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.

A Novel Injection Technique to the Lateral Pterygoid Muscle for Temporomandibular Disorders: A Cadaveric Study.

BACKGROUND: Lateral pterygoid muscle activity is associated with the pathological mechanisms of some temporomandibular disorders. The authors aimed to define and demonstrate a novel, practical, and safe technique for botulinum toxin type A injection to the lateral pterygoid muscle based on their findings. Their secondary aims were to standardize the injection pattern according to the variations of the lateral pterygoid muscle and its surrounding anatomical structures, and to establish its advantages over intraoral injection. METHODS: Twenty cadaver heads were dissected. The lateral pterygoid muscle and its surrounding structures were investigated for anatomical variations. Based on these findings, a standardized extraoral injection protocol was defined and compared with the intraoral technique for accuracy and safety. RESULTS: The average depth of the lateral pterygoid plate from the skin surface was 49.9 ± 2.2 mm, and the mean width of the lateral pterygoid plate was 10.5 ± 3.9 mm. The extraoral injection approach based on the location of the maxillary tuberosity, tragus, and lateral pterygoid plate was consistent in all dissections for the accuracy of the intramuscular injection. In the intraoral approach, standardization of the entry point of the needle through the oral mucosa is difficult, which makes adjustment of the depth of the injection challenging while increasing the risk of neurovascular injury. CONCLUSIONS: The clinical significance of the lateral pterygoid muscle makes it worthwhile to implement minimally invasive treatments before considering more invasive options. The authors define a safe, accurate, and reliable approach with ease of administration in patients with temporomandibular disorders.

Evaluation of the presence of the third head on the lateral pterygoid muscle in adult individuals / Evaluación de la presencia de la tercera cabeza del músculo pteriogoideo lateral en individuos adultos

SUMMARY: The lateral pterygoid muscle (LPM) is one of the muscles involved in jaw movements, and is therefore of great importance in the physiology of the temporomandibular joint. This muscle has classically been considered to have two heads, superior and inferior, however previous studies have indicated the presence of a third head (TH). The object of this research was therefore to evaluate, through a study in cadavers, the presence of the third head of the LPM and its relation with the joint disc of the TMJ in adult individuals. The study used 30 half-skulls of adult individuals, 11 right side and 19 left side. The number of heads on each LPM was analysed, with the length and thickness of each. The Chi-squared, Mann-Whitney U, Kruskall-Wallis and Spearman's correlation coefficient tests were applied, with a significance threshold of 5 %. The TH of the LPM was present in 20 % of the samples. Statistically significant differences were found in the thickness of the superior head (SH) vs. the inferior head (IH) (p<0.001) and between TH vs. SH and TH vs. IH (p=0.010). No correlation was found between the thickness of the heads or in their lengths. The LPM most frequently presents two heads, superior and inferior. The TH is an anatomical variation that may be present in 20 % of cases. The IH usually presents the greatest thickness. The use of cadavers is a good method for analysing the presence of the TH and the morphometry of the various heads of the LPM.

RESUMEN: El músculo pterigoideo lateral (MPL) es uno de los músculos involucrados en los movimientos mandibulares y por consiguiente tiene una gran importancia en la fisiología de la articulación temporomandibular (ATM). Clásicamente se ha considerado como un músculo que presenta dos cabezas, una superior y otra inferior, sin embargo estudios anteriores han señalado la presencia de una tercera cabeza (TC). El objetivo fue evaluar, mediante estudio en cadáveres, la presencia de la tercera cabeza del MPL y su relación con el disco articular de la ATM de individuos adultos. Se utilizaron 30 hemicabezas de individuos adultos, 11 del lado derecho y 19 en el lado izquierdo. Se analizó el número de cabezas, longitud y grosor de cada cabeza. Se aplicaron las pruebas de chi-cuadrado, U-Mann-Whitney, Kruskall-Walis y coeficiente de correlación de Spearman, con umbral de significación de 5 %. La TC del MPL estuvo presente en 20 % de las muestras. Se encontraron diferencias estadísticas significativas para el grosor del la cabeza superior (CS) vs. cabeza inferior (CI) (p<0,001) y entre TC vs. CS y TC vs. CI (p=0,010). No se encontró correlación entre el grosor de las cabezas o para la longitud de las cabezas. El MPL se presenta más frecuentemente con dos cabezas, una superior y otra inferior. La TC es una variación anatómica que puede estar presente en un 20 % de los casos. La CI suele ser la que presenta mayor grosor. En cuanto a los métodos para análisis de presencia de la TC y morfometría de las distintas cabezas del MPL el uso de cadáveres representa una buena alternativa.

Ostmann's Fat Pad-Does it Really Matter?

OBJECTIVE: To compare the size of Ostmann's fat pad (OFP) between healthy ears and ears with chronic otitis media with cholestatoma (COMwC) using magnetic resonance imaging (MRI). METHODS: Twenty-six patients with unilateral COMwC underwent mastoidectomy. Pre-operative MRI records were reviewed retrospectively. The healthy ears served as the control group. OFP is represented by the maximum diameter of the high intensity area medial to the tensor veli palatini muscle (TVP); M1. A reference diameter was defined from the medial border of OFP reaching the medial border of the medial pterygoid muscle; M2. Values of M1, M2 and the ratio of M1:M2 was compared between the healthy and pathological ear in each patient. RESULTS: All 26 patients (16 females,10 males) had unilateral cholestatoma. Mean age was 37.6 years (range 19-83). In the healthy (H) ears group, mean M1H was 2.04 ± 0.53 mm, mean M2H was 9.57 ± 2.57 mm.In the pathological (P) ears group; mean M1P was 2.03 ± 0.55 mm, mean M2P was 9.86 ± 2.37 mm. A comparison of M1 and M2 values between the healthy and pathological ear groups was not statistically significant (P = .853 and P = .509, respectively).Mean M1H:M2H ratio in the healthy ears group was 0.22 ± 0.05, mean M1P:M2P ratio in the pathological ear group was 0.21 ± 0.06. A comparison between these ratios found no significant statistical correlation (P = .607). CONCLUSION: The size of Ostmann's fat pad does not affect the development of chronic otitis media with cholestatoma in adults.

Análisis morfológico y funcional del músculo pterigoideo lateral: una revisión de la literatura / Morphological and functional analysis of the lateral pterygoid muscle: a review of the literature

RESUMEN: El músculo pterigoideo lateral (MPL) es una estructura compleja y variable, poder determinar su anatomía exacta, relaciones vecinas, origen e inserciones, ayuda a los clínicos a comprender de mejor forma su función en el sistema estomatognático. En esta revisión se busca analizar la literatura que ayude a esclarecer la función antagónica de las cabezas del músculo pterigoideo lateral, desde un punto de vista nervioso, la descripción de su origen e inserciones y sus posibles variaciones anatómicas, además del análisis de sus funciones evaluado a través de la literatura tradicional y compararlo con lo descrito en artículos originales. Se analizaron diferentes bases de datos electrónicos y libros, con criterios de inclusión e exclusión claramente definidos, la lectura fue llevada a cabo por dos investigadores de manera independiente consultando de ser necesario con un tercer investigador. Esta revisión incluyo un total de 11 artículos y 4 libros atingentes a nuestro tema de estudio. Se expusieron los resultados a través de tablas de extracción de datos, que incluyó las funciones, inervación, el origen e inserción y las variaciones anatómicas del MPL. Nuestros resultados muestran que se identificaron claramente los elementos comunes de origen del MPL, pero su inserción mostró variaciones entre los distintos estudios, tanto en el porcentaje de fibras unidas como a los elementos anatómicos insertados. Considerando las funciones antagónicas de sus dos cabezas, autores lo han descrito como dos músculos diferentes, sin embargo desde un punto de vista nervioso, esta teoría no es apoyada. Finalmente comprender las funciones del MPL durante su acción es complejo, ya que la gran mayoría de los estudios disponibles utilizan cadáveres o electromiografía por lo que creemos que el desarrollo de metodologías menos invasivas y dolorosas, ayudarían a comprender el comportamiento de este músculo durante su función y como las variaciones anatómicas influyen en estas.

SUMMARY: The Lateral Pterygoid Muscle (LPM) is a complex and variable structure. Being able to determine its exact anatomy, neighboring relationships, origin and insertions, helps clinicians to better understand its function in the stomatognathic system. This review seeks to analyze the literature, in order to clarify the antagonistic function of the lateral pterygoid muscle heads, from a nervous point of view. Furthermore, the description of its origin, aspects of insertions and possible anatomical variations, its functions as reported in traditional literature, are analyzed and compared with original articles. Different electronic databases and books were analyzed, with designated inclusion and exclusion criteria. Two researchers independently reviewed the articles, whennecessary a third researcher resolved any differences. This review includes a total of 11 articles and 4 books related to our study topic. Results were reported using data extraction tables, which included functions, innervation, origin and insertion, and anatomical variations of the LPM. Our results show that the common elements of origin of LPM were clearly identified, but their insertion showed variations between the different studies, both in the percentage of fibers joined and the anatomical elements inserted. Considering the antagonistic functions of the two heads, authors have described it as two different muscles. However from a nervous point of view, this theory is not supported. Finally, understanding the functions of the LPM during its action is complex, since most studies available use cadavers or electromyography. Therefore, we believe that the development of less invasive and painful methodologies, would help to understand the influence of anatomical variations on the function of this muscle.

Importance of knowledge of the lateral pterygoid muscle's anatomy and it's variations

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Anatomy of the lateral pterygoid muscle and its relationship with temporomandibular disorders. A literature review

The lateral pterygoid muscle is a chewing muscle that is found bilaterally in the cranial region. Anatomically, the lateral pterygoid muscle is made up of two bellies, an upper belly and a lower belly. Its anatomical description present in the scientific lit-erature showed that there is an anatomical differ-ence or variation, mainly the insertions of the up-per belly of the lateral pterygoid muscle at the level of the temporomandibular joint, and specifically in the disc and articular condyle, although distribu-tions are reported similarly. They are not entirely accurate in smaller quantities: some articles re-ported variations in the insertion of the lower belly and others the appearance of a third belly of the lateral pterygoid muscle or medial belly. As men-tioned above, a high number of studies that presented some type of lateral pterygoid muscle vari-ation was associated with some type of temporo-mandibular disorders of the joint or some of its in-tra or extra-articular components. A review of the literature in scientific databases was carried out after the selection of the scientific articles, which were analyzed in full text, and the relationship between the anatomy of the lateral pterygoid muscleand the temporomandibular disorders was sought

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[Anatomical study of rat trigeminal motor nucleus-lateral pterygoid muscle projection pathway].

Objective: To determine the opening and closing action of the external muscle, the projection pathway of the axon terminal of trigeminal motor nucleus (Vmo) neuron to the lateral pterygoid muscle was revealed. Methods: In this study, 10 SD rats of 8 weeks old were included. The left lateral pterygoid muscle of SD rats was surgically exposed, and the wound was closed after intramuscular injection of hydroxystilbamidine/fluorogold (FG) 3-5 µl. Seven days after the operation, the experimental animals were perfused, samples collected and sectioned for immunofluorescence staining. After FG injection into the lateral pterygoid muscle, the FG reversed in the Vmo neurons. Results: In the Vmo neurons on the FG injection side (left side), a large number of FG reversed neurons were found in the corpus luteum and dendrites. These neurons were not only distributed in the dorsolateral part of the trigeminal motor nucleus that innervated the closed muscle, but also in the ventral medial portion of the trigeminal nucleus of the open muscle. Conclusions: The neuronal conduction pathway between the Vmo and the lateral pterygoid muscle innervates the lateral pterygoid muscle. The neurons are distributed both in the dorsolateral and in the nucleus of the ventral ventricle. It is concluded that the lateral pterygoid muscle involve in the jaw closing and opening 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.

Characterization of Anatomical Landmarks for Exposing the Internal Carotid Artery in the Infratemporal Fossa Through an Endoscopic Transmasticator Approach: A Morphometric Cadaveric Study.

BACKGROUND: The Eustachian tube and sphenoid spine have been previously described as landmarks for endonasal surgical identification of the most distal segment of the parapharyngeal internal carotid artery (PhICA). However, the intervening space between the sphenoid spine and PhICA allows for error during exposure of the artery. In the present study, we have characterized endoscopic endonasal transmasticator exposure of the PhICA using the sphenoid spine, vaginal process of the tympanic bone, and the "tympanic crest" as useful anatomical landmarks. METHODS: Endonasal dissection was performed in 13 embalmed latex-injected cadaveric specimens. Two open lateral dissections and osteologic analysis of 10 dry skulls were also performed. RESULTS: A novel and palpable bony landmark, the inferomedial edge of the tympanic bone, referred to as the tympanic crest, was identified, leading from the sphenoid spine to the lateral carotid canal. Additionally, the vaginal process of the tympanic bone, viewed endoscopically, was a guide to the PhICA. The sphenoid spine was bifurcate in 20% of the skulls, with an average length of 5.98 mm (range, 3.9-8.2 mm), width of 5.81 mm (range, 3.0-10.6 mm), and distance to the carotid canal of 4.48 mm (range, 2.5-6.1 mm). CONCLUSION: The sphenoid spine and pericarotid space has variable anatomy. Using an endoscopic transmasticator approach to the infratemporal fossa, we found that the closest landmarks leading to the PhICA were the tympanic crest, sphenoid spine, and vaginal process of the tympanic bone.

Changes in cross-sectional measurements of masseter, medial pterygoid muscles, ramus, condyle and occlusal force after bi-maxillary surgery.

PURPOSE: The purpose of this study was to examine changes in masseter and medial pterygoid muscles, ramus, condyle and occlusal force after bi-maxillary surgery in class II and III patients. SUBJECTS AND METHODS: The subjects were 42 patients (84 sides) who underwent sagittal split ramus osteotomy with Le Fort I osteotomy (21 class II cases: mandibular advancement and 21 class III cases: mandibular setback). The cross-sectional measurements of the masseter and medial pterygoid muscles, ramus and condyle were measured in horizontal plane images by computed tomography (CT), before and 1 year after the operation. Occlusal force and contact area were also recorded before and 1 year after the operation. RESULTS: Preoperatively, class II was significantly larger than class III in masseter width (P = 0.0068), masseter area (P < 0.0001) and medial pterygoid length (P < 0.0001). However, class II was significantly smaller than class III in medial pterygoid width (P < 0.0001). After 1 year, class II was significantly smaller than class III in masseter length (P = 0.0017). Class II was still larger than class III in medial pterygoid area after 1 year (P = 0.0343). Class II was significantly larger than class III in condylar angle pre-operatively (P < 0.0001) and after 1 year (P = 0.0006). After 1 year, class II decreased significantly more than class III in condylar thickness (P = 0.0020), condylar width (P < 0.0001) and condylar area (P < 0.0001). CONCLUSION: This study suggested that changes in the cross-sectional measurements of masseter and medial pterygoid muscles and the condyle differed between class II and class III patients, although occlusal force did not significantly change 1 year after surgery in both groups.

Intraoral Endoscopic Ligation of Maxillary Artery in the Infratemporal Fossa.

Ligation of the sphenopalatine and posterior nasal arteries is indicated for posterior epistaxis as initial treatment or when conservative measures fail. In some patients, a transnasal approach or its alternative transantral approach are not possible due to tumor filling the nasal corridor, pterygopalatine fossa, or maxillary sinus. Aim of this study was to evaluate feasibility of endoscopically assisted transoral approach for the ligation of the maxillary artery (MA). Six fresh cadaver specimens (12 sides), previously prepared with intravascular injections of colored latex, were dissected. A combined transnasal and transoral approach exposed the MA from the deep belly of the temporalis muscle laterally to its terminal branches medially. Anatomical relationships of the MA with the deep belly of the temporalis muscle and the lower head of the lateral pterygoid muscle, and feasibility of access to the MA via a transoral approach were assessed. In all specimens, the MA was found at the point where horizontal fibers of the lower head of the lateral pterygoid muscle cross the vertical fibers of the deep belly of the temporalis muscle. In 5 specimens, the artery ran anteriorly and laterally to lower head of the lateral pterygoid muscle, and in 1 specimen, it ran posteriorly and medially to this muscle, diving between its fibers. The modified endoscopically assisted transoral approach is feasible to ligate the MA. It can be used for proximal vascular control in cases when transnasal and transantral approaches are not viable.

The morphological variations of the lateral pterygoid muscle: A systematic review.

BACKGROUND: The lateral pterygoid muscle (LPM) has been described in many anatomical and functional studies. The morphology of the LPM is still under debate because of its deep location in the infratemporal fossa and the difficulties to approach this area with different anatomical methods. Although it has been generally accepted that this muscle is mainly composed of two separate parts, other forms have been described in the past. OBJECTIVES: To conduct a systematic literature review regarding the anatomy and variations of the LPM. METHODS: We included studies published in English, German or French employing anatomical and imaging methods or a combination of the two methods. The cadavers used in the dissections had to be human and without any pathological alterations. Studies were only included when focusing on the anatomy of the LPM or its morphological variations or when taking the frequency of variations into account. We searched 26 biomedical databases including MEDLINE, EMBASE, BIOSIS Previews and Science Citation Index Expanded (part of Web of Science) through October 2014. The review was followed by the dissection of a hemisected head in two different planes. RESULTS: We identified 4279 records (2200 after deduplication) in the databases searches plus 17 articles from manual searches. 81 studies out of these articles were included in this review. 69 articles used anatomical methods, 5 imaging methods and 7 studies a combination of the two methods. 11 studies took into account that the LPM may have variations and also considered the relative frequency of each variation. The frequency of one-headed LPMs ranged between 7.7% and 26.7%, of two-headed LPMs between 61.4% and 91.1% and of three-headed LPMs between 4.0% and 35.0%. Our own dissection showed a three-headed version of the LPM. DISCUSSION: In anatomical studies, different preparation techniques seem to be the main reason for diverging results.

Sexual dimorphism in jaw muscles of the Japanese sparrowhawk (Accipiter gularis).

Materials suitable for anatomical research of raptorial birds are rare. Bird-eating raptors show distinct inter-sexual differences in body size and parental roles. The large females catch larger prey and prepare small morsels to feed their young using their hooked beaks. Here, we investigated the architectural properties of different jaw muscles of the Japanese sparrowhawk (Accipiter gularis) and examined whether there is sexual dimorphism in their architectural design. The results showed that musculus depressor mandibulae, the opener of the lower jaw, was characterized by relatively long fascicle length, whereas musculus pterygoideus was characterized by its larger mass and physiological cross-sectional area (PCSA) in both sexes. Females have the potential capacity to produce rapid and strong bites by their significantly longer fascicle length of M. depressor mandibulae and larger mass and PCSA of M. pterygoideus. For body size-matched gender, jaw muscles of males had fibres of relatively longer length than females, enabling greater velocity and excursion. Architectural characteristics of jaw muscles, together with the absolute dimorphism (the fascicle length of M. depressor mandibulae, the muscle mass and PCSA of M. pterygoideus) and relative dimorphism in the muscle mass of M. pterygoideus, reflect dietary difference and asymmetric parental roles between the sexes.

The Endoscopic Prelacrimal Recess Approach to the Pterygopalatine Fossa and Infratemporal Fossa.

PURPOSE: The authors studied the anatomic importance of the endoscopic prelacrimal recess approach (PLRA) to the pterygopalatine fossa (PPF) and infratemporal fossa (ITF). METHODS: Ten adult heads (20 sides) from cadavers fixed in formalin were dissected using the PLRA. Anatomic dissections were detailed and several crucial landmarks measured. RESULTS: Identification of the infraorbital neurovascular bundle is the crucial step for the detection of other branches of the maxillary artery. The distance from the base of columella to inferior orifice of the nasolacrimal duct, sphenopalatine foramen, pterygold canal, foramen rotundum, foramen ovale was (32.97 ±â€Š3.44), (63.93 ±â€Š4.52), (66.81 ±â€Š3.44), (68.13 ±â€Š4.43), and (85.23 ±â€Š6.25) mm, respectively. The PLRA can be used to expose the entire maxillary sinus and PPF, most parts of the ITF (lateral pterygoid muscle, foramen ovale, mandibular division of the trigeminal nerve, and its divisions), maxillary artery and its branches, and the superior part of the medial pterygoid muscle (upon the floor of the maxillary sinus). The lateral boundary can be reached to visualize the temporomandibular joint and vertically oriented temporalis muscle. CONCLUSION: Use of the PLRA to the PPF and ITF offers a clear visual field, wide range of exposure, as well as preservation of the integrity of nasal structures.

The human medial pterygoid muscle: Attachments and distribution of muscle spindles.

Published descriptions about the sites of origin of the human medial pterygoid muscle vary and there are few reports on the distribution and density of muscle spindles in this muscle. We aimed to: (1) determine the extent of anatomical variability in the origins and insertions of the superficial and deep heads of the human medial pterygoid muscle and (2) determine the extent of variation in the distribution of spindles in the two heads of the muscle. Thirty-nine human cadaver hemi-heads were dissected and the attachments of the medial pterygoid muscle examined. The whole muscle was removed, weighed, cut into segments and embedded in wax for light microscopy. Sections were stained with Weigert-Van Gieson stain and scanned into digital images. Spindles were manually counted. In seven specimens, the deep head of the muscle arose from the medial surface of the lateral pterygoid plate and the pterygoid fossa. In 28 specimens, the origin extended onto the lateral surface of the medial pterygoid plate. There were abundant muscle spindles in the middle of the muscle, slightly fewer 1 cm toward the insertion, significantly fewer 1 cm toward the origin, and few or no spindles near the origins of the superficial and deep heads or near their insertion. In conclusion, firstly, this study shows that in 72% of the specimens examined, the origin of the medial pterygoid is wider than conventionally described in anatomical textbooks. Secondly, the segmental distribution of muscle spindles is described for the first time. Clin. Anat. 30:1064-1071, 2017. © 2017 Wiley Periodicals, Inc.

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.

Correlation between the lateral pterygoid muscle attachment type and temporomandibular joint disc position in magnetic resonance imaging.

OBJECTIVES: The aim of this study was to investigate the correlation between the lateral pterygoid muscle (LPM) attachment type and temporomandibular joint (TMJ) disc position on sagittal and coronal MR scans. METHODS: 191 patients (148 females, 43 males), aged 14-60 years, underwent MR investigations of the TMJs in the intercuspal position (IP) and open-mouth position (OMP). The disc position was evaluated on oblique sagittal and coronal images in the IP and OMP on many MRI sections showing all portions of the joint. Relationships between the LPM attachment patterns and articular disc positions were evaluated by z and χ2 tests. RESULTS: Three types of the LPM attachment were found. There was a statistically significant correlation between the LPM attachment type and the disc position in IP (χ2 = 24.29; p < 0.01). The type of muscle attachment did not determine the prevalence of normal, lateral and medial disc positions. There were differences between the muscle attachment types in the anterior, anteromedial and anterolateral disc positions. There was a statistically significant association between TMJ disc position in OMP and particular attachment types in the sagittal plane (χ2 = 9.702; p < 0.01). CONCLUSIONS: Certain types of the LPM insertion are correlated with TMJ disc position.

Three-dimensional lateral pterygoid muscle volume: MRI analyses with insertion patterns correlation.

We evaluated lateral pterygoid muscle volume in closed and open mouth positions in association with anterior disc displacement, effusion and abnormal articular disc shape from three-dimensional reformations of MRI. A total of 24 MRI of a sample (15 females, 9 males) aged 19-64 years (37.2 years±11.4) were assessed. Segmentation and volumetric assessment of the total, upper and lower heads of the lateral pterygoid muscle were performed using free software. The upper head of the lateral pterygoid muscle had a smaller volume than the lower head at both sides, in the closed- and open-mouth positions. In the open-mouth position, individuals with a subdivided upper head, where one component was inserted in the articular disc and another in the mandibular head, displayed a significantly larger volume of the upper head compared to individuals who had a single attachment to the articular disc (p=0.0130). The lateral pterygoid muscle has different volumes in the closed- and open-mouth positions. Gender affected muscle volume, specifically the upper head component. Insertion type in the upper head also seemed to affect muscle volume.

Surgical landmarks of the nasopharyngeal internal carotid using the maxillary swing approach: A cadaveric study.

OBJECTIVES/HYPOTHESIS: Surgery of the paranasopharyngeal space is very hazardous due to the position of the internal carotid artery, which is surrounded by soft tissue with few anatomical landmarks. STUDY DESIGN: Fresh cadaveric study. METHODS: In this study, we used the maxillary swing procedure to have a broad view of the internal carotid artery using an anterior approach. We sought to establish surgical landmarks, make measurements, and compare them to other imagery and cadaveric studies in the literature. RESULTS: We performed the maxillary swing procedure in 10 subjects (six female and four male, mean deceased age 81 years). The internal carotid artery was found to be in the same sagittal plane as the lateral pterygoid plate, the foramen ovale, and the eustachian tube isthmus. It was always located behind the stylopharyngeal fascia and immediately lateral to the longus capitis muscle. The artery was measured on average 10.7 mm from the pharyngeal recess, 7.3 mm from the eustachian tube isthmus, and 22.8 mm from the torus tubarius. CONCLUSIONS: The eustachian tube isthmus, the longus capitis muscle, and the stylopharyngeal fascia are the main surgical landmarks of the internal carotid artery. The artery can also be found in an oblique sagittal plane including the eustachian tube isthmus, the foramen ovale, and the lateral pterygoid plate. The pharyngeal recess remains a very dangerous area, only millimeters away from the carotid artery. LEVEL OF EVIDENCE: NA Laryngoscope, 126:1562-1566, 2016.