Objective: To provide biomechnical basis for orthodontics of centronuclear myopathy (CNM) patients, we studied the oral and maxillofacial clinical features and MRI image manifestations to explore application of MRI to objective evaluation the affected facial muscles. Methods: The study consisted of 8 patients who were diagnosed as CNM (CNM group) and 20 healthy volunteers (control group). Their medical information were gathered and then we examined the ptosis situation and the facial index calculation of them. To measure the maximal hight of palate and the width of palate, patients and volunteers were made impressions. We also checked their maximum bite force with occlusion pressure tester. And they took lateral cephalometric radiographs to measure mandibular plane-Frankfort horizontal plane angle (MP-FH). At last, they were taken oral and maxillofacial region MRI to observe the affected situation of masseter muscle, medial pterygoid muscle and lateral pterygoid muscle. Results: Six patients were ptosis; 6 patients had inverse V-shaped mouth; 3 patients were difficulty in swallowing; 4 patients were anterior open bites; 4 patients were mouth breathing; 7 patients liked to eat soft foods. Morphological facial index ([91.3±0.5]%), MP-FH (34.9°±2.0°) of CNM group were greater than the control group, male maximal hight of palate ([19.0±0.2] mm), female maximal hight of palate ([18.0±0.6] mm) of CNM group were greater than the control group (P<0.05). Male width of palate ([34.5±0.8] mm), female width of palate ([33.4±1.0] mm), male maximum bite force ([464.3±78.2] N), female maximum bite force ([320.7±13.8] N), maximal opening of mouth ([3.4±0.3] cm) of CNM group were less than the control group (P<0.05). And these had significant difference compared with the control group (P<0.05). In MRI examination, there were 7 patients' masseter muscles, 4 patients' medial pterygoid muscles and 6 patients' lateral pterygoid muscles to atrophy asymmetrically. These three pieces of muscular fatty infiltration were inordinately, focused on Grade 0 to 4 and the both sides were similar. Conclusions: CNM patients with long and thin face, high palatine arches and low bite force together were the biomechanical basis of the maxillofacial deformities. MRI can clearly show the affected masseter muscle, medial pterygoid muscle, lateral pterygoid muscle, and can serve as an objective examination method for the evaluation of facial muscles. It can be worth of clinical popularization and application.
目的： 研究中心核肌病（centronuclear myopathy，CNM）患者口腔颌面部临床特征及颌面肌群MRI表现，为CNM患者口腔正畸治疗提供生物力学依据。 方法： 收集2014年1月至2016年10月于河北医科大学第三医院神经肌肉病科就诊的8例CNM患者（男女各4例，CNM组）及2014年10月至2015年12月于河北医科大学第二医院口腔内科行口腔健康检查的20名健康志愿者（男女各10名，健康对照组）的临床资料，并测量上睑下垂、形态面指数；制备口腔模型，测量最大腭弓高度和腭弓宽度；使用 力测试仪检查最大 力；记录最大开口度；拍摄头颅侧位X线片，测量下颌平面角；颌面部MRI检测咬肌、翼内肌、翼外肌的受累程度，在不同层面观察肌肉内脂肪浸润分级。 结果： CNM组上睑下垂6例、逆V形嘴6例、吞咽困难3例、前牙开 4例、张口呼吸4例、喜进软食7例；CNM组形态面指数为（91.3±0.5）%，均为细长脸型；下颌平面角为34.9°±2.0°；男性和女性最大腭弓高度[（19.0±0.2）和（18.0±0.6）mm]均显著高于健康对照组（P<0.05），而CNM组男性和女性腭弓宽度[（34.5±0.8）和（33.4±1.0）mm]、男性和女性最大 力[（464.3±78.2）和（320.7±13.8）N]、最大开口度[（3.4±0.3）cm]均显著小于健康对照组（P<0.05）；颌面部MRI显示，CNM组7例咬肌、4例翼内肌、6例翼外肌均呈现不同程度的脂肪浸润，受累程度为0至4级，双侧肌肉受累情况基本对称。 结论： CNM患者的细长脸型、高腭弓、 力低下是导致颌面畸形的生物力学基础。MRI可清晰显示患者咬肌、翼内肌、翼外肌受累肌群，可作为评价CNM患者颌面肌群的客观检查方法。.
Keywords: Magnetic resonance imaging; Masticatory muscles; Myasthenic syndromes, congenital; Myopathy, central core.