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.

Sensory innervation of masseter, temporal and lateral pterygoid muscles in common marmosets.

Myogenous temporomandibular disorders is associated with an increased responsiveness of nerves innervating the masseter (MM), temporal (TM), and lateral pterygoid muscles (LPM). This study aimed to examine sensory nerve types innervating MM, TM and LPM of adult non-human primate-common marmosets. Sensory nerves were localized in specific regions of these muscles. Pgp9.5, marker for all nerves, and NFH, a marker for A-fibers, showed that masticatory muscles were primarily innervated with A-fibers. The proportion of C- to A-fibers was highest in LPM, and lowest in MM. All C-fibers (pgp9.5+/NFH-) observed in masticatory muscles were peptidergic (CGRP+) and lacked mrgprD and CHRNA3, a silent nociceptive marker. TrpV1 was register in 17% of LPM nerves. All fibers in masticatory muscles were labeled with GFAP+, a myelin sheath marker. There were substantially more peptidergic A-fibers (CGRP+/NFH+) in TM and LPM compared to MM. MM, TM and LPM NFH+ fibers contained different percentages of trkC+ and parvalbumin+, but not trkB+ fibers. Tyrosine hydroxylase antibodies, which did not label TG, highlighted sympathetic fibers around blood vessels of the masticatory muscles. Overall, masticatory muscle types of marmosets have similarities and differences in innervation patterns.

[A case of atezolizumab- and bevacizumab-induced myositis showing high intensity in the pterygoid muscles, soft palate, and tongue on STIR-MRI].

A 61-year-old woman was treated with atezolizumab plus bevacizumab for hepatocellular carcinoma with peritoneal dissemination. Blood tests revealed elevated creatine kinase (CK) that peaked at 2,657 U/l. After two cycles of atezolizumab plus bevacizumab combination therapy, she complained of progressive dysarthria and dysphagia. Needle electromyography showed myopathic changes. Initial MRI showed high signal intensity in the orbicularis oris muscle, soft palate, tongue, pterygoid muscles, and paravertebral muscles on STIR images. Myositis-specific autoantibodies were not detected. Based on these findings, the patient was diagnosed with immune checkpoint inhibitor-associated myositis. The clinical symptoms improved after administration of oral prednisone, and follow-up MRI showed reduced extent of areas of high signal intensity and almost complete resolution of signal abnormality in the paravertebral muscles. The CK level normalized after 1 months of oral steroid administration. MRI of the head and neck, including the tongue and soft palate, may be useful in diagnosis and for evaluating therapeutic efficiency in cases of bulbar symptoms that occur following the introduction of immune checkpoint inhibitors.

[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.

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.

Arthroscopic assisted release of lateral pterygoid versus scarification of retrodiscal tissue in management of internal derangement of temporomandibular joint-A randomized clinical trial.

The purpose of this study was to compare the effectiveness of arthroscopic-assisted lateral pterygoid muscle release versus scarification of retrodiscal tissues in the treatment of temporomandibular joint internal derangement. A prospective, comparative, randomized clinical trial involved 16 patients with TMJ internal derangement. Arthroscopic assisted release of lateral pterygoid muscle was assigned to one group of patients (Group I). Group II patients received arthroscopic assisted scarification of retrodiscal tissues. Data collected through functional examination including visual analogue scale (VAS), maximum mouth opening, lateral excursion, and clicking sound immediately and after 3, 6, and 12 months. Pre- and post-operative MRI was used to assess disc position. The VAS scores decreased in both groups at the end of the follow-up period (0.45 vs 6.75, and 1.13 vs 6.50 in group I and II respectively; P<0.001). The maximum mouth opening improved to 32.9.50 ± 1.69 mm in group I, and 30.49 ± 0.93 in group II (P<0.001). Lateral excursion improved in both groups (P<0.001). Clicking sounds disappeared in all patients. Within the limitations of the study, it seems that arthroscopic assisted release of lateral pterygoid and scarification of retrodiscal tissues may be beneficial in management of anteriorly displaced discs that don't respond to conservative treatments.

Training of the lateral pterygoid muscle in the treatment of temporomandibular joint disc displacement with reduction: A randomised clinical trial.

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). CONCLUSION: 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.

Elucidation of the relationship between masticatory muscle activity and masticatory movement. Report 1. Mechanism of occlusal force generation.

OBJECTIVES: The purpose of this study was to elucidate how masticatory muscles are involved in the generation of occlusal force. MATERIALS AND METHODS: The experiment was conducted by fabricating an experimental apparatus for a unilateral occlusion model with the masticatory muscles imparted. The experimental apparatus was fabricated by enlarging the lateral photograph of a dried adult skull specimen 3.5 times larger than that of a standard adult and drawing the outlines of the maxilla and mandible, canines and molars of the upper and lower jaws, and temporomandibular joint on a wooden board. The masticatory muscles used in the experiment were the masseter muscle, the temporalis muscle (anterior and posterior muscle bundles), and the lateral pterygoid muscle. For the measurement of the contractile force of the masticatory muscle, we used the spring scale. For the food, we used cut plastic cylinders. RESULTS: The results of the experiment revealed the following: First, the occlusal force was generated under the condition that the contraction forces of all the masticatory muscles were balanced. Second, when the occlusal force was applied to food, the occlusal planes of the upper and lower jaws were parallel. Third, the occlusal force occurred perpendicular to the occlusal plane. Fourth, the occlusal force was generated with a force greater than the contraction force of the individual masticatory muscles. And finally, even if occlusal force was applied to the food, the occlusal force did not load the temporomandibular joint. CONCLUSION: Occlusal force is not generated by the action of a single masticatory muscle but under the balanced contractile force of all masticatory muscles. The occlusal force then emerges with a force greater than the contraction force of all the masticatory muscles, and its direction occurs perpendicular to the occlusal plane.

An Unusual Case of Severe Trismus After Craniotomy.

Myositis ossificans Traumatica (MOT) is a non-neoplastic, heterotrophic ossifying disease process in muscle and soft tissue rarely involving the craniofacial area. Treatment depends on the extent of ossification and functional limitations. We present the first case of MOT of the temporalis muscle following neurosurgical intervention. This is the case of a 28-year-old male patient who underwent numerous neurosurgical interventions and reported progressive trismus following these interventions. Imaging demonstrated a right temporal region radio-opacity consistent with ossification of the temporalis muscle. The patient underwent coronoidectomy with excision of the ossified right temporalis muscle and reconstruction with an anterolateral thigh adipofascial vascular free flap. Postoperatively, he maintained intact function with increased incisal opening and no cosmetic defects. Limited mouth opening after the neurological procedure has a wide differential, and MOT must be considered. Surgical repair and reconstruction are multifaceted problems. Free flap reconstruction should be considered in multiple operated patients.

Efficacy of magnetic resonance imaging texture features of the lateral pterygoid muscle in distinguishing rheumatoid arthritis and osteoarthritis of the temporomandibular joint.

OBJECTIVES: The aim of this study was to assess whether magnetic resonance imaging (MRI) texture features of the lateral pterygoid muscle can distinguish between rheumatoid arthritis (RA) and osteoarthritis (OA) of the temporomandibular joint (TMJ). METHODS: The authors extracted 279 texture features from 36 patients with RA and OA from the region of interest set for the lateral pterygoid muscle on short tau inversion recovery (STIR) images using MaZda Ver.3.3. A total of 10 texture features were selected using Fisher's coefficients, as well as probability of error and average correlation coefficients. Data observed to have a non-normal distribution using the Kolmogorov-Smirnov test were compared using the Mann-Whitney U-test. Receiver operating characteristic (ROC) curves were used to assess the ability of the 10 texture features to distinguish RA and OA of the TMJ. RESULTS: A total of 10 features (5 Correlation, 3 Run Length Nonuniformity, 1 Sigma, and 1 Teta) were selected from 279 texture features. These texture features revealed significant differences between the RA and OA groups (p < 0.01). The sensitivity, specificity, accuracy, and area under the ROC curve of the texture features for distinguishing RA from OA were 0.78-0.94, 0.89-1.0, 0.86-0.92, and 0.89-0.95, respectively. CONCLUSION: MRI texture analysis of the lateral pterygoid muscle may be useful for distinguishing between RA and OA of the TMJ.

Ultrasound-guided lateral pterygoid muscle botulinum toxin: an injection for recurrent temporomandibular joint dislocation in a brain injury patient.

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.

Magnetic resonance image texture analysis of the lateral pterygoid muscle in patients with rheumatoid arthritis: a preliminary report.

OBJECTIVES: 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). METHODS: 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. RESULTS: All seven lateral pterygoid muscle radiomic features indicated significant differences between the non-RA and RA groups (P < 0.05). CONCLUSION: MRI texture analysis shows potential for application in radiomics diagnosis of RA in TMJ.

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.

Quantitative analysis of masticatory muscle changes by Eichner index using diffusion-weighted imaging.

OBJECTIVES: Diffusion-weighted imaging (DWI) provides quantitative functional information about the microscopic movement of water at the cellular level. However, few reports have quantitatively evaluated histological changes in masticatory muscles due to changes in occlusal relationships using DWI. This study aimed to assess the changes in masticatory muscles by Eichner index using DWI. METHODS: We analyzed magnetic resonance imaging (MRI) studies of 201 patients from November 2017 to April 2018. Each Eichner index group, age, and sex were used as criterion variables, and the average apparent diffusion coefficient (ADC) values of the masticatory muscles were the explanatory variable. The mean ADC value differences were analyzed in each Eichner index group. We analyzed the data using the Kruskal-Wallis test and post hoc Mann-Whitney test with Bonferroni adjustment multiple regression analysis with Shapiro-Wilk test and Spearman's correlation coefficients. P < 0.05 was considered statistically significant. RESULTS: The mean ADC values of each Eichner classification group were significantly different, with the lowest value in group C (P < 0.001). There was a negative correlation between the ADC value of the masseter, lateral pterygoid muscle, and age (P < 0.001). There were significant differences between the sex groups (P < 0.001). CONCLUSIONS: ADC values of masticatory muscles were significantly different in the Eichner index groups. The ADC values of masticatory muscles may be useful for the quantitative evaluation of the masticatory muscles affected by the occlusal state.

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 / 中华口腔医学杂志

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.

Efecto de la dibucaína sobre la SERCA del músculo pterigoideo interno / Drug action of dibucaine on the SERCA from medial pterygoid muscle

Objetivo: Determinar el efecto del anestésico local di-bucaína sobre las principales isoformas de la SERCA (calcio ATPasa de retículo sarco-endoplásmico) pre-sentes en músculo pterigoideo interno. Métodos: Se aislaron por centrifugación diferencial membranas de retículo sarcoplásmico de pterigoideo interno de conejo neozelandés macho (n=5). Se separaron las isoformas SERCA1a, 2a y 2b por cromatografía de afinidad. Se determinó in vitro la actividad enzimá-tica en presencia de diferentes concentraciones de dibucaína (0-90 mM) por el método de Fiske y Subba-row, realizando 5 experimentos por duplicado y en paralelo para cada isoforma. Se calculó la media y ES de la CI50 (mM) del anestésico para cada isofor-ma y éstas se compararon por ANOVA de una vía (p<0,05), y prueba Student-Newman-Keuls de com-paraciones múltiples. Resultados: Dibucaína inhibió la actividad enzimática en función de su concentra-ción en las tres isoformas en estudio. Las CI50 fueron: SERCA1a 20,02 ± 0,64 mM, SERCA2a 15,03 ± 0,52 mM y SERCA2b 16,00 ± 0,51 mM y resultaron signi-ficativamente diferentes (F2,27 = 11,08, p<0,001). La prueba post hoc identificó diferencias significativas entre SERCA1a y 2a, 1a y 2b. El efecto inhibitorio re-sultó significativamente mayor sobre las isoformas 2a y 2b, cuya presencia es sustancialmente mayor en músculos masticadores. Conclusión: La dibucaína inhibe a la SERCA de pterigoideo interno a concen-traciones menores que las usadas en clínica médica (29 mM). Es un anestésico local con potencial efecto miotóxico derivado de la inhibición de la SERCA (AU)

Aim: To test the effect of the local anesthetic dibu-caine on the main isoforms of the SERCA (sarco-endosplasmic reticulum calcium-ATPase) in medial pterygoid muscle. Methods: Sarcoplasmic reticulum membranes from male New Zealand rabbits (n=5) were isolated from medial pterygoid muscle by ul-tracentrifugation. The isoforms SERCA1a, 2a and 2b were separated using high affinity chromatography. In vitro enzymatic activity determinations were per-formed in the presence of different dibucaine con-centrations (0-90 mM) using the colorimetric method described by Fiske & Subbarow. Five assays in dupli-cate and run in parallel were performed for each of the isoforms. Mean and SEM of the IC50 (mM) for the effect of the anesthetic on each isoform were calcu-lated and compared by one-way ANOVA (p<0.05), and Student-Newman-Keuls multiple comparisons test. Results: Dibucaine inhibited the enzymatic activity in a concentration-dependent manner for the three studied isoforms. The IC50 values were: SERCA1a 20.02 ± 0.64 mM, SERCA2a 15.03 ± 0.52 mM and SER-CA2b 16.00 ± 0.51 mM. The values were significantly different (F2.27 = 11.08, p<0.001). The post hoc test revealed significant differences between SERCA1a and 2a, 1a and 2b. The inhibitory effect was signifi-cantly higher on 2a and 2b isoforms, whose presence is substantially higher in masticatory muscles. Con-clusion: Dibucaine inhibits SERCA in medial pterygoid muscle at concentrations lower than those used in clinical medicine (29 mM). It is a potentially myotoxic local anesthetic whose toxic effect may derive from SERCA inhibition (AU)

Macroscopic analysis of the insertion points of the lateral pterygoid muscle in adult individuals / Análisis macroscópico de los lugares de inserción del músculo pterigoideo lateral en individuos adultos

SUMMARY: The lateral pterygoid muscle (LPM) is intimately related with the temporomandibular joint (TMJ), playing an important role in its physiology. This makes it of interest to researchers who investigate temporomandibular disorders. The literature indicates that anatomical variations exist in the insertion of the superior fascicle of the LPM. Imaging and cadaver studies have revealed that the LPM may present an accessory fascicle. The study object was to carry out macroscopic analysis of the LPM, examining the origin and insertion of its superior and inferior fascicles. The study used 38 half-heads of adult individuals fixed in formaldehyde 10 %. To carry out macroscopic analysis of the LPM, an initial incision was made along the lower margin of the zygomatic arch; the origin of the masseter muscle was then dissected, separating its insertion on the lateral face of the mandibular ramus and retracting the muscle to posteroinferior. Two incisions were made on the zygomatic arch and the insertion of the temporal muscle on the coronoid process was identified with dissection pincers; it was dissected to gain access to the infratemporal fossa and the two fascicles of the LPM. The superior fascicle (SF) originated on the infratemporal face of the greater wing of the sphenoid, and on the superior third of the lateral face of the lateral lamina of the pterygoid process of the sphenoid in 26 samples. In 12 samples, it originated on the greater wing of the sphenoid and the infratemporal crest of the sphenoid. Type I insertion was found in 20 samples, Type II in 6 samples and Type III in 12 samples. In all the samples analysed, the inferior fascicle (IF) originated on the inferior two thirds of the lateral face of the lateral lamina of the pterygoid process and on the lateral face of the pyramidal process of the palatine, with insertion on the pterygoid fovea. The accessory fascicle (AF) of the LPM was present in 6 samples. The AF originated on the greater wing of the sphenoid in 2 cases and inferior to the superior fascicle in 4 cases; its insertion was on the capsular disc complex in all cases. The results obtained in our study contribute anatomical data on the LPM in Brazilian adult individuals, with evaluation of its insertion points.

El músculo pterigoideo lateral (MPL) presenta íntima relación con la articulación temporomandibular (ATM) y desempeña un rol importante en la fisiología de esta articulación, despertando el interés de investigadores que se dedican al estudio de los trastornos temporomandibulares. La literatura señala que existen variaciones anatómicas del MPL, con respecto a la inserción del fascículo superior. Los estudios cadavéricos e imagenológicos han revelado que el MPL puede presentar un fascículo accesorio. El objetivo del estudio fue realizar un análisis macroscópico del MPL, examinando el origen e inserción de sus fascículos superior e inferior. Se utilizaron 38 hemicabezas de individuos adultos fijadas en formaldehído al 10 %. Para realizar el análisis macroscópico del MPL se realizó inicialmente una incisión a lo largo del margen inferior del arco cigomático, luego se seccionó el origen del músculo masétero separando su inserción en la cara lateral de la rama de la mandíbula, retrayendo al músculo en sentido posteroinferior. Se hicieron dos cortes en el arco cigomático y con pinzas de disección se identificó la inserción del músculo temporal en el proceso coronoides, el cual se seccionó para ingresar a la fosa infratemporal y acceder a ambos fascículos del MPL. El fascículo superior (FS) del MPL se originó en la cara infratemporal del ala mayor del esfenoides y en el tercio superior de la cara lateral de la lámina lateral del proceso pterigoides del esfenoides en 26 muestras. En 12 muestras se originó en el ala mayor del esfenoides y cresta infratemporal del esfenoides. Con relación a su inserción, se encontró el Tipo I en 20 muestras; el Tipo II en 6 muestras y el Tipo III en 12 muestras. En todas las muestras analizadas el origen del fascículo inferior (FI) del MPL fue en los dos tercios inferiores de la cara lateral de la lámina lateral del proceso pterigoides y en la cara lateral del proceso piramidal del palatino insertándose en la fóvea pterigoidea. El fascículo accesorio (FA) del MPL estuvo presente en 6 muestras. El FA se originó en el ala mayor del esfenoides en 2 casos e inferior al fascículo superior en 4 casos y su inserción, en el complejo disco capsular en todos los casos. Mediante los resultados obtenidos en nuestro estudio estamos aportando datos anatómicos en relación al MPL en individuos brasileños adultos, evaluándolo con respecto a sus lugares de inserción.

Pterygoid muscle activity in speech: A preliminary investigation.

BACKGROUND: Speaking depends on refined control of jaw opening and closing movements. The medial pterygoid muscle (MPT), involved in jaw closing, and the lateral pterygoid muscle (LPT), involved in jaw opening, are two key mandibular muscles in mastication and are likely to be recruited for controlled movements in speech. OBJECTIVES: Three hypotheses were investigated, that during speech the MPT and LPT: (1) were both active, (2) but exhibited different patterns of activity, (3) which fluctuated with the vowels and consonants in speech. METHODS: Intramuscular EMG recordings were made from the right inferior head of the LPT and/or the right MPT in five participants during production of 40 target nonsense words (NWs) consisting of three syllables in the form /V1 C1 V2 C2 ə/ (V = vowel; C = consonant; ə = unstressed, reduced vowel), spoken by each participant 10 times per NW; analysis focussed on the target syllable, C1 V2 . RESULTS: Both MPT and LPT exhibited robust increases in EMG activity during utterance of most NWs, relative to rest. Peak LPT activation was time-locked to the final part of the target consonant (C1 ) interval when the jaw begins opening for the target vowel (V2 ), whereas peak MPT activation occurred around the temporal midpoint of V2 , when the jaw begins closing for C2 . EMG amplitude peaks differed in magnitude between "high" vowels, i.e., for which the tongue/jaw are high (e.g., in SEEK), and "low" vowels, i.e., for which the tongue/jaw are low (e.g., in SOCK). CONCLUSIONS: These novel findings suggest a key role for the LPT and MPT in the fine control of speech production. They imply that speech may impose major synergistic demands on the activities of the MPT and the LPT, and thereby provide insights into the possible interactions between speech activities and orofacial activities (e.g. mastication) and conditions (e.g. Temporomandibular Disorders) that involve the masticatory muscles.