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Title Head and Neck Radiation Therapy, Regardless of Beam Angulation, Results in Reduced Maximal Vertical Opening and Decreased Mandibular Function
Clinical Question In adult patients undergoing radiation therapy, would angulating the radiation beam towards the TMJ region compared to the pterygoid muscles cause a decrease in the maximal vertical opening?
Clinical Bottom Line As dose to the temporomandibular joint and pterygoid muscles increases, maximal jaw opening decreases. This is supported by an in vivo study in which maximum jaw opening and mandibular mobility were measured before and after radiation treatment. Further evidence is a prospective study that demonstrated how a higher mean radiation dose to the muscles of mastication led to trismus.
Best Evidence (you may view more info by clicking on the PubMed ID link)
PubMed ID Author / Year Patient Group Study type
(level of evidence)
#1) 10503870M. Goldstein/199958 Adults undergoing radical radiation therapyProspective Cohort Study
Key results•As the radiotherapy radiation dose to TMJ and pterygoid muscles increased, the maximal vertical opening decreased. •As radiation dose increased to the pterygoid muscles, mandibular dysfunction increased. These results didn’t appear with radiation to TMJ. •Development of trismus was more apparent with radiation to the pterygoid muscles alone (31% of patients). •TMJ and pterygoid muscles irradiated with the angle down wedge treatment had clinical effects that were similar to those seen in homolateral wedge pair and parallel pair patients. •Lowest dose to produce functional impairment was 1493 cGy.
#2) 29630433Hague/201820 patients with stage III/IV squamous cell carcinomas of the oral cavity/oropharynxProspective Cohort Study
Key results•All 20 patients that were reviewed all had established trismus after radiation therapy. •Six of the patients had a change in maximal inter-incisor distance (MID) from a baseline of 29mm to 18mm after 6 months from the initial radiation treatment, these patients received a radiation dose of greater than 40 Gy. •For 14 patients, the MID improved from 16mm to 31mm at 6 months, these patients received a radiation dose of less than 40 Gy. •A change of 4%-7% in mouth opening was found per gray of dose to the relevant structures. •Use of proactive exercises both during and after radiotherapy treatment: the MID improved with more exercises performed; however, there was no statistical significance for this relationship. •Mean doses to ipsilateral lateral pterygoid (LP) and masseter were significantly associated with change in MID. •Mean dose to ipsilateral masseter was most correlated with trismus. •No correlation found between 35 and 60 Gy with changes in trismus across all paired muscles. •Higher mean radiation doses to LP and masseter were significantly associated with trismus deterioration. •Radiation dose should be limited to less than 40 Gy.
Evidence Search (“Head and neck radiation therapy”) AND (“TMD effect”)/ (“Trismus”)
Comments on
The Evidence
The study by Goldstein et al. suggests that as radiation dosage to the TMJ and pterygoid muscles increased, the maximal vertical dimension (MVD) decreased. Three (3) groups were categorized based on the type of irradiation, and the results demonstrated that MVD changes are not different between the groups, although the beam orientation may alter the radiation dosage administered to individual muscles. Furthermore, the difference in percentages between pre-radiotherapy and post-radiotherapy MVD increased among the 3 groups based on the type of irradiation. This methodology of study is great for examining radiation therapy over a 2-year period, although the sample size was small, and age and gender were not considered. Clinical assessments were also completed in a timely manner, between 6-12 months after radiation therapy. This cohort study is reasonably high on the evidence pyramid and eliminated any observational bias by having a single operator who measured the MVD on all patients using a standard Bouley gauge. The outcomes of the study were obtained without considering other contributing factors. For instance, the MVD was measured in edentulous patients from the maxillary alveolar ridge to the mandibular ridge over 2 years without considering the physiological natural resorption of the alveolar bone. Additionally, the study considered the effect of irradiation alone on mandibular dysfunction without considering effect of the tumor progression itself over 2 years. The study by Hague et al. suggests that patients receiving radiation dosage greater than 40Gy experienced trismus that deteriorated at 6 months. This indicates that dosage of the radiation greatly affects the TMJ and the muscles. Twenty patients from one center with stage III/IV squamous cell carcinoma in the oral cavity or oropharynx were evaluated. Similar to the Goldstein study, this study focused on how the radiation affects the maximal inter-incisor distance (MID). The results indicated that six patients experienced a deteriorated MID. These patients received a higher radiation dose, compared to the 14 patients whose MID improved and were recipients of a lower radiation dose. These findings were not observed to have associations with age, gender, smoking, alcohol status, exercise compliance, tumor size or stage. The findings indicate that a radiotherapy radiation dose to the structures related to the TMJ and muscles of mastication should be limited to less than 40Gy. Any future studies should consider a larger sample size, the patient's ethnicity, age, and gender, and similar types of head and neck carcinomas.
Applicability Dental clinicians should be aware that patients presenting with a history of radiation therapy to the head and neck region are more likely to be experiencing TMD and/or limited mouth opening, especially patients receiving radiation therapy to the TMJ or pterygoid muscle regions. Clinicians who prescribe the radiation dosage for radiotherapy for cancer patients need to be aware of the maximal dosage limit, especially for orofacial and neck cancers, as they can significantly impact the patient's ability to function with their TMJ/oral cavity.
Specialty/Discipline (Oral Medicine/Pathology/Radiology) (General Dentistry) (Oral Surgery) (Prosthodontics) (Restorative Dentistry)
Keywords Radiation therapy, TMD, Trismus
ID# 3498
Date of submission: 11/26/2022spacer
E-mail samara@uthscsa.edu
Author Asma Samara
Co-author(s) Janet Park
Co-author(s) e-mail parkj11@livemail.uthscsa.edu
Faculty mentor/Co-author Soo Cheol Jeong
Faculty mentor/Co-author e-mail jeongs2@uthscsa.edu
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