Contribution of the complex comprising the masticatory fascia, disc, and capsule to temporomandibular joint stabilization: An anatomical study

BACKGROUND

Anterior displacement of the temporomandibular joint (TMJ) disc is the most typical pathological condition of TMJ disorders. Structures attached to the articular disc may support the disc in various directions and contribute to stabilizing the TMJ. However, the relationship between the articular disc, capsule, and masticatory muscles remains unclear. Therefore, this study aimed to clarify the relationship between the masticatory muscles, related masticatory fascia, articular disc, and capsule.

METHODS

We examined 10 halves from adult Japanese cadavers, with five halves macroscopically analyzed and the remaining five histologically analyzed. The TMJ was dissected from the lateral aspect for gross anatomical analysis. For histological analysis, the relationship between the temporal and masseteric fasciae and the articular capsule was observed in the coronal section. Additionally, we evaluated relationships among the disc, capsule, temporal fascia, and masseteric fascia in 10 living and healthy volunteers using magnetic resonance imaging.

RESULTS

The articular disc was attached to the capsule without a clear border. The capsule continued into the masseteric and temporal fasciae. Consequently, the articular disc, capsule, masseteric, and temporal fasciae were considered a single complex.

CONCLUSIONS

The single complex of the temporalis, masseter, capsule, masticatory fascia, and disc may antagonize the force in the posterolateral direction through the fascia.

Hemodynamic changes in the temporalis and masseter muscles during acute stress in healthy humans

PURPOSE

Autonomic control of orofacial areas is an integral part of the stress response, controlling functions such as pupil dilatation, salivation, and skin blood flow. However, the specific control of blood flow in head muscles during stress is unknown. This study aims to investigate the hemodynamic response of temporalis and masseter muscles in response to five different stressors.

METHODS

Sixteen healthy individuals were subjected to a randomized series of stressors, including cold pressor test, mental arithmetic test, apnea, isometric handgrip, and post-handgrip muscle ischemia, while in the sitting posture. Finger-pulse photoplethysmography was used to measure arterial blood pressure, heart rate, and cardiac output. Near-infrared spectroscopy was used to measure changes in tissue oxygenation and hemoglobin indices from the temporalis and masseter muscles.

RESULTS

All stressors effectively and significantly increased arterial blood pressure. Tissue oxygenation index significantly increased in both investigated head muscles during mental arithmetic test (temporalis: 4.22 ± 3.52%; masseter: 3.43 ± 3.63%) and isometric handgrip (temporalis: 3.45 ± 3.09%; masseter: 3.26 ± 3.07%), suggesting increased muscle blood flow. Neither the masseter nor the temporalis muscles evidenced a vasoconstrictive response to any of the stressors tested.

CONCLUSION

In the different conditions, temporalis and masseter muscles exhibited similar hemodynamic patterns of response, which do not include the marked vasoconstriction generally observed in limb muscles. The peculiar sympathetic control of head muscles is possibly related to the involvement of these muscles in aggressive/defensive reactions and/or to their unfavorable position with regard to hydrostatic blood levels.

Modified Osteotomy for TMJ Ankylosis in Paediatric Patients with Deficient Interpositional Temporalis Muscle Mass and Buccal Fat Pad - A case Series and Literature Review

Ankylosis of the temporomandibular joint (TMJ) is a bony or fibrous fusion of the articular surfaces of the mandibular condyle and the glenoid fossa. Gap arthroplasty, Interpositional arthroplasty, Condyle reconstruction with autogenic or alloplastic grafts and total joint replacement are some common modalities of management. In this article, we discuss a series of three cases of unilateral TMJ ankylosis in paediatric patients, managed by gap arthroplasty using a modified osteotomy cut. The modification was adapted due to inadequate interpositionable temporalis muscle or buccal fat on the affected side and chances of adaptive remodelling of the CCG (Costochondral graft), if placed were rendered negative.

Electromyographic Assessment of Masticatory Muscles & their Asymmetries in Adult Indian Population

Objective

To study the surface electromyography (sEMG) and it is asymmetry under resting and dynamic conditions in masticatory muscles.

Materials and Methods

sEMG of the masticatory muscles (bilateral masseter & temporalis) was done in 61 healthy subjects (mean age 28.5 ± 8.8 years) with bilateral functional molar occlusal relationship. Root mean square (RMS) values sEMG for each activity (rest, clenching, maximum mouth opening (MMO), left and right excursion) for a 10 s period were recorded and analyzed. Indices for asymmetry of muscles, relative activity and resultant torque were assessed and analyzed.

Results

RMS values of sEMG during clenching were significantly higher for all masticatory muscles in males compared to females (p < 0.05). During excursive mandibular movement a statistically significant difference seen in ipsilateral temporalis muscle in males. sEMG of masticatory muscles during rest as well as functional activities of mandible was asymmetrical. A predominant masseteric activity was observed for all functional activities of mandible except during rest for which temporalis muscle activity was higher. Right sided torque was observed during rest, MMO and right lateral movements while a predominant left sided torque was present during left lateral movement and clenching.

Conclusion

sEMG values of masticatory muscles obtained in our study can be used as reference for healthy Indian population. A perfect muscular symmetry might be illusive and a controlled asymmetry criterion appears to be more useful which corresponds to reality.

Three-dimensional Analysis of the Muscles Related to the So-Called "Pterygomandibular Raphe": An Anatomical and Histological Study

The pterygomandibular raphe (PMR) is a tendinous bundle between the bucinator (BM) and the superior constrictor of pharynx (SC) and has been considered essential for swallowing. Despite its functional significance, previous studies reported that the PMR is not always present. Another study reported presence of the connecting fascia between the BM and deep temporalis tendon (dTT). Therefore, the present study analyzed the three-dimensional relationship between the BM, SC, and dTT. We examined 13 halves of 11 heads from adult Japanese and Caucasian cadavers: eight halves macroscopically and five halves histologically. There was no clear border between the BM and SC in any specimens macroscopically. The BM attachment varied depending on its levels. At the level of the superior part of the internal oblique line, the BM fused with the SC with no clear border. At the level of the midpart of the internal oblique line of the mandible, the BM attached to the dTT directly, and the SC attached to the dTT via collagen fibers and the BM. Based on these results, these muscles should be described as the BM/dTT/SC (BTS) complex. The three-dimensional relationship of the BTS complex might result in the so-called "pterygomandibular raphe." The BTS complex could be important as a muscle coordination center in chewing and swallowing.

Temporalis and masseter muscle thickness as predictors of post-stroke dysphagia after endovascular thrombectomy

PURPOSE

Post-stroke dysphagia (PSD) is a common sequela of stroke. Given the association between dysphagia and sarcopenia, we aimed to investigate the association between PSD and temporal muscle thickness (TMT) and masseter muscle thickness (MMT) following endovascular thrombectomy (EVT) in patients with large-vessel occlusion (LVO).

METHODS

This retrospective cohort study included hospitalized patients with LVO stroke who underwent EVT between January 1, 2018, and October 31, 2022. TMT and MMT were measured using brain computed tomography (CT) angiography. The correlation between relevant clinicodemographic factors and both TMT and MMT was examined. The relationship between each of two parameters (TMT and MMT) and PSD, which was defined as the retention of the nasogastric (NG) tube at 4 and 12 weeks, was evaluated in adjusted logistic regression models.

RESULTS

Among the 148 participants, the mean TMT and MMT was 5.9 ± 1.6 and 11.2 ± 2.3 mm, respectively. Lower age, male sex, higher body mass index (BMI), higher albumin levels, and a lower initial National Institute of Health Stroke Scale (NIHSS) score were associated with higher TMT and MMT (p < 0.05). In the logistic regression analysis adjusted for age, sex, BMI, serum albumin, and NIHSS score, lower TMT and MMT significantly correlated with PSD at weeks 4 and 12 (p < 0.001).

CONCLUSION

TMT and MMT are associated with age, sex, BMI, albumin, and the initial NIHSS score. Both TMT and MMT are independent indicators of post-EVT PSD in stroke patients and serve as reliable predictors of NG removal.

Traumatic Myositis Ossificans of Temporalis Muscle: Systematic Review, Meta-Analysis and Case Reports

Introduction

Traumatic myositis ossificans is rare pathology affecting muscles/soft tissue. Its involvement in temporalis muscle is rarely reported in literature. The aetiopathogenesis is unknown, the diagnosis is based on clinco-radiological findings. Surgical management and follow-up are paramount.

Materials and Methods

A database search was done using Science Direct and PubMed search engines along with other published and unpublished literature. The final publications were tabulated using a custom made Performa. The available publications were subjected to appropriate statistical analysis. The data were recorded on excel spreadsheet (Microsoft Inc), and review was made using Review Manager (Rev Man) software for meta-analysis.

Results

A total of 21 articles were considered for systemic review and meta-analysis. Forest plotting for demographics included the gender predilection/age of involvement. The data segregation was done with "temporalis involved" group and "other than temporalis involved" group. The study was free of homogeneity ( τ 2 = 0.26 I 2 = 5%) for gender and age. The overall analysis revealed that Temporalis muscle although rare to be affected shows greater propensity for involvement. This is supported by a lesser degree of heterogeneity ( τ 2 = 0.000) with a I 2 value of (The test showed a higher degree of significance for overall effect of muscle involvement (Z = 2.33, p = 0.02) (< 25%). The test showed a higher degree of significance for overall effect of muscle involvement (Z = 2.33, p = 0.02) (< α = 0.05).Case reports.Two male cases with similar age predilection, reported after sustaining trauma. Both the cases presented with limited mouth opening and ultrasound was done for the first time to arrive at clinic-radiological diagnosis. The management was conservative with temporalis myotomy and coronidectomy.

Conclusion

Traumatic myositis ossificans presents as a rare disorder that poses a dilemma to the treating surgeon. The present article makes an attempt to critically analyse the pathology that is scantly reported in the literature.

Review of cysticercosis of maxillofacial region and report of two cases

Cysticercosis is a parasitic infection caused by the larval stage of Taenia solium, which very rarely manifests in the maxillofacial region. It usually presents as a painless swelling. The most common site for maxillofacial cysticercosis are the tongue and lips. When humans accidently ingest the eggs of Taenia solium, they become the intermediate host, a role which is typically played by pig. This paper describes two cases of cysticercosis cellulosae, presenting as non-tender swelling of left buccal mucosa and left temporalis region respectively. Case reports available on PubMed were searched and a review was performed. Excision of cystic lesion was the treatment modality in majority of published reports. It is emphasised that cysticercosis should be considered in differential diagnosis of solitary painless swellings of oral and maxillofacial region, especially in patients from an endemic region.

Strategic tunnelling of superficial temporal artery during bypass surgery for moyamoya disease

BACKGROUND

The superficial temporal artery to middle cerebral artery bypass remains the favoured direct technique of cerebral revascularization in moyamoya angiopathy. We describe a novel technique of tunnelling the superficial temporal artery through the temporalis muscle.

METHODS

The temporalis muscle is raised as a flap off the temporal bone. A triangular window is created on the temporalis fascia, and a tunnel is created for the superficial temporal artery to pass through the muscle belly.

CONCLUSION

This innovative technique allows passage of the superficial temporal artery to the brain without kink or compression ensuring good bypass function and improves long-term patency.

Cosmetic outcome after electrocautery versus non-electrocautery dissection of the temporalis muscle for pterional craniotomy

Objective

Despite the usefulness of pterional craniotomy (PC), its cosmetic outcome is questionable. Electrocautery (EC) causes injuries to adjacent structures, and it could be a factor that affects the cosmetic outcome. Evaluation of cosmetic outcome is difficult because it is often determined by patient’s subjective criteria. The objective of this study is to compare the cosmetic outcome after EC versus non-electrocautery (NEC) dissection of the temporalis muscle for PC by analyzing long-term follow-up data determined from both physician and patient’s aspects.

Methods

Patients at follow-ups between January 2014 and April 2021 after PCs were enrolled. The keyhole (KH) site, the inferior margin of the temporal line of the frontal bone (ITL), the mid-temporal (mid-T) area, and the posterior incision line (PIL) were inspected by a physician to check the presence of depressions. Patient’s cosmetic satisfaction was categorized into satisfactory, intermediate, or unsatisfactory by a survey. The presence of osteolysis was checked from the radiological images. Patients were classified into two groups; one with EC dissection and another with NEC retrograde dissection using a double-ended dissector.

Results

The incidences of depression at the mid-T area and osteolysis were higher in the EC group (p=0.001, p＜0.001). The percentage of satisfactory cosmetic outcome was lower in the EC group (p=0.002). The presences of depression at the mid-T area and osteolysis were related with lower rate of satisfactory outcomes (p＜0.001, p＜0.001).

Conclusions

NEC dissection causes less destruction to adjacent structures and brings better cosmetic outcome after PC.

Basal protein synthesis rates differ between vastus lateralis and rectus abdominis muscle

BACKGROUND

In vivo muscle protein synthesis rates are typically assessed by measuring the incorporation rate of stable isotope labelled amino acids in skeletal muscle tissue collected from vastus lateralis muscle. It remains to be established whether muscle protein synthesis rates in the vastus lateralis are representative of muscle protein synthesis rates of other muscle groups. We hypothesized that post-absorptive muscle protein synthesis rates differ between vastus lateralis and rectus abdominis, pectoralis major, or temporalis muscle in vivo in humans.

METHODS

Twenty-four patients (62 ± 3 years, 42% female), scheduled to undergo surgery, participated in this study and underwent primed continuous intravenous infusions with l-[ring-¹³ C₆ ]-phenylalanine. During the surgical procedures, serum samples were collected, and muscle tissue was obtained from the vastus lateralis as well as from the rectus abdominis, pectoralis major, or temporalis muscle. Fractional mixed muscle protein synthesis rates (%/h) were assessed by measuring the incorporation of l-[ring-¹³ C₆ ]-phenylalanine into muscle tissue protein.

RESULTS

Serum l-[ring-¹³ C₆ ]-phenylalanine enrichments did not change throughout the infusion period. Post-absorptive muscle protein synthesis rates calculated based upon serum l-[ring-¹³ C₆ ]-phenylalanine enrichments did not differ between vastus lateralis and rectus abdominis (0.032 ± 0.004 vs. 0.038 ± 0.003%/h), vastus lateralis and pectoralis major, (0.025 ± 0.003 vs. 0.022 ± 0.005%/h) or vastus lateralis and temporalis (0.047 ± 0.005 vs. 0.043 ± 0.005%/h) muscle, respectively (P > 0.05). When fractional muscle protein synthesis rates were calculated based upon tissue-free l-[ring-¹³ C₆ ]-phenylalanine enrichments as the preferred precursor pool, muscle protein synthesis rates were significantly higher in rectus abdominis (0.089 ± 0.008%/h) compared with vastus lateralis (0.054 ± 0.005%/h) muscle (P < 0.01). No differences were observed between fractional muscle protein synthesis rates in vastus lateralis and pectoralis major (0.046 ± 0.003 vs. 0.041 ± 0.008%/h) or vastus lateralis and temporalis (0.073 ± 0.008 vs. 0.083 ± 0.011%/h) muscle, respectively.

CONCLUSIONS

Post-absorptive muscle protein synthesis rates are higher in rectus abdominis when compared with vastus lateralis muscle. Post-absorptive muscle protein synthesis rates do not differ between vastus lateralis and pectoralis major or temporalis muscle. Protein synthesis rates in muscle tissue samples obtained during surgery do not necessarily represent a good proxy for appendicular skeletal muscle protein synthesis rates.

Role of coronoidectomy and temporalis myotomy in surgical management of oral submucous fibrosis

PURPOSE

The involvement of temporalis muscle fibers by oral submucous fibrosis (OSMF) and the procedure of coronoidectomy and temporalis myotomy in the surgical treatment protocol for the disease is a controversy. The primary objective of this study is to evaluate the histopathological changes in temporalis muscle fibers in patients undergoing surgical treatment for OSMF and to authenticate the importance of temporalis myotomy and coronoidectomy in surgical treatment protocol.

METHOD

A 3-year prospective study was conducted to assess the histopathological changes in temporalis muscle in surgically treated OSMF cases. The predictor variables were drawn from demographic characteristics (age and gender) etiology, and mouth opening. The outcome variables were histopathological assessment of temporalis muscle fibers for parameters suggestive of degenerative changes and fibrosis changes at cellular level.

RESULTS

Out of 56 patients, 30 patients were had surgical intervention. Twenty-eight (93.3%) were male and 2 (6.6%) were female with a ratio of 14:1. Histopathological examination of temporalis muscle fibers revealed hyalinization of muscle fibers in 80% of the patients followed by loss of striation (73.33%), fragmentation (60%), nucleus internalization (33.33%), infiltration of macrophages and other inflammatory cells (20.67%), multiple nuclei (20%), and swollen muscle fibers (6.67%). Mean preoperative mouth opening was 12.4 and post-operatively 41.3 mm on 1-year follow-up and this was stable on further follow-up.

CONCLUSION

The results of this study suggest involvement of temporalis muscle with disease itself and the justification for coronoidectomy and temporalis myotomy in the surgical protocol was established.

Effect of botulinum toxin-A on pain and mouth opening following surgical intervention in oral submucous fibrosis - A controlled clinical trial

The purpose of this trial was to study the effect on pain and mouth opening of intramuscular injection of botulinum toxin-A into masticatory muscles following surgical intervention in oral submucous fibrosis (OSMF) cases. Injections of either botulinum toxin A (BTX-A) (study group) or normal saline (control group) were given 2 weeks prior to surgical intervention in OSMF patients, into the bilateral masseter and temporalis muscles. All patients were evaluated for pain and ease of active physiotherapy at 1 week and 1, 3, and 6 months after surgery using a numerical rating scale and appropriate questionnaires, with comparisons made between the study and control group patients. Electromyographic studies of the masticator muscles were also carried out in all patients before injection, and at 1 month and 6 months after injection. 20 OSMF patients were equally divided into study and control groups (n = 10 each). At 1, 3, and 6 months after surgery, the study group patients showed significantly greater decreases in pain (p-values of 0.007, 0.001, and 0.005, respectively) and greater ease in physiotherapy compared with the control group. EMG recordings of masticator muscles showed a transient drop in microvolt value in the study group 1 month after injection, unlike the control group recordings. It was concluded that preoperative BTX-A injection was a good addition to surgical therapy in the patient group.

Fiber-type phenotype of the jaw-closing muscles in Gorilla gorilla, Pan troglodytes, and Pan paniscus: A test of the Frequent Recruitment Hypothesis

Skeletal muscle fiber types are important determinants of the contractile properties of muscle fibers, such as fatigue resistance and shortening velocity. Yet little is known about how jaw-adductor fiber types correlate with feeding behavior in primates. Compared with chimpanzees and bonobos, gorillas spend a greater percentage of their daily time feeding and shift to herbaceous vegetation when fruits are scarce. We thus used the African apes to test the hypothesis that chewing with unusually high frequency is correlated with the expression in the jaw adductors of a high proportion of type 1 (slow, fatigue-resistant) fibers at the expense of other fiber types (the Frequent Recruitment Hypothesis). We used immunohistochemistry to determine the presence and distribution of the four major myosin heavy chain (MHC) isoforms in the anterior superficial masseter (ASM), superficial anterior temporalis, and deep anterior temporalis of four Gorilla gorilla, two Pan paniscus, and four Pan troglodytes. Serial sections were stained against slow (MHC-1/-α-cardiac) and fast (MHC-2/-M) fibers. Fibers were counted and scored for staining intensity, and fiber cross-sectional areas (CSAs) were measured and used to estimate percentage of CSA of each MHC isoform. Hybrid fibers accounted for nearly 100% of fiber types in the masseter and temporalis of all three species, resulting in three main hybrid phenotypes. As predicted, the gorilla ASM and deep anterior temporalis comprised a greater percentage of CSA of the slower, fatigue-resistant hybrid fiber type, significantly so for the ASM (p = 0.015). Finally, the results suggest that fiber phenotype of the chewing muscles contributes to behavioral flexibility in ways that would go undetected in paleontological studies relying solely on morphology of the bony masticatory apparatus.

Temporal tendinosis: A cause of chronic orofacial pain

PURPOSE OF REVIEW

Diverse musculoskeletal disorders and neuropathic symptoms of the face pose significant diagnostic challenges. In particular, temporal tendinosis is generally overlooked in the medical and dental literature and is therefore a poorly understood topic and often problematic cause of chronic orofacial pain. In this article, we explore temporal tendinosis as a cause of unresolved orofacial pain by reviewing the complex anatomy of the temporalis muscle, common presentations of temporal tendinosis, possible etiologies for injury and place a strong emphasis on required diagnostic evaluation and clinical management.

RECENT FINDINGS

Temporal tendinosis remains under diagnosed due to a combination of anatomical complexity and incomplete description in the majority of general anatomy medical textbooks. The two main presentations are unilateral facial pain with or without temporal headache and pain radiating from the distal temporalis tendon to the temporalis muscle. Diagnosis should be made with a combination of focused history, physical examination and specialised imaging, preferably with ultrasound but with MRI an alternate option. While many management options are available, optimal treatment remains unclear. Temporal tendinosis is an under-recognised and under-treated condition. Despite the fact that orofacial pain is one of the single most common complaints of patients presenting to physicians or dentists, it is widely acknowledged that training for diagnosis and manage of temporal tendinopathy among primary care physicians in both medical and dental professions is inadequate. This may result in extensive workups, leading to suboptimal management and chronic pain syndromes.

The influence of masseter and temporalis sarcomere length operating ranges as determined by laser diffraction on architectural estimates of muscle force and excursion in macaques (Macaca fascicularis and Macaca mulatta)

OBJECTIVE

Determine sarcomere length (L_s) operating ranges of the superficial masseter and temporalis in vitro in a macaque model and examine the impact of position-dependent variation on L_s and architectural estimates of muscle function (i.e., fiber length, PCSA) before and after L_s-normalization.

DESIGN

Heads of adult Macaca fascicularis (n = 4) and M. mulatta (n = 3) were bisected postmortem. One side of the jaw was fixed in occlusion, the other in maximum gape. L_s was measured bilaterally using laser diffraction and these measurements were used to estimate sarcomere-length operating ranges. Differences in fiber length and PCSA between sides were tested for significance prior to and following L_s-normalization.

RESULTS

Sarcomere-length operating ranges were widest for the anterior superficial masseter and narrowest for the posterior temporalis. Compared with other mammals, macaque operating ranges were wider and shifted to the right of the descending limb of a representative length-tension curve. Fibers were significantly stretched by as much as 100%, and PCSAs reduced by as much as 43%, on the maximally gaped compared with occluded sides. L_s-normalization substantially reduced position-dependent variance.

CONCLUSIONS

The superficial masseter ranges between 87-143% and the temporalis between 88-130% of optimal L_s from maximum gape to occlusion, indicating maximum relative L_s for these macaque muscles exceeds the upper end range previously reported for the jaw muscles of smaller mammals. The wider macaque operating ranges may be functionally linked to the propensity for facially prognathic primates to engage in agonistic canine display behaviors that require jaw-muscle stretch to facilitate production of wide jaw gapes.

Tongue exercise and ageing effects on morphological and biochemical properties of the posterior digastric and temporalis muscles in a Fischer 344 Brown Norway rat model

OBJECTIVE

This study sought to examin effects of age and tongue exercise on the posterior digastric (opener) and the temporalis (closer). We hypothesized 1) age would result in differing morphological (cross sectional area) and biochemical (myosin heavy chain isoform) components of these muscles; 2) tongue exercise would result in coactivation of these muscles inducing a decrease in age-related differences between age groups.

DESIGN

Young adult (9 months) and old (32 months) Fischer 344 Brown Norway rats were randomized into a tongue exercise or control group. Post-training, posterior digastric and temporalis muscles were harvested and analyzed using: 1) Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) to assess percent myosin heavy chain (MyHC) content; 2) Immunohistochemical staining to determine cross sectional area (CSA).

RESULTS

A larger proportion of slowly contracting MyHC isoforms in the posterior digastric and temporalis muscles were found in old. No significant main effects for age or exercise in fiber size were found in posterior digastric muscle. An interaction between age and exercise for temporalis cross sectional area indicated the old exercise group had smaller average cross sectional area than all other groups. CONCLUSIONS FINDINGS: suggest that: 1) Increasing age induces biochemical changes in muscles of the jaw, specifically showing an increase the proportion of slower contracting MyHC isoforms; 2) Increasing age and tongue exercise induce a reduction in muscle fiber cross sectional area in the temporalis muscle only. However, continued study of these cranial muscle systems is warranted to better understand these changes that occur with age and exercise.

Anatomical connections between the buccinator and the tendons of the temporalis

The aim of this study was to clarify the anatomical relationship between the buccinator and the temporalis in order to improve understanding of the precise and coordinated movements of the mouth and the mandible. The buccinator and the temporalis were investigated in 72 hemifaces from Korean cadavers. Removing the buccal fat pad from the buccinator revealed that the fascia encircled the space between the superficial and deep tendons of the temporalis laterally, and the external surface of the buccinator medially in all specimens (100%). The fascia was located between the buccinator and the tendons of the temporalis, thereby connecting these two muscles. The fascial space was filled with connective tissue, and the buccal nerve and artery passed through this space. The inferior fibers of the buccinator arose from the anterior portion of the deep tendon of the temporalis in all specimens (100%). The anterior portion of the deep tendon of the temporalis extended forward obliquely between the ramus and body of the mandible. Thus, both the anterior portion of the deep tendon of the temporalis and its attaching inferior muscle fibers of the buccinator coursed obliquely. The above observations indicate that the connecting fascia between the buccinator and tendons of the temporalis and the inferior fibers of the buccinator that were attached to the deep tendon of the temporalis could assist in coordinatation of the movements of the mandibular region and the mouth angle in the timing and strength of contraction of the muscles during mastication, facial expression, and speech.

Establishing the ferret as a gyrencephalic animal model of traumatic brain injury: Optimization of controlled cortical impact procedures

BACKGROUND

Although rodent TBI studies provide valuable information regarding the effects of injury and recovery, an animal model with neuroanatomical characteristics closer to humans may provide a more meaningful basis for clinical translation. The ferret has a high white/gray matter ratio, gyrencephalic neocortex, and ventral hippocampal location. Furthermore, ferrets are amenable to behavioral training, have a body size compatible with pre-clinical MRI, and are cost-effective.

NEW METHODS

We optimized the surgical procedure for controlled cortical impact (CCI) using 9 adult male ferrets. We used subject-specific brain/skull morphometric data from anatomical MRIs to overcome across-subject variability for lesion placement. We also reflected the temporalis muscle, closed the craniotomy, and used antibiotics. We then gathered MRI, behavioral, and immunohistochemical data from 6 additional animals using the optimized surgical protocol: 1 control, 3 mild, and 1 severely injured animals (surviving one week) and 1 moderately injured animal surviving sixteen weeks.

RESULTS

The optimized surgical protocol resulted in consistent injury placement. Astrocytic reactivity increased with injury severity showing progressively greater numbers of astrocytes within the white matter. The density and morphological changes of microglia amplified with injury severity or time after injury. Motor and cognitive impairments scaled with injury severity.

COMPARISON WITH EXISTING METHOD(S)

The optimized surgical methods differ from those used in the rodent, and are integral to success using a ferret model.

CONCLUSIONS

We optimized ferret CCI surgery for consistent injury placement. The ferret is an excellent animal model to investigate pathophysiological and behavioral changes associated with TBI.

Radiological evaluation of sphenozygomatic suture fixation for restoration of orbital volume: A retrospective study

PURPOSE

Lateral displacement of fracture zygomaticomaxillary complex (ZMC) can cause significant increase in orbital volume leading to enophthalmos. The aim of this study was to radiologically evaluate the efficacy of sphenozygomatic (SZ) suture fixation for restoration of orbital volume after elevation of the temporalis in cases of fracture ZMC where the fixation of zygomatic arch (ZA) was deemed necessary through latero-posterior approach.

MATERIALS & METHODS

43 operated cases of fracture ZMC using 4-point fixation were divided into two groups. Group I (n = 24) cases had undergone reduction and fixation of SZ suture as fourth point of fixation by elevating temporalis muscle using hemicoronal approach. Group II (n = 19) cases had undergone reduction and fixation of Infraorbital (IO) rim as fourth point of fixation using preseptal transconjunctival approach. Both the groups were analyzed separately and compared for restoring the increased orbital volume on CT.

RESULTS

Difference in the pre-surgical orbital volume of both the groups was found to be statistically insignificant [p = .678]. In group I, the average bony orbital volume significantly reduced by 3.6 cc from 25.5 cc to 21.9 cc [p = .000] post-surgically. In group II, the average bony orbital volume reduced by 1.5 cc from 25.6 cc to 24.1 cc post-surgically There was a significant difference in the reduction of the increased orbital volume among the 2 groups (Group I: 3.6 cc, group II: 1.5 cc). The amount of reduction was more and statistically significant [p = .000] in the group I than group II.

CONCLUSION

SZ suture fixation is reliable in reducing fractures ZMC and restoring the increased orbital volume where the fixation of zygomatic arch (ZA) was deemed necessary through latero-posterior approach.

Functional Evaluation of the Behavior of Masticatory Muscles in Zygomaticomaxillary Complex Fracture: A Prospective Study

AIMS

The purpose of this study is to functionally evaluate the behavior of the masticatory muscles (masseter and temporalis) following zygomaticomaxillary complex (ZMC) fractures by assessing bite force, electromyography (EMG), and mandibular movements.

MATERIALS AND METHODS

Group I consisted of 20 patients with unilateral ZMC fractures who were treated surgically with one-, two-, or three-point fixations at the frontozygomatic, infraorbital, or zygomaticomaxillary buttress region as per clinical and radiological assessments. Group II control group included 20 normal patients. The muscle activity was functionally evaluated before and after the surgery for a period of 6 months. The evaluation consisted of bite force measurement, EMG analysis of masseter and temporalis muscles, and measurements of mandibular movements.

RESULTS

There was an increase in bite force and EMG activity throughout the evaluated postoperative period, but at the end of 6 months, the values were still below the control levels for majority of the patients. Maximum mouth opening increased considerably after the surgery.

CONCLUSION

According to bite force and EMG, the masticatory musculature returned to near normal levels by the 3rd month after the surgery.

CLINICAL SIGNIFICANCE

Management of fractures of the zygoma by open reduction and fixation raises the question of the location of fixation points owing to the action of masseter and temporalis on the ZMC. This study supports the current clinical concept of minimized fixation in treating ZMC fractures.

An anatomic study of the attachments on the condylar process of the mandible: muscle bundles from the temporalis

PURPOSE

The aim of this study was to evaluate anatomically the relationship between bone and muscles by detailed observation of the bone shape and the structure of muscles to facilitate an understanding of the function of the muscles involved in jaw movement.

METHODS

36 specimens of 24 Japanese cadavers were examined. The insertion areas were marked using a radiopaque marker and examined by micro-computed tomography. For morphological observation, we used 101 condylar processes. In addition, we made histological sections in some specimens to observe the detailed attachments of the muscle.

RESULTS

Based on the micro-CT images and dissection findings, the lateral pterygoid muscle was found to be most frequently inserted into the anterior impression and attached to the medial impression of the process. According to the histological observations, the lateral pterygoid muscle mainly inserted to the condylar process. The micro-CT images indicated that the obvious bony ridge was lateral to the pterygoid fovea on the condylar process in all specimens. The midmedial muscle bundle of the temporalis was attached to the ridge. Based on the morphological observations, the ridge was situated on the lateral area of the condylar process.

CONCLUSIONS

Since dysfunction of the temporomandibular joint is likely closely related to both the lateral pterygoid muscle and also the temporalis, further studies are necessary to evaluate the function of these muscles and consider jaw movement.

A Simple Method for Reconstruction of the Temporalis Muscle Using Contourable Strut Plate after Pterional Craniotomy: Introduction of the Surgical Techniques and Analysis of Its Efficacy

Objective

Pterional craniotomy (PC) using myocutaneous (MC) flap is a simple and efficient technique; however, due to subsequent inferior displacement (ID) of the temporalis muscle, it can cause postoperative deformities of the muscle such as depression along the inferior margin of the temporal line of the frontal bone (DTL) and muscular protrusion at the inferior portion of the temporal fossa (PITF). Herein, we introduce a simple method for reconstruction of the temporalis muscle using a contourable strut plate (CSP) and evaluate its efficacy.

Materials and Methods

Patients at follow-ups between January 2014 and October 2014 after PCs were enrolled in this study. Their postoperative deformities of the temporalis muscle including ID, DTL, and PITF were evaluated. These PC cases using MC flap were classified according to two groups; one with conventional technique without CSP (MC Only) and another with reconstruction of the temporalis muscle using CSP (MC + CSP). Statistical analyses were performed for comparison between the two groups.

Results

Lower incidences of ID of the muscle (p < 0.001), DTL (p < 0.001), and PITF (p = 0.001) were observed in the MC + CSP than in the MC Only group. The incidence of acceptable outcome was markedly higher in the MC + CSP group (p < 0.001). ID was regarded as a causative factor for DTL and PITF (p < 0.001 in both).

Conclusion

Reconstruction of the temporalis muscle using CSP after MC flap is a simple and efficient technique, which provides an outstanding outcome in terms of anatomical restoration of the temporalis muscle.

Myotendinous rupture of temporalis muscle: A rare injury following seizure

Seizures are one of the most common pediatric neurologic disorders. Many complications secondary to seizures have been described in the literature including head trauma, fractures, drowning and burns. However, to the best of our knowledge, rupture of the myotendinous insertion of the temporalis muscle on the mandible secondary to a seizure has never been described in the literature. We report the case of a unilateral temporalis muscle rupture in a 16-year-old boy who developed unilateral facial swelling following new onset tonic-clonic seizures. We emphasize on the computed tomography and magnetic resonance imaging findings in this case report. Two mechanisms have been proposed to explain such an injury. The favored mechanism in our patient is a pull on the temporalis myotendinous insertion on the mandible following vigorous and brisk deviation of the head and neck during seizure. Radiologists should be familiar with this type of injury following seizures in order to prevent misdiagnosis and subsequently mistreatment.

Revisiting orthodromic temporalis transfer in treating long-standing facial paralysis

The treatment of long-standing facial paralysis through temporalis muscle transfer has stood the test of time. Herein, we present a modification in temporalis muscle transfer for lower facial reanimation. Instead of the traditional stripping of the temporalis muscle from its origin, its insertion is stripped from the coronoid process through an intraoral approach. The detached fibers were then sutured to a fascia lata graft, which was passed and secured to the orbicularis oris to reanimate the corner of the mouth. The procedure is less extensive and provides a direct "orthodromic" line of pull with good muscular excursion and power. This simple procedure has been applied to 12 consecutive cases with long-standing complete facial paralysis presenting to the Plastic and Reconstructive Surgery Clinic at the Ain-Shams University Hospital over the past 2 years. In addition to symmetry at rest, this easy procedure allowed for good movement of the corner of the mouth with restoration of a balanced smile.

Titanium mesh reconstruction to maintain scalp contour after temporalis musculofascial flap reconstruction of the floor of the middle cranial fossa: a technical note and report of two cases

OBJECTIVE

Temporalis musculofascial rotational flaps can provide excellent tissue for reconstruction of defects in the floor of the middle cranial fossa. This technique can, however, result in cosmetic deformity of the temporal fossa with an asymmetric contour of the head. We report a technique that uses titanium mesh and autologous abdominal adipose to maintain a normal scalp contour.

CLINICAL PRESENTATION

Two patients, one with a large middle cranial fossa and infratemporal schwannoma, and another with penetrating trauma secondary to a rifle accident, required surgical repair of defects of the floor of the middle cranial fossa.

INTERVENTION

The repair was achieved in both cases using a temporalis musculofascial rotational flap. Normal contour of the scalp was maintained with titanium mesh and autologous abdominal adipose reconstruction.

CONCLUSION

The temporalis musculofascial flap, combined with titanium mesh and autologous adipose reconstruction, provided excellent closure of defects of the floor of the middle cranial fossa while preserving normal cosmetic scalp contour.