Low-Intensity Photobiomodulation Decreases Neuropathic Pain in Paw Ischemia-Reperfusion and Spared Nervus Ischiadicus Injury Experimental Models.

BACKGROUND: There is a wide range of animal models available today for studying chronic pain associated with a variety of etiologies and an extensive list of clinical manifestations of peripheral neuropathies. Photobiomodulation is a new tool for the treatment of pain in a convenient, noninvasive way. OBJECTIVE: The aim of this work is to elucidate the effects of infrared light-emitting diodes (LEDs) on behavioral responses to nociceptive stimuli in chronic pain models. METHODS: Forty-eight Swiss male mice weighing 25 to 35 g were used. Two chronic pain models, ischemia-reperfusion (IR) and spared spinal nerve injury, were performed and then treated with infrared LED irradiation (390 mW, 890 nm, 17.3 mW/cm2 , 20.8 J/cm2 , for 20 minutes). The behavioral tests used were a mechanical hypersensitivity test von Frey test) and a cold allodynia test (acetone test). RESULTS: The results showed that, in the IR model, the infrared LED had a significant effect on mechanical stimulation and cold allodynia on every day of treatment. In the spared nerve injury model, an analgesic effect was observed on every treatment day (when started on the 3rd and 7th days after the surgery). In both models, the effect was abolished when the treatment was interrupted. CONCLUSIONS: These findings suggest that photobiomodulation therapy may be a useful adjunct treatment for chronic pain.

Sensitivity analysis of neurodynamic and electromagnetic simulation parameters for robust prediction of peripheral nerve stimulation.

Peripheral nerve stimulation (PNS) has become an important limitation for fast MR imaging using the latest gradient hardware. We have recently developed a simulation framework to predict PNS thresholds and stimulation locations in the body for arbitrary coil geometries to inform the gradient coil optimization process. Our approach couples electromagnetic field simulations in realistic body models to a neurodynamic model of peripheral nerve fibers. In this work, we systematically analyze the impact of key parameters on the predicted PNS thresholds to assess the robustness of the simulation results. We analyze the sensitivity of the simulated thresholds to variations of the most important simulation parameters, including parameters of the electromagnetic field simulations (dielectric tissue properties, body model size, position, spatial resolution, and coil model discretization) and parameters of the neurodynamic simulation (length of the simulated nerves, position of the nerve model relative to the extracellular potential, temporal resolution of the nerve membrane dynamics). We found that for the investigated setup, the subject-dependent parameters (e.g. tissue properties or body size) can affect PNS prediction by up to ~26% when varied in a natural range. This is in accordance with the standard deviation of ~30% reported in human subject studies. Parameters related to numerical aspects can cause significant simulation errors (>30%), if not chosen cautiously. However, these perturbations can be controlled to yield errors below 5% for all investigated parameters without an excessive increase in computation time. Our sensitivity analysis shows that patient-specific parameter fluctuations yield PNS threshold variations similar to the variations observed in experimental PNS studies. This may become useful to estimate population-average PNS thresholds and understand their standard deviation. Our analysis indicates that the simulated PNS thresholds are numerically robust, which is important for ranking different MRI gradient coil designs or assessing different PNS mitigation strategies.

Radiotherapy for Melanoma with Perineural Invasion: University of Florida Experience.

PURPOSE: Outcomes after adjuvant radiotherapy for cutaneous melanoma with perineural invasion (PNI). METHODS: Seven patients (5 cutaneous, 2 recurrent nerve lesions) received radiotherapy. RESULTS: At a median 4.5 years: Two patients did not recur; no local failures occurred. Three patients who omitted nodal irradiation developed regional failures (2 out-of-field, 1 in-field). Three patients developed distant metastases. Four died with disease (median, 3.6 years); 1 died from intercurrent disease (13.0 years). Two are alive without disease (6.8 and 11.6 years). No patient experienced grade ≥3 toxicity. CONCLUSIONS: Postoperative radiotherapy can reduce local recurrences; primary radiotherapy for unresectable disease is recommended.

A histopathological and biochemical evaluation of oxidative injury in the sciatic nerves of male rats exposed to a continuous 900-megahertz electromagnetic field throughout all periods of adolescence.

The effects on human health of the electromagnetic field (EMF) emitted by mobile phones, used by approximately 7 billion people worldwide, have become an important subject for scientific research. Studies have suggested that the EMF emitted by mobile phones can cause oxidative stress in different tissues and age groups. Young people in adolescence, a time period when risky behaviors and dependences increase, use mobile phones more than adults. The EMF emitted by mobile phones, which are generally carried in the pocket or in bags when not in use, will very probably affect the sciatic nerve. No previous study has investigated the effect of mobile phone use in adolescence on peripheral nerve. This study was planned accordingly. Twenty-four male Sprague Dawley rats aged 21 days were divided equally into control (CGr), Sham (SGr) and EMF (EMFGr) groups. No procedure was performed on CGr rats. EMFGr were exposed to the effect of a 900-megahertz (MHz) EMF for 1 h at the same time every day between postnatal days 21-59 (the entire adolescent period) inside a cage in the EMF apparatus. SGr rats were placed inside the cage for 1 h every day without being exposed to EMF. All rats were sacrificed at the end of the study period, and 1 cm sections of sciatic nerve were extracted. Malondialdehyde (MDA), glutathione, catalase (CAT) superoxide dismutase (SOD) values were investigated biochemically in half of the right sciatic nerve tissues. The other halves of the nerve tissues were subjected to routine histopathological tissue procedures, sectioned and stained with hematoxylin and eosin (H&E) and Masson's trichrome. Histopathological evaluation of slides stained with Masson's trichrome and H&E revealed a normal appearance in Schwann cells and axons in all groups. However, there was marked thickening in the epineurium of sciatic nerves from EMFGr rats. MDA, SOD and CAT levels were higher in EMFGr than in CGr and SGr at biochemical analyses. Apoptotic index (AI) analysis revealed a significant increase in the number of TUNEL (+) cells when EMFGr was compared with CGr and SGr. In conclusion, our study results suggest that continuous exposure to a 900-MHz EMF for 1 h throughout adolescence can cause oxidative injury and thickening in the epineurium in the sciatic nerve in male rats.

Spectrally distinct channelrhodopsins for two-colour optogenetic peripheral nerve stimulation.

Technologies for peripheral nerve stimulation have conventionally relied on the anatomic placement of electrodes adjacent to subsets of sensory fibres or motor fibres that selectively target an end effector. Here, we demonstrate the use of optogenetics to directly target the innervating fibres of an end effector by relying on retrograde transfection of adeno-associated virus serotype 6 to restrict axonal opsin expression to the desired fibre targets. By using an in vivo screen in rats, we identify the first channelrhodopsins as well as a halorhodopsin that respond to red light in the peripheral nerve. Combining two channelrhodopsins with spectrally distinct activation profiles allowed us to drive opposing muscle activity via two-colour illumination of the same mixed nerve. We also show halorhodopsin-mediated reductions in electrically evoked muscle tremor spectrally optimized for deep peripheral nerves. Our non-invasive peripheral neurostimulator with targeted multi-fascicle resolution enables scientific and clinical exploration, such as motor control in paralysis, biomimetic sensation feedback for amputees and targeted inhibition of muscle tremor.

Photobiomodulation in Neuroscience: A Summary of Personal Experience.

OBJECTIVE: This review summarizes personal experience with laser photobiomodulation and its potentials for the treatment of peripheral and central nerve system injuries. METHODS AND RESULTS: Laser photobiomodulation was shown to induce nerve cell activation, have a positive effect on metabolism of the nerve cells, and to stimulate nerve sprouting processes. Studies investigating the effects of laser photobiomodulation on injured peripheral nerves in rats reported immediate protective effects which increase the functional activity of the nerve, decrease or prevent scar tissue formation at the injured site, prevent or decrease degeneration in corresponding motor neurons of the spinal cord, and significantly increase axonal growth and myelinization. A direct application of laser on the spinal cord had a positive impact on the corresponding injured peripheral nerve and promoted recovery. A 780-nm laser phototherapy was applied following peripheral nerve reconstruction using a guiding nerve tube. Results showed myelinated axons crossing through the nerve tube and the continuation of axonal sprouting through the tube toward the distal part of the nerve. In a double-blind, placebo-controlled randomized pilot clinical trial in patients with incomplete stable long-term peripheral nerve injury (PNI), 780-nm laser irradiation progressively improved peripheral nerve function and led to substantial functional recovery. Muscle atrophy represents a major challenge in restorative medicine. Laser phototherapy was shown to increase biochemical activity and improve morphological recovery in muscle and, thus, could have a direct therapeutic application, especially during progressive muscle atrophy resulting from PNI. The effectiveness of composite implants of cultured embryonal nerve cells and the role of laser irradiation on regeneration and repair of the completely transected rat spinal cord were examined. Results suggested that laser photobiomodulation treatment accelerates the axonal growth. CONCLUSIONS: The significance of the performed experimental and clinical studies is in the provision of new laser technology in field of cell therapy and its therapeutic value for peripheral nerve and spinal cord injuries. Additional well-designed clinical studies are needed to evaluate the effectiveness and role of laser photobiomodulation treatment in a clinical setting.

Magnetic Field Reference Levels for Arbitrary Periodic Waveforms for Prevention of Peripheral Nerve Stimulation.

Guidelines for prevention of peripheral nerve stimulation from exposure to low frequency magnetic fields have been developed by standard-setting bodies. Exposure limits or reference levels (RLs) are typically set in terms of the maximum root-mean-square amplitude of a sinusoidal waveform; however, environmental flux densities are often periodic, non-sinusoidal waveforms. This work presents a procedure for deriving RLs for any generalized periodic waveform using the empirical nerve-stimulation threshold data obtained from human volunteer MRI experiments. For this purpose, the "Law of Electrostimulation" (LOE), which sets forth conditions of a waveform necessary to trigger the action potential required to depolarize cell membranes, is applied to various waveforms. The results of the LOE analysis are waveform-specific, amplitude thresholds of stimulation that are found in terms of the empirically-derived rheobase threshold time-rate-of-change flux density and chronaxie from trapezoidal pulse MRI experiments. The thresholds are converted to amplitude RLs in two asymptotic frequency regimes as per the usual practice in standard setting. The resulting RLs have the same frequency dependence as in existing standards (i.e., inverse-frequency below a transition frequency and flat above). It is shown that the transition frequency is dependent only on the shape of the waveform. Both sinusoidal and non-sinusoidal waveforms have identical peak-to-peak amplitude RLs above their respective transition frequencies. Below these frequencies, all peak-to-peak amplitude RLs have the same functional dependence on frequency when the frequency is normalized to the waveform-specific transition frequency. This results in simple criteria for testing the amplitude of any arbitrary periodic waveform against potential for stimulation. These criteria are compared to guidance given for non-sinusoidal waveforms in the ICNIRP 1 Hz-100 kHz exposure standard.

Inconsistency of a recently proposed method for assessing magnetic field exposure for protection against peripheral nerve stimulation in occupational situations.

A non-binding guide to practical implementation of European Directive 2013/35/EU concerning the limitation of occupational exposure against electromagnetic fields has been published recently. With regard to exposure assessment this guide proposes practically applicable assessment methods for non-uniform and non-sinusoidal environmental electric and magnetic fields, respectively. For non-sinusoidal magnetic fields in the low frequency range this guide proposes a time domain assessment (TDA) method, claimed to reduce the overestimation of exposure inherent to other assessment methods while being based on fundamental physiological principles regarding nerve stimulation. In the present paper we demonstrate that the proposed TDA method is not consistent with the obvious underlying principles of directive 2013/35/EU. Based on practically relevant waveforms and general considerations it can be shown that external magnetic fields may be deemed compliant by the TDA method although the underlying exposure limit values defined in 2013/35/EU may be exceeded. We therefore strongly recommend that the TDA method is removed from the guide for implementing 2013/35/EU as soon as possible.

Controversies related to electromagnetic field exposure on peripheral nerves.

Electromagnetic field (EMF) is a pervasive environmental presence in modern society. In recent years, mobile phone usage has increased rapidly throughout the world. As mobile phones are generally held close to the head while talking, studies have mostly focused on the central and peripheral nervous system. There is a need for further research to ascertain the real effect of EMF exposure on the nervous system. Several studies have clearly demonstrated that EMF emitted by cell phones could affect the systems of the body as well as functions. However, the adverse effects of EMF emitted by mobile phones on the peripheral nerves are still controversial. Therefore, this review summarizes current knowledge on the possible positive or negative effects of electromagnetic field on peripheral nerves.

Dosimetric Uncertainties: Magnetic Field Coupling to Peripheral Nerve.

The International Commission on Non-ionizing Radiation Protection (ICNIRP) and the Institute for Electrical and Electronic Engineers (IEEE) have established magnetic field exposure limits for the general public between 400 Hz (ICNIRP)/759 Hz (IEEE) and 100 kHz to protect against adverse effects associated with peripheral nerve stimulation (PNS). Despite apparent common purpose and similarly stated principles, the two sets of limits diverge between 3.35-100 kHz by a factor of about 7.7 with respect to PNS. To address the basis for this difference and the more general issue of dosimetric uncertainty, this paper combines experimental data of PNS thresholds derived from human subjects exposed to magnetic fields together with published estimates of induced in situ electric field PNS thresholds to evaluate dosimetric relationships of external magnetic fields to induced fields at the threshold of PNS and the uncertainties inherent to such relationships. The analyses indicate that the logarithmic range of magnetic field thresholds constrains the bounds of uncertainty of in situ electric field PNS thresholds and coupling coefficients related to the peripheral nerve (the coupling coefficients define the dosimetric relationship of external field to induced electric field). The general public magnetic field exposure limit adopted by ICNIRP uses a coupling coefficient that falls above the bounds of dosimetric uncertainty, while IEEE's is within the bounds of uncertainty toward the lower end of the distribution. The analyses illustrate that dosimetric estimates can be derived without reliance on computational dosimetry and the associated values of tissue conductivity. With the limits now in place, investigative efforts would be required if a field measurement were to exceed ICNIRP's magnetic field limit (the reference level), even when there is a virtual certainty that the dose limit (the basic restriction) has not been exceeded. The constraints on the range of coupling coefficients described in this paper could facilitate a re-evaluation of ICNIRP and IEEE dose and exposure limits and possibly lead toward harmonization.

A µm-Scale Computational Model of Magnetic Neural Stimulation in Multifascicular Peripheral Nerves.

There has been recurring interest in using magnetic neural stimulation for implantable localized stimulation. However, the large stimulation voltages and energies necessary to evoke neuronal activity have tempered this interest. To investigate the potential of magnetic stimulation as a viable methodology and to provide the ability to investigate novel coil designs that can result in lower stimulation threshold voltages and energies, there is a need for a model that accurately predicts the magnetic field-tissue interaction that results in neuronal stimulation. In this study, we provide a computational framework to accurately estimate the stimulation threshold and have validated the model with in vivo magnetic stimulation experiments. To make such predictions, we developed a micrometer-resolution anatomically driven computational model of rat sciatic nerve and quantified the effect of tissue heterogeneity (i.e., fascicular organization, axon distribution, and density) and axonal membrane capacitance on the resulting threshold. Using the multiresolution impedance method, we computed the spatial-temporal distribution of the induced electric field in the nerve and applied this field to a Frankenhaeuser-Huxley axon model in NEURON to simulate the nonlinear mechanisms of the membrane channels. The computational model developed predicts the stimulation thresholds for four magnetic coil designs with different geometrical parameters within the 95% confidence interval (experiments count = 4) of measured in vivo stimulation thresholds for the rat sciatic nerve.

Peripheral nerve stimulation-optimal gradient waveform design.

PURPOSE: Modern magnetic resonance imaging scanners with high-performance gradient systems have high maximum gradient strength (Gmax ) and slew rate (Smax ). Peripheral nerve stimulation (PNS) is often a more limiting factor for gradient waveform design than Gmax and Smax . Traditionally, the slew rate is derated globally to adhere to PNS limitations. METHODS: In this work, the PNS limitation is already included in the gradient waveform design in the form of a time-varying slew rate, hence shortening the overall gradient duration. RESULTS: Spiral and echo-planar imaging trajectories were designed with a multitude of parameters, and it was demonstrated that trajectory durations from conventional to PNS-optimal design can be shortened by 8 and 3%, respectively. CONCLUSION: Including PNS-limits in the gradient waveform design can shorten the duration of gradient trajectories, thereby reducing associated artifacts.

Noninvasive and painless magnetic stimulation of nerves improved brain motor function and mobility in a cerebral palsy case.

Motor deficits in cerebral palsy disturb functional independence. This study tested whether noninvasive and painless repetitive peripheral magnetic stimulation could improve motor function in a 7-year-old boy with spastic hemiparetic cerebral palsy. Stimulation was applied over different nerves of the lower limbs for 5 sessions. We measured the concurrent aftereffects of this intervention on ankle motor control, gait (walking velocity, stride length, cadence, cycle duration), and function of brain motor pathways. We observed a decrease of ankle plantar flexors resistance to stretch, an increase of active dorsiflexion range of movement, and improvements of corticospinal control of ankle dorsiflexors. Joint mobility changes were still present 15 days after the end of stimulation, when all gait parameters were also improved. Resistance to stretch was still lower than prestimulation values 45 days after the end of stimulation. This case illustrates the sustained effects of repetitive peripheral magnetic stimulation on brain plasticity, motor function, and gait. It suggests a potential impact for physical rehabilitation in cerebral palsy.

Direct effect of radiation on the peripheral nerve in a rat model.

Radiation neuropathy is one of the severe complications of radiotherapy. Entrapment neuropathy, caused by surrounding soft tissue fibrosis induced by radiation, plays a key role in the onset of this neuropathy. Meanwhile, the pathophysiology of the direct effect of radiation on the peripheral nerve is not yet fully understood. The aim of this study is to investigate the direct effects of radiation on rat sciatic nerves that are isolated from surrounding soft tissue. In the radiation group (R group), only the exposed sciatic nerve was irradiated with 90 Gy X-radiation. In the sham group (S group), the surgical procedures were completed without radiation. The sciatic functional index (SFI) result demonstrated no statistical differences between the R group and S group. However, even though the surrounding soft tissue was not irradiated, the macroscopic and histological findings of the R group at 24 weeks after radiation showed scar formation around the radiated nerve. These findings on radiation neuropathy indicate that neurohumoral factors derived from the radiated nerve itself may cause fibrosis. The electromyographic and histological examination showed axonal degeneration in the R group. Furthermore, the axon diameter and axon packing density in the R group demonstrated the axonal degeneration, even though it was 0.5 cm more proximal to the radiated portion than the axon packing density in the S group. This appearance was assumed to be "dying-back" neuropathy. It is believed that this study is a first step toward identifying an accurate pathophysiology for intractable radiation-induced peripheral neuropathy.

The use of shock waves in peripheral nerve regeneration: new perspectives?

Low-energy extracorporeal shock wave treatment (ESWT) is a relatively new therapeutic tool that is widely used for the treatment of epicondylitis and plantar fasciitis and to foster bone and wound healing. Shock waves, sonic pulses with high energy impact, are thought to induce biochemical changes within the targeted tissues through mechanotransduction. The biological effects of ESWT are manifested in improved vascularization, the local release of growth factors, and local anti-inflammatory effects, but the target cells too are influenced. ESWT appears to have differential effects on peripheral nerves and has been proved to promote axonal regeneration after axotomy. This review discusses the effects of ESWT on intact and injured peripheral nerves and suggests a multiple mechanism of action.

The role of skin conductivity in a low frequency exposure assessment for peripheral nerve tissue according to the ICNIRP 2010 guidelines.

Based on numerical computations using commercially available finite difference time domain code and a state-of-the art anatomical model of a 5-year old child, the influence of skin conductivity on the induced electric field strength inside the tissue for homogeneous front-to-back magnetic field exposure and homogeneous vertical electric field exposure was computed. Both ungrounded as well as grounded conditions of the body model were considered. For electric field strengths induced inside CNS tissue the impact of skin conductivity was found to be less than 15%. However, the results demonstrated that the use of skin conductivity values as obtainable from the most widely used data base of dielectric tissue properties and recommended by safety standards are not suitable for exposure assessment with respect to peripheral nerve tissue according to the ICNIRP 2010 guidelines in which the use of the induced electric field strengths inside the skin is suggested as a conservative surrogate for peripheral nerve exposure. This is due to the fact that the skin conductivity values derived from these data bases refer to the stratum corneum, the uppermost layer of the skin, which does not contain any nerve or receptor cells to be protected from stimulation effects. Using these skin conductivity values which are approximately a factor 250-500 lower than skin conductivity values used in studies on which the ICNIRP 2010 guidelines are based on, may lead to overestimations of the induced electric field strengths inside the skin by substantially more than a factor of 10. However, reliable conductivity data of deeper skin layers where nerve and preceptor cells are located is very limited. It is therefore recommended to include appropriate background information in the ICNIRP guidelines and the dielectric tissue property databases, and to put some emphasis on a detailed layer-specific characterization of skin conductivity in near future.

The role of the sensory nerve response in ultrasound accelerated fracture repair.

This study was designed to test the hypothesis that the sensory innervation of bone might play an important role in sensing and responding to low-intensity pulsed ultrasound and explain its effect in promoting fracture healing. In 112 rats a standardised mid-shaft tibial fracture was created, supported with an intramedullary needle and divided into four groups of 28. These either had a sciatic neurectomy or a patellar tendon resection as control, and received the ultrasound or not as a sham treatment. Fracture union, callus mineralisation and remodelling were assessed using plain radiography, peripheral quantitative computed tomography and histomorphology. Daily ultrasound treatment significantly increased the rate of union and the volumetric bone mineral density in the fracture callus in the neurally intact rats (p = 0.025), but this stimulating effect was absent in the rats with sciatic neurectomy. Histomorphology demonstrated faster maturation of the callus in the group treated with ultrasound when compared with the control group. The results supported the hypothesis that intact innervation plays an important role in allowing low-intensity pulsed ultrasound to promote fracture healing.

The effects of low-dose radiation in the treatment of sciatic nerve injury in rats.

AIM: Peripheral nerve regeneration is often blocked by scar formation and misdirection of axon sprouts. The aim of this study is to evaluate electrophysiological and histopathological effects of low-dose radiation therapy on the prevention of intraneural scar formation in peripheral nerve injury. MATERIAL AND METHODS: In this experimental study, twenty rats were randomly divided into two groups. Left sciatic nerves were exposed and clipped by temporary aneurysm clip for 5 minutes in both groups. In all animals, electrophysiological recordings were performed between 22-24 hours after sciatic nerve injury. The control group was not given any treatment. In the experimental group, 700 cGy low-dose radiation was administered on the left sciatic nerves 24 hours after clipping. Six weeks after injury, electrophysiological recordings were performed in both groups and animals were sacrificed to evaluate the injured nerves histopathologically. RESULTS: We observed that low-dose radiotherapy increased the amplitude and improved latency measurements in electrophysiological examinations. Histopathologically, more axonal degeneration and vacuolization was observed in the control group comparing with the experimental group. Endoneural space increased slightly more in the control group than the experimental group. CONCLUSION: It was observed that low-dose radiotherapy may prevent intraneural scar formation and may improve electrophysiological recovery in sciatic nerve injury performed in rats.

Inhibitory effects of laser irradiation on peripheral mammalian nerves and relevance to analgesic effects: a systematic review.

OBJECTIVE: The objective of this review was to systematically identify experimental studies of non-ablative laser irradiation (LI) on peripheral nerve morphology, physiology, and function. The findings were then evaluated with special reference to the neurophysiology of pain and implications for the analgesic effects of low-level laser therapy (LLLT). BACKGROUND: LLLT is used in the treatment of pain, and laser-induced neural inhibition has been proposed as a mechanism. To date, no study has systematically evaluated the effects of LI on peripheral nerve, other than those related to nerve repair, despite the fact that experimental studies of LI on nerves have been conducted over the past 25 years. METHODS: We searched computerized databases and reference lists for studies of LI effects on animal and human nerves using a priori inclusion and exclusion criteria. RESULTS: We identified 44 studies suitable for inclusion. In 13 of 18 human studies, pulsed or continuous wave visible and continuous wave infrared (IR) LI slowed conduction velocity (CV) and/or reduced the amplitude of compound action potentials (CAPs). In 26 animal experiments, IR LI suppressed electrically and noxiously evoked action potentials including pro-inflammatory mediators. Disruption of microtubule arrays and fast axonal flow may underpin neural inhibition. CONCLUSIONS: This review has identified a range of laser-induced inhibitory effects in diverse peripheral nerve models, which may reduce acute pain by direct inhibition of peripheral nociceptors. In chronic pain, spinal cord changes induced by LI may result in long-term depression of pain. Incomplete reporting of parameters limited aggregation of data.

Histological analysis of low-intensity laser therapy effects in peripheral nerve regeneration in Wistar rats / Avaliação histológica dos efeitos da laserterapia de baixa potência sobre os processos de regeneração nervosa periférica em ratos Wistar

Purpose: Analyze the influence of low-intensity laser therapy in the sciatic nerve regeneration of rats submitted to controlled crush through histological analysis. Methods: Were used 20 Wistar rats, to analyze the influence of low-intensity laser therapy in the sciatic nerve regeneration, where the injury of the type axonotmesis was induced by a haemostatic clamp Crile (2nd level of the rack). The animals were randomly distributed in 2 groups. Control group (CG n = 10) and Laser group (LG n = 10). These were subdivided in 2 subgroups each, according to the euthanasia period: (CG14 _ n = 5 and CG21 _ n = 5) and (LG14 _ n = 5 and LG21 _ n = 5). At the end of treatment, the samples were removed and prepared for histological analysis, where were analyzed and quantified the following findings: Schwann cells, myelinic axons with large diameter and neurons. Results: In the groups submitted to low-intensity laser therapy, were observed an increase in the number of all analyzed aspects with significance level. Conclusion: The irradiation with low intensity laser (904nm) influenced positively the regeneration of the sciatic nerve in Wistar rats after being injured by crush (axonotmesis), becoming the nerve recovery more rapid and efficient.

Objetivo: Verificar a influência da terapia com laser de baixa potência na regeneração histológica do nervo ciático de ratos submetidos à neuropraxia controlada. Métodos: Foi utilizada a amostra de 20 ratos da linhagem Wistar, para verificar a influência da terapia com laser de baixa intensidade na regeneração nervosa periférica, onde a lesão do tipo axoniotmese foi induzida por meio de preensão com pinça hemostática de Crile. Os animais foram distribuídos randomicamente dois grupos. Grupo controle (CG n = 10), e Grupo laser (LG n = 10). Cada um destes grupos foi subdividido em dois subgrupos dependendo do período da eutanásia: (CG14 - n = 5 e CG21 - n = 5) e (LG14 - n = 5 e LG21 - n = 5). Ao final do tratamento, amostras do nervo foram retiradas e analisadas histologicamente, nas quais foi adotado na pesquisa a análise do número de neurônios, de células de Schwann (CS) e de axônios mielínicos de grande diâmetro. Resultados: Nos grupos submetidos à terapia com laser de baixa potencia foi observado aumento do número de todos os aspectos analisados com diferença estatisticamente significante. Conclusão: A irradiação com o laser de baixa intensidade (904nm) influenciou positivamente na regeneração do nervo ciático de ratos da linhagem Wistar pós neuropraxia controlada (axonotmese), tornando a recuperação nervosa mais rápida e eficiente.