Photobiomodulation in Neuroscience: A Summary of Personal Experience

Photobiomodulation: An Emerging Treatment Modality for Depression

Major depressive disorder (MDD) is considered a global crisis. Conventional treatments for MDD consist of pharmacotherapy and psychotherapy, although a significant number of patients with depression respond poorly to conventional treatments and are diagnosed with treatment-resistant depression (TRD). Transcranial photobiomodulation (t-PBM) therapy uses near-infrared light, delivered transcranially, to modulate the brain cortex. The aim of this review was to revisit the antidepressant effects of t-PBM, with a special emphasis on individuals with TRD. A search on PubMed and ClinicalTrials.gov tracked clinical studies using t-PBM for the treatment of patients diagnosed with MDD and TRD.

Beneficial Effect of Bee Venom and Its Major Components on Facial Nerve Injury Induced in Mice

Peripheral nerve injury (PNI) is a health problem that affects many people worldwide. This study is the first to evaluate the potential effect of bee venom (BV) and its major components in a model of PNI in the mouse. For that, the BV used in this study was analyzed using UHPLC. All animals underwent a distal section-suture of facial nerve branches, and they were randomly divided into five groups. Group 1: injured facial nerve branches without any treatment. Group 2: the facial nerve branches were injured, and the normal saline was injected similarly as in the BV-treated group. Group 3: injured facial nerve branches with local injections of BV solution. Group 4: injured facial nerve branches with local injections of a mixture of PLA2 and melittin. Group 5: injured facial nerve branches with local injection of betamethasone. The treatment was performed three times a week for 4 weeks. The animals were submitted to functional analysis (observation of whisker movement and quantification of nasal deviation). The vibrissae muscle re-innervation was evaluated by retrograde labeling of facial motoneurons in all experimental groups. UHPLC data showed 76.90 ± 0.13%, 11.73 ± 0.13%, and 2.01 ± 0.01%, respectively, for melittin, phospholipase A2, and apamin in the studied BV sample. The obtained results showed that BV treatment was more potent than the mixture of PLA2 and melittin or betamethasone in behavioral recovery. The whisker movement occurred faster in BV-treated mice than in the other groups, with a complete disappearance of nasal deviation two weeks after surgery. Morphologically, a normal fluorogold labeling of the facial motoneurons was restored 4 weeks after surgery in the BV-treated group, but no such restoration was ever observed in other groups. Our findings indicate the potential of the use of BV injections to enhance appropriate functional and neuronal outcomes after PNI.

Neural Correlates of Delay Discounting in the Light of Brain Imaging and Non-Invasive Brain Stimulation: What We Know and What Is Missed

In decision making, the subjective value of a reward declines with the delay to its receipt, describing a hyperbolic function. Although this phenomenon, referred to as delay discounting (DD), has been extensively characterized and reported in many animal species, still, little is known about the neuronal processes that support it. Here, after drawing a comprehensive portrait, we consider the latest neuroimaging and lesion studies, the outcomes of which often appear contradictory among comparable experimental settings. In the second part of the manuscript, we focus on a more recent and effective route of investigation: non-invasive brain stimulation (NIBS). We provide a comprehensive review of the available studies that applied transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) to affect subjects’ performance in DD tasks. The aim of our survey is not only to highlight the superiority of NIBS in investigating DD, but also to suggest targets for future experimental studies, since the regions considered in these studies represent only a fraction of the possible ones. In particular, we argue that, based on the available neurophysiological evidence from lesion and brain imaging studies, a very promising and underrepresented region for future neuromodulation studies investigating DD is the orbitofrontal cortex.

Efficacy of LED Photobiomodulation for Functional and Axonal Regeneration After Facial Nerve Section-Suture

Facial nerve damage can lead to partial or total facial nerve palsy. Photobiomodulation has been reported to improve and accelerate functional recovery following peripheral nerve lesion, depending on the type of lesion and the light exposure parameters used. The aim of this study was to investigate the effects of infrared exposure on functional and axonal regeneration after section-suture of the distal branches of the facial nerve: the buccal and marginal mandibular branches and the distal pes. The animals underwent surgery and were irradiated with infrared light at 850 nm twice daily from day 1 to day 16. The recovery of facial function was then studied at both the behavioral and morphological levels. Behavioral analyses were performed by videoscoring with a high-speed camera and using various devices to assess the recovery of whisker movement on the lesioned side from day 1 to day 30. We also assessed nasal deviation toward the intact side and the ability to close the ipsilateral eyelid completely from day 1 to day 38 and from day 1 to day 50, respectively. For morphological analyses, we assessed the re-establishment of facial motoneuron labeling with Fluorogold®, an immunofluorescent retrograde marker of axonal transport injected into the vibrissae, on D10, D14 and D30. We found that whisker movements recovery was significantly faster in treated than in control mice. A complete disappearance of nasal deviation was observed at 2 weeks in infrared-treated lesioned mice and at 5 weeks in controls. Complete eyelid closure was observed 3 weeks after surgery in treated animals and 6 weeks after surgery in controls. Finally, normal fluorogold labeling of the facial nuclei complex was restored 30 days after surgery in the treated animals, but no such restoration was ever observed in control animals. In conclusion, our data show that IR treatment at a distal site has a significant positive effect on facial nerve recovery. These findings pave the way for the clinical use of infrared photobiomodulation in patients with nerve lesions.

The use of photobiomodulation therapy for the prevention of chemotherapy-induced peripheral neuropathy: a randomized, placebo-controlled pilot trial (NEUROLASER trial)

PURPOSE

The purpose of this study was to investigate the effectiveness of photobiomodulation (PBM) therapy for the prevention of chemotherapy-induced peripheral neuropathy (CIPN) in breast cancer patients.

METHODS

A prospective, randomized placebo-controlled pilot trial (NEUROLASER) was set up with 32 breast cancer patients who underwent chemotherapy (ClinicalTrials.gov; NCT03391271). Patients were randomized to receive PBM (n = 16) or placebo treatments (n = 16) (2 × /week) during their chemotherapy. The modified Total Neuropathy Score (mTNS), six-minute walk test (6MWT), Numeric pain Rating Scale (NRS), and Functional Assessment of Cancer Therapy/Gynecologic Oncology Group Taxane (FACT/GOG-Taxane) were used to evaluate the severity of CIPN and the patients' quality of life (QoL). Outcome measures were collected at the first chemotherapy session, 6 weeks after initiation of chemotherapy, at the final chemotherapy session, and 3 weeks after the end of chemotherapy (follow-up).

RESULTS

The mTNS score increased significantly over time in both the control and the PBM group. A significantly higher score for FACT/GOG-Taxane was observed in the PBM group during chemotherapy compared to the control group. Questions of the FACT/GOG-Taxane related to sensory peripheral neuropathy symptoms showed a significant increase in severeness over time in the control group, whereas they remained constant in the PBM group. At follow-up, a (borderline) significant difference was observed between both groups for the 6MWT and patients' pain level, in benefit of the PBM group.

CONCLUSIONS

This NEUROLASER trial shows promising results concerning the prevention of CIPN with PBM in breast cancer patients. Furthermore, a better QoL was observed when treated with PBM.

Photobiomodulation Therapy Applied after 6 Months for the Management of a Severe Inferior Alveolar Nerve Injury

Despite its significant negative impact on the quality of life, the methods for the management of the inferior alveolar nerve (IAN) injury are still limited. In this case report, the patient did not show any improvement from the day of the iatrogenic accident until 6 months. A significant improvement of the symptoms started to appear only at 6 months when PBMT was applied. A total of 42 sessions of PBMT took place. The application zone included intraoral and extraoral areas. The parameters were: Delivery power of 0.1 W, for 40 s, continuous wave (CW), contact mode, and delivered energy of 4 J. The delivered energy density related to the fiber diameter was 1415 J/cm². Each treated point was considered to be 1 cm² of diameter. At the end of the treatment, all of the symptoms disappeared except for an abnormal sensation on touching the mucosa and gingiva of the concerned area. No side effects were noted. This case report shows that PBMT can be a very promising approach for the management of severe cases that are not improving with conventional methods.

Effects of photobiomodulation therapy on functional recovery, angiogenesis and redox status in denervated muscle of rats

Objective:

To evaluate the effects of photobiomodulation therapy in redox status, angiogenesis marker – vascular endothelial growth factor – and in the functional recovery in denervated muscle.

Methods:

A total of 32 female Wistar rats underwent a crush injury and were randomly divided into four groups: Light Emitting Diode Group 2 and Control Group 2 (muscle collected 2 days after injury), and Light Emitting Diode Group 21 and Control Group 21 (muscle collected 21 days afterinjury). Light Emitting Diode Group 2 and Light Emitting Diode Group 21 received two and ten light emitting diode applications (630±20nm, 9J/cm², 300mW), respectively, and the Control Group 2 and Control Group 21 did not receive any treatment. The function was evaluated by grasping test at four moments (pre-injury, 2, 10 and 21 post-injury days). The flexor digitorum muscle was collected for analysis of immunolocalization of vascular endothelial growth factor and redox parameters.

Results:

Functional improvement was observed at the second and tenth post-injury day in treated groups compared to control (p<0.005). The muscle tissue of treated groups presented higher immunohistochemical expression of vascular endothelial growth factor. Photobiomodulation therapy decreased the oxidative damage to lipid in Light Emitting Diode Group 2 compared to Control Group 2 (p=0.023) in the denervated muscle.

Conclusion:

Photobiomodulation therapy accelerated the functional recovery, increased angiogenesis and reduced lipid peroxidation in the denervated muscle at 2 days after injury.

Use of 1064 nm Nd:YAG Laser Biostimulation for Immediate Reversal of a Long-Standing Paresthesia of the Superior Labial Branch of the Infraorbital Nerve Following a Root Coverage Procedure: A Case Report

INTRODUCTION

Paresthesia is a common cause of dental malpractice litigation. Symptoms range from minimal to severely affecting the quality of life. Effective treatments of post-traumatic paresthesias are scarce. This case report documents the first reported use of laser biostimulation to reverse a long-standing paresthesia of the infraorbital nerve, resulting from a root coverage procedure of the maxillary right canine.

CASE PRESENTATION

A coronally repositioned flap with enamel matrix derivative was used to treat gingival recession on the buccal surface of tooth #6 of a 35-year-old Caucasian female. One week later the patient reported lip numbness. The patient declined further treatment, and the paresthesia remained unchanged for the next 13 months. The patient then consented to laser biostimulation with a 1064 nm neodymium:yttrium aluminum garnet laser. A single laser biostimulation treatment resulted in an immediate and dramatic improvement of lip sensation. The patient's symptoms improved over the next 2½ years without further treatment.

CONCLUSION

The cause of the paresthesia and the exact mechanism of its reversal remain unknown, although speculated causes and the possible mechanisms of action of low-level laser therapy are discussed. Laser biostimulation for treatment of peripheral nerve injury is noninvasive and may eliminate the need for corticosteroids or other more invasive treatment modalities. It may not be effective in all paresthesia cases, but when used properly, laser therapy offers a safe treatment alternative for an often troubling problem.

Low-power lasers on bacteria: stimulation, inhibition, or effectless?

Clinical protocols based on low-power lasers have been widely used for inflammation process resolution improvement, pain relief, wound healing, and nerve regeneration. However, there are concerns if exposure to such lasers could have negative effects on infected organs and tissues. There are experimental data suggesting exposure to radiations emitted by low-power lasers either induces stimulation, inhibition, or it is effectless on bacterial cultures. Thus, this review aimed to carry out a review of studies and to propose a hypothesis to explain why exposure to low-power lasers could stimulate, inhibit, or have no effect on bacteria. A literature search was carried out for assessment of published reports on effect of low-power lasers on bacteria. The experimental data suggest that keys for determining laser-induced effects on bacteria are specific physical laser and biological parameters. Final consequence on bacterial cells could depend on exposure to low-power laser which could either cause more stimulation of endogenous photoacceptors, more excitation of endogenous photosensitizers, or a balance between such effects.

Effects of laser acupuncture in a patient with a 12-year history of facial paralysis: A case report

Background

Traumatic facial palsy, whether accidental or iatrogenic, is a common cause of facial paralysis. Laser acupuncture therapy (LAT) is a non-invasive, pain-free method to stimulate traditional acupuncture points with non-thermal laser irradiation. Low-level laser therapy has proven beneficial in the regeneration of peripheral nerves. This case report describes the feasibility of this innovative treatment in a patient with a 12-year history of traumatic facial palsy and severe sequelae.

Case summary

A52-year-old male presented with a severe left-sided facial paralysis that had lasted for 12 years. At initial presentation, the man could not fully close his left eye and had difficulty eating solid foods. The paralysis of his left-sided facial muscles had resulted in dysarthria. He was administered 30 LAT sessions in the Acupuncture Department of China Medical University Hospital, Taichung, Taiwan, over a 4-month period. His recovery was monitored by scores on the Facial Disability Index, the Sunnybrook Facial Nerve Grading System and measurements of the vertical palpebral distance in his left eye. Photographs were taken after every treatment. On the 10th treatment, a change in closure of the left eye was noticed and facial muscle strength was improved. After 22 treatments, the patient could fully close his left eye.

Conclusion

LAT significantly improved the sequelae of long-term facial paralysis in this patient. Large-scale prospective studies are needed to confirm this observation [added]