Clinicians should consider disorders of masticatory muscle including lateral pterygoid muscle as a differential diagnosis in patients presenting with dysphagia and trismus after tooth extraction.

Objective: This study aimed to investigate the selected anatomical factors that can potentially influence temporomandibular joint (TMJ) clicking in young adults by assessing TMJ structures and lateral pterygoid muscle (LPM) function using magnetic resonance imaging (MRI). Methods: The patients were divided into four groups: the healthy control group; the clicking on mouth opening group; the clicking on mouth closing group; and the clicking on mouth opening and closing group. Additionally, we used clinical palpation to evaluate the masticatory muscles\' functional state and employed MRI using the OCOR-T1WI-FSE-CLOSED, OSAG-PDW-FSE-CLOSED, and OSAG-PDW-FSE-OPEN sequences to analyze the texture of the lateral pterygoid muscle (LPM). Results: The proportion of any articular disc or condylar morphology class did not differ significantly between the TMJ clicking and HC groups. The articular disc position did not differ significantly between the TMJ clicking and HC groups. In the TMJ clicking group, the presence of masticatory muscle dysfunction differed significantly between the clicking and non-clicking sides. Moreover, the LPM accounted for the highest proportion among masticatory muscles with tenderness in all TMJ clicking subgroups (77.78%-100%). Therefore, in the TMJ clicking group, the LPM texture was less defined, more uniform in gray scale, and more similar to local texture (p < 0.0001). Conclusion: The occurrence of TMJ clicking in young adults is unrelated to the TMJ structure but related to the function of masticatory muscles, particularly the LPM.

The goal of surgical treatment of mandibular head fracture is to restore anatomical relations; however, it also carries other implications. The purpose of this study is to present the alteration in the size of lateral pterygoid muscles after surgical treatment of unilateral mandibular head fractures and the impact of this change on the range of motion of the mandible. Another issue addressed is the persistence of changes in the appearance of the lateral pterygoid muscles after surgical treatment. In this study, 66 patients with unilateral mandibular head fracture were included. An additional 15 patients from this group who were treated only conservatively were separated as an extra reference group to exclude completely the effect of surgery on the appearance of the pterygoid lateral muscle (even on the opposite side to the surgically treated side). The range of mandibular movements was measured at specific time intervals up to 24 months post-operationally. Then, the lengths and widths of the lateral pterygoid muscles on the operated and healthy site were measured in CT images. The results were compared with a control group which consisted of muscles of the intact site (opposite site to the fracture). A significant reduction in the length-to-width ratio of the lateral pterygoid muscle on the operated side by approx. 20% is observed. This suggests that the muscle becomes more spherical, and thus the range of lateral movement to the contralateral side is permanently reduced.

BACKGROUND: Disc displacement with reduction (DDwR) therapy should be performed only when pain or discomfort is presented. Data on treatment options for painful DDwR are very limited.
OBJECTIVE: The aim was to investigate whether isometric training of the lateral pterygoid muscle (LPM) is equivalent to stabilisation appliance therapy with regard to the treatment of painful DDwR. The training program is based on the science of Janda.
METHODS: This was a prospective, randomised study with a comparative treatment group. Sixty patients (≥18 years) with DDwR and pain were randomly assigned to two groups: (1) muscle training and (2) stabilisation appliance. The following variables were recorded at baseline examination and after 2, 4 and 6 months: changes in orofacial pain, clicking sounds of the temporomandibular joint (TMJ), force degrees for the lateral movement of the mandible and interincisal opening distance. p values of <.05 were considered statistically significant but 95% confidence intervals were also presented.
RESULTS: A decrease in orofacial pain intensity was seen in both groups (p < .0001). Registered TMJ clicking disappeared after 6 months of treatment in 37% (n = 11) of the patients in the training group and in 27% (n = 8) of the appliance group (p = .0009 and p = .0047). Muscle training showed 27 improvements in Janda force degrees at the end of the study (p < .0001).
CONCLUSIONS: Muscle training and appliance therapy improved mouth opening and reduced pain intensity in both patient groups. Muscle training might be a promising option in the treatment of patients suffering from painful DDwR.

Pain and clicking are the primary complaints in patients suffering from temporomandibular joint disc displacement with reduction (DDwR), negatively affecting the patients\' quality of life, making the treatment essential. This prospective randomized controlled trial (RCT) was conducted to evaluate the effectiveness of botulinum toxin type-A (BTX-A) and low level laser therapy (LLLT) in comparison to anterior repositioning appliance (ARA) for the treatment of DDwR.
A total of 27 patients were randomly allocated to 3 groups; ARA (control group), BTX-A, and LLLT; with 9 patients each. All patients were evaluated before and 3 months after the treatment using a visual analogue scale (VAS) and magnetic resonance imaging (MRI).
At 3 months follow-up, all groups showed a significant reduction in pain assessed by VAS (P = 0.007). Measured on MRI, there was a significant improvement in disc position and joint space index (JSI) in BTX-A group (P < 0.001, P = 0.011) and LLLT group (P = 0.002, P = 0.017) in comparison to the control group (P = 0.087, P = 0.066) respectively. As for time of recovery, a statistically significant difference was observed in BTX-A group (P < 0.001) and LLLT (P < 0.001) group in comparison to ARA group, which showed the most prolonged duration for reduction of DDwR symptoms.
We concluded that BTX-A and LLLT could be considered effective alternative treatment modalities to ARA regarding reducing joint pain, clicking, and improving disc position in patients with symptomatic DDwR.
This prospective double-blinded RCT has been registered at ClinicalTrials.gov with identification number: NCT05194488, 18/1/2022.

OBJECTIVE: To use quantitative MRI to assess gender differences in lateral pterygoid muscle (LPM) characteristics in patients with anterior disk displacement (ADD).
METHODS: Lateral pterygoid muscle of 51 patients diagnosed with temporomandibular joint disorders (TMD) who underwent T1-weighted Dixon and T1-mapping sequences were retrospectively analyzed. There were 34 female patients (10 with bilateral normal position disk [NP]; 24 with bilateral ADD) and 17 male patients (eight with bilateral NP; nine with bilateral ADD) among them. After controlling for age, differences in fat fraction, T1 value, volume and histogram features related to gender and disk status were tested with 2-way ANCOVA or Quade ANCOVA with Bonferroni correction.
RESULTS: Volume of LPM in NP was significantly smaller than that of ADD (p < 0.001). Fat fraction of LPM in females with NP was significantly higher than males with NP (p < 0.05). Females with ADD showed a significantly higher T1 value (p < 0.05), and higher intramuscular heterogeneity than males with ADD.
CONCLUSIONS: Lateral pterygoid muscle in female TMD patients presented more fatty infiltration in the NP stage and might present more fibrosis in the ADD stage compared with males. Together, this leads to more serious intramuscular heterogeneity during the pathogenesis of ADD in females.

Magnetic resonance imaging (MRI) is useful for assessing temporomandibular disorders (TMDs). However, few studies have attempted texture analysis of the lateral pterygoid muscle in patients with rheumatoid arthritis (RA). This study aims to investigate the usefulness of MRI texture analysis of the lateral pterygoid muscle of patients with RA of the temporomandibular joint (TMJ).
We analyzed the data from 36 patients (18 non-RA patients and 18 RA patients) who complained of pain and underwent MRI between April 2008 and August 2021. From the MRI scans of these patients, 279 radiomics features were extracted using STIR image data of the ROIs on the lateral pterygoid muscle of patients with RA and analyzed using MaZda ver. 3.3. Seven gray-level co-occurrence matrix features (Sum entropy, Sum variance) were picked up using the Fisher coefficient, for comparison between the RA and non-RA groups. Data analysis was performed using the Mann-Whitney U test A P value of < 0.05 was considered as statistically significant.
All seven lateral pterygoid muscle radiomic features indicated significant differences between the non-RA and RA groups (P < 0.05).
MRI texture analysis shows potential for application in radiomics diagnosis of RA in TMJ.

Temporomandibular disorder (TMD) is the main cause of non-dental pain in orofacial area. The most common symptoms of TMD are joint pain, joint sound and limitation of jaw function. Botulinum toxin (BTX) injection is considered a potential treatment for TMD due to its pain-relieving properties and its ability to reduce muscle activity. Most of the studies are case series and further investigations are required to prove the efficacy of this treatment modality. Thus, in this study, we aimed to investigate the effect of BTX-A injection on the lateral pterygoid (LP) muscle and to evaluate its efficacy regarding TMD.
Thirty-eight patients (19 women and 19 men; mean age of 26.53 years) with painful unilateral temporomandibular joint click and LP muscle tenderness were enrolled in this study. They were divided into two groups; one received an extraoral BTX-A injection in the LP muscle, and the other received a placebo injection. Pain severity, jaw movements, click severity, and Helkimo index were recorded at the first visit, as well as one week, one month, and three months after the intervention. Data were analyzed using repeated-measures analysis of variance and t-tests.
The results showed that click severity was not significantly different between the BTX-A and placebo groups (P = 0.07). Pain and Helkimo index decreased significantly in the BTX group (P = 0.00 and P = 0.006, respectively); however, there was no significant difference between the two groups (P = 0.22 and P = 1, respectively). There was a significant difference in lateral movements between the groups (P = 0.00) but not in protrusive movement (P = 0.095).
It can be concluded that although some studies have stated that BTX injection can make the click sound disappear, in this study, we did not find a significant difference between the two groups. Furthermore, our results showed that click and pain severity decreased, but the difference was not statistically significant. Therefore, further studies with a higher dosage of BTX and more participants are recommended. Trial registration The local Ethics Committee of Shiraz University of Medical Sciences approved this research (IR.SUMS.REC. 01/10/2018 and IRCT20130521013406N3).

It has been suggested that the variations in the trajectory of the maxillary artery (MA) near the lateral pterygoid muscle (LPM) play a critical role in Botulinum neurotoxin (BoNT) injections in patients with jaw-opening/deviation dystonia (JOD). In the case of a lateral course to the LPM, an extraoral injection entails risks of MA injury, pain, and hematoma. Previous reports suggest geographical differences in variations of the MA-LPM relationship. We aimed to determine these variations in Turkish individuals and highlight the need to establish a consensus on approach to LPM injections. In 284 individuals, contrast-enhanced magnetic resonance angiography (MRA) images were evaluated by two radiologists on both sides for the variations in the course of the MA in the infratemporal fossa. Images of 44 were excluded due to trauma, arteriovenous malformation, mass, surgery, and imaging artifacts. Of the included, 62.1% were female. In 480 evaluations of 240 individuals, the MA passed lateral to the LPM in 65.6% (n = 315). No sex difference was noted. In 51 individuals (21.3%), the MA course differed on the right and left sides (medial-lateral asymmetry). These results confirm that the lateral course of the MA is more frequent. In patients with JOD, the trajectory of the MA should be determined with imaging prior to extraoral BoNT injections. In the case of a lateral course, an intraoral approach seems to be safer to avoid a potential MA injury.

Botulinum toxin type A (BTX-A) injection using nerve stimulation or electromyography for recurrent temporomandibular joint (TMJ) dislocation has been reported for several years. However, using the available equipment like a nerve stimulator or an electromyograph is uncommon, and ultrasound guidance is convenient and requires no additional resources. In this report, we used ultrasound as a tool to achieve BTX-A injections in a patient with a traumatic brain injury to treat her TMJ dislocation. One week after the injections, she had no more dislocation. She remained symptom free during the 3 months of follow-up, and her clinical symptoms improved without significant complications. This is the first report using ultrasound guidance for BTX-A injections to treat recurrent TMJ dislocation. This treatment is an effective and safe technique that could be performed timely and locally without referral to a center with electromyography facilities.