The Maxillomandibularis Muscle.

Fibers of the lateral pterygoid muscle (LPM) occasionally originate on the posterior surface of the maxilla. Anatomic exploration of an adult patient's cone beam computed tomography files revealed a previously unreported unilateral anatomic variant of the LPM. The variant consisted of a distinctive muscular slip that originated on the tuberosity of the maxilla and coursed postero-laterally through the notch of the mandible to insert on an accessory pterygoid fovea on the outer condylar pole. This maxillomandibular muscle was lateral to the inferior head of the LPM. Therefore, it could contribute to the antero-inferior displacement and medial rotation of the mandibular condyle during the movements of the temporomandibular joint. The maxillomandibular muscle should be added to the extensive spectrum of anatomical variations of the LPM; however, prevalence studies should assess whether its maxillary attachment is the rule or the exception.

The sphenopterygoid canal and pterygoid foramen.

BACKGROUND: In human anatomy, there are well-known the foramina of the greater sphenoidal wing, the foramen rotundum, the foramen ovale, the foramen spinosum, as well as the inconstant sphenoidal emissary foramen of Vesalius and the foramen of Arnold. Different canals are found in several species of rodents, such as the alisphenoid and sphenopterygoid (SPC) canals. METHOD: It was re-explored an archived computed tomography angiogram of a 60 y.o. female case. RESULTS: Bilateral superior recesses of the pterygoid fossae (SRPF) and a right SPC were found. The SRPF on each side penetrated the non-lamellar pterygoid root and superiorly reached the sphenoidal sinus wall. Upper fibres of medial pterygoid muscles were inserted into each SRPF. An unexpected SPC was found on the right side. It opened superiorly on the lateral side of the foramen rotundum and inferiorly at a pterygoid foramen in the superior end of the posterior margin of the lateral pterygoid plate. A sphenoidal emissary vein traversed that SPC to drain into the pterygoid plexus. CONCLUSION: The SRPF and SPC could also be found in humans. As the sphenoidal emissary veins are surgically relevant, they should not be further regarded as exclusively crossing the foramen of Vesalius but also the SPC.

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.

Evaluation of lateral pterygoid muscle in patients with temporomandibular joint anterior disk displacement using T1-weighted Dixon sequence: a retrospective study.

BACKGROUND: Pathological alterations of lateral pterygoid muscle (LPM) are implicated in temporomandibular joint anterior disk displacement (ADD). However, quantification of the fatty infiltration of LPM and its correlation with ADD have rarely been reported. The aim of this study was to evaluate the fatty infiltration, morphological features and texture features of LPM in patients with ADD using T1-weighted Dixon sequence. METHODS: This retrospective study included patients who underwent temporomandibular joint MRI with T1-weighted Dixon sequence between December 2018 and August 2020. The temporomandibular joints of the included patients were divided into three groups according to the position of disk: Normal position disk (NP) group, Anterior disk displacement with reduction (ADDWR) group and Anterior disk displacement without reduction (ADDWOR) group. Fat fraction, morphological features (Length; Width; Thickness), and texture features (Angular second moment; Contrast; Correlation; Inverse different moment; Entropy) extracted from in-phase image of LPM were evaluated. One-way ANOVA, Welch's ANOVA, Kruskal-Wallis test, Spearman and Pearson correlation analysis were performed. Intra-class correlation coefficient was used to evaluate the reproducibility. RESULTS: A total of 53 patients with 106 temporomandibular joints were evaluated. Anterior disk displacement without reduction group showed higher fat fraction than normal position disk group (P = 0.024). Length of LPM was negatively correlated with fat fraction (r = -0.22, P = 0.026). Angular second moment (ρ = -0.32, P < 0.001), correlation (ρ = -0.28, P = 0.003) and inverse different moment (ρ = -0.27, P = 0.005) were negatively correlated with fat fraction, while positive correlation was found between entropy and fat fraction (ρ = 0.31, P = 0.001). The intra-class correlation coefficients for all values were ranged from 0.80 to 0.97. CONCLUSIONS: Patients with ADDWOR present more fatty infiltration in the LPM compared to NP or ADDWR patients. Fatty infiltration of LPM was associated with more atrophic and higher intramuscular heterogeneity in patients with ADD. Fat fraction of LPM quantitatively and noninvasively evaluated by Dixon sequence may has utility as an imaging-based marker of the structural severity of ADD disease process, which could be clinical helpful for the early diagnose of ADD and predication of disease progression.

Surgical anatomy of the lingual nerve for palate surgery: where is located and how to avoid it.

PURPOSE: To describe the anatomic relationship of the lingual nerve with the lateral oropharyngeal structures. METHODS: An anatomic dissection of the lateral oropharyngeal wall was conducted in eight sides from four fresh-frozen cadaveric heads. Small titanium clips were placed along the lingual nerve and the most anterior and medial border of the medial pterygoid muscle. Radiological reconstructions were employed for optimal visualization; the coronal view was preferred to resemble the surgical position. The distance between the lingual nerve and the medial pterygoid muscle at its upper and lower portion was measured radiologically. The trajectory angle of the lingual nerve with respect to the pterygomandibular raphe was obtained from the intersection between the vector generated between the clips connecting the upper and lower portion of the medial pterygoid muscle with the vector generated from the lingual nerve clips. RESULTS: The mean distance from the upper portion of the medial pterygoid muscle and superior lingual nerve clips was 10.16 ± 2.18 mm (mean ± standard deviation), and the lower area of the medial pterygoid muscle to the lingual nerve was separated 5.05 ± 1.49 mm. The trajectory angle of the lingual nerve concerning to the vector that describes the upper portion of the most anterior and medial border of the medial pterygoid muscle with its lower part was 43.73º ± 11.29. CONCLUSIONS: The lingual nerve runs lateral to the lateral oropharyngeal wall, from superiorly-inferiorly and laterally-medially, and it is closer to it at its lower third.

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.

Lateral Pterygoid Muscle Location in Relation to Preauricular Skin Measured from CT Scans among a Sample of Yemeni Adults.

AIM: The aim of this study was to determine the lateral pterygoid muscle (LPM) in relation to preauricular skin measured from computed tomography (CT) scan measurements. MATERIALS AND METHODS: CT scans of 160 patients aged between 18 and 75 years were retrospectively collected and analyzed, and the distances were measured to determine the location of the LPM center in relation to the preauricular skin. On axial CT crossing the maximum muscle width, two lines [the first line is below the center of the zygomatic arch (first position), while the second line was 5 mm posterior to the first one (second position)] were drawn from the preauricular skin to the medial border and then extended to the lateral border of the muscle. These measurements were used to calculate the distance to the center of the muscle mathematically. Data were statistically analyzed, and the differences between both genders and both sides were investigated. The level of significance was set at p-value <0.05. RESULTS: Males displayed larger mean values in two positions (36.6 ± 2.25 and 35.97 ± 4.19, respectively) than females (33.66 ± 4.46 and 32.80 ± 3.21, respectively). The difference between both genders was found to be statistically significant. Measurements on the right side were also larger than those on the left side, but with no significant difference. CONCLUSION: LPM center can be approached safely in males by inserting the needle about 36 mm at the first position and 33 mm at the second position. However, in females, these distances are located 3 mm shorter in both positions. CLINICAL SIGNIFICANCE: The outcome of this study will provide the clinicians with measurements that can help in directing the needle or electromyography (EMG) electrode during the extraoral injection technique of the LPM. How to cite this article: Al-Tairi NH, Al-Sharaee YA, Alhajj MN. Lateral Pterygoid Muscle Location in Relation to Preauricular Skin Measured from CT Scans among a Sample of Yemeni Adults. J Contemp Dent Pract 2021;22(5):522-526.

[Evaluation of Lateral Pterygoid Muscle Contraction in Patients with Temporomandibular Disorders Based on 3D-T2 Weighted Imaging].

Objective To evaluate lateral pterygoid muscle(LPM)contraction in the patients with temporomandibular disorders(TMD)based on 3D-T2 weighted imaging(3D-T2WI).Multiplanar reconstruction(MPR)was employed to measure the length of LPM in the images taken in closed-and open-mouth positions. Methods Seventeen TMD patients [age of(29.82±10.70)years,males/females=8/9] and 13 normal volunteers [control,age of(23.54±3.31)years,males/females=6/7] received 3D-T2WI of the temporomandibular joints in closed-and open-mouth positions from November 2019 to April 2020 in Department of Radiology,Hainan Hospital of Chinese PLA General Hospital.According to the position of the discs,the subjects were classified into the following groups:TMD with disc displacement without reduction(TMD-DDwoR),TMD with disc displacement with reduction(TMD-DDwR),TMD without disc displacement(TMDwoDD),and normal control without disc displacement(NCwoDD).MPR was employed to measure the maximal length of the superior belly of LPM.One-way analysis of variance,receiver operating characteristic curve,and permutation test were employed for the statistical analyses. Results The contraction of LPM was significantly shorter in TMD-DDwoR group [(3.36±1.96)mm] than in TMDwoDD group [(7.90±3.95)mm],NCwoDD group [(8.77±3.13)mm](F=12.891,P=0.000),and TMD-DDwR group[(7.12±3.69)mm](χ2=5.314,P=0.031). Conclusion This study confirmed that the contraction of LPM decreased in patients with TMD-DDwoR,which provided imaging evidence for the study of disc displacement mechanism in TMD patients.

Imaging features of chondrosarcoma of the temporomandibular joint: report of nine cases and literature review.

AIM: To investigate the imaging features of chondrosarcoma of the temporomandibular joint (TMJ) and review the literature. MATERIALS AND METHODS: Computed tomography (CT), magnetic resonance imaging (MRI), and integrated positron-emission tomography (PET)/CT images of nine patients with histopathologically confirmed chondrosarcoma of the TMJ were reviewed retrospectively. Imaging features regarding the direction of lesion growth, bone destruction, infiltration into the tendon of the lateral pterygoid muscle (LPM) in the pterygoid fovea, enhancement pattern, calcification, periosteal reaction, markedly hyperintense T2 signal area, and qualitative PET signal intensity were evaluated. RESULTS: Seven of nine patients (77.8%) presented with lesion growth that was outward from the medulla of the mandibular condyle. Infiltration into the tendon of LPM in the pterygoid fovea was observed in all cases, and 77.8% (7/9) of them demonstrated >50% infiltration. All the lesions showed a mixed peripheral and internal enhancement, and revealed a markedly hyperintense T2 signal intensity area, which showed no enhancement. Although five of nine cases demonstrated higher FDG uptake compared with that of the liver, the other four cases showed less FDG uptake than that of the liver. CONCLUSION: Chondrosarcoma of the TMJ demonstrated several imaging features, including outward growth from the mandibular condyle, resultant infiltration into the tendon of LPM in the pterygoid fovea, various patterns of internal enhancement, and a markedly hyperintense T2 signal intensity area. These imaging features may be helpful to differentiate chondrosarcoma from other lesions of the TMJ.

Lateral Pterygoid Muscle Biometric Modifications in Pterygoid Process Fractures Associated With Mandibular Fractures.

PURPOSE: Pterygoid process fractures (PPFs) are classically associated with Lefort fractures but can also be encountered in association with other facial fractures such as mandibular fractures. The aim of this study was to estimate the frequency of PPFs associated with mandibular fractures and identify factors associated with PPF. MATERIALS AND METHODS: We conducted a retrospective cross-sectional study using computed tomography scanning of patients having a mandibular fracture between November 2018 and April 2020. PPFs were classified using the classification by An et al. Volume, length, and width of both lateral pterygoid muscles have been evaluated by using an image processing software. Study population has been divided into 2 groups: fracture of pterygoid process or the absence of PPF. To evaluate the implication of lateral pterygoid muscle in the pathophysiology of PPF, we compared lateral pterygoid muscle volume, its maximal length, and width between both groups. Patients with bilateral fractures were excluded from this analysis. RESULTS: About 304 patients with at least 1 mandibular fracture have been included in this study. About 18 patients presenting an association of mandibular fracture and PPF were finally selected. About 83.33% of the patients were concerned by a fracture of the posterior part of the mandible. The PPF was classified as type IIA by the classification of An et al for 94.4% of patients. The lateral pterygoid muscle volumes were significantly larger on the side of the PPF (P = .02). However, there were no significant differences in the maximum length (P = .49) and width (P = .1) of lateral pterygoid muscle. CONCLUSIONS: Our study showed an association between mandibular fractures (mainly ipsilateral posterior) and isolated PPF through a lateral pterygoid muscle volume increase.

Association of volume and voxel intensity of the articular disc and lateral pterygoid muscle in migraine patients: a study with magnetic resonance imaging.

Objectives: To compare the volume and voxel intensity of articular disc and lateral pterygoid muscle (LPM) between a group of migraine patients and a control group (those without history of headache) by using magnetic resonance imaging (MRI).Patients and methods: MRI scans of 17 migraine patients and 15 healthy controls subjects were analysed and processed, using ITK-SNAP software, by a single investigator, for calculation of volumes and voxel intensity of articular disc and superior and inferior head of LPM.Results: There were statistically significant differences between migraine patients and controls regarding the volume and voxel intensity of articular disc and inferior head of LPM, increasing in migraine patients. Intra-rater was highly consistent and reproducible (intra-class correlation coefficient [ICC] = 1).Conclusions: Higher voxel intensity in disc and inferior head of LPM of MRI scans was linked to the increased volume of articular disc, inferior head of LPM and migraine.

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.

Analysis of masticatory muscle coordination during unilateral single-tooth clenching using muscle functional magnetic resonance imaging.

In a previous study, we used muscle functional magnetic resonance imaging to show that the anterior movement of the occlusal point increased the activity of the superior head of the ipsilateral lateral pterygoid muscle (ipsilateral SHLP) during unilateral single-tooth clenching. The purpose of this study was to verify the hypothesis that the increased activity of the ipsilateral SHLP described above serves to antagonise the occlusal force acting on the condyle. In total, 9 healthy volunteers were requested to perform left unilateral clenching at the first molar or first premolar region for 1 minute at 20% or 40% maximum voluntary clenching force. Changes in the mean proton transverse relaxation time (∆T2) were examined from the magnetic resonance images obtained before and after each clenching act as an index of the activity in all masticatory muscles. Correlation analyses of the mean ΔT2 for each volume of interest were performed with the first molar or premolar clenches to analyse the correlation between the activities in each muscle. A statistically significant correlation was exhibited between the ipsilateral temporal and ipsilateral SHLP (r = .651, P = .003) during first premolar clenching. However, no significant correlations were observed in the ipsilateral SHLP during first molar clenching. The results of this study suggest that the ipsilateral SHLP may contribute to the pulling of the mandibular condyle forward against the occlusal force generated by the ipsilateral temporal muscle.

Restricted Mandibular Movement Attributed to Ossification of Mandibular Depressors and Medial Pterygoid Muscles in Patients With Fibrodysplasia Ossificans Progressiva: A Report of 3 Cases.

Fibrodysplasia ossificans progressiva (FOP) is an extremely rare genetic condition characterized by congenital malformation and progressive heterotopic ossification (HO) caused by a recurrent single nucleotide substitution at position 617 in the ACVR1 gene. As the condition progresses, HO leads to joint ankylosis, breathing difficulties, and mouth-opening restriction, and it can shorten the patient's lifespan. This report describes 3 cases of FOP confirmed by genetic testing in patients with restricted mouth opening. Each patient presented a different onset and degree of jaw movement restriction. The anatomic ossification site of the mandibular joint was examined in each patient using reconstructed computed tomographic (CT) images and 3-dimensional reconstructed CT (3D-CT) images. A 29-year-old woman complained of jaw movement restriction since 13 years of age. 3D-CT image of the mandibular joint showed an osseous bridge, formed by the mandibular depressors that open the mouth, between the hyoid bone and the mentum of the mandible. A 39-year-old man presented with jaw movement restriction that developed at 3 years of age after a mouth injury. 3D-CT image of the jaw showed ankylosis of the jaw from ossification of the mandibular depressors that was worse than in patient 1. CT images showed no HO findings of the masticatory muscles. To the authors' knowledge, these are the first 2 case descriptions of the anatomic site of ankylosis involving HO of the mandibular depressors in the jaw resulting from FOP. In contrast, a 62-year-old bedridden woman with an interincisal distance longer than 10 mm (onset, 39 years of age) had no HO of the mandibular depressors and slight HO of the medial pterygoid muscle on the right and left sides. These findings suggest that restricted mouth opening varies according to the presence or absence of HO of the mandibular depressors.

The maxillary artery and its variants: an anatomical study with neurosurgical applications.

BACKGROUND: The maxillary artery (MA) has gained attention in neurosurgery particularly in cerebral revascularization techniques, intracranial endonasal approaches and endovascular procedures. OBJECTIVES: To describe and illustrate the anatomy of the MA and its neurosurgical importance in a detailed manner. METHODS: Six cadaveric heads (12 MAs) were injected with latex. The arteries and surrounding structures were dissected and studied using microsurgical techniques. The dimensions, course and branching patterns of the MA were recollected. In addition, 20 three-dimensional reconstruction CT head and neck angiograms (3D CTAs) of actual patients were correlated with the cadaveric findings. RESULTS: The MA can be divided in three segments: mandibular, pterygoid and pterygopalatine. Medial and lateral trunk variants regarding its course around the lateral pterygoid muscle can be found. The different branching patterns of the MA have a direct correlation with the course of its main trunk at the base of the skull. Branching and trunk variants on one side do not predict the findings on the contralateral side. CONCLUSION: In this study the highly variable course, branching patterns and relations of the MA are illustrated and described in human cadaveric heads and 3D CTAs. MA 3D CTA with bone reconstruction can be useful preoperatively for the identification of the medial or lateral course variants of this artery, particularly its pterygoid segment, which should be taken into account when considering the MA as a donor vessel for an EC-IC bypass.

Variability in muscle activation of simple speech motions: A biomechanical modeling approach.

Biomechanical models of the oropharynx facilitate the study of speech function by providing information that cannot be directly derived from imaging data, such as internal muscle forces and muscle activation patterns. Such models, when constructed and simulated based on anatomy and motion captured from individual speakers, enable the exploration of inter-subject variability of speech biomechanics. These models also allow one to answer questions, such as whether speakers produce similar sounds using essentially the same motor patterns with subtle differences, or vastly different motor equivalent patterns. Following this direction, this study uses speaker-specific modeling tools to investigate the muscle activation variability in two simple speech tasks that move the tongue forward (/ə-ɡis/) vs backward (/ə-suk/). Three dimensional tagged magnetic resonance imaging data were used to inversely drive the biomechanical models in four English speakers. Results show that the genioglossus is the workhorse muscle of the tongue, with activity levels of 10% in different subdivisions at different times. Jaw and hyoid positioners (inferior pterygoid and digastric) also show high activation during specific phonemes. Other muscles may be more involved in fine tuning the shapes. For example, slightly more activation of the anterior portion of the transverse is found during apical than laminal /s/, which would protrude the tongue tip to a greater extent for the apical /s/.

The medial pterygoid muscle: a stabiliser of horizontal jaw movement.

There is limited information of the normal function of the human medial pterygoid muscle (MPt). The aims were to determine whether (i) the MPt is active throughout horizontal jaw movements with the teeth apart and (ii) whether single motor units (SMUs) are active during horizontal and opening-closing jaw movements. Intramuscular electrodes were placed in the right MPt of 18 participants who performed five teeth-apart tasks: (i) postural position, (ii) ipsilateral (i.e. right) jaw movement, (iii) contralateral movement, (iv) protrusive movement and (v) opening-closing movement. Movement tasks were guided by a target and were divided into BEFORE, OUT, HOLDING, RETURN and AFTER phases according to the movement trajectories recorded by a jaw tracking system. Increased EMG activity was consistently found in the OUT, HOLDING and RETURN phases of the contralateral and protrusive movement tasks. An increased RETURN phase activity in the ipsilateral task indicates an important role for the MPt in the contralateral force vector. Of the 14 SMUs active in the opening-closing task, 64% were also active in at least one horizontal task. There were tonically active SMUs at the postural jaw position in 44% of participants. These new data point to an important role for the MPt in the fine control of low forces as required for stabilisation of vertical mandibular position not only to maintain postural position, but also throughout horizontal jaw movements with the teeth apart. These findings provide baseline information for future investigations of the possible role of this muscle in oro-facial pain conditions.

Schwannoma With Cystic Changes in the Pterygomandibular Space.

Schwannomas are tumors that arise from Schwann cells. Although schwannomas can occur almost anywhere in the body where nerve cells are present, they rarely occur in the head and neck region, including the oral and maxillofacial region. Cystic changes in schwannomas are extremely rare. This report is on a case of schwannoma with cystic changes that occurred in the pterygomandibular space.A 46-year-old woman presented with a complaint of limited mouth opening and pain on the left side of the mandible for 3 months. On panoramic radiography, radiolucency was seen on the left mandibular ramus. On enhanced computed tomography, a 4 × 3 cm cystic mass was found along the inner side of the left mandibular ramus area. Magnetic resonance imaging showed a multiseptated, well-demarcated cystic lesion on the inner side of the mandibular ramus on the left side. Under general anesthesia, the tumor was excised. The final diagnosis was schwannoma with cystic changes. Lower lip hypoesthesia occurred postoperatively. At the 1-year postoperative follow-up, maximum mouth opening was increased to 44 mm, and lip hypoesthesia was improved.

New anatomo-radiological findings of the lateral pterygoid muscle.

PURPOSE: The discrepancies in the literature regarding the anatomy of the temporomandibular joint (TMJ), particularly at the level of the lateral pterygoid muscle, led us to compare plastinated section techniques and magnetic resonance imaging (MRI) to enable the better interpretation of both, and to describe the features of the lateral pterygoid muscle and the exact location of its insertions. METHODS: A total of 24 blocks of human TMJ were used. Seven were studied by MRI, obtaining images of the oblique-sagittal, oblique-coronal, and axial planes. Four of these blocks were then cut and processed by means of the E12 plastination technique. The remaining blocks were dissected. Finally, we performed a comparative morphological analysis of the different techniques used. RESULTS: New aspects about the morphology and the insertions of the lateral pterygoid muscle are described. The muscle is inserted into the disc, capsule, condyle, and the pterygoid fovea, through muscle and tendon fibres that alternate, giving it the characteristic of a multipennate muscle. This insertion caudally exceeded the pterygoid fovea and descends to near the lingula of mandible. A profuse pterygoid venous plexus surrounds the whole joint complex, and also the insertion zone of the lateral pterygoid muscle. CONCLUSIONS: We consider that the use of transparent-plastinated anatomical sections and its good correlation with MRI images (in axial and oblique-sagittal planes) led to an accurate identification of TMJ structures, especially in relation to the lateral pterygoid muscle, that is now described as a multipennate muscle.

Three-dimensional computed tomographic assessment of mandibular muscles in growing subjects with different vertical facial patterns.

AIM: The present study was undertaken to assess the relationship between the mandibular muscles and dentofacial skeletal morphology in children with different underlying vertical facial patterns, using three-dimensional computed tomography (3D-CT). METHOD: Thirty children (mean age 12.24 ± 1.57 years) underwent cranial CT examination for diagnostic purposes. 3D-CT images were reconstructed for the evaluation of the cross-sectional size, volume, and spatial orientation of the masseter and medial pterygoid muscles. These muscle parameters were also assessed in relation to the vertical facial pattern, gender and skeleto-dental form. RESULTS: Significant differences were found in muscular angulation for subjects with different underlying patterns. Greater masseter volumes were associated with increased facial width. Greater intermolar widths were found in brachyfacial subjects, with less acute muscular angulations in relation to horizontal reference lines, compared with dolichofacial subjects. This was also more obvious in the maxillary arch. CONCLUSION: Clinicians should note the likely differences in masseter and medial pterygoid orientation and volume in subjects with different underlying vertical facial patterns and that these differences may, in turn, be related to both facial skeletal width and naturally-occurring transverse dental arch dimensions.