(2), spot of 0.028 cm(2)) was started on the postsurgical first day, above the site of injury, and was continued for 21 consecutive days. Functional recovery was evaluated at 3 weeks postoperatively by measuring the sciatic functional index (SFI) and sciatic static index (SSI) at weekly intervals. The treated rats showed improvement in motion pattern. The SFI and SSI results were significant when comparing two groups on the 14th and 21st postoperative days (p < 0.05). There were intra-group differences detected in laser group in different periods (p < 0.05). Low-level laser irradiation, with the parameters used in the present study, accelerated and improved sciatic nerve function in rats after crushing injury.

Effects of laser therapy in peripheral nerve regeneration

OBJECTIVE:

The influence of dose of low power lasertherapy (AsGaAl, 830 nm) on the regeneration of the fibular nerve of rats after a crush injury was evaluated by means of the functional gait analysis and histomorphometric parameters.

METHODS:

Controlled crush injury of the right common fibular nerve, immediately followed by increasing doses (G1: no irradiation; G2: simulated; G3: 5 J/cm²; G4: 10 J/cm²; G5: 20 J/cm²⁾ laser irradiation directly on the lesion site for 21 consecutive days. Functional gait analysis was carried out at weekly intervals by measuring the peroneal/fibular functional index (PFI). The animals were killed on the 21^st postoperative day for removal of the fibular nerve, which was prepared for the histomorphometric analysis.

RESULTS:

The PFI progressively increased during the observation period in all groups, without significant differences between them (p>0.05). The transverse nerve area was significantly wider in group 2 than in groups 3 and 4, while fiber density was significantly greater in group 4 than in all remaining groups.

CONCLUSION:

The low power AsGaAl laser irradiation did not accelerate nerve recovery with any of the doses used. Level of Evidence I, Therapeutic Studies Investigating the Results of Treatment.

Lack of effectiveness of laser therapy applied to the nerve course and the correspondent medullary roots

OBJECTIVE:

To investigate the influence of low intensity laser irradiation on the regeneration of the fibular nerve of rats after crush injury.

METHODS:

Twenty-five rats were used, divided into three groups: 1) intact nerve, no treatment; 2) crushed nerve, no treatment; 3) crush injury, laser irradiation applied on the medullary region corresponding to the roots of the sciatic nerve and subsequently on the course of the damaged nerve. Laser irradiation was carried out for 14 consecutive days.

RESULTS:

Animals were evaluated by functional gait analysis with the peroneal functional index and by histomorphometric analysis using the total number of myelinated nerve fibers and their density, total number of Schwann cells, total number of blood vessels and the occupied area, minimum diameter of the fiber diameter and G-quotient.

CONCLUSION:

According to the statistical analysis there was no significant difference among groups and the authors conclude that low intensity laser irradiation has little or no influence on nerve regeneration and functional recovery. Laboratory investigation.

Neural stimulation with optical radiation

This paper reviews the existing research on infrared neural stimulation, a means of artificially stimulating neurons that has been proposed as an alternative to electrical stimulation. Infrared neural stimulation (INS) is defined as the direct induction of an evoked potential in response to a transient targeted deposition of optical energy. The foremost advantage of using optical radiation for neural stimulation is its spatial resolution. Exogenously applied or trans-genetically synthesized fluorophores are not used to achieve stimulation. Here, current work on INS is presented for motor nerves, sensory nerves, central nervous system, and in vitro preparations. A discussion follows addressing the mechanism of INS and its potential use in neuroprostheses. A brief review of neural depolarization involving other optical methods is also presented. Topics covered include optical stimulation concurrent with electrical stimulation, optical stimulation using exogenous fluorophores, and optical stimulation by transgenic induction of light-gated ion channels.

Effect of pulsing in low-level light therapy

BACKGROUND AND OBJECTIVE

Low level light (or laser) therapy (LLLT) is a rapidly growing modality used in physical therapy, chiropractic, sports medicine and increasingly in mainstream medicine. LLLT is used to increase wound healing and tissue regeneration, to relieve pain and inflammation, to prevent tissue death, to mitigate degeneration in many neurological indications. While some agreement has emerged on the best wavelengths of light and a range of acceptable dosages to be used (irradiance and fluence), there is no agreement on whether continuous wave or pulsed light is best and on what factors govern the pulse parameters to be chosen.

STUDY DESIGN/MATERIALS AND METHODS

The published peer-reviewed literature was reviewed between 1970 and 2010.

RESULTS

The basic molecular and cellular mechanisms of LLLT are discussed. The type of pulsed light sources available and the parameters that govern their pulse structure are outlined. Studies that have compared continuous wave and pulsed light in both animals and patients are reviewed. Frequencies used in other pulsed modalities used in physical therapy and biomedicine are compared to those used in LLLT.

CONCLUSION

There is some evidence that pulsed light does have effects that are different from those of continuous wave light. However further work is needed to define these effects for different disease conditions and pulse structures.

In vivo low-level light therapy increases cytochrome oxidase in skeletal muscle

Low-level light therapy (LLLT) increases survival of cultured cells, improves behavioral recovery from neurodegeneration and speeds wound healing. These beneficial effects are thought to be mediated by upregulation of mitochondrial proteins, especially the respiratory enzyme cytochrome oxidase. However, the effects of in vivo LLLT on cytochrome oxidase in intact skeletal muscle have not been previously investigated. We used a sensitive method for enzyme histochemistry of cytochrome oxidase to examine the rat temporalis muscle 24 h after in vivo LLLT. The findings showed for the first time that in vivo LLLT induced a dose- and fiber type-dependent increase in cytochrome oxidase in muscle fibers. LLLT was particularly effective at enhancing the aerobic capacity of intermediate and red fibers. The findings suggest that LLLT may enhance the oxidative energy metabolic capacity of different types of muscle fibers, and that LLLT may be used to enhance the aerobic potential of skeletal muscle.

Laser Needle Acupuncture at Neiguan (PC6) Does Not Mediate Heart Rate Variability in Young, Healthy Men

OBJECTIVE

The aim of this randomized, double-blinded, placebo-controlled trial was to evaluate specific effects of laser needle acupuncture at the Neiguan point (PC6) on sympathetic and parasympathetic nerve activity in healthy subjects using heart rate variability (HRV) analysis.

BACKGROUND DATA

Acupuncture at the Neiguan point (PC6) has been shown to modulate the autonomic nervous system.

METHODS

Forty-five healthy non-smoking males were randomly divided into a placebo group (n = 20) with no laser irradiation and into an intervention group (n = 25) for which laser needle irradiation (36.8 kJ/cm(2)) was performed on the right forearm. Monitoring of HRV was performed before, during, and after intervention.

RESULTS

Repeated-measures MANOVA did not show statistically significant main effects of time (F = 1.29, p = 0.27) or of group (F = 1.67, p = 0.16). The time by group interaction was also not statistically significant (F = 0.95, p = 0.54).

CONCLUSION

Our results suggest that heart rate variability was not influenced by laser needle acupuncture at the Neiguan point (PC6).

Low-Power Laser Treatment for Shoulder Pain

OBJECTIVE

The objective of this study is to investigate the effect of low-power gallium-arsenide laser treatment on the patients with shoulder pain.

BACKGROUND DATA

Low-energy laser therapy has recently been popularized in the treatment of various rheumatologic, neurologic, and musculoskeletal disorders such as osteoarthritis, rheumatoid arthritis, fibromyalgia, carpal tunnel syndrome, rotator cuff tendinitis, and chronic back pain syndromes.

METHODS

A total of 40 patients who applied to our clinic with shoulder pain and complied with the selection criteria were included in the study. The patients were randomly assigned into Group I (n = 20, laser treatment) and Group II (n = 20, control). In Group I, patients were given laser treatment and an exercise protocol for 10 sessions during a period of 2 weeks. Laser was applied over tuberculum majus and minus, bicipital groove, and anterior and posterior faces of the capsule, regardless of the existence of sensitivity, for 1 min at each location at each session with a frequency of 2000 Hz using a GaAs diode laser instrument (Roland Serie Elettronica Pagani, wavelength 904 nm, frequency range of 5-7000 Hz, and maximum peak power of 27 W, 50 W, or 27 x 4 W). In Group II, placebo laser and the same exercise protocol was given for the same period. Patients were evaluated according to the parameters of pain, palpation sensitivity, algometric sensitivity, and shoulder joint range of motion before and after treatment.

RESULTS

Analysis of measurement results within each group showed a significant posttreatment improvement for some active and passive movements in both groups, and also for algometric sensitivity in Group I (p < 0.05-0.01). Posttreatment palpation sensitivity values showed improvement in 17 patients (85%) for Group I and six patients (30%) for Group II. Comparison between two groups showed superior results (p < 0.01 and p < 0.001) in Group I for the parameters of passive extension and palpation sensitivity but no significant difference for other parameters.

CONCLUSIONS

The results of our study have shown better results in palpation sensitivity and passive extension, but no significant improvement in pain, active range, and algometric sensitivity in laser treatment group compared to the control group in the patients with shoulder pain.

Phototherapy for enhancing peripheral nerve repair: a review of the literature

Posttraumatic nerve repair continues to be a major challenge of restorative medicine. Although enormous progress has been made in surgical techniques over the past three decades, functional recovery after a severe lesion of a major nerve trunk is often incomplete and sometimes unsatisfactory. It is thus particularly important to investigate clinical protocols to enhance nerve regeneration after surgical nerve repair. The present article reviews literature on one possible rehabilitation approach for enhancing nerve recovery, namely phototherapy. The number of experimental studies that have reported on the promoting action of phototherapy on peripheral nerve regeneration, together with the few known side effects related to the use of this type of physical therapy, make it possible to suggest that the time for broader clinical trials has come.

Neurotransmitter release changes induced by low power 830 nm diode laser irradiation on the neuromuscular junctions of the mouse

BACKGROUND AND OBJECTIVE

Treating patients with a Gallium-Aluminum-Arsenide (GaAlAs) infrared (IR) diode laser reduces muscle spasm and increases mobility in the muscles. The effect of low intensity laser irradiation on nerve function, growth, and repair mechanisms is a contentious area of research. We have addressed one aspect of this controversy by systematically examining the influence of 830 nm laser radiation on neurotransmitter release in neuromuscular junctions (NMJ) of the mouse diaphragm.

STUDY DESIGN/MATERIALS AND METHODS

Thirty adult mice were studied. Diode laser GaAlAs 830 nm (4 and 12 J/cm2) was used. Neurotransmitter release was studied by conventional intracellular recording techniques on curarized muscles or high magnesium media. The quantal content, amplitude, and latency of the end-plate potentials (EPPs) were analyzed. Frequency and amplitude were evaluated for the miniature end-plate potentials (MEPPs). Facilitation of the neurotransmitter release was also evaluated by paired pulse stimulation.

RESULTS AND CONCLUSIONS

The irradiated (12 J/cm2) muscles showed a significant reduction in quantal content (P = 0.01) and EPP amplitude (P = 0.04), but the latency, spontaneous transmitter release (MEPPs) and paired pulse facilitation did not change. No alterations were observed in NMJ irradiated with 4 J/cm2. We conclude that 830 nm diode laser irradiation (at a dose of 12 J/cm2) can affect the evoked neurotransmitter release in the mouse motor endplates.

Low-power laser biostimulation enhances nerve repair after end-to-side neurorrhaphy: a double-blind randomized study in the rat median nerve model

Previous studies have shown that low-power laser biostimulation (lasertherapy) promotes posttraumatic nerve regeneration. The objective of the present study was to investigate the effects of postoperative lasertherapy on nerve regeneration after end-to-side neurorrhaphy, an innovative technique for peripheral nerve repair. After complete transection, the left median nerve was repaired by end-to-side neurorrhaphy on the ulnar "donor" nerve. The animals were then divided into four groups: one placebo group, and three laser-treated groups that received lasertherapy three times a week for 3 weeks starting from postoperative day 1. Three different types of laser emission were used: continuous (808 nm), pulsed (905 nm), and a combination of the two. Functional testing was carried out every 2 weeks after surgery by means of the grasping test. At the time of withdrawal 16 weeks postoperatively, muscle mass recovery was assessed by weighing the muscles innervated by the median nerve. Finally, the repaired nerves were withdrawn, embedded in resin and analyzed by light and electron microscopy. Results showed that laser biostimulation induces: (1) a statistically significant faster recovery of the lesioned function; (2) a statistically significant faster recovery of muscle mass; (3) a statistically significant faster myelination of the regenerated nerve fibers. From comparison of the three different types of laser emissions, it turned out that the best functional outcome was obtained by means of pulsed-continuous-combined laser biostimulation. Taken together, the results of the present study confirm previous experimental data on the effectiveness of lasertherapy for the promotion of peripheral nerve regeneration and suggest that early postoperative lasertherapy should be considered as a very promising physiotherapeutic tool for rehabilitation after end-to-side neurorrhaphy.