Differences in cervical sagittal parameters and muscular function among subjects with different cervical spine alignments: a surface electromyography-based cross-sectional study.

Background: We analyzed cervical sagittal parameters and muscular function in different cervical kyphosis types. Methods: This cross-sectional study enrolled subjects with cervical spine lordosis (cervical curvature < -4°) or degenerative cervical kyphosis (cervical curvature > 4°), including C-, S-, and R-type kyphosis. We recorded patients' general information (gender, age, body mass index), visual analog scale (VAS) scores, and the Neck Disability Index (NDI). Cervical sagittal parameters including C2-C7 Cobb angle (Cobb), T1 slope (T1S), C2-C7 sagittal vertical axis (SVA), spino-cranial angle (SCA), range of motion (ROM), and muscular function (flexion-relaxation ratio (FRR) and co-contraction ratio (CCR) of neck/shoulder muscles on surface electromyography). Differences in cervical sagittal parameters and muscular function in subjects with different cervical spine alignments, and correlations between VAS scores, NDI, cervical sagittal parameters, and muscular function indices were statistically analyzed. Results: The FRR of the splenius capitis (SPL), upper trapezius (UTr), and sternocleidomastoid (SCM) were higher in subjects with cervical lordosis than in subjects with cervical kyphosis. FRRSPL was higher in subjects with C-type kyphosis than in subjects with R- and S-type kyphosis (P < 0.05), and was correlated with VAS scores, Cobb angle, T1S, and SVA. FRRUTr was correlated with NDI, SCA, T1S, and SVA. FRRSCM was correlated with VAS scores and Cobb angle. CCR was correlated with SCA and SVA. Conclusion: Cervical sagittal parameters differed among different cervical kyphosis types. FRRs and CCRs were significantly worse in R-type kyphosis than other kyphosis types. Cervical muscular functions were correlated with cervical sagittal parameters and morphological alignment.

The functional role of the rabbit digastric muscle during mastication.

Muscle spindle abundance is highly variable in vertebrates, but the functional determinants of this variation are unclear. Recent work has shown that human leg muscles with the lowest abundance of muscle spindles primarily function to lengthen and absorb energy, while muscles with a greater spindle abundance perform active-stretch-shorten cycles with no net work, suggesting that muscle spindle abundance may be underpinned by muscle function. Compared with other mammalian muscles, the digastric muscle contains the lowest abundance of muscle spindles and, therefore, might be expected to generate substantial negative work. However, it is widely hypothesised that as a jaw-opener (anatomically) the digastric muscle would primarily function to depress the jaw, and consequently do positive work. Through a combination of X-ray reconstruction of moving morphology (XROMM), electromyography and fluoromicrometry, we characterised the 3D kinematics of the jaw and digastric muscle during feeding in rabbits. Subsequently, the work loop technique was used to simulate in vivo muscle behaviour in situ, enabling muscle force to be quantified in relation to muscle strain and hence determine the muscle's function during mastication. When functioning on either the working or balancing side, the digastric muscle generates a large amount of positive work during jaw opening, and a large amount of negative work during jaw closing, on average producing a relatively small amount of net negative work. Our data therefore further support the hypothesis that muscle spindle abundance is linked to muscle function; specifically, muscles that absorb a relatively large amount of negative work have a low spindle abundance.

Advanced US of the Skin, Nerves, and Muscles of the Neck: Pearls and Pitfalls with Use of High-Frequency Transducers.

High-frequency US provides excellent visualization of superficial structures and lesions, is a preferred diagnostic modality for anatomic characterization of neck abnormalities, and has a central role in clinical decision making. Recent technological advancements have led to the development of transducers that surpass 20 MHz, elevating high-frequency US to a highly valuable diagnostic tool with broader clinical use and enabling greater spatial resolution in the assessment of skin and superficial nerves and muscles. The authors focus on evolving applications of high-frequency US in neck imaging, emphasizing practical insights and strategies in skin and neuromuscular applications. ©RSNA, 2024 Supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

The Posterior Triangle and Posterior Muscles of the Neck in 3-Dimensions: Creating a Digital Anatomic Model Using Peer-Reviewed Literature, Radiographic Imaging, and an Experienced Medical Illustrator.

INTRODUCTION: The posterior cervical triangle houses an important nodal basin in the spread of several cancers in the head and neck, particularly cutaneous malignancies of the scalp. A safe and effective Level V neck dissection necessitates thorough understanding of the neurovascular structures housed within the region. Conventional 2D anatomical representations offer insights into the named structures, but fall short in illustrating the spatial relationships crucial in surgery. Here, we aim to develop an anatomically-precise 3D virtual model of the posterior cervical triangle and its constituent structures. METHODS: Musculature and neurovasculature were segmented from the computerized tomography (CT) angiogram of a healthy 29-year-old female. Literature review of cadaveric studies was performed to identify the most common variants, relevant surgical relationships, and usual dimensions of structures contained in the model. Structures unable to be visualized on imaging were created de novo using data obtained in the literature review. A medical illustrator then used this data to develop a 3D anatomical model using ZBrush. RESULTS: The musculature (sternocleidomastoid, trapezius, omohyoid, scalenes, erector spinae, and transversospinalis muscles) and neurovasculature (spinal accessory nerve, phrenic nerve, vertebral artery, subclavian artery, and brachial plexus) were characterized through literature review. Musculature and vasculature were segmented from CT angiography while neural structures were created de novo. Both radiographic and anatomic data were used to inform the creation of a 3D model, which will be uploaded to an online database for open access viewing. CONCLUSIONS: A dynamic understanding of the spatial relationships existing among structures housed within the posterior triangle of the neck is imperative when operating in the region. The development of an accurate 3D anatomical model of such structures based upon predominant variants found in the literature will supplement the education of practicing and aspiring head and neck surgeons.

Reliability and usability of a novel inertial sensor-based system to test craniocervical flexion movement control.

BACKGROUND: Neck pain has a significant global impact, ranking as the fourth leading cause of disability. Recurrent neck pain often leads to impaired sensorimotor control, particularly in craniocervical flexion (CFF). The Craniocervical Flexion Test (CCFT) has been widely investigated to assess the performance of deep cervical flexor muscles. However, its use requires skilled assessors who need to subjectively detect compensations, progressive increases in range of motion (ROM) or excessive superficial flexor activation during the test. The aim of this study was to design and develop a novel Craniocervical Flexion Movement Control Test (CFMCT) based on inertial sensor technology and real-time computer feedback and to evaluate its safety and usability, as well as inter and intra-rater reliability in both healthy individuals and patients with neck pain. METHODS: We used inertial sensor technology associated with new software that provides real-time computer feedback to assess CCF movement control through two independent test protocols, the progressive consecutive stages protocol (including progressive incremental stages of ROM) and the random stages protocol (providing dynamic and less predictable movement patterns). We determined intra and inter-rater reliability and standard error of the measurement for both protocols. The participants rated their usability was analysed through the System Usability Scale (SUS) and possible secondary effects associated with the tests were registered. RESULTS: The progressive consecutive stages protocol and the random stages protocol were safe and easy to use (SUS scores of 82.00 ± 11.55 in the pain group and 79.56 ± 13.36 in the asymptomatic group). The progressive consecutive stages protocol demonstrated good inter-rater reliability (intraclass correlation coefficient [ICC] ≥ 0.75) and moderate to good intra-rater reliability (ICC 0.62-0.80). However, the random stages protocol exhibited lower intra-rater reliability, especially in the neck pain group, where the reliability values were poor in some cases (ICC 0.48-0.72). CONCLUSION: The CFMCT (progressive consecutive stages protocol) is a promising instrument to evaluate CCF motor control in patients with chronic neck pain. It has potential for telehealth assessment and easy adherence for exercise prescription and seems to be a safe and usable tool for patients with pain and asymptomatic individuals. Its use as a test or for exercise needs to be further investigated to facilitate its transfer to clinical practice.

Effects of Integrating Jaw Opening and Closing Movements with Active Neck Exercises in the Management of Chronic Non-Specific Neck Pain: A Randomized Controlled Trial.

Background and Objectives: It has been seen that jaw opening is associated with neck extension and jaw closing is associated with neck flexion. This natural association between the jaw and neck can be used as a novel approach to treat chronic non-specific neck pain, although the effects of this concept have never been previously evaluated as a treatment strategy. This article intends to study the effects of integrating jaw opening and closing movements along with active neck exercises versus active neck exercises alone in the management of chronic non-specific neck pain. Materials and Methods: A total of 80 patients, aged 20 to 50, with chronic non-specific neck pain were included in a double-blind randomized controlled trial, conducted at the Sindh Institute of Physical Medicine and Rehabilitation, Karachi, Pakistan from 2018 to 2022. The patients were divided into two groups: Group A patients were assigned jaw movements with active neck exercises, while Group B patients were assigned only active neck exercises. Both groups were assigned isometric strengthening exercises and self-resisted strengthening exercises for cervical spine muscles as a home plan. The study used various outcome measures, including the numerical pain rating scale (NPRS), neck disability index (NDI), neck flexion endurance (NFE), neck extension endurance (NEE), the neck proprioception error (NPE): neck flexion proprioception error (NFPE), neck extension proprioception error (NEPE), neck right rotation proprioception error (NRRPE), and neck left rotation proprioception error (NLRPE), with measurements taken at week 1 and week 6, respectively; the mean differences between the groups were measured using a two-way repeated ANOVA. Results: The experimental group showed better improvements compared to the control group, NPRS (73%), NDI (57%), NFE (152%), NEE (83%), NFPE (58%), NEPE (65%), NRRPE (65%), and NLRPE (62%), with a significant difference (p < 0.05). Conclusions: Active neck extension and flexion movements combined with jaw opening and closing are more effective in reducing pain and disability, improving neck muscles endurance and normalizing neck proprioception in patients with chronic neck pain.

Evolving Dynamics of Neck Muscle Activation Patterns in Dental Students: A Longitudinal Study.

Cervical pain has been linked to increased motor unit activity, potentially associated with the initiation and progression of chronic neck pain. Therefore, this study aimed to compare the time-course changes in cervical superficial muscle activation patterns among dental students with and without neck pain throughout their initial semester of clinical training. We used an online Nordic Musculoskeletal Questionnaire for group allocation between neck pain (NP) (n = 21) and control group (CG) (n = 23). Surface electromyography (sEMG) of the sternocleidomastoid and upper bilateral trapezius was recorded before starting their clinical practice and after their first semester while performing a cranio-cervical flexion test (CCFT) in five increasing levels between 22 mmHg and 30 mmHg. After the first semester, both the CG (p < 0.001) and NP (p = 0.038) groups showed decreased sternocleidomastoid activation. The NP group exhibited a concomitant increase in upper trapezius coactivation (p < 0.001), whereas the muscle activation pattern in asymptomatic students remained unchanged (p = 0.980). During the first semester of clinical training, dental students exhibited decreased superficial flexor activity, but those with neck pain had increased co-contraction of the upper trapezius, likely to stabilize the painful segment. This altered activation pattern could be associated with further dysfunction and symptoms, potentially contributing to chronicity.

The deflection of fatigued neck.

The human neck is a unique mechanical structure, highly flexible but fatigue prone. The rising prevalence of neck pain and chronic injuries has been attributed to increasing exposure to fatigue loading in activities such as prolonged sedentary work and overuse of electronic devices. However, a causal relationship between fatigue and musculoskeletal mechanical changes remains elusive. This work aimed to establish this relationship through a unique experiment design, inspired by a cantilever beam mechanical model of the neck, and an orchestrated deployment of advanced motion-force measurement technologies including dynamic stereo-radiographic imaging. As a group of 24 subjects performed sustained-till-exhaustion neck exertions in varied positions-neutral, extended, and flexed, their cervical spine musculoskeletal responses were measured. Data verified the occurrence of fatigue and revealed fatigue-induced neck deflection which increased cervical lordosis or kyphosis by 4-5° to 11°, depending on the neck position. This finding and its interpretations render a renewed understanding of muscle fatigue from a more unified motor control perspective as well as profound implications on neck pain and injury prevention.

Functional involvement of the sternohyoid muscle during breathing and swallowing in rats.

The sternohyoid muscle depresses the hyoid bone, but it is unclear whether the muscle contributes to respiratory and swallowing mechanisms. This study aimed to clarify whether the sternohyoid muscle participates in the respiration and swallowing reflex and how the activity is modulated in two conditions: with airway stenosis and with a fixed sternohyoid muscle length. Electromyographic activity in the sternohyoid, digastric, thyrohyoid, and diaphragm muscles was recorded in anesthetized rats. The sternohyoid muscle activity was observed in the inspiratory phase and during swallowing, and was well coordinated with digastric and thyrohyoid muscle activity. With airway stenosis, the respiratory activity per respiratory cycle was facilitated in all assessed muscles but the facilitation of activity per second occurred only in the digastric, thyrohyoid, and sternohyoid muscles. With airway stenosis, the swallowing activity was facilitated only in the digastric muscle but not in the thyrohyoid and sternohyoid muscles. Swallowing activity was not observed in the sternohyoid muscle in the condition with the sternohyoid muscle length fixed, although increased inspiratory activity remained. The current results suggest that 1) the sternohyoid muscle is slightly activated in the inspiratory phase, 2) the effect of airway stenosis on respiratory function may differ between the upper airway muscles and diaphragm, and 3) swallowing activity in the sternohyoid muscle is not dominantly controlled by the swallowing central pattern generator but instead occurs as a myotatic reflex.NEW & NOTEWORTHY We found that the sternohyoid muscle was activated in the inspiratory phase. However, increased airway resistance had different effects on the extrathoracic muscles than on the diaphragm. The swallowing activity of the sternohyoid disappeared when the muscle length was fixed. These findings suggest that the sternohyoid muscle may be activated not by the swallowing central pattern generator but as a myotatic reflex.

The association between mobile phone usage duration, neck muscle endurance, and neck pain among university students.

The mobile phone is essential in daily life, especially during the pandemic. Prolonged use can cause postural issues, leading to common neck pain. This study aims to determine the correlation between mobile phone use duration, addiction, neck muscle endurance, and neck pain in university students. The study included 62 participants (30 female, 32 male) aged 18-35 years. Inclusion criteria required participants to have experienced neck pain at least twice in the past year and to have no other concomitant issues, as well as to volunteer for the study. Demographic information and daily mobile phone usage time were collected. Neck pain was assessed with the Visual Analogue Scale, smartphone addiction with the Smartphone Addiction Scale, and cervical muscle endurance was evaluated. Correlation analysis reveals a moderate relationship between neck pain severity (NPS) and cervical extensor muscle endurance (CEME), a strong relationship between NPS and cervical flexor muscle endurance (CFME), as well as a strong relationship among daily phone usage time (DPUT), CFME, and NPS, with a moderate relationship between DPUT and CEME. Participants were divided into two groups based on their DPUT, revealing that those who used their phone for four hours or more showed significantly higher levels of pain (p < 0.05) and reduced endurance in cervical flexor muscles. Our study found a strong correlation between neck pain, muscle endurance, and daily phone usage. Participants using their phones for more than four hours daily reported increased neck pain and decreased muscle endurance. We suggest integrating phone usage duration into neck pain assessments, promoting ergonomic practices, and offering detailed usage guidelines for users.

Sex differences in cervical disc height and neck muscle activation during manipulation of external load from helmets.

Neck pain associated with helmet-wear is an occupational health problem often observed in helicopter pilots and aircrew. Whether aircrew helmet wearing is associated with physiological and biomechanical differences between sexes is currently unknown. This study investigated neuromuscular activation patterns during different helmet-wearing conditions. The helmet load was manipulated through a novel Helmet Balancing System (HBS) in healthy, non-pilot male and female participants (n = 10 each, age 19-45 years) in two phases. Phase A assessed the acute effects of helmet-wear on neck muscles activation during head movements. Phase B examined changes in muscle activity and cervical disc height after wearing a helmet for 45 min. In Phase A, muscle activity was similar between sexes in many movements, but it was higher in female participants when wearing a helmet than in males. The HBS reduced muscle activity in both sexes. In Phase B, female participants exhibited a greater level of muscular fatigue, and male participants' cervical disc height was significantly decreased [5.7 (1.4) vs. 4.4 (1.5) mm, P < 0.001] after continuous wearing. Both sexes showed no significant change in muscle fatigue and disc height [male: 5.0 (1.3) vs. 5.2 (1.4) mm, P = 0.604] after applying HBS. These findings demonstrate sex-specific physiological and biomechanical responses to wearing a helmet. They may indicate different postural and motor control strategies, associated with different neck pain aetiologies in male and female aircrew, the knowledge of which is important to reduce or prevent musculoskeletal injuries associated with helmet wearing.

Radiological assessment of the dissection area in supraomohyoid neck dissection.

PURPOSE: The current supraomohyoid neck dissection (SOHND) is performed above the omohyoid muscle to dissect levels I, II, and III in the levels of cervical lymph nodes. However, the anatomical boundary between levels III and IV is the inferior border of the cricoid cartilage. We investigated the anatomical relationship between the omohyoid muscle and cricoid cartilage using contrast-enhanced CT (CE-CT) images to assess the validity of the current SOHND. METHODS: CE-CT images of the head and neck regions in patients were reviewed. The patients were divided into two groups: "malignant tumors" and "others". The vertebral levels corresponding to the positions of anatomical structures such as the intersection of the omohyoid muscle and internal jugular vein (OM-IJ), and the inferior border of the cricoid cartilage (CC), were recorded. RESULTS: The OM-IJ was located around the seventh cervical to the first thoracic vertebra. There was a significant difference between the malignant tumor and others groups in females (p = 0.036). The CC was located around the sixth to seventh cervical vertebrae. There was a significant sex difference in each group (malignant tumor: p < 0.0001; others: p = 0.008). Both sexes tended to have lower OM-IJ than CC, and females had significantly lower OM-IJ than males. CONCLUSION: This study provides clear anatomical evidence showing the difference between the SOHND dissection area and levels I, II, and III. It could be considered that in most cases SOHND invades level IV, not just levels I, II, and III, especially in female patients.

Neck muscle function improves after neck exercises in individuals with whiplash-associated disorders: a case-control ultrasound study with speckle-tracking analyses.

A whiplash injury can alter neck muscle function, which remains years after the injury and may explain why symptoms such as persistent pain and disability occur. There is currently limited knowledge about dynamic neck muscle function in chronic whiplash-associated disorders (WAD), and about the extent to which altered muscle function can improve after rehabilitation. Ultrasound can detect mechanical neck muscle function by measuring real-time deformation and deformation rate in the muscles. This method was used for five dorsal neck muscles in participants with chronic WAD versus matched controls in resistant neck rotation. We obtained real-time, non-invasive ultrasound measurements using speckle tracking, multivariate analyses, and mixed-design ANOVA analyses. The results showed altered deformation in the three deepest neck muscle layers, with less deformation area in the WAD group compared to controls in rotation to the most painful side at baseline. Participants in the WAD group performed three months of neck-specific exercises, resulting in improved deformation in the deep neck muscles in WAD and with a similar deformation pattern to controls, and the significant group differences ceased. We reveal new and important insights into the capability of ultrasound to diagnose altered neck muscle function and evaluate an exercise intervention.

Endoscopic minimally invasive treatment of congenital muscular torticollis in children.

BACKGROUND: This study aimed to investigate the clinical efficacy of minimally invasive endoscopic treatment of children with congenital muscular torticollis (CMT). METHODS: In total, 72 children (41 male, 31 female) with CMT who underwent endoscopic surgery at the Department of Orthopedics, Xi'an Children's Hospital, between January 2021 and January 2023 were included. Their mean age was 54 ± 36.1 (range, 12-141) months. Of these, 29 (40.3%) cases involved the left side while 43 (59.7%) involved the right side. Preoperative preparation involved precise body surface markings of the sternocleidomastoid muscle(SCM), clavicle, and important nerve and blood vessels, followed by the establishment of surgical channels through passive separation techniques. An arthroscope and a low-temperature plasma knife were utilized for accurate localization and surgical release of the clavicular and sternal heads of the SCM. The duration of surgery, blood loss, postoperative hospital stay, neck range of motion measurements, and any intraoperative or postoperative complications were analyzed using the rank sum test. Cervical and thoracic braces were applied for three months postoperatively, with follow-up assessments conducted using Cheng's scoring system. RESULTS: All patients successfully underwent endoscopic surgery, without the need for conversion to open surgery. No intra- or postoperative complications were observed. The average surgical duration was 56.4 ± 15.7 min, with minimal intraoperative bleeding (1-5 mL) and no need for blood transfusion. The mean postoperative hospital stay was 2.7 ± 0.8 days. Over a mean follow-up period of 22.2 ± 5.5 (range, 14-32) months, significant improvements were observed in neck rotation (from 20.2° [17.7° to 25°] to only 3.6° [2° to 6.7°]) and lateral flexion (from 19° [17° to 22.6°] to only 3° [2° to 7.8°]) restrictions (p < 0.05). According to Cheng's scoring system, 70 (97.2%) patients achieved excellent or good clinical outcomes, while 2 (2.8%) had average outcomes. The torticollis deformity was corrected during the follow-up period, and all surgical incisions healed without noticeable scarring. CONCLUSION: Endoscopic release is a safe, effective, and minimally invasive treatment option for CMT in children.

Between-Session Reliability of Field-Based Assessments of Isometric Neck Strength.

The reliability of the fixed-frame dynamometer for measuring isometric neck strength is established, but with limited field-based applications. This study aimed to establish the inter- and intra-session reliability of the peak force for neck flexors, extensors, and side flexors using the VALD ForceFrame and DynaMo and the force-time characteristics in the quadruped position (ForceFrame). Twenty-seven recreationally active males performed three repetitions of isometric neck flexion, extension, and side flexion over two sessions in random order using the VALD ForceFrame and DynaMo. Both devices demonstrated acceptable reliability, with the Forceframe ICC > 0.8 and CV% < 13.8% and the DynaMo ICC > 0.76 and CV% < 13.8%. No systematic or proportional differences were found using the Passing-Bablock procedure, and Bland-Altman analysis confirmed agreement across measures. Reliability was shown for right-side (ICC > 0.76) and left-side (ICC > 0.79) flexion and flexion (ICC > 0.75) across 50, 100, 150, and 200 ms. Statistical parametric mapping indicated no differences in ForceFrame-generated isometric force-time curves between sessions, though the CV was highest in the force development phase. The findings suggest that both tools can reliably assess neck strength, supporting their use in sports and clinical settings. However, assessment methods are not interchangeable, emphasising the need for standardised neck strength assessment approaches.

Fatty infiltration and morphology of cervical muscles in patients with temporomandibular disorders: A case-control study.

BACKGROUND: Changes in the fatty infiltration and/or muscle volume of neck muscles can alter cervical spine alignment and cranial load distribution, which may cause pain in the orofacial region. OBJECTIVES: The aim of the study was to examine the muscle volume and fatty infiltration of neck muscles in patients with temporomandibular disorders (TMD). MATERIAL AND METHODS: This case-control study included 18 patients with TMD and 18 ageand sex-matched controls. The muscle volume and fatty infiltration of the neck muscles of the participants were measured using magnetic resonance imaging (MRI) and ITK-SNAP software. The 3D models of the sternocleidomastoid (SCM), splenius capitis (SPLC), semispinalis cervicis (SC)-semispinalis capitis (SCP), and multifidus (M) muscles within the C3-C7 range were created using ITK-SNAP, a semi-automatic segmentation software. The models were used to determine the volumes and fatty infiltration levels. The Neck Disability Index (NDI) was used to assess neck pain-related disability. The severity of TMD was determined using the Fonseca Anamnestic Index (FAI), while jaw-related disability was measured with the Jaw Functional Limitation Scale-20 (JFLS-20). Pain levels were recorded at rest and during chewing using the numeric rating scale (NRS). RESULTS: There were no statistically significant differences in total muscle volume, fatty infiltration volume and fatty infiltration percentage of the SCM, SPLC, SCP, SC, and M muscles between the 2 groups (p > 0.05). The patient group had higher NDI scores compared to the controls (p < 0.001). The NDI scores correlated positively with the JFLS-20 (r = 0.831, p < 0.001), FAI (r = 0.815, p < 0.001) and NRS scores at rest (r = 0.753, p < 0.001) and during chewing (r = 0.686, p < 0.001). CONCLUSIONS: The present study did not identify any significant differences in the neck muscle volume or fatty infiltration between the TMD patients and controls. However, the severity of neck disability was found to correlate with jaw function, pain and TMD levels.

Navigating the void: outcomes and adaptations during parotid surgery in the absence of posterior belly of digastric muscle.

It is well known that the digastric posterior belly is one of the essential landmarks for facial nerve identification during parotid surgery. While there were multiple reports about variations of the digastric anterior belly, only a few anatomical variations of the posterior belly of the digastric muscle have been described.In this article, we describe an anatomical variation of the posterior belly of digastric muscle found during superficial parotidectomy of a patient with pleomorphic adenoma. This anatomical variation also led to an anatomical variation in the position of the facial nerve.To our knowledge, this is the first report of an absent posterior belly of digastric muscle found during live parotid surgery. The knowledge of current anatomical variation may help to avoid facial nerve injury during parotid surgery and preserve the function of muscles of facial expression.

Retinoic acid signalling regulates branchiomeric neck muscle development at the head/trunk interface.

Skeletal muscles of the head and trunk originate in distinct lineages with divergent regulatory programmes converging on activation of myogenic determination factors. Branchiomeric head and neck muscles share a common origin with cardiac progenitor cells in cardiopharyngeal mesoderm (CPM). The retinoic acid (RA) signalling pathway is required during a defined early time window for normal deployment of cells from posterior CPM to the heart. Here, we show that blocking RA signalling in the early mouse embryo also results in selective loss of the trapezius neck muscle, without affecting other skeletal muscles. RA signalling is required for robust expression of myogenic determination factors in posterior CPM and subsequent expansion of the trapezius primordium. Lineage-specific activation of a dominant-negative RA receptor reveals that trapezius development is not regulated by direct RA signalling to myogenic progenitor cells in CPM, or through neural crest cells, but indirectly through the somitic lineage, closely apposed with posterior CPM in the early embryo. These findings suggest that trapezius development is dependent on precise spatiotemporal interactions between cranial and somitic mesoderm at the head/trunk interface.

[Hyoid epiglottis combined with sternocleidomastoid muscle clavicle flap for repairing laryngeal defect after laryngeal trauma infection: a case report].

The initial treatment of open laryngeal trauma must be implemented immediately, with the primary focus on saving lives. However, in the later stages, various factors may cause changes in the structure and function of the larynx, which requires special attention. This article reports on the treatment process of a patient with depression who suffered from laryngeal trauma. Due to the late stage of laryngeal infection causing laryngeal defects, a hyoid epiglottis combined with sternocleidomastoid muscle clavicular flap repair was performed. Additionally, personalized functional exercise was performed, ultimately resulting in recovery.