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Myositis ossificans traumatica (MOT) is a rare condition characterized by nonneoplastic, heterotopic bone formation in the masticatory muscles following acute trauma. It usually occurs between the second and seventh decades of life in both genders. Although MOT of the masticatory muscles is not frequently reported in the literature, a common clinical finding is the progressive limitation of motion in the mandible. Managing this condition can be challenging. The available evidence regarding the effectiveness of conservative management, such as physical therapy and interpositional materials, is inconclusive based on the literature. Therefore, the preferred treatment for MOT is the surgical excision of the osseous mass. Under general anesthesia, the calcified muscle is completely removed. Surgical excision often leads to remission, although some patients may experience recurrent episodes. The purpose of this article is to review and discuss cases of MOT of masticatory muscles reported from 2014 to date. In addition to this literature review, we report a rare case involving a 9-year-old boy with recurring MOT of the right medial pterygoid muscles. The boy had a history of receiving a right-side mandibular nerve block injection and subsequently experienced a gradual decrease in the maximum incisal opening.

Aim: The objective of this study is to utilize artificial intelligence for the segmentation of masticatory muscles in ultrasound images. Materials and Methods: The study comprised a cohort of 60 pediatric patients with ultrasonographic images of the masseter, anterior temporal, and lateral pterygoid muscles, 120 images for each muscle, right and left, totaling 360 muscle images. Within the context of this research, the YOLOv8-Seg deep learning model was employed to automatically conduct the segmentation of the masseter, anterior temporal and lateral pterygoid muscles within ultrasonography images. In this study, an artificial intelligence algorithm (Roboflow, Inc., Des Moines, Iowa, USA) was developed to autonomously carry out the segmentation of the masseter, anterior temporal and lateral pterygoid muscles. A total of 120 images for each muscle group were randomly divided into training, validation and test sets. Results: For the muscle segmentations on the test data, the true positive (TP), false positive (FP) and false negative (FN) values were 18, 0, 0 for masseter muscle, 18, 0, 0 for temporal muscle and 16, 1, 1 for lateral pterygoid muscle, respectively. The model's F1 score, precision and sensitivity values are 1.0, 1.0 and 1.0 for masseter muscle, 1.0, 1.0 and 1.0 for temporal muscle and 0.92, 0.94 and 0.94 for lateral pterygoid, respectively. Conclusion: In summary, segmentation techniques based on deep learning for analyzing ultrasonography images of anatomical structures like masticatory muscles have great potential in clinical applications. Precise segmentation of muscles through this technology can play a crucial role in the diagnosis and follow-up of diverse medical conditions and diseases. [ABSTRACT FROM AUTHOR]

Purpose: The study aimed to determine the muscle pattern of medial pterygoid, lateral pterygoid, and masseter (length, cross-section, and angulation) in adult non-orthodontic patients and its effect on craniofacial structures. Methods: The study was conducted from January 14, 2019 to January 14, 2020. Ethical clearance of this study was obtained from the ethical committee Ethical Clearance was obtained from Faculty of Dental Sciences, IMS, BHU, Institutional Ethical Committee with Ref no. Dean/2019/EC/1824 dated 23.04.2019 of the university. The sample size was estimated using the G-power statistical program. Power analysis indicated a minimum sample size of 27. Inclusion and exclusion criteria were set. Consent was taken from participants. Seventy-seven subjects who were willing to participate and have given written consent were enrolled for the study. Participants were sent for lateral cephalometry (Dolphin Cephalometric software) Dolphin Imaging and management solution, for 6 angular and 11 linear measurements. Nineteen subjects did not turn up for the scan. Twenty-eight participants underwent MRI (magnetic resonance imaging) to evaluate muscle patterns (masseter, medial, and lateral pterygoid). The intra-class correlation coefficient (ICC), Kolmogorov-Smirnov (KS) test, descriptive statistics, and multiple regression analysis were computed. The P value was set as =0.001(highly statistically significant) and =0.05 (significant relation). Results: There was a highly statistically significant (p = 0.001) association between masseter length to upper facial height (N-Ans) and ramal length (Cd-Go). Length of medial pterygoid was significantly related (p = 0.05) with SNB and length of body of mandible (Pog-Go). The cross-section of this muscle showed significant relation with upper facial height (N-Ans) and ramal length (Cd-Go). The correlation of the length of lateral pterygoid with upper facial height (N-Ans) and maxillary length (A-Ptm) was highly significant. Conclusion: The muscle pattern has a significant correlation with maxillofacial morphology. The masseter muscle is the longest and thickest (cross-section) and is angulated vertically than the other two muscles (medial pterygoid and lateral pterygoid). Of the three muscles, the medial pterygoid influences more common craniofacial parameters suggestive of its symbiotic activity. Lateral pterygoid affects the maxillary length and facial height. [ABSTRACT FROM AUTHOR]

Cerebral palsy (CP) is a group of non-progressive disorders of motor function in children resulting from an injury to an immature brain. In addition to abnormal limb and trunk movement, individuals with CP can experience involuntary muscle contractions of the lower facial muscle groups, causing oromandibular dystonia (OMD). Contraction of the lateral pterygoids and submandibular muscles depresses the mandible. OMD involving the lateral pterygoids can therefore lead to involuntary jaw opening posture, affecting the ability to feed and speak effectively. We present a case series of five patients with CP and OMD that received novel ultrasound-guided onabotulinumtoxinA to the lateral pterygoid muscles. Our goal was to determine if chemodenervation would improve the mouth-closing ability, thus in turn improving the ability to swallow, chew, manage secretions, and communicate. We describe this unique injection method and report a subjective improvement in eating abilities and communication, in addition to a positive upward trend in most patients' weights, with no significant adverse side effects. [ABSTRACT FROM AUTHOR]

Myositis ossificans traumatica rarely affects the muscles of mastication. Since 1924, there has only been one case reported to affect the muscles of mastication in the paediatric population. The purpose of this paper is to present an 11-year-old girl with calcification of her right lateral pterygoid muscle with no evidence of previous trauma to the muscle. The clinical history and radiographic features resembled an extremely rare form of myositis ossificans also known as myositis ossificans idiopathica.

Abstract Recurrent dislocation of the temporomandibular joint (TMJ) is rare. It is distinct from acute or chronic dislocation and is associated with considerable morbidity and deterioration in quality of life. To formulate a practical surgical treatment algorithm, we retrospectively reviewed the management and long-term outcomes of 14 patients who presented to a single hospital department over a period of six years (2010–2016), and collected data on demographics, clinical features, operation, and outcome. Patients were followed up for a minimum of 12 months and a maximum of seven years. Results showed effective long-term resolution of symptoms after a combination of eminectomy and disc plication (meniscopexy). Patients whose symptoms had resulted from dystonia of the lateral pterygoid muscle also benefitted from additional lateral pterygoid myotomy. A combination of eminectomy and disc plication (meniscopexy) effectively provides successful long-term outcomes in this group of patients. [ABSTRACT FROM AUTHOR]

The author describes the case of a 53-year-old male whose jaw spontaneously locked the day after his dental visit. There was no history of temporomandibular problems. Dental procedure was completed in a routine manner. There was no infective or systemic pathology, or muscle spasm as a cause of trismus. Temporomandibular joint dysfunction was initially suspected, but dynamic ultrasonographic examination and MRI revealed a completely patent articular disc and normal temporomandibular joint. The patient did not have a mechanical restricted movement of the joint, but rather a severe, local pain upon depressing the mandible, which inhibited further opening. Intraoral palpation of the lateral pterygoid muscle (LPM) reproduced his symptoms, and thus suggested a myogenic etiology rather than arthropathy. Probably overstretching and subsequent inflammation of the LPM occurred due to prolonged mandibular depression. The patient was prescribed strengthening exercises for the LPM, which completely resolved his problem within 6 weeks. This case study suggests that overuse with subsequent inflammation of the LPM may cause locking of the jaw, mimicking articulopathy. [ABSTRACT FROM AUTHOR]

The aim of this paper is to propose a biomechanical model that could serve as a tool to overcome some difficulties encountered in experimental studies of the mandible. One of these difficulties is the inaccessibility of the temporomandibular joint (TMJ) and the lateral pterygoid muscle. The focus of this model is to study the stresses in the joint and the influence of the lateral pterygoid muscle on the mandible movement. A finite element model of the mandible, including the TMJ, was built to simulate the process of unilateral mastication. Different activation patterns of the left and right pterygoid muscles were tried. The maximum stresses in the articular disc and in the whole mandible during a complete mastication cycle were reached during the instant of centric occlusion. The simulations show a great influence of the coordination of the right and left lateral pterygoid muscles on the movement of the jaw during mastication. An asynchronous activation of the lateral pterygoid muscles is needed to achieve a normal movement of the jaw during mastication. [ABSTRACT FROM AUTHOR]

Purpose: Abnormal communications among the branches of mandibular nerve especially the posterior division are significant due to various procedures undertaken in this region. These variations are worth reporting as they pose serious implications in several interventions in this region, and may even lead to false diagnosis. Methods: During routine dissection, the mandibular nerve and its branches were dissected in the infratemporal fossa. The branches from the posterior division of the mandibular nerve namely the inferior alveolar and auriculotemporal nerves were carefully dissected, and their abnormal branching pattern was noted. Results: There was a communicating branch between left inferior alveolar and auriculotemporal nerve. There was also a variant recurrent branch from the left inferior alveolar nerve that supplied the lateral pterygoid muscle. Conclusions: Such variant branches and communications between the branches of mandibular nerve as seen in this case have an embryological basis and are clinically important in this region especially for dental surgeries and anesthesia. [ABSTRACT FROM AUTHOR]

Objective In adults, the lateral pterygoid muscle (LPM) is usually divided into the upper and lower head, between which the buccal nerve passes. Recent investigations have demonstrated foetal developmental changes in the topographical relationship between the human LPM and buccal nerve. However, as few studies have investigated this issue, we clarified the expression of desmin and nerve terminal distribution during embryonic development of the LPM in mice. Methods We utilized immunohistochemical staining and reverse transcription chain reaction (RT-PCR) to clarify the expression of desmin and nerve terminal distribution. Results We observed weak expression of desmin in the LPM at embryonic day (ED) 11, followed by an increase in expression from embryonic days 12-15. In addition, starting at ED 12, we observed preferential accumulation of desmin in the vicinity of the myotendinous junction, a trend that did not change up to ED 15. Nerve terminal first appeared at ED 13 and formed regularly spaced linear arrays at the centre of the muscle fibre by ED 15. The results of immunohistochemical staining agreed with those of RT-PCR analysis. Conclusion We found that desmin accumulated in the vicinity of the myotendinous junction starting at ED 12, prior to the onset of jaw movement. We speculate that the accumulation of desmin is due to factors other than mechanical stress experienced during early muscle contraction. Meanwhile, the time point at which nerve terminals first appeared roughly coincided with the onset of jaw movement. [ABSTRACT FROM AUTHOR]

L'articulation temporo-mandibulaire (ATM) est une articulation complexe, les surfaces articulaires non concordantes s'adaptant grâce au tendon du muscle ptérygoïdien latéral qui coulisse entre elles lors de tous les mouvements mandibulaires. Il n'existe pas de parallélisme anatomoclinique entre l'importance de l'atteinte articulaire et la gravité des symptômes ressentis par le patient. L'anatomie descriptive de l'ATM est bien connue, malgré une certaine variabilité, mais son aspect dynamique l'est moins en l'absence d'un système d'imagerie adapté au suivi tridimensionnel d'un sujet en temps réel. L'abord pluridisciplinaire de la pathologie des dysfonctions de l'ATM a fait progresser la connaissance de l'anatomie fonctionnelle de cette articulation. Le nerf mandibulaire en assure l'innervation motrice et sensitive pouvant initier un cercle vicieux entre spasmes et douleurs. L'imputabilité des symptômes otologiques, présents lors de certains cas de dysfonctions de l'ATM, ne peut être retenue de façon systématique. The temporomandibular joint (TMJ) is a complex joint, with the mismatched articular surfaces adapting to one another via the tendon of the lateral pterygoid muscle which slides between them during all jaw movements. There are no anatomical or clinical correlations between the significance of a joint condition and the severity of symptoms experienced by the patient. The descriptive anatomy of the TMJ is well-known despite some variability, but its dynamic aspects are less so due to the lack of an imaging system adapted to three-dimensional follow-up of an individual in real time. A multidisciplinary approach to TMJ dysfunctions has prompted a more in-depth knowledge on the functional anatomy of this joint to be developed. Motor and sensory innervation is derived from the mandibular nerve, which may lead to a vicious circle between spasms and pain. A causal relationship with otological symptoms present in some cases of TMJ dysfunctions cannot be considered as standard. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the relationship of the temporomandibular joint (TMJ) internal derangement and lateral pterygoid muscle (LPM) by magnetic resonance imaging (MRI). In this study, 115 subjects with TMJ internal derangement (total 230 TMJs) and 21 subjects without clinical symptoms (total 42 TMJs) were included. TMJ disc position and LPM were evaluated using MRI. LPM attachments were categorized into two different types: type 1, where fibers of the superior head of the LPM (SLPM) were attached to the disc and fibers of the inferior head of the LPM (ILPM) were attached to condyle, and type 2, where fibers of the SLPM were attached to the disc and condyle, and fibers of the ILPM were attached to condyle. The presence of muscle atrophy and degeneration were also evaluated. LPM attachments were observed in two different parts. Disc displacements were common in the muscle attachments of both types. Type 1 muscle attachments were seen in 85.9% of all the anterior disc displacement without reduction (ADD) TMJs (total 64 TMJs). Atrophy was seen in a higher proportion (43.7%) in TMJs with ADD (28/64) than in TMJs with normal and anterior disc displacement with reduction (ADDR). Out of 74 TMJs with atrophy, 68 had type 1 muscle attachment. Four TMJs had atrophy in both superior and inferior heads of the lateral pterygoid. However, atrophy was not present only in the ILPM. It has been concluded that since the SLPM only attached to the disc in type 1, the disc may displace anteriorly very easily. Therefore, this situation will reduce the function of the SLPM. Reduced muscle function may cause muscle atrophy. The activity of the SLPM may be more reduced since the disc permanently dislocated in TMJs with ADD. Finally, spasm of the LPM causes disc displacement and atrophy and then the degeneration of the LPM may follow disc displacement. [ABSTRACT FROM AUTHOR]

The infratemporal fossa (ITF) contains many critical neurovascular structures and the muscles of mastication. Infections of the ITF are rare and carry significant pathologic implications due to nearby structures. Abscesses of the ITF often occur due to odontogenic spread and present with trismus and facial pain. We present the case of a 26-year-old male with an uncommon ITF abscess of the lateral pterygoid following maxillary wisdom tooth extraction. The abscess resolved following bedside and operative intraoral drainage in addition to intravenous antibiotic therapy. We highlight the rarity of lateral pterygoid abscesses and the importance of distinguishing ITF abscesses from other similarly presenting conditions such as temporomandibular joint dysfunction., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2022, Daines et al.)

While the adductor musculature of the primate jaw has been extensively analyzed within the context of dietary and social ecology, little is known about the corresponding muscles of jaw abduction. Nonetheless, these muscles significantly contribute to a species' maximum gape potential, and thus might constrain dietary niche diversity and impact social display behaviors. In this study, we quantify the architectural properties of the digastric (a jaw abductor) and lateral pterygoid (a jaw abductor and anterior translator) across a broad sample of male and female anthropoid primates. We test the hypothesis that the abductor musculature reflects specialization to dietary and behavioral ecology. Our sample comprises 14 catarrhine and 13 platyrrhine species spanning a wide range of dietary and social categories. All specimens were sharp dissected and muscles subsequently chemically digested using a standardized protocol. Our findings demonstrate that relative fascicle lengths within the lateral pterygoid (but not the digastric) are significantly greater within species that habitually consume larger food items. Meanwhile, canine length is more strongly associated with fascicle lengths in the digastric than in the lateral pterygoid, particularly within males. Neither dietary mechanical resistance nor the intensity of social competition relates to the size or architectural properties of the jaw abductors. These findings suggest that dietary-and to a lesser extent, socioecological-aspects of a primate's life history may be reflected in the architecture of these muscles, albeit to varying degrees. This underlines the importance of considering the complete masticatory apparatus when interpreting the evolution of the primate jaw., (© 2021 American Association for Anatomy.)

Abstract: Oromandibular dystonia (OMD) is a rare neurological condition infrequently seen by oral and maxillofacial surgeons which may result in inappropriate deviation of the mandible, subluxation and intraoral soft tissue trauma. A case is presented of a patient suffering from spasmodic torticollis and lateral pterygoid dystonia and currently under treatment with botulinum A toxin (Botox) injections. Botox has emerged as the most effective form of symptomatic treatment for abnormabilities in muscle movement, namely dystonia with oromandibular symptoms. [Copyright &y& Elsevier]

Conventionally temporalis myofascial flap is popular for interposition in TMJ ankylosis. Medial pterygoid and masseter also has been used in the past for interposition. We introduce here lateral pterygoid for interposition in cases of mild ankylosis where condylar bony architecture is not distorted. [ABSTRACT FROM AUTHOR]

Introduction: The masticatory muscles play an important part in determining the morphology of the facial skeleton. Skeletal typology and the characteristics of the masticatory muscles are closely linked. Several authors have studied muscle characteristics as related to facial typology. The aim of this work is to study the relationship between vertical and transverse skeletal dimensions and the dimensions (length, width and thickness) of two muscles of mastication, the masseter and the lateral pterygoid., Materials and Method: Our study was based on CT-scan examinations of a sample composed of patients consulting the X-ray department of the Rabat-Salé Teaching Hospital, and for whom a CT-scan had been requested. Forty CT examinations of the skull, performed in the context of sinus explorations or pre-surgical work-ups in the radiology department of the Rabat-Salé Teaching Hospital, were selected for this study. The sample comprised 19 women and 21 men aged between 20 and 45, with a mean of 40.9 ± 12.8. A Siemens 32-row 64-slice spiral CT-scan device was used for spiral acquisition of data around the facial bones, with the mouth closed. The study was carried out in the parenchymal window for the muscle measurements, in the axial and coronal planes. Bone measurements were performed after 3D reconstruction in VRT mode., Results: Our study showed that, for the masseter muscle, thickness is the dimension that correlates significantly with skeletal dimensions in the vertical, transverse and sagittal directions. For the lateral pterygoid muscle, length and width both present significant correlations with transverse skeletal dimensions. Analysis of these results shows that the dimensional characteristics of the masticatory muscles vary according to the vertical and transverse skeletal typology of the subjects concerned., (Copyright © 2013. Published by Elsevier Masson SAS.)