Gender differences in lateral pterygoid muscle in patients with anterior disk displacement.

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.

Lateral Pterygoid Muscle Ossification After Intraoral Condylectomy.

PURPOSE: Lateral pterygoid muscle ossification has not been reported in condylectomy patients. This study aimed to explore the incidence, risk factors, and imaging characteristics of 38 cases with lateral pterygoid muscle ossification among 54 patients after condylectomy via intraoral approach. METHODS: This retrospective study included 54 patients following simultaneous orthognathic surgery and condylectomy with coronoid process resection via intraoral approach. The authors evaluated the preoperative, 1 week, 6 months, and 1 year or more postoperative computed tomographic (CT) scans for the presence of lateral pterygoid muscle ossification and its characteristics. Sex, age at the time of surgery, disease course, affected side, preoperative alkaline phosphatase, pathology diagnosis, the height of the removed condyle, condylar shape, operator, preoperative temporomandibular joint movement, and clinical symptoms were assessed as risk factors for ossification. RESULTS: No incidence of lateral pterygoid muscle ossification was found on preoperative CT images. Various small-size osseous masses were observed in the lateral pterygoid muscles on postoperative 6 months CT images in 38/54 patients (70.37%) after condylectomy. But no apparent enlargement of the osseous masses was found. No patients complained of clinical discomfort or functional disorder during the follow-up period (23.11 ± 13.16 months). No significant risk factors for ossification were found. CONCLUSIONS: Lateral pterygoid muscle ossification is relatively common in patients after condylectomy via intraoral approach. However, its enlargement is self-limited and remains stable 6 months after surgery. it has no adverse effects on the temporomandibular joint functional movement.

Prevalence, morphology, and morphometry of the pterygospinous bar: a meta-analysis.

PURPOSE: The purpose of the study was to analyze the total prevalence, morphologic, and morphometric characteristics of the pterygospinous (PS) bar and its gender and ethnic differences among populations. PS bar is an ossified anatomic structure stretching between the posterior margin of the lateral pterygoid lamina to the angular spine of the undersurface of the sphenoid, with potential clinical implications. There is no consensus in the literature on its prevalence, morphologic, and morphometric characteristics. METHODS: A thorough search of databases was conducted. Data on the prevalence, morphology, i.e., ossification type (complete and incomplete), side, gender, laterality, and morphometrics, of the PS bar were extracted and pooled into a meta-analysis. RESULTS: A total of 35 studies (n = 14,047 subjects) were analyzed. The overall pooled prevalence of a complete PS bar was 4.4% (95% CI 3.7-5.1), while the overall pooled prevalence of an incomplete PS bar was significantly higher (11.6% [95% CI 8.5-15.2]). A complete PS bar was more prevalent among males and was more commonly unilaterally, on the left side. CONCLUSION: The overall prevalence of PS bar is quite common. It could be of importance for clinicians who should consider its potential presence when planning surgical approaches to the retropharyngeal and parapharyngeal space.

Myositis Ossificans Traumatica of the Medial Pterygoid Muscle After Third Molar Tooth Extraction: A Case Report and Review of Literature.

Myositis ossificans (MO) is a rare non-neoplastic disorder characterized by heterotopic ossification in soft tissues, mainly muscles. MO traumatica is characterized by ossification of the soft tissues after acute or repetitive trauma, burns, or surgical intervention. Muscular or soft tissue trauma is usually present as the underlying etiology. MO traumatica usually involves the extremity muscles. The number of reported cases involving the masticatory muscles is extremely low. The most common clinical sign of this condition is progressive limitation of mouth opening. Surgical resection of the ossified tissue has been the most commonly used treatment for this disorder, with a high postoperative recurrence rate. We report a case of traumatic MO of the medial pterygoid muscle to draw attention to the possibility of the condition in patients with a limited mouth opening and to review the reported data about MO traumatica involving the medial pterygoid muscle.

Outcome of compartment resection of locally advanced oral cancers extending to infratemporal fossa: a tertiary rural hospital experience.

Locally advanced oral cancers extending to infratemporal fossa (ITF) are a challenge to head and neck surgeons. These tumors are classified as T4b whenever the masticator space (MS), pterygoid muscles (PM), and pterygoid plates (PP) are involved according to AJCC classification. Until recently, these tumors were considered inoperable and treated only with palliative intent. However, a few studies in the last decade showed that many of these tumors could be resected with a reasonably favorable prognosis by compartment resection of ITF, particularly when the tumor was below sigmoid notch of mandible. A few studies attempted to downstage these tumors by neo-adjuvant chemotherapy before attempting resection. Oral Squamous cell carcinoma has a high prevalence in South India. Majority of these patients are females addicted to tobacco quid chewing and present with locally advanced disease. In this retrospective analysis, we evaluated the outcome of treatment of oral squamous cell carcinoma extending to ITF and staged T4b in 52 patients. All patients underwent Composite resection including compartment resection of ITF followed by adjuvant treatment. 20 patients had received neo-adjuvant chemotherapy. Pectoralis major myocutaneous flap was the mainstay of reconstruction. After mean follow-up of 2 years, 31 patients are alive and disease free. 14 patients had local recurrence in ITF and 2 patients had recurred in cervical nodes. 8 patients died due to disease and 6 are on palliative care. Neo-adjuvant chemotherapy did not benefit the outcome. Close margins of resection, extra nodal spread from lymph nodes and supra notch and involvement of posterior part of ITF were factors which predisposed to recurrence.

Proposal for the 8th edition of the AJCC/UICC staging system for nasopharyngeal cancer in the era of intensity-modulated radiotherapy.

BACKGROUND: An accurate staging system is crucial for cancer management. Evaluations for continual suitability and improvement are needed as staging and treatment methods evolve. METHODS: This was a retrospective study of 1609 patients with nasopharyngeal carcinoma investigated by magnetic resonance imaging, staged with the 7th edition of the American Joint Committee on Cancer (AJCC)/International Union Against Cancer (UICC) staging system, and irradiated by intensity-modulated radiotherapy at 2 centers in Hong Kong and mainland China. RESULTS: Among the patients without other T3/T4 involvement, there were no significant differences in overall survival (OS) between medial pterygoid muscle (MP) ± lateral pterygoid muscle (LP), prevertebral muscle, and parapharyngeal space involvement. Patients with extensive soft tissue involvement beyond the aforementioned structures had poor OS similar to that of patients with intracranial extension and/or cranial nerve palsy. Only 2% of the patients had lymph nodes > 6 cm above the supraclavicular fossa (SCF), and their outcomes resembled the outcomes of those with low extension. Replacing SCF with the lower neck (extension below the caudal border of the cricoid cartilage) did not affect the hazard distinction between different N categories. With the proposed T and N categories, there were no significant differences in outcome between T4N0-2 and T1-4N3 disease. CONCLUSIONS: After a review by AJCC/UICC preparatory committees, the changes recommended for the 8th edition include changing MP/LP involvement from T4 to T2, adding prevertebral muscle involvement as T2, replacing SCF with the lower neck and merging this with a maximum nodal diameter > 6 cm as N3, and merging T4 and N3 as stage IVA criteria. These changes will lead not only to a better distinction of hazards between adjacent stages/categories but also to optimal balance in clinical practicability and global applicability.

Influence of the lateral pterygoid muscle on traumatic temporomandibular joint bony ankylosis.

BACKGROUND: The pathogenesis of traumatic TMJ ankylosis remains unclear. This study aimed to verify the role of the lateral pterygoid muscle in the pathogenesis of traumatic temporomandibular joint (TMJ) bony ankylosis. METHODS: Eight 6-month-old male sheep were used in this study. Bilateral TMJ osteotomies were performed to induce sagittal fractures of the mandibular condyle. The lateral one-fourth segment of the disc was removed to establish a model of TMJ bony ankylosis. Subsequently, the function of the left and right lateral pterygoid muscles was blocked (experimental group) or maintained (control group), respectively. At 12 weeks postoperatively, animals were sacrificed and TMJ complex samples were evaluated by gross observation, spiral computed tomography (CT), micro-CT, and histological examinations. RESULTS: Gross observation revealed bony ankylosis in the control TMJs and fibrous adhesions in the experimental TMJs. Spiral CT and micro-CT demonstrated that, compared to the experimental group, the control group showed calcified callus formation in the joint space and roughened articular surfaces after new bone formation, which protruded into the joint space. Maximum mediolateral and anteroposterior condylar diameters were significantly larger in the control group than in the experimental group. Micro-CT also showed that the primary growth orientation of new trabeculae was consistent with the direction of lateral pterygoid traction in the control group, but not in the experimental group. Histological examination showed fibro-osseous ankylosis in the control group, but not in the experimental group. CONCLUSIONS: The lateral pterygoid simulates the effects of distraction osteogenesis, which is an important factor in the pathogenesis of TMJ bony ankylosis during the healing of sagittal condylar fractures.

Keratocystic odontogenic tumor arising at the mandibular ramus with an impacted tooth: a case report and mimic lesions.

OBJECTIVES: To consider the biologic behaviors of keratocystic odontogenic tumors (KCOTs) and ameloblastomas and dentigerous cysts. METHODS: A 63-year-old Japanese man presented with swelling and discomfort in the left cheek during jaw movement. Examination revealed a multilocular lesion within the mandible extending from the left second premolar to the left mandibular ramus and coronoid process; the lesion contained a deviated impacted tooth. The tumor had expanded beyond the bone and was invading the masseter and medial pterygoid muscles. Marginal mandibulectomy with a free iliac bone graft was performed. RESULTS: No recurrence was observed during a 7-year follow-up. DISCUSSION: The histopathological diagnosis of the lesion showed it was a KCOT. These tumors usually grow within the bone, causing bone expansion. However, this tumor had expanded beyond the bone and invaded surrounding muscles. Thus, KCOTs can, in rare cases, manifest themselves as described here. Evaluating preoperative images and histopathological findings is important to determine the optimal treatment strategy.

Minimally Invasive Treatment of Temporomandibular Joint Ankylosis and Fibrosis of Temporalis Muscle.

A case of severe mandibular hypomobility due to fibrosis of the left temporalis tendon, combined with ankylosis of the temporomandibular joint, is presented. This case emphasizes the importance of reconstructing the historical timeline to establish a correct diagnosis, ultimately leading to appropriate treatment. The use of minimally invasive surgical techniques and the importance of postoperative rehabilitation are emphasized.

Inferior displacement of the lower belly of the lateral pterygoid muscle: a sign of temporomandibular joint lesions.

OBJECTIVE: The purposes of this article are to report the imaging finding of inferior displacement of the lower belly of the lateral pterygoid muscle (LPM) in patients with lesions arising from the temporomandibular joint (TMJ) and to propose that this imaging finding is suggestive of the presence of a TMJ lesion. MATERIALS AND METHODS: We reviewed computed tomographic and magnetic resonance images of 9 patients with lesions involving the TMJ. Images were evaluated for identification of an inferiorly displaced lower belly of the LPM. Pathology reports were reviewed to determine the histopathologic diagnosis of the TMJ lesion. RESULTS: Inferior displacement of the lower belly of the LPM was observed in all cases on magnetic resonance images, computed tomographic images, or both. In 2 cases, the diagnosis was calcium pyrophosphate deposition disease. The remaining cases were ganglion cyst, joint effusion due to dermatomyositis, septic arthritis, chondromyxoid fibroma, synovial chondromatosis, pigmented villonodular synovitis, and giant cell tumor of bone. CONCLUSIONS: Inferior displacement of the lower belly of the LPM is a useful radiologic sign to suggest that a lesion arises from the TMJ.

Prognostic value of grading masticator space involvement in nasopharyngeal carcinoma according to MR imaging findings.

PURPOSE: To derive a suitable method for grading masticator space invasion in nasopharyngeal carcinoma on the basis of magnetic resonance (MR) images and to determine its prognostic value in patients undergoing intensity-modulated radiation therapy. MATERIALS AND METHODS: After institutional review board approval and informed consent were acquired, 808 patients with nasopharyngeal carcinoma who were treated with definitive intensity-modulated radiation therapy were analyzed retrospectively. The anatomic sites of masticator space involvement were identified with MR imaging. Overall survival, local relapse-free survival, and distant metastasis-free survival were calculated by using the Kaplan-Meier method and were compared by using the log-rank test. Potential prognostic factors were identified by means of multivariate analysis. RESULTS: Masticator space involvement was diagnosed in 163 of 808 patients (20.2%). Patients with lateral invasion (involvement of the lateral pterygoid muscle of the masticator space and beyond) had significantly poorer overall survival and distant metastasis-free survival than those with medial invasion (involvement of the medial pterygoid muscle of the masticator space) (P = .035 and P = .026, respectively). Furthermore, their overall survival, local relapse-free survival, and distant metastasis-free survival were significantly poorer compared with patients with stage T2 or T3 disease (all P ≤ .023) but similar to patients with stage T4 disease. The grade of masticator space involvement was an independent prognostic factor for overall survival, local relapse-free survival, and distant metastasis-free survival (all P ≤ .023). CONCLUSION: Masticator space involvement in nasopharyngeal carcinoma should be graded as medial (stage T2 disease) or lateral (stage T4 disease). This can facilitate staging of nasopharyngeal carcinoma and may be a suitable prognostic indicator of survival.

Bilateral masseter and internal pterygoid muscle hypertrophy: a diagnostic challenge.

OBJECTIVE: To describe an unusual case of bilateral masseter and pterygoid muscle hypertrophy. CLINICAL PRESENTATION AND INTERVENTION: A 53-year-old female patient presented with a bilateral, painless swelling at the parotid areas without improvement after using antibiotics/systemic corticosteroids/nonsteroidal anti-inflammatory agents. Her medical history included thyroid nodules, but no dental/occlusal disorders were observed. The initial differential diagnosis included salivary gland/jaw bone/masseter pathology, but the CT/MRI revealed only an increase in the size of the masseter and pterygoid muscles. The patient was informed of the benign nature of the swelling and was advised to discontinue the use of nonsteroidal anti-inflammatory agents. CONCLUSION: The bilateral hypertrophy of masseter muscles should be considered in differential diagnosis in cases of unilateral or bilateral swelling of the parotid or lateral mandible area.

Use of coblation in resection of juvenile nasopharyngeal angiofibroma.

We present a series of 4 patients with juvenile nasopharyngeal angiofibroma (JNA) who underwent Coblation-assisted endoscopic resection after preoperative embolization, and discuss the use and advantages of endoscopic Coblation-assisted resection of JNA. Our limited case series suggests that Coblation may be used in the resection of JNA after embolization in a relatively safe, efficient, and effective manner. Coblation allows for decreased bleeding, less need for instrumentation, and improved visualization. There are limited published data in the literature to date on the use of Coblation in endoscopic JNA resection. We describe its use in a more extensive tumor than those previously reported. Further studies are needed to fully define the safety and utility of Coblation technology for this application.

Clinical study of magnetic resonance imaging-based texture analysis and fasciculation of the lateral pterygoid muscle in young patients with temporomandibular disorder.

OBJECTIVE: We aimed to evaluate the effectiveness of clinical examination combined with texture analysis of magnetic resonance imaging (MRI) and fasciculation patterns of the lateral pterygoid muscle (LPM) in distinguishing among the different anatomic causes of temporomandibular disorder. METHODS: We divided the patients into four groups: healthy control (HC), disk without displacement (DWoD), disk displacement with reduction (DDWR), and disk displacement without reduction (DDWoR). Demographic information and clinical symptoms of patients in each group were recorded. LPM textures were compared among groups. LPM fasciculation was examined. P<0.05 indicated significant difference. RESULTS: Several clinical symptoms and signs, but not age or sex, differed significantly among groups. Oblique sagittal planar MRI revealed significant differences in the parameters of Angular Second Moment, Contrast, Correlation, Inverse Difference Moment, and Entropy between the healthy controls and the 3 patient groups. MRI of the patients, both without and with disk displacement, demonstrated relative uniformity in gray distribution and correlation of gray values, with greater complexity but an unclear texture and no obvious regularity. The proportion of type B LPM fascicles was significantly higher in the DDWR and DDWoR groups CONCLUSION: Temporomandibular disorder, without and with disk displacement, is associated with clinical symptoms and texture analysis values that differ from healthy muscle. The types of LPM fascicles are related to the position of the articular disk.

Quantitative volume and area assessment of masticatory muscles through magnetic resonance imaging in patients with temporomandibular joint disorders.

OBJECTIVE: To compare volume and surface area measurements of the lateral pterygoid (LPM), medial pterygoid (MPM), and masseter muscles (MM) as calculated on magnetic resonance imaging (MRI) based on the position of the temporomandibular joint disk, mouth position, and patient sex, and to calculate the correlations of the measurements among the muscles. STUDY DESIGN: Measurements of muscle volume and area were performed on the MRIs of 51 patients. Wilcoxon, Kruskal-Wallis, and Mann-Whitney U tests were used to calculate the significance of differences in measurements. The Spearman correlation coefficient calculated the correlation of measurements among the muscles. The significance of difference was established at P < .05. RESULTS: Volume and area of the left MPM in patients with disk displacement without reduction (DDWOR) were larger than in patients with normal disk position (P ≤ .040). MM volumes were smaller with DDWOR than with DD with reduction bilaterally (P ≤ .031). The volume and area of LPM and MM were significantly different between closed and open mouth positions (P < .001). Differences in volume and area between females and males were significant for all muscles in volume (P ≤ .021) and for MPM and MM in area (P ≤ .021). Significant positive correlations were found among all muscles for volume and area. CONCLUSION: Volume and area measurements of the masticatory muscles varied according to disk and mouth position and patient sex and exhibited significant positive correlations.

[Evaluation of the relationship between the attachment type of lateral pterygoid muscle and the position of temporomandibular joint disc in patients with temporomandibular joint disorders based on wireless amplified MRI detector high resolution imaging].

Objective: To explore the correlation between the attachment type of lateral pterygoid muscle (LPM) and the position of temporomandibular joint (TMJ) disc in patients with temporomandibular disorders (TMD) by using wireless amplified magnetic resonance imaging detector (WAND) coupled with conventional head and neck joint coil for high resolution imaging of TMJ. Methods: Eighty-five patients with TMD diagnosed by oral and maxillofacial surgeons of Guizhou Provincial People's Hospital from October 2019 to January 2022 were collected. A total of 160 TMJ were included. There were 16 males and 69 females, aged (32.7±14.2) years. All patients were scanned with open, closed oblique sagittal and coronal WAND coupled head and neck coils with bilateral TMJ. Based on TMJ and LPM high resolution imaging, to explore the correlation between LPM attachment types and the position of TMJ disc in TMD patients, and to evaluate the potential clinical value of LPM attachment types in TMD patients. χ2 test and Pearson correlation analysis were used to evaluate the correlation between LPM attachment type and TMJ disc location. Results: There were three types of LPM attachment: type Ⅰ in 51 cases [31.9% (51/160)], type Ⅱ in 77 cases [48.1% (77/160)] and type Ⅲ in 32 cases [20.0% (32/160)]. There was a significant correlation between the type of LPM attachment and the position of articular disc (χ2=28.20, P=0.002, r=0.776). There was no statistical significance between the type of LPM attachment and the reversible displacement of articular disc (χ2=0.24, P=0.887, r=0.825). Conclusions: There is a correlation between the attachment type of LPM and the position of the disc in TMD patients. WNAD coupled with conventional head and neck joint coil TMJ high resolution scan can provide reliable imaging evidence for TMD patients in evaluating the type of LPM attachment and the location of disc.

Osteoma in medial pterygoid muscle: an unusual case.

Soft tissues osteoma is an execeedingly rare tumour. It is a benign often asymptomatic neoplasm. The exact etiology and pathogenesis of osteomas are unclear. This paper report a case of peripheral osteoma located in the middle part of the medial pterygoid muscle of the right infratemporal region in a 60-year-old woman. Clinical examination did not reveal any extraoral swelling, facial asymmetry or difficulty in mouth opening, and the regional lymph nodes were non-palpable. Panoramic radiograph show a round well-circumscribed free/independent radiopaque mass located in the middle part of the right infratemporal region. Intraoperatively, the mass was surrounded by muscle fibers with no attachment to bone. Microscopic examination revealed mature bone without special characteristics. The precise location of an osteoma in the muscle is usually in close proximity to regions of muscle attachment it is possible that muscle traction may play a role in its development.

Conservative treatment of bilateral temporalis muscle hypertrophy in a pregnant woman.

BACKGROUND: Hypertrophy of the masticatory muscles may affect the temporalis, masseter, and pterygoid muscles in several different combinations. METHODS: A case of bilateral temporalis muscle hypertrophy, with masseter and pterygoid involvement, in a 26-year-old white woman in the fourth month of gestation is reported. Magnetic resonance imaging and physical examination were used for diagnosis. Hypertrophy was considered to be of acquired nature. The patient was managed using alternative, noninvasive methods. RESULTS: After 2 months, visible reduction was observed. Clinical symptoms of muscle discomfort were also reported. CONCLUSIONS: In the presented case, we were able to use an alternative, noninvasive form of treatment, which provided our patient with an overall improvement in physical and psychologic aspects.

Evaluation of the effects of chronic qat chewing on lateral pterygoid muscle using MRI.

Objective: This study explored the effect of qat chewing (QC) on the lateral pterygoid muscle (LPM), using magnetic resonance imaging (MRI).Methods: Forty qat chewers (QG), divided into three subgroups, according to duration of QC, and 20 non-qat chewers (NQG) were included. MRI sections were obtained to assess hypertrophy and atrophy of the superior belly (SB) and inferior belly (IB) of the LPM on the chewing and contralateral non-chewing side.Results: There was a significantly higher prevalence of atrophy of the IB (p < 0.001) and hypertrophy of the SB and IB (p = 0.002) in the QG. Hypertrophy of SB and IB was marked (p = 0.001) on the chewing side. Conversely, SB atrophy was marked on the non-chewing side (p = 0.003). MRI demonstrated a positive correlation between LPM alterations and the duration of QC in subgroup analysis.Conclusion: Unilateral QC might be a cause of LPM alterations.

The Role of the Lateral Pterygoid Muscle in Articular Disc Displacement: A Cross-sectional Magnetic Resonance Imaging Study.

OBJECTIVE: The objective of the study is to determine the role of Lateral Pterygoid Muscle LPM in the articular disc displacement ADD, which is considered controversial due to the variations in the pattern of insertion of the Superior Lateral Pterygoid Muscle SPLM. BACKGROUND: It is well understood that the superior head of the lateral pterygoid muscle has only a single insertion pattern among individuals, in which the muscle is attached to the articular disc and capsule. However, recent findings in many studies have shown a noticeable variation in the insertion pattern of the upper LPM. METHODS: MRI examinations were collected at King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia. Scans of 61 patients (41 females, 20 males; mean age 33 years old) with symptoms of temporomandibular dysfunction were reviewed retrospectively. The direction of their articular disc displacement was evaluated through sagittal and coronal views in both open and closed mouth positions. RESULTS: There was no statistical significance found between the LPM attachment types and TMJ disc position. The chi-square test also showed no significant difference between the type of LPM attachment and the condylar location. Forty-five percent of the articular discs were located between the articular eminence and the glenoid fossa. The majority of the disc displacement was in the anterior direction. CONCLUSION: There was no statistically significant association found between the type of LPM attachments and the direction of disc displacement.