Photobiomodulation therapy in improvement of harmful neural plasticity in sodium salicylate-induced tinnitus.

Tinnitus is a common annoying symptom without effective and accepted treatment. In this controlled experimental study, photobiomodulation therapy (PBMT), which uses light to modulate and repair target tissue, was used to treat sodium salicylate (SS)-induced tinnitus in a rat animal model. Here, PBMT was performed simultaneously on the peripheral and central regions involved in tinnitus. The results were evaluated using objective tests including gap pre-pulse inhibition of acoustic startle (GPIAS), auditory brainstem response (ABR) and immunohistochemistry (IHC). Harmful neural plasticity induced by tinnitus was detected by doublecortin (DCX) protein expression, a known marker of neural plasticity. PBMT parameters were 808 nm wavelength, 165 mW/cm2 power density, and 99 J/cm2 energy density. In the tinnitus group, the mean gap in noise (GIN) value of GPIAS test was significantly decreased indicated the occurrence of an additional perceived sound like tinnitus and also the mean ABR threshold and brainstem transmission time (BTT) were significantly increased. In addition, a significant increase in DCX expression in the dorsal cochlear nucleus (DCN), dentate gyrus (DG) and the parafloccular lobe (PFL) of cerebellum was observed in the tinnitus group. In PBMT group, a significant increase in the GIN value, a significant decrease in the ABR threshold and BTT, and also significant reduction of DCX expression in the DG were observed. Based on our findings, PBMT has the potential to be used in the management of SS-induced tinnitus.

Acoustic and optoacoustic stimulations in auditory brainstem response test in salicylate induced tinnitus.

As a common debilitating disorder worldwide, tinnitus requires objective assessment. In the auditory brainstem response (ABR) test, auditory potentials can be evoked by acoustic or optoacoustic (induced by laser light) stimulations. In order to use the ABR test in the objective assessment of tinnitus, in this study, acoustic ABR (aABR) and optoacoustic ABR (oABR) were compared in the control and tinnitus groups to determine the changes caused by sodium salicylate (SS)-induced tinnitus in rat. In both aABR and oABR, wave II was the most prominent waveform, and the amplitude of wave II evoked by oABR was significantly higher than that of aABR. Brainstem transmission time (BTT), which represents the time required for a neural stimulation to progress from the auditory nerve ending to the inferior colliculus, was significantly shorter in oABR. In the tinnitus group, there was a significant increase in the threshold of both ABRs and a significant decrease in the amplitude of wave II only in the oABR. Based on our findings, the ABR test has the potential to be used in the assessment of SS-induced tinnitus, but oABR has the advantages of producing more prominent waveforms and significantly reducing the amplitude of wave II in tinnitus.

Photobiomodulation therapy in mood disorders: a systematic review.

Mood disorders are common, debilitating and impose a high-cost burden on society. Side effects and resistance to psychiatric drugs justify finding new treatment methods. Photobiomodulation therapy (PBMT) uses photons of light to repair, modulate and improve the function of target tissue. The purpose of this study is to systematically review the use of PBMT for the treatment of mood disorders and to identify the useful parameters of PBMT, the level of evidence of its effectiveness, and the degree of its practical recommendation. "Google scholar," "Pub Med," "Scopus," and "Science direct" online databases were searched based on Preferred Reporting Items for Systematic Reviews and meta-analyses (PRISMA) guidelines. The human or animal studies written in English and published from January 2009 to August 2021 were included. Sixteen studies, which included four randomized controlled trials (RCTs), met the inclusion criteria. Infrared wavelength ranges from 800 to 830 nm, power density of 250 mW/cm2 and energy density of 60 to 120 J/ cm2 were the most used PBMT parameters. Bias risk assessment was performed to evaluate the quality of RCTs in which 2 out of 4 RCTs were evaluated as high quality. Based on grade practice recommendations, PBMT can be classified as strongly recommended for moderate grade of major depressive disorder (MDD) and recommended for anxiety disorder. In bipolar disorder, further studies are needed to recommend this therapeutic method.

Transcranial photobiomodulation in the management of brain disorders.

Transcranial photobiomodulation (tPBM) is the process of delivering light photons through the skull to benefit from its modifying effect. Brain disorders are important health problems. The aim of this review was to determine the existing evidence of effectiveness, useful parameters, and safety of tPBM in the management of traumatic brain injury, stroke, Parkinson, and Alzheimer's disease as the common brain disorders. Four online databases, including Cochrane, Pub Med, Embase, and Google scholar were searched according to the Preferred Reporting Items for Systematic Reviews and meta-analyses (PRISMA) guidelines. 4728 articles were obtained in the initial search. Only those articles that were published until September 2020 and designed as randomized clinical trials (RCTs) or animal-controlled studies were included. 6 RCTs, 2 related supplementary articles, and 38 controlled animal studies met the inclusion criteria of this study. No RCTs were performed in the fields of Alzheimer's and Parkinson's diseases. The human RCTs and animal studies reported no adverse events resulted from the use of tPBM. Useful parameters of tPBM were identified according to the controlled animal studies. Since the investigated RCTs had no homogenous results, making an evidence-based decision for definite therapeutic application of tPBM is still unattainable. Altogether, these data support the need for large confirmatory well-designed RCTs for using tPBM as a novel, safe, and easy-to-administer treatment of brain disorders. EVIDENCE BEFORE THIS STUDY: High prevalence and complications of brain disorders and also side effects of neuropsychiatric medications have encouraged researchers to find alternative therapeutic techniques which tPBM can be one of them. In present review we tried to determine the existing evidence of effectiveness, useful parameters, and safety of tPBM in the management of traumatic brain injury, stroke, Alzheimer, and Parkinson's disease as common brain disorders. Four online databases, including "Cochrane", "Pub Med", "Embase", and "Google scholar" were searched. Only those articles that were published until September 2020 and designed as RCTs or animal-controlled studies were included. Search keywords were the followings: transcranial photobiomodulation" OR "transcranial low-level laser therapy" AND "stroke" OR "traumatic brain injury" OR "Alzheimer" OR "Parkinson". Several studies have confirmed effectiveness of tPBM in treatment of different brain disorders but the level of evidence of its effectiveness remain to be determined. ADDED VALUE OF THIS STUDY: In this study we systematically reviewed human RCTs to determine the existing evidence of tPBM effectiveness in management of four mentioned brain disorders. Since the outcomes of the reviewed RCTs were not homogeneous, further well-designed RCTs are required to decide more definitively on the evidence of this noninvasive and probably safe therapeutic intervention. We hypothesized that non-homogeneous outcomes could be due to inefficiency of PBM parameters. Controlled animal studies have the advantage of using objective tests to evaluate the results and compare them with the control group. We determined useful tPBM parameters based on these studies. IMPLICATIONS OF ALL THE AVAILABLE EVIDENCE: This research is part of our main project of tinnitus treatment using photobiomodulation (PBM). Evidence of central nervous system involvement in tinnitus led us to believe that treatment protocol of tinnitus should also include transcranial PBM. The determined useful parameters can be helpful in designing more efficient tPBM protocols in the management of brain disorders and tinnitus as a common debilitating symptom that can be associated with these disorders.

The Effect of Combination of Red, Infrared and Blue Wavelengths of Low-Level Laser on Reduction of Abdominal Girth: A Before-After Case Series.

Introduction: The objective of this study was to assess the efficacy of a combination of 3 wavelengths (including red, infra-red, and blue) of low-level laser (LLL) as a non-invasive therapeutic method to reduce abdominal girth. To achieve biochemical activity on adipocytes, a red laser was used in our selective laser combination. Near-infrared laser was used to increase depth of penetration. Nitrosyl complexes of hemoglobin (NO-Hb) are sensitive to blue light, thereby leading to increase in release of biologically active nitric oxide (NO), which can affect tissue perfusion. Thus, a blue LED was added to the laser combination. Methods: Eighteen females participated in the study. Twelve sessions of laser therapy were performed, 2 sessions per week for each subject. Continuous wave diode lasers, including red (630 nm), infra-red (808 nm), and a blue LED (450 nm) were applied and were all designed by the Canadian Optic and Laser Center. Results: Statistical analyses revealed that upper abdomen size significantly decreased from pre- (91.86 ± 11.16) to post- (87.41 ± 10.52) low-level laser therapy (LLLT) (P<0.001). Middle abdomen size showed significant reduction from pre- (97.02 ± 8.82) to post- (91.97 ± 8.49) LLLT (P<0.001). Lower abdomen size significantly decreased from pre- (100.36 ± 9.45) to post- (95.80 ± 8.52) LLLT (P<0.001). Conclusion: Based on this case series pilot investigation, the combination of 3 different wavelengths of LLL was effective for abdominal girth reduction in 100% of our subjects (P<0.001), without any side effects. Future studies will assess the long-term benefits of this laser combination for reduction of subcutaneous fat deposits.

Alterations in Auditory Electrophysiological Responses Associated With Temporary Suppression of Tinnitus Induced by Low-Level Laser Therapy: A Before-After Case Series.

Introduction: Tinnitus is the phantom auditory perception of sound in the absence of an external or internal acoustic stimulus. The treatment is difficult due to multiple etiologies and great psychological influence. The purpose of this study was to determine alterations in auditory physiological and electrophysiological responses associated with temporary suppression of tinnitus induced by low-level laser (LLL) irradiation. Methods: This study was conducted on 20 subjects with subjective tinnitus. All subjects signed the informed consent form and satisfied all the study eligibility criteria. Visual analog scale (VAS) for loudness, loudness matching of tinnitus (LMT), pitch matching of tinnitus (PMT), Persian-tinnitus questionnaire (P-TQ) and Persian-tinnitus handicap inventory (P-THI) were conducted pre- and post-low level laser therapy (LLLT) for all the subjects. Electrocochleography (ECochG) and distortion product otoacoustic emissions (DPOAEs) were recorded in 11 subjects. Continuous wave diode lasers, including red (630 nm) and infra-red (808 nm) were applied, and were both designed by the Canadian Optic and Laser (COL) Center. Twelve sessions of laser therapy were performed, 2 sessions per week for each subject. Total dose was 120 Joule/ ear/session. Results: LLL irradiation could cause a significant decrease in subjective tests scores consisting of VAS for loudness, PMT, P-TQ, P-THI, but did not result in a significant improvement of objective evaluating parameters except for compound action potential (CAP) amplitude. Conclusion: LLLT might be a subjectively effective treatment for short-term improvement of tinnitus. Defining a new protocol for optimizing LLLT parameters may be an option to improve parameters of objective tests.