Wu Vincent Wc, Ying Michael Tc, Kwong Dora Lw
1 Department of Health Technology and Informatics, Hong Kong Polytechnic University, Hong Kong, Hong Kong SAR.
2 Department of Clinical oncology, University of Hong Kong, Pokfulam, Hong Kong.
Br J Radiol. 2017 Dec;90(1080):20170375. doi: 10.1259/bjr.20170375. Epub 2017 Oct 27.
Radiation-induced trismus, which is resulted from damage of the temporomandibular joint (TMJ), is one of the common late complications in nasopharyngeal carcinoma (NPC) patients after radical radiotherapy. This study investigated the radiation induced TMJ changes using ultrasonography in post-radiotherapy (post-RT) NPC patients.
114 NPC patients, who had completed radiotherapy for more than 4 years, were assessed with the maximum incisal distance (MID) and ultrasonography examination of TMJ from which the maximum disc thickness of the joint disc, the condyle irregularity (CI), joint vascularity (JV) and relative muscle echogenicity were assessed. The same assessments were conducted on 100 age-matched normal subjects. The results were compared among the patients with and without trismus, and the control group. The mean doses to the TMJ were estimated using the treatment planning system and their correlation with the magnitude of MID was also investigated by the Pearson correlation test.
39 out of the 114 patients (34.2%) presented with trismus. The average mean TMJ for all patients was 41.4 Gy, in which patients with trismus was significantly higher than patients without trismus (p = 0.017). The mean MID of patient group was significantly lower than control group (p < 0.001). The mean maximum disc thickness of the patient group was significantly smaller than the control group, whereas the mean CI and JV were significantly higher in patient group. For relative muscle echogenicity, a higher percentage of the control group showed hyperechoic pterygoid muscle than the patient group. The mean total dose to the TMJs for the patient group was 41.4 Gy and there was a mild negative correlation between the mean TMJ dose and the MID (r = -350).
The TMJ in post-RT NPC patients showed reduction of disc thickness, increase of CI and JV. Patients with trismus demonstrated thinner disc thickness and higher JV than those without trismus. Advances in knowledge: Our study was the first cross-sectional comparative study involving over 100 patients and normal subjects that used ultrasound to assess the radiation-induced morphological changes of TMJ. Post-RT TMJ changes characterized by the reduction of disc thickness, increase of CI and JV were detected in the NPC patients. The parameters used in this study were able to detect the morphological differences between the patient group and control group, and therefore can be effectively used to monitor the TMJ condition of post-RT NPC patients.
放射性牙关紧闭是颞下颌关节（TMJ）受损所致，是鼻咽癌（NPC）患者根治性放疗后常见的晚期并发症之一。本研究采用超声检查放疗后（放疗后）NPC患者放射性诱导的TMJ变化。
对114例完成放疗4年以上的NPC患者进行最大切牙距离（MID）评估及TMJ超声检查，评估关节盘最大厚度、髁突不规则度（CI）、关节血管化（JV）和相对肌肉回声。对100例年龄匹配的正常受试者进行同样的评估。比较有和无牙关紧闭的患者以及对照组的结果。使用治疗计划系统估计TMJ的平均剂量，并通过Pearson相关检验研究其与MID大小的相关性。
114例患者中有39例（34.2%）出现牙关紧闭。所有患者的平均TMJ平均剂量为41.4 Gy，其中有牙关紧闭的患者明显高于无牙关紧闭的患者（p = 0.017）。患者组的平均MID明显低于对照组（p < 0.001）。患者组的平均关节盘最大厚度明显小于对照组，而患者组的平均CI和JV明显更高。对于相对肌肉回声，对照组显示翼状肌高回声的百分比高于患者组。患者组TMJ的平均总剂量为41.4 Gy，平均TMJ剂量与MID之间存在轻度负相关（r = -350）。
放疗后NPC患者的TMJ显示关节盘厚度减小、CI和JV增加。有牙关紧闭的患者与无牙关紧闭的患者相比，关节盘厚度更薄，JV更高。知识进展：我们的研究是第一项涉及100多名患者和正常受试者的横断面比较研究，使用超声评估放射性诱导的TMJ形态变化。在NPC患者中检测到以关节盘厚度减小、CI和JV增加为特征的放疗后TMJ变化。本研究中使用的参数能够检测患者组和对照组之间的形态差异，因此可有效用于监测放疗后NPC患者的TMJ状况。
