The role of Photobiomodulation therapy in the treatment of head and neck radiotherapy-related trismus: a single-arm clinical trial

Abstract

Background Trismus is a common adverse effect in patients with head and neck cancer. Patients have a limitation of mouth opening (< 35mm), which can compromise maxillomandibular function. The cancer treatment itself can lead to its emergence, with surgery and radiotherapy being the most involved. This study aimed to evaluate the efficacy of a PBMT protocol for treating and reducing the severity of trismus in patients undergoing radiotherapy for head and neck cancer. Material and Methods Sixteen patients who had a mouth opening < 35mm and were undergoing RT were included. The patients were evaluated daily before and after the PBMT application, measuring mouth opening and performing pain scores for the masticatory muscles using the VAS scale. We used the infrared laser (~ 808nm) extraoral, 0.1W power, 3J energy, 30s (30.61/cm2) per point, applied to temporalis anterior, masseter, and TMJ muscles. We used one intraoral point with the same wavelength and energy density as the others for the medial pterygoid muscle. Results The mean mouth opening of the patients increased by more than 7 mm throughout the treatment. The pain scores on the initial days showed an immediate reduction after PBMT on the ipsilateral side in the muscles and TMJ. Throughout PBMT applications, there was a significant reduction in pain scores in all muscles and the TMJ. The radiation dose of all patients was above 40Gy, which is the threshold dose for the risk of developing trismus. PBMT in patients with mouth opening < 35mm has been responsible for long-term improvement in mouth opening limitation and pain during mouth opening. Conclusion It is suggested that PBMT helps in pain control by anti-inflammatory muscle pathways. Further studies are needed to evaluate the preventive capacity of this or other PBMT protocols in trismus related to RT of HNC.