The use of phototherapy in peripheral nerve regeneration: an updated critical review

Abstract

This review describes the possible factors that may have contributed to the variability of the results between studies that have assessed the effects of phototherapy on peripheral nerve regeneration. Furthermore, it aims to make recommendations to overcome the methodological shortcomings identified. A search of the literature was conducted. In vitro and in vivo experimental studies and clinical trials were included. Twenty five studies were critically reviewed and showed considerable variability in irradiation parameters, techniques, approaches, length of irradiation courses, experimental injury tools and procedures. Many studies that have investigated the use of phototherapy in nerve regeneration produce positive results. However, the majority of these studies suffered from a number of shortcomings: no evidence of blinding and/or randomizing procedures, lack of specification of irradiation parameters, unspecified and/or inadequate tests in their experimental injury procedures, inappropriate irradiation parameters and/or poor experimental conditions.

Keywords::

• laser therapy
• nerve regeneration
• nerve repair
• peripheral nerve injury
• phototherapy

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Many different methods have been used to facilitate nerve regeneration. The success rates are variable and some of these methods, for example, neuroregenerative drugs, are associated with various side effects.

• Substantial numbers of experimental studies have shown phototherapy as a supportive factor for accelerating and enhancing axonal growth and regeneration after injury. Furthermore, its beneficial therapeutic effects can be obtained without undesired side effects.

• Evidence for the possible positive findings of phototherapy is encouraging. There is, therefore, much scope for further large-scale, well-designed comparative trials.

• Many studies that have investigated the use of phototherapy in the nerve regeneration produce positive results, but further carefully controlled studies are needed to define the optimum treatment parameters and techniques.

• Phototherapy has employed, with encouraging results, to improve peripheral function of patients with injured peripheral nerves. Future research should aim to improve the experimental methods and provide more evidence that allow clinical translation.