## 3 Discussion
Reduction of the masseter muscle volume was evident after approximately 1 month and 17 out of 19 patients were satisfied with the results [2]. [PERSON] et al. compared the effect of masseter muscle reduction based on radiofrequency and botulinum toxin A injection. Masseter muscle thickness decreased up to 6 months post-treatment but increased afterwards until 12 months following the injection while muscle thickness steadily decreased over 12 months with radiofrequency. Thus, the authors concluded that the effect of masseter muscle reduction using radiofrequency was more significant than that from botulinum toxin A injection [27]. There is only one case study about masseteric nerve neurotomy using radiofrequency for the treatment of masseter muscle hypertrophy [2]. Recently, some clinicians are attempting masseteric nerve neurotomy for the treatment of TMD symptoms. Unfortunately, there is only a single case report that described worsening of myofasical pain following masseteric nerve neurotomy [28]. In case 1, MRI analysis resulted in the diagnosis of inflammatory myositis. Medication and physical therapy were effective in relieving symptoms including mouth opening limitation. From this case, it can be seen that side-effects that may occur with masseter muscle reduction using radiofrequency based coagulation may also occur with masseter nerve neurotomy. Mouth opening limitation is generally known to resolve over time, but caution is required since cases of permanent mouth opening limitation have been reported [25]. In case 2, it is presumed that the occlusal discomfort may have been caused by asymmetry in the masseter muscles due to the imbalanced application of radiofrequency on each side. Animal study results showed that the degree of masseter muscle reduction was dependent on the number of radiofrequency applications [29]. Another possible cause is the pre-existing degenerative joint disease of the TM] codyles of this patient; joint disease could be identified on CBCT images taken prior to the first visit to our clinic. Procedures done on the orofacial region may have resulted in increased awareness of a previously existing malocclusion. The prevalence of TM] degenerative joint disease in adults is 9.8% [30] and conventional treatment includes occlusal splint, medication, and physical therapy [31]. TENS therapy that blocks nociceptive transmission by activating A\(\beta\) fibers is known as an efficient method to treat multifactorial pain such as cervical pain and TMD [32]. Prior to performing masseteric nerve neurotomy, which is an invasive treatment with irreversible results, conservative treatment should have been considered first. Since the effects of masseter muscle reduction are permanent, occlusal adjustment or orthodontic treatment could be considered if necessary, after TMD related symptomsare sufficiently relieved. The psychological evaluation scores were high with the patient of case 2 and as chronic pain is commonly associated with psychological conditions such as anxiety and depression that can affect long-term prognosis [8], psychological evaluation of the patient could be another aspect to consider in the evaluation process of a TMD patient for successful treatment results with radiofrequency neuroectomy. Before considering masseteric nerve neuroectomy, close and thorough clinical examinations are necessary to avoid poor treatment response and unwanted side-effects. Myogenous TMD constitutes approximately 45% of all TMD cases [33] and in spite of its high prevalence, the underlying mechanism remains elusive. Evidence shows that masticatory muscle hyperactivity could be irrelevant to the generation of persistent orofacial muscle pain [34]. Additionally, a previous study showed that there was no significant difference in masseter muscle width between myofasical pain patients and pain free controls [35]. Evidence supports the role of a central nociceptive pathway in myogenous pain [36].