The Digastric Muscle: Its Anatomy and Functions Revisited / El Músculo Digástrico: Revisión de su Anatomía y Funciones

SUMMARY: As one of the suprahyoid muscles, the digastric muscle is characterized by two separate bellies of different embryologic origins. The origin of the anterior belly is the digastric fossa, while the origin of the posterior belly is the mastoid notch. They share a common insertion: the intermediate tendon. When the digastric muscle contracts, the hyoid bone is raised. Opening of the jaw and swallowing of food boli are associated with digastric muscle activity. This review discusses the general anatomic features of the digastric muscle and its variation, primary functions, and clinical implications focused on surgical reconstruction and rejuvenation.

Como uno de los músculos suprahioideos, el músculo digástrico se caracteriza por dos vientres separados, de diferentes orígenes embriológicos. El origen del vientre anterior es la fosa digástrica, mientras que el origen del vientre posterior es la incisura mastoidea. Comparten una inserción común, El tendón intermedio. Cuando el músculo digástrico se contrae, el hueso hioides se eleva. La apertura de la mandíbula y la deglución del bolo alimenticio se asocian con la actividad del músculo digástrico. Esta revisión analiza las características anatómicas generales del músculo digástrico y su variación, funciones primarias e implicaciones clínicas centradas en la reconstrucción y el rejuvenecimiento quirúrgico.

Surface Electromyography for Evaluating the Effect of Aging on the Coordination of Swallowing Muscles.

Swallowing function can deteriorate with age, leading to a risk of dysphagia. Swallowing evaluation by surface electromyography (sEMG) can be easily and extensively applied for an elderly population. This study evaluated the temporal events observed by sEMG to clarify how aging affects the coordination among the masticatory and suprahyoid muscles. We recruited elderly individuals (over 65 years old) who denied dysphagia. The sEMG activities of anterior temporalis, masseter, and suprahyoid muscles were recorded during 3, 15, and 30 ml water swallowing tests (WST). We calculated the time interval between anterior temporalis and suprahyoid peak activity (T-SH interval) and masseter and suprahyoid peak activity (M-SH interval) and analyzed their correlation with age. The subjects who could and could not swallow 30 ml of water in one gulp were further assigned into the one-gulp and piecemeal groups, respectively, for subgroup analysis. We recruited 101 subjects, among whom 75 (26 males and 49 females) were analyzed after excluding those with suspected dysphagia or low-quality sEMG recordings. Age was significantly correlated with the bilateral T-SH (left: r = 0.249, p = 0.031; right: r = 0.412, p < 0.01) and right M-SH (r = 0.242, p = 0.037) intervals in the 30 ml WST. The correlation between intervals and age were observed in both subgroups. sEMG can be used to investigate the effect of aging on the temporal coordination between masticatory and suprahyoid contraction. Further studies are needed to verify the validity of screening subclinical dysphagia in the elderly.

Thermography in complementary assessments of head and neck muscles: A scoping review.

INTRODUCTION: Infrared thermography has the potential to help assess human head and neck muscles, as thermal variation measurements due to muscle imbalance can contribute to the evaluation and therapeutic follow-up of various clinical conditions in the field of health. OBJECTIVE: This study investigated, with a scoping review, the use of infrared thermography in complementary assessments of human head and neck muscles to determine the extent of research on the topic, what methodologies are used in thermal assessment and thermographic analysis, what regions are assessed, and what results are expected in thermography. METHODS: LILACS, MEDLINE, SciELO, and Web of Science were the databases searched to identify articles published on the topic, with no restriction of language or time of publication. Descriptive, analytical, and experimental observational studies on the assessment of the human head and neck muscle surface temperature with infrared thermography were included. Case studies, case series, methodological accuracy, literature review, animal studies, studies that assessed patients with head and neck cancer, and studies that did not assess head and neck muscle temperature with thermography were excluded. The articles were analysed with a protocol developed by the authors, with data on author, year, country, type of study, sample characterisation, muscles assessed, outcomes investigated, thermal assessment methodology, thermographic analysis methodology and thermography measurements. RESULTS: This review identified and analysed 27 articles. The studies assessed thermal distribution in normal individuals and those with pathologies related to hyper- and hypofunctional head and neck muscle conditions for diagnosis or therapeutic follow-up. The masseter, temporal, digastric, anterior cervical region, orbicularis oris, frontalis, buccinator, suprahyoid, trapezius, sternocleidomastoid and levator scapulae muscles were assessed. Quantitative analyses with area selection tool predominated, considering absolute temperatures and temperature differences. The studies investigated temperature and its relationship with myogenic pain, quantitative assessment of muscle parameters and blood flow velocity. The mean temperature ranged from 32.97°C (±2.21) to 34.90°C, and hyper-radiant and/or asymmetric regions were observed in hyperfunctional conditions and normal subjects after muscle activation. CONCLUSION: Thermography is used in complementary assessments of head and neck muscles, identifying hyper-radiant regions and thermal asymmetry related to muscle tension and activation state. Papers are limited to specific clinical conditions and few muscle groups, besides having great methodological variability.

Elasticity of neck muscles in cervicogenic headache.

AIM: To compare the elasticity of the sternocleidomastoid and trapezius muscles in patients with cervicogenic headache and in healthy volunteers. METHODS: The medical history of 23 patients with cervicogenic headache was taken with a focus on pain characteristics. Elasticity of the sternocleidomastoid and trapezius muscles was measured by using shear wave elastography. Results were then compared with 23 healthy volunteers. RESULTS: The sternocleidomastoid muscle was significantly stiffer in patients with cervicogenic headache compared to healthy volunteers. The stiffness increased gradually from the parasternal area, where it was negligible, to the area near the mastoid process where it reached over 20 kPa. There was no difference in the stiffness of the trapezius muscle. The stiffness of the sternocleidomastoid muscle does show a significant dependence on headache characteristics (e.g., laterality, severity, or frequency). CONCLUSION: The results of this pilot study show that patients with cervicogenic headache have a higher stiffness of the sternocleidomastoid muscle than healthy volunteers. These findings suggest that elastography could be used as a diagnostic tool in cervicogenic headache.

Ansa Cervicalis Stimulation: A New Direction in Neurostimulation for OSA.

BACKGROUND: Hypoglossal nerve stimulation (HNS) is an alternative treatment option for patients with OSA unable to tolerate positive airway pressure but implant criteria limit treatment candidacy. Previous research indicates that caudal tracheal traction plays an important role in stabilizing upper airway patency. RESEARCH QUESTION: Does contraction of the sternothyroid muscle with ansa cervicalis stimulation (ACS), which pulls the pharynx caudally via thyroid cartilage insertions, increase maximum inspiratory airflow (VImax)? STUDY DESIGN AND METHODS: Hook-wire percutaneous electrodes were used to stimulate the medial branch of the right hypoglossal nerve and right branch of the ansa cervicalis innervating the sternothyroid muscle during propofol sedation. VImax was assessed during flow-limited inspiration with a pneumotachometer. RESULTS: Eight participants with OSA were studied using ACS with and without HNS. Compared with baseline, the mean VImax increase with isolated ACS was 298%, or 473 mL/s (95% CI, 407-539). Isolated HNS increased mean VImax from baseline by 285%, or 260 mL/s (95% CI, 216-303). Adding ACS to HNS during flow-limited inspiration increased mean VImax by 151%, or 205 mL/s (95% CI, 174-236) over isolated HNS. Stimulation was significantly associated with increase in VImax in both experiments (P < .001). INTERPRETATION: ACS independently increased VImax during propofol sedation and drove further increases in VImax when combined with HNS. The branch of the ansa cervicalis innervating the sternothyroid muscle is easily accessed. Confirmation of the ansa cervicalis as a viable neurostimulation target may enable caudal pharyngeal traction as a novel respiratory neurostimulation strategy for treating OSA.

Relação entre os músculos masseter e esternocleidomastoideo nas situações de flexão e rotação da coluna cervical, em mastigação e máxima intercuspidação habitual, analisados através da atividade eletromiográfica / Relationship between the masseter and sternocleidomastoid muscles in the flexion and rotation functions of the cervical, chewing and maximum habitual intercuspation, analyzed by the electromyographic activity

Na atualidade, com as frequentes inovações tecnológicas agregadas aos telefones celulares favorecendoseu uso excessivo, altos níveis de estresse e o ritmo acelerado da vida, inconscientemente, as pessoas têmadotado novas e diferentes posturas corporais, que direta ou indiretamente interferem na posição da colunavertebral. Um importante músculo postural do pescoço é o esternocleidomastoideo, cuja relevante função éa de estabilizar. Objetivo: analisar a possível relação entre os músculos masseter e esternocleidomastoideo,em diferentes posições da cabeça e da coluna cervical, nas situações de mastigação, repouso e máximaintercuspidação habitual. Metodologia: os dados foram coletados inicialmente com cabeça e coluna eretas,em repouso e em máxima intercuspidação habitual. Em seguida, coletou-se, sempre em mastigação, com acabeça e a coluna eretas, inclinadas para frente, para trás, para direita, para esquerda, giradas para direita epara esquerda. Todos os momentos de coleta de dados ocorreram por 5 segundos em cada posição. Resultados:nota-se um aumento na atividade elétrica do músculo esternocleidomastoideo quando a mastigaçãoacontece com a cabeça e a coluna fora da posição ereta. Em algumas posições da cabeça, esse aumento, emvalores absolutos, não é observado de forma relevante no sexo feminino, sendo notado no masculino. Conclusões:existe uma relação de trabalho entre os músculos masseter e esternocleidomastoideo. Essa relaçãosugere que o segundo músculo trabalha na tentativa de estabilizar a cabeça para otimizar o ato mastigatório,ação essa notadamente encontrada no sexo masculino e de forma menos ativa no sexo feminino.(AU)

Nowadays, with the frequent technological innovations added to cell phones favoring their excessive use, high levels of stress and the fast pace of life, people have unconsciously adopted new and different body postures that directly or indirectly interfere in the position of the spine. An important postural muscle of the neck is the sternocleidomastoid, whose important function is to stabilize it. Objective: to analyze the possible relationship between the masseter and sternocleidomastoid muscles, in different positions of the head and cervical spine, in situations of chewing, resting and maximum habitual intercuspation. Methodology: data were collected initially with head and spine erect, at rest and at maximum habitual intercuspation. Then, it was collected, always chewing, with the head and column erect, tilted forward, backward, right, left, turned to the right and turned to the left. All moments of data collection occurred for 5 seconds in each position. Results: An increase in the electrical activity of the sternocleidomastoid muscle is observed when chewing occurs with the head and spine out of the upright position. In some positions of the head this increase, in absolute values, is not observed in a relevant way in the female sex, being noticed in the male. Conclusions: there is a working relationship between the masseter and sternocleidomastoid muscles. This relationship suggests that the second muscle works in an attempt to stabilize the head to optimize the masticatory act, an action that is notably found in men and less actively in women.(AU)

Is the proprioceptive neuromuscular facilitation technique superior to Shaker exercises in swallowing rehabilitation?

PURPOSE: This prospective study was planned to investigate whether the combined isotonic technique of proprioceptive neuromuscular facilitation (PNF) is superior to Shaker exercises in improving the function of swallowing muscles. METHODS: Fifty individuals (30 females and 20 males; mean age 68 ± 3.89 years) with swallowing difficulties were separated into two groups randomly. The treatment groups were Shaker and PNF groups, which performed these exercises three times in a week for6 weeks. Swallowing difficulties were determined with the Turkish version of the eating assessment tool (T-EAT-10). The 100 ml-water swallow test was used to measure capacity, volume, and speed of swallowing. Contraction amplitude changes used as a universal measurement of motor unit activity during the muscle action were measured with superficial electromyography. RESULT: After 6 weeks of exercise training, T-EAT-10 scores decreased in both groups (p < 0.001). Water swallowing capacity and volume improved in both groups (p < 0.001). There was no change in swallowing speed in both groups (p > 0.05). Maximal voluntary contraction values of suprahyoid muscles were higher in PNF than the Shaker group (p < 0.05). CONCLUSION: Both the types of exercise can be used in the rehabilitation of swallowing difficulties. However, the PNF technique increased the contraction amplitude values that occur during maximum contraction more than the Shaker exercises. Different functional evaluations are needed to determine the effectiveness of PNF on swallowing difficulty.

Quando exercícios de fortalecimento da língua refletem na região cervical / When tongue strength exercises reflect in the cervical region

RESUMO Objetivo: Comparar o impacto do exercício isocinético "sucção da língua contra o palato" na região cervical em participantes Classe I e Classe II/2.ª Divisão, considerando a média e a simetria do Root Means Square (RMS) dos músculos supra-hióideos e suboccipitais, e relatos sensoriais cervicais. Método: Onze participantes Classe I e 19 Classe II/2.ª Divisão, ambos os gêneros, média de idade 33,4 ±14,1 anos. Para análise da média do RMS e da simetria, realizou-se eletromiografia dos músculos suboccipitais e supra-hióideos, bilateralmente, no repouso e na sucção de água nas fases inicial, intermediária e final. A sensação cervical foi avaliada qualitativamente durante os exercícios. Resultados: A média do RMS não apresentou diferença entre Classes (p=0,7), mas revelou, na fase intermediária, elevação na musculatura suboccipital (p=0,0001) e diminuição na musculatura supra-hióidea. Na simetria, a musculatura supra-hióidea mostrou diferença significativa entre classes (p=0,0001) durante a fase intermediária. No participante Classe I, foi restabelecida a simetria na fase final, fato que não ocorreu na Classe II/2.ª Divisão. Em relação à sensação cervical, somente os Classe II/2.ª Divisão apresentaram queixas expressivas. Conclusão: O exercício isocinético de sucção da língua contra o palato repercutiu de forma expressiva com relatos de desconforto e dor cervical nos participantes Classe II/2.ª Divisão. Na média do RMS, não houve diferença entre as classes, mas, na fase intermediária, a musculatura suboccipital apresentou elevação de atividade significativa. A simetria na musculatura supra-hióidea teve diferença significativa entre as classes e assimetria na fase intermediária.

ABSTRACT Purpose: To compare the impact of isokinetic exercise (tongue suction on the palate) in the cervical region of Class I and Class II / 2nd Division participants, considering the average and the symmetry of Root Means Square (RMS) of suprahyoid and suboccipital muscles and cervical sensory reports. Method: 11 participants Class I and 19 Class II / 2nd Division, both genders, mean age 33.4 ± 14.1 years. For the analysis of RMS average and symmetry, electromyography was performed in the suboccipital and suprahyoid muscles, bilaterally, at rest and suction of water in the initial, intermediate and final phases. The cervical sensation was evaluated qualitatively during the exercises. Results: the mean RMS did not differ between Classes (p=0.7), but showed an increase in the intermediate phase in the suboccipital musculature (p=0.0001) and decrease in the suprahyoid musculature. In symmetry, the suprahyoid musculature showed a significant difference between classes (p=0.0001) during the intermediate phase. In the Class I participant the symmetry was reestablished in the final phase, a fact that did not occur in Class II / 2nd Division. Regarding the cervical sensation, only the Class II / 2nd Division had expressive complaints. Conclusion: The Isokinetic suctioning exercise of the tongue against the palate, had an expressive repercussion with reports of discomfort and neck pain in the Class II / 2nd Division participants. On average RMS, there was no difference between the classes, but in the intermediate phase, the suboccipital muscles showed a significant increase in the activity. Symmetry in the suprahyoid musculature had a significant difference between the classes and asymmetry in the intermediate phase.

Splenius capitis: sensitive target for the cVEMP in older and neurodegenerative patients.

BACKGROUND: The vestibular evoked myogenic potential (VEMP) is a technique used to assess vestibular function. Cervical VEMPs (cVEMPs) are obtained conventionally from the sternocleidomastoid (SCM) muscle; however, the dorsal neck muscle splenius capitis (SPL) has also been shown to be a reliable target alongside the SCM in young subjects. OBJECTIVE: This study aimed to compare cVEMPs from the SCM and SPL in two positions across young, older, and Parkinson's disease (PD) patients. METHOD: Experiments were carried out using surface EMG electrodes placed over the SCM and SPL. cVEMPs were measured using a 30 s, 126 dB sound stimulus with 222 individual tone bursts, while subjects were in a supine and head-turned posture (also known as the head elevation method), and in a seated head-turned posture. RESULTS: When comparing cVEMPs across positions, the incidence of supine and seated SCM-cVEMPs diminished significantly in older and PD patients in comparison with young subjects. However, no statistically significant differences in incidences were found in seated SPL-cVEMPs when comparing young, older and PD patients. SPL-cVEMPs were present significantly more often than seated SCM-cVEMPs in PD patients. CONCLUSIONS: SPL-cVEMPs are not altered to the same extent that SCM-cVEMPs are by aging and disease and its addition to cVEMP testing may reduce false-positive tests for vestibulopathy.

[Preliminary observation of galvanic vestibular stimulation-vestibular evoked myogenic potentials in healthy young people].

Objective: To introduce the method of galvanic vestibular stimulation-vestibular evoked myogenic potentials (GVS-VEMP) as well as to observe and analyze the parameters and elicited rate of GVS-cVEMP and GVS-oVEMP in healthy young people in China. Methods: Twenty six normal young subjects were recruited for conventional examinations of GVS-VEMP. The subjects were 21-37 years old, average age was (25.8±3.7) years old, including 13 males and 13 females. The galvanic stimulation intensity of 3 mA/1 ms was used to evoke cVEMP and oVEMP on the sternocleidomastoid and inferior extraocular muscles respectively, and the intensity of stimulus was decreased until the response disappeared, the threshold, latency, amplitude, interval phase and interaural amplitude ratio(IAR) were calculated. SPSS18.0 software was used for statistical analysis. Results: All subjects were elicited normal GVS-cVEMP and GVS-oVEMP under 3 mA/1 ms, the elicited rate was 100%. The threshold of GVS-cVEMP was (1.18±0.47) mA, p1 latency was (10.43±1.54) ms, n1 latency was (17.91±1.20) ms, the amplitude was (102.47±56.77) uV and IAR was (0.26±0.20). The threshold of GVS-oVEMP was (1.12±0.50) mA, n1 latency was (8.46±1.05) ms, p1 latency was (11.83±1.27) ms, the amplitude was (9.12±6.82) uV and IAR was (0.25±0.20). In terms of gender and lateral comparison, only the GVS-oVEMP amplitude was higher for male than for female, which had significant statistical difference (P<0.05), and there was no statistical difference in the other parameters between GVS-cVEMP and GVS-oVEMP. Conclusion: GVS-cVEMP and GVS-oVEMP could be elicited in healthy youth population, and the parameters could provide reference for subsequent vestibular function evaluation.

Novel Classifications for Muscular Contraction of the Lower Face and Neck.

BACKGROUND: Currently, there are no scales that address lower-face muscular contraction patterns, and there is only one that addresses platysmal bands. OBJECTIVE: The goal of this article is to create scales to classify the strength and contraction patterns of the lower face and neck based on (1) the muscular anatomy and contraction patterns of the platysma and (2) the strength of the depressor anguli oris (DAO). METHODS: Three hundred sixty patients participated in the study. Standardized photogarphs were taken in an effort to characterize muscle contraction patterns. RESULTS: A novel classification measuring the strength of the DAO is presented. For the DAO, 4 different contraction patterns were observed: Type 1 (38%), Type 0 (26.3%), Type 2 (25.2%), and Type 3 (8.6%). The remainder (1.9%) used asymmetric contraction. For platysmal bands, 3 different contraction patterns were observed: complete contraction (64.53%), lateral contraction (19.83%), and central contraction pattern (11.73%). A small percentage of patients (3.91%) had an asymmetric contraction pattern. CONCLUSION: Categorization of contraction of the DAO and platysmal bands into these proposed classifications provides objective measurements that can be helpful for designing treatment protocols and assessing response to treatment.

Effectiveness of the muscle energy technique on respiratory muscle strength and endurance in patients with fibromyalgia.

BACKGROUND: Fibromyalgia is characterized by a chronic and common musculoskeletal system pain that affects cervical mobility and inspiration. This may cause changes in thoracic mechanics. OBJECTIVE: To investigate the effectiveness of the muscle energy technique applied to cervical accessory respiratory muscles on respiratory muscle strength and endurance in patients with fibromyalgia. METHODS: The participants were 37 women diagnosed with fibromyalgia. They were assessed for their respiratory muscle strength, respiratory muscle endurance, pain and fatigue severity, flexibility and disability. The muscle energy technique was applied to the scalene, upper trapezius, and sternocleidomastoid muscles after a superficial heat application. The treatment was continued for 3 weeks with 3 sessions per week. RESULTS: After the treatment, expiratory muscle strength and respiratory muscle endurance increased significantly. Severity of pain and fatigue and disability were reduced, cervical flexibility increased significantly (p< 0.05). The effect size was r⩾ 0.4 for all the variables. CONCLUSION: The muscle energy technique applied to cervical accessory respiratory muscles in patients with fibromyalgia who had complaints in the neck and back region positively increased respiratory muscle strength and endurance, cervical flexibility, and decrease pain intensity, fatigue and disability. It is recommended that subsequent randomized studies are carried out with a placebo control group.

Muscle-Preserving Selective Laminectomy Maintained the Compensatory Mechanism of Cervical Lordosis After Surgery.

STUDY DESIGN: A retrospective single-center study. OBJECTIVE: The aim of this study was to evaluate the compensatory mechanism of cervical lordosis (CL), the changes in cervical sagittal alignment, and range of motion (ROM) after muscle-preserving selective laminectomy (SL). SUMMARY OF BACKGROUND DATA: CL increases as a compensatory mechanism for the adjustment of cervical sagittal balance or horizontal gaze. However, laminoplasty invades this mechanism and causes kyphosis in higher T1 (C7) slope patients. METHODS: SL is a posterior surgery selecting the decompression laminae without disturbing the extensor musculature and facet joints. The clinical features and radiological findings of 125 cervical compressive myelopathy patients who underwent C6 single-level SL, C5-C6 two consecutive levels SL, C4-C6 three consecutive levels SL, and C3-C6 four consecutive levels SL were enrolled. Cervical spine lateral radiography was performed before surgery and at the final follow-up. The patients were divided into two groups according to the preoperative C7 slope. Postoperative cervical alignment change was compared between the higher and lower C7 slope groups. Subsequently, pre- and postoperative cervical alignment and cervical ROM were analyzed according to the number of consecutive laminae surgically treated. RESULTS: Patients with higher C7 slope had greater lordotic cervical alignment and larger C2-C7 sagittal vertical axis (SVA) pre- and postoperatively. No kyphotic alignment change was observed, even in the higher C7 slope group. C6 SL and C5-C6 SL did not affect C2-C7 angle, and did not increase C2-C7 SVA after surgery. Although C4-C6 SL and C3-C6 SL demonstrated postoperative slight increase in C2-C7 SVA, C2-C7 angle never decreased after surgery. Cervical ROM slightly reduced in the C4-C6 SL and C3-C6 SL groups; however, no reduction of ROM was observed in the C6 SL and C5-C6 SL groups. CONCLUSION: SL preserved the inherent compensatory CL that had been observed preoperatively and maintained cervical sagittal balance after surgery. LEVEL OF EVIDENCE: 4.

Effect of practicing yoga on cervical vestibular evoked myogenic potential.

The present study attempted to determine the effect of practicing yoga on functioning of sacculo-collic pathway using cervical vestibular evoked myogenic potential (cVEMP). cVEMP was recorded from 40 participants (20 who practice yoga regularly and 20 who do not practice yoga regularly). The differences in amplitude of P1, N1, P1-N1 complex, asymmetry ratio and latencies of P1 and N1 of cVEMP were compared between both the groups. The results of the study showed that there was a significant increase (p < 0.05) in the amplitude of P1, N1 and P1-N1 complex and a significant reduction in latency (p < 0.05) for experimental group. The asymmetry ratio in individuals who practice yoga was significantly lower (Mean = 6.73) compared to the control group (Mean = 19.13). Multivariate regression analyses suggested that the number of years of yoga practice significantly predicted the amplitude of P1-N1 complex (ß = 0.70, p < 0.01) and amplitude ratio (ß = 0.72, p < 0.01). Thus, practicing yoga improves postural control and strengthens the muscles and vestibular system leading to enhanced cVEMP responses. The plastic changes in the vestibular system and increased muscular strength because of constant practicing of yoga could have led to changes in cVEMP responses. However, further studies on a larger group of individuals are essential for better clinical applicability of the results.

Shear wave elastography parameters of normal soft tissues of the neck.

BACKGROUND: Shear wave elastography is a relatively new method of quantitative measurement of tissue elasticity. Assuming that malignant lesions are stiffer than benign ones, elastography may provide supplementary information for their discrimination. However, potential confounding factors impacting tissue stiffness should be investigated first. AIMS: The objective of this study was to measure the stiffness of selected tissues of the head and neck in a normal population and to evaluate its relationship to age, sex, and body mass index. METHODS: Stiffness of the thyroid, submandibular and parotid glands, masseter and sternocleidomastoid muscles, and cervical lymph nodes was measured bilaterally in 128 healthy volunteers (83 female and 45 male). At least 20 subjects in each decade of life (20-29, 30-39‥, 70+) were enrolled. Shear wave elastography was performed by a single radiologist in all the subjects. The stiffnesses obtained were correlated with age, sex, and body mass index. RESULTS: The mean stiffness was 9.5 ± 3.6 kPa for the thyroid, 9.5 ± 4.6 kPa for the lymph node, 11.0 ± 3.4 kPa for the submandibular gland, 9.0 ± 3.5 kPa for the parotid gland, 9.9 ± 4.1 kPa for the sternocleidomastoid, and 10.0 ± 4.3 kPa for the masseter muscle. A slight general decrease in stiffness with increasing age was found. BMI and weight had a small impact on the minimum and maximum stiffness values. The sex of the subject did not affect elasticity. CONCLUSION: The mean stiffness of healthy head and neck organs has a relatively narrow distribution around 11 kPa. The changes of stiffness with age, BMI, and weight that were identified are too small to have clinical impact.

Functional anatomy of the accessory nerve studied through intraoperative electrophysiological mapping.

OBJECTIVE Classically the 11th cranial nerve (CN XI, or accessory nerve) is described as having a cranial and a spinal root, the latter arising from the upper segments of the spinal cord through a number of very fine rootlets. According to classical knowledge, the cranial root gives motor innervation to the vocal cords, whereas the spinal root provides the motor innervation of the sternocleidomastoid muscle (SCM) and of the upper portions of the trapezius muscle (TZ). The specific function of each of the rootlets of the spinal component is not well known. Therefore the authors aimed to map, using intraoperative direct electrical stimulation and electromyographic (EMG) recordings, the innervation territory of these rootlets in relation to their exit level from the CNS. METHODS Forty-nine patients undergoing surgery with intradural exposure at the craniocervical junction were enrolled in the study. The EMG recordings included the sternal and clavicular parts of the SCM (SCM-S and SCM-C), the superior and middle parts of the TZ (TZ-S and TZ-M), and whenever possible the vocal cords. The main trunk of CN XI, its roots (both cranial and spinal), and when possible the fine cervical rootlets, were stimulated at predetermined locations, from the jugular foramen down to the lowest cervical level exposed. The EMG responses were collected, and a map of the responses was drawn up. RESULTS Monitoring and stimulation of the spinal root were performed in all cases, whereas for the cranial root this was possible in only 19 cases. A total of 262 stimulation sites were explored: 70 at the common trunk of the nerve, 19 at the cranial root, 136 at various levels on the spinal root, and 37 at the cervical rootlets. A vocal cord response was obtained by stimulation of the cranial root in 84.2% (16/19); absence of response was considered to have a technical origin. In no case did the vocal cords respond to the stimulation of the spinal root or rootlets. Stimulation of the cervical rootlets yielded responses that differed according to the level of stimulation: at C-1 the SCM-S responded 95.8% of the time (23/24); at C-2 the SCM-C responded 90.0% of the time (9/10); at C-3 the TZ-S responded 66.6% of the time (2/3); and below that level only the TZ-M responded. The spinal root stimulated at its various levels responded accordingly. CONCLUSIONS The function of each of the rootlets of CN XI appears to be specific. The cranial root contributes, independently of the spinal root, to the innervation of the vocal cords, which makes it a specific entity. The spinal root innervates the SCM and TZ with a cranio-caudal motor organization of its cervical rootlets.

Effects of 2 Resistive Exercises on Electrophysiological Measures of Submandibular Muscle Activity.

OBJECTIVE: To compare the electrophysiological activity in submandibular hyolaryngeal muscles during performance of 2 exercises that incorporate resistance against muscular contraction. DESIGN: Within-subject repeated-measures design. SETTING: Academic research laboratory. PARTICIPANTS: Healthy, young adult women (N=26; mean age, 24.1y) without a history of dysphagia, cervical spine conditions, neurologic disease, or head/neck cancer. INTERVENTIONS: Participants performed 2 isometric exercises requiring contraction against resistance to the submandibular hyolaryngeal muscles: one requiring jaw opening against a semirigid brace (chin-to-chest [CtC] exercise) and one requiring a chin tuck against an air-inflated rubber ball (chin tuck against resistance [CTAR] exercise). Measures of electrophysiology using surface electromyography (sEMG) were obtained during exercise performance. MAIN OUTCOME MEASURES: Microvolts as measured from sEMG electrode sensors placed on the skin surface above the hyolaryngeal muscles (surface of skin above geniohyoid, mylohyoid, and anterior digastric). Dependent variables included peak contraction amplitude (in µV) and mean contraction amplitude (in µV) across 10 seconds of sustained contraction. RESULTS: Significant effects of exercise on peak and mean contraction amplitudes were present when both exercises were compared with baseline sEMG activity. (P<.001 for both). Normalized values of peak contraction amplitude and mean contraction amplitude during performance of CtC were not significantly different compared with CTAR. CONCLUSIONS: This study provides supporting evidence for the influence of 2 published exercises on motor unit recruitment in the submandibular hyolaryngeal muscles, both of which have been previously proposed as rehabilitative modalities. Theoretical and clinical implications are discussed.

Dura-evoked neck muscle activity involves purinergic and N-methyl-D-aspartate receptor mechanisms.

We have previously demonstrated that noxious stimulation of craniofacial tissues including the frontal dura reflexly evokes significant increases in neck muscle electromyographic (EMG) activity. The primary aim of this study was to determine whether purinergic receptor mechanisms may be involved in these EMG effects, and whether N-methyl-D-aspartate (NMDA) receptor processes modulate the purinergic mechanisms. Application of the P2X1, P2X3 and P2X2/3 receptor agonist α,ß-methylene ATP (but not vehicle) to the dural surface evoked a significant (P<0.05) increase in ipsilateral neck EMG activity that could be suppressed by dural or intrathecal application of the selective P2X1, P2X3 and P2X2/3 receptor antagonist 2',3'-O-(2,4,6-trinitrophenyl) ATP (TNP-ATP) but not by vehicle; the intrathecal application of 2-amino-5-phosphonopentanoic acid, an NMDA receptor antagonist, also significantly reduced the neck EMG activity evoked by dural application of α,ß-methylene ATP. These data suggest that purinergic receptor mechanisms contribute to the increased neck activity that can be reflexly evoked by noxious stimulation of the frontal dura, and that NMDA as well as purinergic receptor mechanisms in the medulla may modulate these purinergic-related effects.

Cervical vestibular evoked myogenic potentials in children / Potencial evocado miogênico vestibular cervical em crianças

INTRODUCTION: Cervical vestibular evoked myogenic potential is a test used in neurotological examination. It verifies the integrity of vestibular function through a muscular response evoked by an acoustic stimulation which activates the saccular macula. Normal standards in adults have been established, however, there are few published data on the normal responses in children.OBJECTIVE: To establish normal standards for vestibular myogenic responses in children without neurotological complaints.METHODS: This study's design is a cohort with cross-sectional analysis. The sample consisted of 30 subjects, 15 females (50%) and 15 males (50%).RESULTS: The age of the subjects ranged between 8 and 13 years, with a mean of 10.2 (± 1.7). P1 peak showed an average latency of 17.26 (± 1.78) ms and a mean amplitude of 49.34 (± 23.07) µV, and the N2 peak showed an average latency of 24.78 (± 2.18) ms and mean amplitude of 66.23 (± 36.18) µV. P1-N2 mean amplitude was 115.6 (± 55.7) µV. There were no statistically significant differences when comparing by gender or by laterality.CONCLUSION: We established normal values of cervical myogenic vestibular responses in children between 8 and 13 years without neurotological complaints.

INTRODUÇÃO: O potencial evocado miogênico vestibular cervical (cVEMP) vem sendo empregado como exame complementar em estudos otoneurológicos. Avalia a função vestibular através da resposta muscular originada a partir de uma estimulação acústica que ativa a mácula sacular. O exame foi padronizado em adultos, entretanto, há escassez de dados publicados sobre as respostas obtidas em crianças.OBJETIVO: Estabelecer valores de normalidade das respostas miogênicas vestibulares em crianças sem queixas otoneurológicas.MÉTODO: Estudo de coorte histórica com corte transversal, de 30 sujeitos sem queixas otoneurológicas, 8 a 13 anos.RESULTADOS: A amostra foi composta de 15 meninos e 15 meninas, com idade média de 10,2 (± 1,7 anos). A curva P1 apresentou uma latência média de 17,26 ms (± 1,78) e uma amplitude média −49,34 µV(± 23,07), enquanto a curva N2 apresentou uma latência média de 24,78 ms (±2,18) e uma amplitude média de 66,23 µV (± 36,18). A amplitude P1−N2 foi 115,6 µV (± 55,7). O índice de assimetria foi de 21,3% (± 18,6). Não foram encontradas diferenças estatisticamente significativas quando comparados os sexos. Da mesma forma, não se observou efeito significativo da lateralidade nos resultados.CONCLUSÃO: Foram estabelecidos os valores de normalidade das respostas miogênicas vestibulares cervicais em crianças entre 8 e 13 anos sem queixas otoneurológicas.

The effect of pillow height on muscle activity of the neck and mid-upper back and patient perception of comfort.

OBJECTIVE: The purpose of this study was to evaluate the comfort and the electromyographic (EMG) activity of the neck and mid-upper back of asymptomatic adults using foam pillows of 3 different heights. METHODS: Twenty-one asymptomatic adults used foam pillows of 3 different heights (1: 5 cm, 2: 10 cm, and 3: 14 cm). Comfort was assessed using a 100-mm visual analog scale. Electromyographic activity was assessed in the lateral position. We calculated the root mean square (RMS) in 500-millisecond windows of bilateral EMG activity of the sternocleidomastoid and upper and middle trapezius, normalized by maximal isometric contraction of each individual. The RMS of the EMG signals was compared among pillow heights using repeated-measures analysis of variance (P < .05). RESULTS: The middle trapezius muscle of the down-side showed the highest RMS in height 1 when compared with heights 2 (P = .0163) and 3 (P = .0313), with no statistical significance between pillow heights 2 and 3 for this muscle. There were no statistical differences between pillows 2 and 3 in any muscle activity. Height 2 was considered the most comfortable (P < .001) compared with heights 1 and 3, and height 1 the least comfortable (P < .001) compared with the other heights. CONCLUSION: For the participants in this study, there was an association among pillow height, myoelectric activity, and comfort.