Characterization of the pterygomeningeal artery based on branching pattern and muscular distribution.

PURPOSE: The pterygomeningeal (accessory meningeal) artery arises from the middle meningeal or maxillary artery. Although there is the potential that this artery may be wounded by the surgery for the temporomandibular joint disorder, the current state of anatomical knowledge is insufficient. This study investigated the appearance and the branching pattern of this artery as a means to its characterization. METHODS: The pterygomeningeal artery was dissected in 14 cadavers and its branches and their distributions to the muscles inside the mandible were examined. RESULTS: The maxillary artery passed lateral to the lateral pterygoid muscle. The pterygomeningeal artery arose from the middle meningeal or maxillary artery. It ascended anteriorly and coursed medial or lateral to the mandibular nerve. It passed above the pterygospinous ligament and then descended. The ascending trunk gave some lateral branches to the lateral pterygoid muscle. The branches sometimes passed lateral to the mandibular nerve even if the pterygomeningeal artery coursed medial. The descending trunk was divided into middle and medial branches, which supplied the medial pterygoid muscle and the tensor veli palatini, respectively. The pterygomeningeal artery was sometimes equally bifurcate near the origin, and the counterparts passed lateral and medial to the mandibular nerve. The distributions of the medial and lateral counterparts were equivalent to those of the descending trunk and the lateral branches, respectively. CONCLUSION: The pterygomeningeal artery contains three groups of muscular branches, which sometimes appear in a bifurcate form. Their positions relative to the mandibular nerve and the pterygospinous ligament characterize the artery; this information may help to avoid iatrogenic injury.

Trifurcated external carotid artery and complete gamma-loop of its maxillary branch.

The external carotid artery (ECA) normally bifurcates terminally with the superficial temporal artery (STA) and the maxillary artery (MA). From the horizontally coursing, mandibular segment of the MA leaves the middle meningeal artery (MMA). We hereby report a previously unknown anatomic possibility, incidentally found during an angio-CT scan in an adult female patient. Unilaterally, the ECA was terminally trifurcated, sending off the MA, STA, and MMA. On that side, the mandibular segment of the MA had a gamma-loop and the contralateral one had a U-loop; both these loops were inferior to the lateral pterygoid muscle, closely approaching the respective lingula of the mandible. These findings are relevant during surgery of the parotid gland and infratemporal fossa, approaches of the MMA, and inferior alveolar nerve blocks. The modified origin of the MMA could be explained by an altered development of the primitive stapedial artery.

Microsurgical anatomy of the infratemporal fossa.

The objective of this study is to clearly and precisely describe the topography and contents of the infratemporal fossa. Ten formalin-fixed, adult cadaveric specimens were studied. Twenty infratemporal fossa were dissected and examined using micro-operative techniques with magnifications of 3-40×. Information was obtained about the inter-relationships of the contents of the infratemporal fossa. The infratemporal fossa lies at the boundary of the head and neck, and the intracranial cavity. It is surrounded by the maxillary sinus anteriorly, the mandible laterally, the pterygoid process anteromedially, and the parapharyngeal space posteromedially. It contains the maxillary artery and its branches, the pterygoid muscles, the mandibular nerve, and the pterygoid venous plexus. The course and the anatomic variation of the maxillary artery and the branches of the mandibular nerve were demonstrated. The three-dimensional (3D) relationships between the important bony landmarks and the neurovascular bundles of the infratemporal fossa were also shown. The skull base anatomy of the infratemporal fossa is complex, requiring neurosurgeons and head and neck surgeons to have a precise knowledge of 3D details of the topography and contents of the region. A detailed 3D anatomic knowledge is mandatory to manage benign or malignant lesions involving the infratemporal fossa without significant postoperative complications.

Radiologic assessment of the relationship between the maxillary artery and the lateral pterygoid muscle.

OBJECTIVE: The course of the second part of the maxillary can vary among different races. The aim of this study was to evaluate the relation between the maxillary artery and the lateral pterygoid muscle in a white population sample on computed tomographic (CT) angiograms. MATERIALS AND METHODS: We retrospectively reviewed multidetector CT angiograms of 209 patients (134 men and 75 women). The images were taken using a 64-row multidetector CT scanner. The imaging parameters were 0.5 × 64-mm slice thickness, 0.5- or 0.3-mm increment, 120 kV, 250 mA s, 0.5-second rotation time, 0.641 pitch, and 512 matrix. The relationship between the pterygoid portion of the maxillary artery and the lateral pterygoid muscle was assessed on axial, sagittal, and coronal multiplanar reformatted images with the Vitrea 2 software program. RESULTS: A total of 572 maxillary arteries in 286 patients were assessed. Of these maxillary arteries, 418 (68.42%) had a superficial course to the pterygoid muscle and 132 (31.58%) had a deep course. In 165 (78.94%) of 286 patients, there was a cross-lateral symmetry of the course of the artery; that is, both vessels were superficial or deep. In 44 (21.1%) of 209 patients, an asymmetric course was observed. CONCLUSIONS: Because of the incidence of the asymmetric presentations, generalization regarding such a controversial topic should not be based on findings of cadaveric studies and each hemi head should be considered as a single entity. Therefore, advanced imaging systems are useful tools in preoperative planning and play a key role in the avoidance of hemorrhagic complications.

A Case Treated With Photoimmunotherapy Under a Navigation System for Recurrent Lesions of the Lateral Pterygoid Muscle.

BACKGROUND: Head and neck photoimmunotherapy specifically destroys tumor cells by irradiating them with 690 nm red light after administering cetuximab sarotalocan sodium. The key point in the technique of photoimmunotherapy is to set the irradiation area precisely with a margin added to the target lesion while securing a safety zone with large vessels such as the internal carotid artery. CASE REPORT: At our Institution, we performed photoimmunotherapy in combination with use of a navigation system on a male patient in his 70s with maxillary gingival carcinoma who had a recurrent lesion deep in the lateral pterygoid muscle. Three months after photoimmunotherapy, the superficial lesion had disappeared, the area of contrast within the lateral pterygoid muscle had improved, and the patient was deemed to have a complete response. CONCLUSION: The Navigation System was successfully used in combination with photoimmunotherapy. Additionally, this allowed the location of the internal carotid artery to be confirmed in real time.

Ultrastructural and biochemical changes of the medial pterygoid muscle induced by unilateral exodontia.

The aim of the present study was to investigate the histological, biochemical and ultrastructural effects of occlusal alteration induced by unilateral exodontia on medial pterygoid muscle in guinea pigs, Cavia porcellus. Thirty (n=30) male guinea pigs (450g) were divided into two groups: experimental-animals submitted to exodontia of the left upper molars, and sham-operated were used as control. The duration of the experimental period was 60 days. Medial pterygoid muscles from ipsilateral and contralateral side were analyzed by histological (n=10), histochemical (n=10), and ultrastructural (n=10) methods. The data were submitted to statistical analysis. When the ipsilateral side was compared to the control group, it showed a significantly shorter neuromuscular spindle length (P<0.05), lower oxidative metabolic activity, and microvessel constriction, in spite of the capillary volume and surface density were not significantly different (P>0.05). In the contralateral side, the neuromuscular spindles showed significantly shorter length (P<0.05), the fibers reflected a higher oxidative capacity, the blood capillaries showed endothelial cell emitting slender sprouting along the pre-existing capillary, and significantly higher blood capillary surface density, and volume density (V(v)=89% Mann-Whitney test, P<0.05). This finding indicated a complex morphological and functional medial pterygoid muscle adaptation to occlusal alteration in this experimental model. Considering that neuromuscular spindles are responsible for the control of mandibular positioning and movements, the professional should consider if these changes interfere in the success of clinical procedures in medical field involving stomatognathic structures.

Morphological and histological effects on the medial pterygoid muscle after unilateral exodontia in gerbils.

Morphological effects on the medial pterygoid muscle were evaluated in 20 male gerbils (average weight, 55 g) after occlusal alterations induced by extraction of left side molar teeth. Controls were only submitted to surgical stress. Sixty days after surgery, the groups were divided into two subgroups for the following studies: (1) observation of macroscopic morphology and vessels distribution (n=10); (2) light microscopy histological analysis (n=10). Group results were statistically compared using the Wilcoxon and Mann-Whitney tests, with a significant value of p<0.05. Statistical differences in biometric data were found between the left and right sides of the experimental group (p=0.043), and between the left side of the control group when compared to the same side in the experimental group (p=0.044). Vessels supplied by bundles of the external carotid artery in the medial pterygoid muscle did not show distribution differences in group comparisons. Histological alterations were found in the ipsilateral side of the experimental group, with a central localization of the nucleus and degenerative aspect of the fibers, usually near to internal aponeurosis. Fiber diameters seemed reduced and the neuromuscular spindles were localized near internal aponeurosis and had a modified appearance. It is concluded that the medial pterygoid muscle in the gerbil is sensitive to alterations of the masticatory movements.

Metabolic and vascular pattern in medial pterygoid muscle is altered by chronic stress in an animal model of hypodontia.

Psychological stress is an important perpetuating, worsening and risk factor for temporomandibular disorders of muscular or articular origin. Occlusion instability, by the way, is considered a risk factor of this pathology and can be reproduced in some experimental animal models. The exact physiologic mechanism underlying these relations however, remains unclear. Our purpose was to test the hypothesis that chronic stress and unilateral exodontia induce metabolic and vascular changes in the medial pterygoid muscle of rats. Adult Wistar rats were submitted to chronic unpredictable stress and/or unilateral exodontia and their plasma and medial pterygoid muscle were removed for analysis. The parameters evaluated included plasma levels of corticosterone, metabolic activity by succinate dehydrogenase, oxidative capacity by nicotinamide adenine dinucleotide diaphorase, capillary density by laminin and alfa-CD staining and reactive oxidative species production. Chronic unpredictable stress as an isolated factor, increased oxidative metabolism, capillary density and reactive oxygen species production at medial pterygoid muscle. Conversely, exodontia has a main effect in metabolism, promoting glycolytic transformation of muscle fibers. Association of both factors induced a major glycolytic pattern in muscle and vascular changes. Our findings provide insights into the mechanisms, possibly inducing metabolic and vascular alterations on medial pterygoid muscle of rats, by which chronic stress and occlusal instabilities might be involved as risk factors in the pathophysiology of temporomandibular disorders with muscular components.

Involvement of pterygoid venous plexus in patulous eustachian tube symptoms.

CONCLUSIONS: The pterygoid venous plexus (PVP) is an important factor in the mechanism of eustachian tube (ET) closure under conditions that can cause increased venous pressure in the head, such as during neck compression and postural change from the sitting/standing to the recumbent position. OBJECTIVES: The symptoms of patulous ET are usually improved by neck compression or postural change (from sitting/standing to recumbent position). Venous congestion around the ET and/or gravitational change may be involved in the changing degree of symptoms, but its mechanism is not understood. This study investigated whether the PVP is involved. MATERIALS AND METHODS: The dimensions of soft tissues surrounding ET were measured on magnetic resonance images before and after neck compression. RESULTS: The lateral pterygoid muscle became enlarged after neck compression. Simultaneously, the volume of venous plexus observed between the medial pterygoid muscle and tensor veli palatini muscle was increased. Such enlargement was probably due to blood pooling in the PVP, resulting in protrusion of the ET anterior wall to the luminal side, and decreased ET patency.

Divided maxillary artery in relation to the lateral pterygoid muscle.

We describe an anatomical variation of the right maxillary artery. The variation loops deep, giving off a middle meningeal artery with an extremely short extracranial segment, then bifurcates into unequal branches. The smaller branch passes superficial to the lateral pterygoid head and distributes primarily to the masticatory muscles. The larger partially pierces the lateral pterygoid lower head, re-emerges superficially, branches again and passes into the pterygopalatine fossa. The larger lies superficial to the lingual and inferior alveolar nerves and deep to the buccal nerve. An embryonic development origin of the cranial arteries is suggested.

Chronic stress effects in contralateral medial pterygoid muscle of rats with occlusion alteration.

Temporomandibular disorder (TMD) has a high prevalence in our society, characterized by a severe pain condition of the masticatory muscles and temporomandibular joint. Despite the indication of multiple factor initiators of TMD, there is still controversy about its etiology and its pathophysiology is poorly understood. Using rats as experimental animals we investigated the effect of unpredictable chronic stress with or without unilateral molar extraction on the contralateral medial pterygoid muscle. Our hypothesis is that these two factors induce changes in morphology, oxidative metabolism and oxidative stress of muscle fibers. Young adult male Wistar rats (±200g) were divided into four groups: a group with extraction and unpredictable chronic stress (E+US); with extraction and without stress (E+C); without extraction and with unpredictable chronic stress (NO+US); and a control group without either extraction or stress (NO+C). The animals were subjected to unilateral extraction of the upper left molars, under intraperitoneal anesthesia with 4% Xylazine (10mg/kg) and 10% Ketamine (80mg/kg) on day zero. The rats of groups E+US and NO+US were submitted to different protocols of stress, from the 14th day after the extraction. The protocols were different every day for five consecutive days, which were repeated from the 6th day for five days more. Contralateral medial pterygoid muscles were obtained on the 24th day after the start of the experiment for morphological, metabolic, capillary density, and oxidative stress analysis. The data from capillary density showed a decrease of capillaries in animals subjected to dental extraction, compared with those without extraction and an increase of laminin expression in the group submitted to the unpredictable chronic stress when compared to the unexposed to stress. SDH test revealed a decrease of light fibers in the group submitted to unilateral extraction of molars, compared with this area in the control group. In E+US and NO+US groups, the deeply stained fibers increased compared to NO+C.·The exodontia factor was able to increase the ROS activity in muscle, whereas the stress factor does not significantly alter ROS in this tissue. It was concluded that both unpredictable chronic stress and the extraction induce metabolic and density of capillary changes in the contralateral medial pterygoid muscle to extraction, suggesting that these factors for a longer period of this experiment could induce muscle damage related to TMD.

Accessory meningeal artery: an anatomic misnomer.

The accessory meningeal artery is misnamed in view of the territory the artery supplies. The name implies that the vessel is an important addition to the middle meningeal artery in supplying the meninges. This is incorrect, because no more than approximately 10% of the blood flow of the accessory meningeal artery reaches the intracranial territory; 90% of the blood is carried to the extracranial structures. After reviewing the anatomy of the accessory meningeal artery we support the notion that the proper name of the vessel should be arteria pterygomeningica, or pterygomeningeal artery.

Volume changes in human masticatory muscles between jaw closing and opening.

Most jaw muscles are complex, multipennate with multiple components. The morphologic heterogeneity of masticatory muscles reflects their functions. We hypothesized that the volume of masticatory muscles changes between jaw closing and opening, and that there is a difference in the volume change among the muscles. Magnetic resonance images of the entire head were obtained in ten normal young adult subjects before and after maximum jaw opening. The volume changes of the masseter, medial, and lateral pterygoid muscles were measured. Only slight changes were seen in the masseter and medial pterygoid muscles. The lateral pterygoid muscle, however, significantly decreased its volume during jaw opening. The results provide normative values of muscle volume in living subjects, and suggest that the volume changes differ among jaw muscles.

Angiofibroma confined to the pterygoid muscle region: CT and MR demonstration.

We report a case of angiofibroma confined to the pterygoid muscle plane without involvement of the sphenopalatine foramen or nasopharynx. The lesion was demonstrated on CT, MR, and angiography with typical findings of a hypervascular mass and was surgically resected after embolization.

Histological features of endomysium, perimysium and epimysium in rat lateral pterygoid muscle.

The distribution of the endomysium, perimysium, and epimysium and their constituent connective tissue fiber types in the mature rat lateral pterygoid muscle was examined with the light microscope. The endomysium and perimysium were relatively thin and consisted mainly of reticular fibers. The epimysium was thicker than the intramuscular sheaths and consisted of both collagen and reticular fibers; however, the thickness and constitutent connective tissue fiber types of these sheaths varied regionally. Near the articular capsule and disc, the endomysium, perimysium, and epimysium were all thicker than in other regions of the muscle and consisted of collagen, reticular, and elastic fibers. The perimysium bound the bundles of muscle fibers together and frequently included blood vessels and nerves. As the superior head of the pterygoid muscle approached its insertion, sheaths of perimysium divided this head into smaller and smaller bundles of muscle fibers. In the inferior head, some of the perimysial sheaths and part of the epimysium were aponeurotic, and many muscle fibers attached to them. There were few such aponeurotic regions in the superior head.

The angioarchitecture of the rat mandibular joint synovium.

The synovium (or synovial membrane) lines all intra-articular surfaces of synovial joints except for the articulating surfaces. This study describes the angioarchitecture of the synovium of the adult rat temporomandibular joint using microvascular corrosion casts and scanning electron microscopy. To corroborate findings, India ink-injected, thick-sectioned specimens (200 microns) and haematoxylin and eosin-stained tissue sections (7 microns) were analysed. Rostrally, the synovial membrane was fed by several layers of vessels branching towards the superficial lining of highly convoluted capillary loops. Arterioles were rare, and venules organized in large plexuses. The membrane thinned out in the caudal direction. Villi were present on the surface. They were flat, with a core of two parallel linear feeder vessels, one arteriole and one venule, which were interconnected by capillary loops. At the periphery of the articulating surfaces, the vessels of the synovial layer were flatter. Caudally, the synovial membrane of the richly vascularized retrodiscal pad showed many synovial folds. Feeder vessels were directed rostrally and branched in all directions. The number of subdivisions depended on the size of the synovial fold. Again, venules were organized in plexuses and lining capillaries were convoluted. The densely capillarized synovial membrane with its folds and villi is considered well adapted to serve synovial fluid production and joint dynamics.

The angioarchitecture of the rat mandibular joint bilaminar zone.

In mammals, temporomandibular-joint articular disc attachments have a bilaminar pattern. The three-dimensional angioarchitecture of the bilaminar zone in the adult rat was described using scanning election microscopy of microvascular corrosion casts (47 specimens) and light microscopy of Indian ink-injected, cleared, thick-sectioned temporomandibular joints (6 specimens). The bilaminar zone had an axial core of feeder vessels composed primarily of flat venules which were organized in plexuses. Arterioles were few and slender. In both laminae, there were usually three branching levels until vessels approached the surface of the lamina, where a dense capillary meshwork was formed. Both laminae ended abruptly at the periphery of the avascular disc with a single, slightly undulating marginal vessel. This marginal vessel, which faced the avascular disc, was definitely larger in diameter than the other superficial capillaries and was rather a postcapillary venule than a capillary. Functionally, this marginal venule might be important in sustaining nutrition of the avascular disc centre by allowing bidirectional blood flow during jaw movements.

Massive congenital arteriovenous malformation of the pterygomaxillary space.

A case is presented of a massive congenital, extracranial arteriovenous malformation (AVM). The origins and hemodynamic considerations that led to prior treatment failure are discussed. A sudden accelerated growth in the AVM, caused by an alteration in the hemodynamics of the feeding and draining vessels, mandated further surgical management. The treatment of choice is complete surgical excision at the time of diagnosis, if possible. Ligation of the feeding vessels alone is unsatisfactory and, like other adjunctive treatments, may lead to disastrous complications.

Trigeminal neuralgia as a consequence of circulatory disorders in the infratemporal and pterygopalatine fossae.

An extensive review of the well documented experimental and clinical findings related to trigeminal neuralgia shows, that it is possible to set up an unifying theory for trigeminal neuralgia, which would explain most clinical features of the disease and also would be congruent with several other theories that have previously been presented. Thus, trigeminal neuralgia is proposed to be the result of a combination of predisposing anatomical variations, impaired arterial and venous circulation, and morphological changes in the infratemporal fossa and cavum Meckeli. The process is initiated by disturbances of dental occlusion and mandibular function, resulting in muscular hypertrophy, which finally leads to increased perineural pressure and hypoxia in the nervous tissue. Through a series of related events this results in massive afferent discharges in the trigeminal nerve, which are strong enough to break through an inhibitory gating mechanism in the nucleus caudalis, and which are experienced by the patient as a pain attack. But the tissue hypoxia, which partly has elicited the pain, will finally also be the critically delimiting factor for further signal transmission, thereby stopping the pain attack.