Roberta Chow

A systematic review of low level laser therapy with location-specific doses for pain from chronic joint disorders

We investigated if low level laser therapy (LLLT) of the joint capsule can reduce pain in chronic joint disorders. A literature search identified 88 randomised controlled trials, of which 20 trials included patients with chronic joint disorders. Six trials were excluded for not irradiating the joint capsule. Three trials used doses lower than a dose range nominated a priori for reducing inflammation in the joint capsule. These trials found no significant difference between active and placebo treatments. The remaining 11 trials including 565 patients were of acceptable methodological quality with an average PEDro score of 6.9 (range 5-9). In these trials, LLLT within the suggested dose range was administered to the knee, temporomandibular or zygapophyseal joints. The results showed a mean weighted difference in change of pain on VAS of 29.8 mm (95% CI, 18.9 to 40.7) in favour of the active LLLT groups. Global health status improved for more patients in the active LLLT groups ( relative risk of 0.52; 95% CI 0.36 to 0.76). Low level laser therapy with the suggested dose range significantly reduces pain and improves health status in chronic joint disorders, but the heterogeneity in patient samples, treatment procedures and trial design calls for cautious interpretation of the results.

Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomised placebo or active-treatment controlled trials

BACKGROUND Neck pain is a common and costly condition for which pharmacological management has limited evidence of efficacy and side-effects. Low-level laser therapy (LLLT) is a relatively uncommon, non-invasive treatment for neck pain, in which non-thermal laser irradiation is applied to sites of pain. We did a systematic review and meta-analysis of randomised controlled trials to assess the efficacy of LLLT in neck pain. METHODS We searched computerised databases comparing efficacy of LLLT using any wavelength with placebo or with active control in acute or chronic neck pain. Effect size for the primary outcome, pain intensity, was defined as a pooled estimate of mean difference in change in mm on 100 mm visual analogue scale. FINDINGS We identified 16 randomised controlled trials including a total of 820 patients. In acute neck pain, results of two trials showed a relative risk (RR) of 1.69 (95% CI 1.22-2.33) for pain improvement of LLLT versus placebo. Five trials of chronic neck pain reporting categorical data showed an RR for pain improvement of 4.05 (2.74-5.98) of LLLT. Patients in 11 trials reporting changes in visual analogue scale had pain intensity reduced by 19.86 mm (10.04-29.68). Seven trials provided follow-up data for 1-22 weeks after completion of treatment, with short-term pain relief persisting in the medium term with a reduction of 22.07 mm (17.42-26.72). Side-effects from LLLT were mild and not different from those of placebo. INTERPRETATION We show that LLLT reduces pain immediately after treatment in acute neck pain and up to 22 weeks after completion of treatment in patients with chronic neck pain. FUNDING None.

830 nm laser irradiation induces varicosity formation, reduces mitochondrial membrane potential and blocks fast axonal flow in small and medium diameter rat dorsal root ganglion neurons: implications for the analgesic effects of 830 nm laser.

Abstract  We report the formation of 830 nm (cw) laser‐induced, reversible axonal varicosities, using immunostaining with β‐tubulin, in small and medium diameter, TRPV‐1 positive, cultured rat DRG neurons. Laser also induced a progressive and statistically significant decrease (p < 0.005) in MMP in mitochondria in and between static axonal varicosities. In cell bodies of the neuron, the decrease in MMP was also statistically significant (p < 0.05), but the decrease occurred more slowly. Importantly we also report for the first time that 830 nm (cw) laser blocked fast axonal flow, imaged in real time using confocal laser microscopy and JC‐1 as mitotracker.

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.

Inhibitory effects of visible 650-nm and infrared 808-nm laser irradiation on somatosensory and compound muscle action potentials in rat sciatic nerve: implications for laser-induced analgesia

Low‐level laser therapy (LLLT) has been shown in clinical trials to relieve chronic pain and the World Health Organization has added LLLT to their guidelines for treatment of chronic neck pain. The mechanisms for the pain‐relieving effects of LLLT are however poorly understood. We therefore assessed the effects of laser irradiation (LI) on somatosensory‐evoked potentials (SSEPs) and compound muscle action potentials (CMAPs) in a series of experiments using visible (λ = 650 nm) or infrared (λ = 808 nm) LI applied transcutaneously to points on the hind limbs of rats overlying the course of the sciatic nerve. This approximates the clinical application of LLLT. The 650‐nm LI decreased SSEP amplitudes and increased latency after 20 min. CMAP proximal amplitudes and hip/ankle (H/A) ratios decreased at 10 and 20 min with increases in proximal latencies approaching significance. The 808‐nm LI decreased SSEP amplitudes and increased latencies at 10 and 20 min. CMAP proximal amplitudes and H/A ratios decreased at 10 and 20 min. Latencies were not significantly increased. All LI changes for both wavelengths returned to baseline by 48 h. These results strengthen the hypothesis that a neural mechanism underlies the clinical effectiveness of LLLT for painful conditions.

A Pilot Study of Low-Power Laser Therapy in the Management of Chronic Neck Pain

Objective: This pilot study was undertaken to test techniques of application of laser therapy, appropriate outcome measures and to determine effect sizes in order to facilitate the performance of a larger, clinical trial of laser therapy in chronic neck pain. Methods: We conducted a randomized double-blind, placebo-controlled study of low level laser therapy in 20 patients with chronic neck pain. The primary outcome measure was change in a 10 cm Visual Analogue Scale [VAS] for pain. Other measures used included a Self-Reported Improvement in pain [SRI], measured by a VAS, Short-Form 36 Quality-of-Life questionnaire [SF-36], Northwick Park Neck Pain Questionnaire [NPNPQ] and the McGill Pain Questionnaire [MPQ]. Measurements were taken at baseline, at the end of 7 weeks treatment and at 12 weeks from baseline. Results: We found a positive, pain-relieving effect in the treated group compared with those given placebo using the VAS [P < 0.039], SRI [P < 0.001], NPNPQ [P < 0.002] and the MPQ [P < 0.009]. The results of the SF-36 did not differ significantly between the two groups. Patients in the treated group experienced an average pain score improvement of 66.7% compared with 16.6% in the placebo group. Conclusion: Low-power laser therapy, at the parameters used in this pilot study, may provide a non-invasive, non-pharmaceutical therapy for chronic neck pain for patients in general practice. Further study of this technique in a large-scale trial would be justified on the basis of the findings of this pilot study.

Electrophysiological Effects of Single Point Transcutaneous 650 and 808 nm Laser Irradiation of Rat Sciatic Nerve: A Study of Relevance for Low-Level Laser Therapy and Laser Acupuncture

OBJECTIVE The purpose of this study was to evaluate effects of transcutaneous 650 and 808 nm laser irradiation (LI) to a single point overlying rat sciatic nerve; a comparison to four point LI and relevance to the clinical application of low-level laser therapy (LLLT) and laser acupuncture (LA). BACKGROUND DATA Transcutaneous LI inhibits somatosensory and motor conduction when delivered to four points overlying sciatic nerve; however, effects of the same total energy delivered to a single point over the nerve, equating to laser acupuncture, are undefined. METHODS Transcutaneous 808 nm, 450 mW, (13.5 or 54 J) continuous wave (cw) mode or 650 nm, 35 mW, (1.1 or 4.4 J), cw LI or sham LI, was applied for 30 or 120 sec to a single point overlying the midpoint of rat sciatic nerve. Somatosensory evoked potentials (SSEPs) and compound muscle action potentials (CMAPs) were then recorded after 10 and 20 min, and after 24 and 48 h. RESULTS 120 sec of 808 nm LI increased SSEP amplitudes only at 10 min, with no effect of 30 or 120 sec at other time points on SSEPs or on CMAPs. LI 650 nm for 30 or 120 sec did not alter SSEPs or CMAPs at any time point. CONCLUSIONS Localized transcutaneous 808 LI to a single point overlying sciatic nerve increases SSEP amplitudes when compared with delivery of the same total energy to four points, which causes decreased SSEP amplitudes and conduction block. Therefore, the area and duration of delivery are important, independent variables with implications for clinical delivery of both LLLT and LA.

Efficacy of 300 mW, 830 nm Laser in the Treatment of Chronic Neck Pain: A Survey in a General Practice Setting

We evaluated the effectiveness of 300 mW, 830 nm laser in the management of patients with chronic neck pain, in general practice, between May 1998 and June 1999. Data was obtained from 78 patients who rated self-assessed improvement of symptoms on a visual analog scale. An average improvement of 67.5 percent was found in 48 patients who reported a positive response to treatment. Number of treatments was the only factor that correlated with a positive response reaching a plateau by 15. Low level laser therapy using this wavelength and power of infrared laser may provide a nondrug, noninvasive option for the management of neck pain. This study lends support for a randomized-controlled trial to further evaluate this therapy.

Neuroprotective Effects Against POCD by Photobiomodulation: Evidence from Assembly/Disassembly of the Cytoskeleton

Postoperative cognitive dysfunction (POCD) is a decline in memory following anaesthesia and surgery in elderly patients. While often reversible, it consumes medical resources, compromises patient well-being, and possibly accelerates progression into Alzheimers disease. Anesthetics have been implicated in POCD, as has neuroinflammation, as indicated by cytokine inflammatory markers. Photobiomodulation (PBM) is an effective treatment for a number of conditions, including inflammation. PBM also has a direct effect on microtubule disassembly in neurons with the formation of small, reversible varicosities, which cause neural blockade and alleviation of pain symptoms. This mimics endogenously formed varicosities that are neuroprotective against damage, toxins, and the formation of larger, destructive varicosities and focal swellings. It is proposed that PBM may be effective as a preconditioning treatment against POCD; similar to the PBM treatment, protective and abscopal effects that have been demonstrated in experimental models of macular degeneration, neurological, and cardiac conditions.

How to analyze the Visual Analogue Scale: Myths, truths and clinical relevance

Abstract Background and aims The Visual Analogue Scale (VAS) is a popular tool for the measurement of pain. A variety of statistical methods are employed for its analysis as an outcome measure, not all of them optimal or appropriate. An issue which has attracted much discussion in the literature is whether VAS is at a ratio or ordinal level of measurement. This decision has an influence on the appropriate method of analysis. The aim of this article is to provide an overview of current practice in the analysis of VAS scores, to propose a method of analysis which avoids the shortcomings of more traditional approaches, and to provide best practice recommendations for the analysis of VAS scores. Methods We report on the current usage of statistical methods, which fall broadly into two categories: those that assume a probability distribution for VAS, and those that do not. We give an overview of these methods, and propose continuous ordinal regression, an extension of current ordinal regression methodology, which is appropriate for VAS at an ordinal level of measurement. We demonstrate the analysis of a published data set using a variety of methods, and use simulation to compare the power of the various methods to detect treatment differences, in differing pain situations. Results We demonstrate that continuous ordinal regression provides the most powerful statistical analysis under a variety of conditions. Conclusions and Implications We recommend that in the situation in which no covariates besides treatment group are included in the analysis, distribution-free methods (Wilcoxon, Mann–Whitney) be used, as their power is indistinguishable from that of the proposed method. In the situation in which there are covariates which affect VAS, the proposed method is optimal. However, in this case, if the VAS scores are not concentrated around either extreme of the scale, normal-distribution methods (t-test, linear regression) are almost as powerful, and are recommended as a pragmatic choice. In the case of small sample size and VAS skewed to either extreme of the scale, the proposed method has vastly superior power to other methods.