Anterior Belly Research Articles

Difference in the Electromyographic Behavior of the Masticatory and Swallowing Muscles During Cued Versus Spontaneous Swallowing

The risk of dysphagia and/or aspiration is determined using screening tests, such as the repeated saliva swallowing test and modified water swallowing test, which evaluate cued swallowing. However, humans masticate and swallow foods with various consistencies, forms, and amounts, without conscious awareness. Therefore, this study aimed to examine the difference in the behavior of masticatory and swallowing muscles during spontaneous versus cued swallowing through a series of mastication and swallowing processes by evaluating surface electromyogram (sEMG) signals. The effect of the consistency and amount of food on the behavior of these muscles was also investigated. The sEMG recordings of the masseter muscles and anterior belly of the digastric muscle for 12 subjects, and genioglossus muscle for 5 subjects were obtained. The genioglossus activity was recorded using custom-made ball electrodes. The test foods were cookies and tofu, in amounts of 2 g and 4 g. The normalized muscle activity (integrated EMG), duration of the muscle activity, initial activation timepoint of each muscle, and total duration of swallowing were compared among four conditions. The activity of each muscle was significantly higher during the swallowing of cookies than tofu, for 4 g vs 2 g, and for cued versus spontaneous swallowing. The duration of each muscle activity, initial activation timepoint, and total duration of swallowing were significantly longer for cookies versus tofu, for 4 g vs 2 g, and for spontaneous versus cued swallowing. These results suggest that the behavior of the masticatory and swallowing muscles is affected by cued swallowing and by the consistency and amount of food.

Morphological study of the anatomical variations of anterior belly of digastric muscle in Brazilian cadavers.

Cases of variations in anterior belly of the digastric muscle must be carefully identified to avoid misinterpretations and assist in the correct surgical or aesthetic procedure and help in the teaching of anatomy. The aim of this study was to describe the anatomical variations of anterior belly of digastric muscle in Brazilian cadavers. Thirty-one human heads were selected, from adult cadavers (18-80 years, 29 males and 2 females). The morphology of the anterior belly of the digastric muscle was observed, identifying the possible anatomical variations that were characterised and classified according to the amount of muscle bellies, fibre direction and place of origin and insertion. The morphometric measurements were performed using a digital calliper. To analyse the data obtained, photographic documentation, anatomical description and individual morphometric description of each muscle belly were performed. The incidence of anatomical variation was obtained in percentage (%). The anatomical variation of the anterior belly of the digastric muscle was present in 6 cadavers (19.31%; 1 female and 5 male). All anatomical variations presented an accessory belly to the anterior belly. However, these accessory bellies were configured differently in the location, direction of muscle fibres and in their dimensions (length and width). The gross anatomy of the anterior belly of the digastric muscle and their variations is important to assist in surgical procedures, pathological or diagnostic function. In addition, asymmetrical variations in the submental region must be carefully identified to avoid misinterpretations.

Variations and thicknesses of anterior belly of the digastric muscle: an ultrasonographic study.

This study aims to evaluate the anatomy and anatomical variations of the anterior belly of the digastric muscle. Hundred and fifty one ultrasonographic images of the digastric muscle pairs were evaluated in Near East University Faculty of Dentistry Department of Dentomaxillofacial Radiology. Morphological variations were recorded using the classification of the digastric muscle into 12 types by Kim et al. For the analysis, the Mann-Whitney U test and Chi-square test were used, and for the correlational analysis, Spearman's rho test was applied. P < 0.05 was considered statistically significant in all tests. Seventy female and 81 male patients aged 19-60years were evaluated. Type 1 digastric muscle was observed in 145 of 151 patients, Type 2 in 3 patients, and Type 7 in 3 patients. The thicknesses of the right and left digastric muscles were measured, and a statistically significant difference was observed between the groups when the genders were compared. It was observed that both right and left digastric muscle thicknesses were higher in males than females. There was a statistically significant positive high correlation between right and left digastric muscle thicknesses (p = 0.000; r = 0.736). No statistically significant difference was found between genders (p = 0.596) in terms of anatomical variations. Considering that the variations of the digastric muscle may have a clinical significance role, the normal anatomy and variations of this muscle should be well known by maxillofacial surgeons and radiologists.

P.099 A novel electrophysiologic reflex in neurovascular compression syndromes serving as a marker of pain resolution

Background: Radiofrequency rhizotomy is a commonly used percutaneous technique for treatment of trigeminal neuralgia especially in cases not eligible for microvascular decompression. This technique is usually performed with the patient under conscious sedation. We devised a method for performance of this technique under general anesthetic with neurophysiology monitoring. Methods: The patient is put under general anaesthetic and EMG monitoring is set up. Needles are placed in temporalis muscle, masseter and mylohyoid or anterior belly of digastric. Resting activityis monitored. Rhizotomy is then performed under fluoroscopic guidance, with monitoring of EMG potentials pre- and post-lesioning, with specific attention paid to presence of an abnormal electrophysiologic reflex. Results: A total of 38 procedures were performed in 23 patients. Of these, 15 were revision procedures. Patients had improvement from BNI pain scale 3.8 ±0.8 to 1.3 ±1.5, and had a reduction in number of medications from 1.9 ±1.0 to 0.8 ±0.9. Survey results indicate greater practitioner satisfaction with this technique. Conclusions: Radiofrequency rhizotomy can be performed under GA with IONM guidance with good results. We present a novel method for EMG-based monitoring. Further study is required to validate this technique.

Deep Neck Contouring with a Focus on Submandibular Gland Vascularity: A Cadaver Study.

Opening the neck through submental incision allows accurate management of deep neck structures and obtain exceptional neck contours. The authors aimed to evaluate the distribution of deep neck structures and investigate the detailed vascular anatomy of the submandibular gland. A total of 26 fresh frozen cadaver heads (15 female, 11 male) were used. The authors evaluated the weights of the excised tissues simulating cosmetic resections including subcutaneous fat, subplatysmal fat, anterior belly of digastric muscle and submandibular glands. The vascular supply of the submandibular gland and intracapsular vessel diameters were also investigated. While female cadavers had greater mean tissue weight removed from the supraplatysmal plane (mean 20.9 g, 56.6%) than subplatysmal plane (16 g, 43.4%), male cadavers had higher mean tissue weight removed from subplatysmal plane (10.5 g, 60.7%) than supraplatysmal plane (mean 6.8 g, 39.3%). The mean subcutaneous (6.8 g) and subplatysmal (6.4 g) fat weights were almost equal in male cadavers, mean subcutaneous fat weight (20.9g) was 3 times higher than subplatysmal fat weight (6.8 g) in female cadavers. There was a statistically significant relationship between body mass index and fat removed. The intraglanduler vessel diameters increased as resections approached the main feeding vessels located posterosuperior (facial artery) and anterosuperior (submental artery) of the submandibular gland. The results suggest that in order to achieve exceptional neck contour, the structures deep to platysma often need to be addressed. The submandibular gland reduction can be safely performed with comprehensive understanding of its vascular anatomy.

Visual evaluation for the elasticity of suprahyoid muscles using sonographic elastography during tongue pressure measurement: A pilot study.

Suprahyoid muscles behavior during the tongue lifting movement has not yet been elucidated. The purpose of this study was to investigate the potential of elastography imaging to examine developmental oral dysfunction in children and oral hypofunction in older adults using sonography. Tongue pressure was measured using a manometer with a probe. The tongue pressure was measured with simultaneously scanning the geniohyoid muscle (GHM) and the anterior belly of the digastric muscle (DGM) using sonographic elastography. Sagittal images of the GHM and coronal images of the DGM were used for the strain ratio measurement. The strain ratio of the muscles was measured three times for each subject with the tongue pressure values of 0-30kPa. The strain ratio of the GHM were higher than those of the DGM at tongue pressure of 10, 20 and 30kPa. The strain ratio of the GHM increased as the tongue pressure increased in all participants. In contrast, the strain ratio of the DGM tended to slowly decrease as tongue pressure increased in female participants. Sonographic elastography is useful for visual and quantitative evaluation of elastic properties in suprahyoid muscles during tongue lifting movements.

Submental island flap - should we be worried about lymph node transfer? An anatomical and histological study

The submental island flap has been increasing in popularity for both oncological and non-oncological reconstruction of the head and neck. However, the original description of this flap left it with the unfortunate designation as a lymph node flap. There has thus been significant debate on the oncological safety of the flap. In this cadaveric study the perforator system suppling the skin island is delineated and the lymph node yield of the skeletonised flap is analysed histologically. A safe and consistent approach to raising the perforator flap modification is described and the pertinent anatomy, and an oncological discussion with regards to the submental island perforator flap histological lymph node yield discussed. Ethical approval was received from Hull York Medical School for the anatomical dissection of 15 sides of cadavers. 6 x 4cm submental island flaps were raised following a vascular infusion of a 50/50 mix of acrylic paint. The flap size mimics the T1/T2 tumour defects these flaps would usually be used to reconstruct.The submental vascular anatomy, including length, diameter, venous drainage patterns, and the skin perforator system was documented. The dissected submental flaps were then histologically examined for the presence of lymph nodes by a head and neck pathologist at Hull University Hospitals Trust department of histology. The total length of the submental island arterial system, the distance from where the facial artery branches off from the carotid to the submental artery perforator entering the anterior belly of digastric or skin, averaged 91.1mm with anaverage facial artery length of 33.1mm and submental artery of 58mm. Vessel diameter for microvascular reconstruction was 1.63mm for the submental artery and 3mm for the facial artery. The most common venous anatomy drainage pattern was the submental island venaecomitantes draining to the retromandibular system then to the internal jugular vein. Almost half the specimens had a dominant superficial submental perforator allowing the ability to raise this as a skin only system. There were generally 2-4 perforators passing through the anterior belly of digastric to supply the skin paddle.73.3% (11/15) of the skeletonised flaps contained no lymph nodes on histological examination. The perforator version of the submental island flap can be safely and consistently raised with inclusion of the anterior belly of digastric. In approximately half the cases a dominant superficial branch allows for a skin only paddle. Due to the vessel diameter, free tissue transfer is predictable.Venous anatomy is variable and care needs to be taken when raising this flap. The skeletonised version of the perforator flap is largely devoid of nodal yield and on oncological review a 16.3% recurrence rate is equivalent to current standard treatment.

Surface Electromyographic Analysis of Masticatory and Neck Muscles in Skeletal Class II Division 1 Malocclusion with EMG Indices - A In Vivo Study

Background amp Objectives To evaluate the activity of oro-facial and neck muscles in skeletal class II division 1 malocclusion with horizontal and vertical growth patterns using surface electromyography.Methods Twenty non-growing patients comprising males and females 18-30 years were selected and grouped into horizontal and vertical growth patterns using lateral cephalograms. sEMG of masseter temporalis sternocleidomastoid and anterior belly of digastric muscles were performed and percentage overlapping coefficient activity Index asymmetry Index and torque Index were recorded.Results The percentage overlapping coefficient was recorded as 112.3 in horizontal and 92.35 in vertical growers. The activity index for horizontal growers was 14.28 microVsec indicating a predominance of the masseter muscle and in vertical growers it was -8.94 microVsec indicating a predominance of anterior temporalis. The asymmetry index for horizontal growers observed was 17.75 microVsec indicating the predominance of rightside muscles and was -10.77 microVsec showing the dominance of left-side muscles in vertical growers. Torque index in horizontal and vertical growth patterns were 24.56 and -43.76 respectively inferring a right-sided mandibular movement in horizontal growers and vice versa. The mean value of sternocleidomastoid muscle observed was 18.74 microVsec in horizontal growers and 14.15 microVsec in vertical growers. The mean values of the anterior belly of digastric muscles were 18.87 microVsec in horizontal growth pattern and 19.57 microVsec in vertical growers.Conclusion There was symmetry between muscles and an increased predominance of the masseter group in horizontal growers while an increased predominance of the temporalis muscle was observed in vertical growers. There was increased activity of right-sided muscles and right-sided mandibular movement in horizontal growers while an increased activity of left-sided muscles and left-sided mandibular movements was noted in vertical growers.

Application of Real-time Submental Ultrasonography to Assess Swallowing.

Speech and swallowing dysfunction are common problems in head-and-neck cancer (HNC) survivors. Ultrasound (US) is a good method to assess suprahyoid muscles and hyoid bone movement, and it can provide valuable information on swallowing. The aims of this study were to measure the biometry of the supraglottic muscles and hyoid bone movement during swallowing and elucidate the application of real-time US for assessing swallowing dysfunction. We collected data from HNC and thyroid cancer patients with dysphagia symptoms and healthy controls without a history of cancer or dysphagia symptoms for comparison. Real-time submental US was used to check the anterior belly of the digastric muscle, geniohyoid (GH) muscles, and hyoid bone movement during swallowing. Logistic regression analysis was used to explore significant US predictors of dysphagia. Based on the regression coefficients of independent variables, we established the nomogram prediction model for dysphagia. There were significant differences in GH size at contraction, GH size increase percentage, GH length at rest, GH length increase percentage, anterior displacement of the hyoid bone and superior displacement of the hyoid bone between the cancer survivors with dysphagia and volunteers without dysphagia. In multivariate logistic analysis, after adjusting for sex and age, the proportion of GH length contraction <22% (odds ratio [OR]: 6.8 95% confidence interval [CI]: 1.1-42.6) and hyoid bone superior displacement <3.3 mm (OR: 10.7, 1.8-64.1) were associated with a higher risk of dysphagia (P < 0.05). We confirmed that GH muscle and hyoid bone movement are important for normal swallowing function. US is a good method to assess the suprahyoid muscles and hyoid bone movement, which could provide valuable information on swallowing.

Repair of postoperative defects of oral cancer with submental island flaps based on vascular pedicles of different states: a multicenter retrospective study

Submental island flap has certain advantages in repairing postoperative defects of oral cancer, and it can often achieve similar or even better effects compared with those of the free tissue flap. In this study, according to the different characteristics of patients and postoperative defects of oral cancer, submental island flaps with different states of vascular pedicle were prepared, and its repair methods, safety, and clinical effects in treating postoperative defects of oral cancer were investigated. 83 patients with oral cancer who met the inclusion criteria were selected. According to the different characteristics of the patients and postoperative defects of oral cancer, the traditional submental island flap vascular pedicle was modified into three different states: submental artery perforator flap, vascular pedicled flap with the anterior belly of digastric muscle but without the submandibular gland (SIF with anterior belly of DM), and vascular pedicled flap with the anterior belly of the digastric muscle and the submandibular gland (SIF with anterior belly of DM and SG). The types of the submental artery and the drainage vein, flap survival, and complications, were observed. The flap was successfully harvested for all patients, and the submental artery could be found or separated for all of them, with the venous drainage to the internal jugular vein in 57 (57/83, 68.67%), to the external jugular vein in 18 (18/83, 21.69%), and to the anterior jugular vein in eight (8/83, 9.64%) cases. Submental artery perforator flap was used for 11 cases, complete necrosis occurred in two cases (2/11, 18.18%), partial necrosis occurred in one case (1/11, 9.09%); SIF with anterior belly of DM was used for 49 cases, complete necrosis occurred in one case (1/49, 2.04%), partial necrosis occurred in four cases (4/49, 8.16%); SIF with anterior belly of DM and SG was used for 23 cases, including chimeric flap combining the submental island flap and the submandibular gland used for 15 cases, there were no cases of complete or partial necrosis. Submental island flap was effective in repairing postoperative defects of oral cancer. Submental island flaps with three different states of vascular pedicle could repair oral cancer-affected tissues with different defect characteristics.

The Difference in Electromyographic Activity While Wearing a Medical Mask in Women with and without Temporomandibular Disorders

Wearing a medical mask influences resting activity of the temporalis anterior and masseter muscles in healthy young women. However, no studies link medical mask-wearing with masticatory muscle activity in patients with temporomandibular disorders (TMDs). Therefore, this study aims to compare electromyographic patterns while wearing a medical mask between women with and without temporomandibular disorders. Based on the Research Diagnostic Criteria for Temporomandibular Disorders, 115 adult women qualified for the study. Participants were divided into the following two groups: diagnosed TMDs (n = 55; mean age: 23.5 ± 2.3 years) and healthy women (n = 60; mean age: 23.7 ± 2.6 years). Examinations of the resting and functional electromyographic activity of the temporalis anterior (TA), superficial masseter (MM), anterior bellies of the digastric muscle (DA), and the middle part of the sternocleidomastoid muscle (SCM) were carried out using the BioEMG III™. Both groups showed statistically significant decreases in resting masticatory muscle activity during medical mask examination compared to no mask measurement. The significant differences in no mask measurement between both groups were noted regarding resting masticatory activity, clenching in the intercuspal position, and clenching on dental cotton rollers. During medical mask examination, women with TMDs showed differences in resting masticatory activity and clenching on dental cotton rollers compared to the healthy group. In all analyzed variables, both groups showed similar electromyographic patterns in the maximum mouth opening measurement during medical mask and no mask examination. A medical mask influences the resting bioelectric activity of the masticatory muscles in women with temporomandibular disorders and healthy women. We observed differences and some similarities in resting and functional electromyographic patterns within masticatory and neck muscles in both groups during medical mask and no mask examination.

A Rare Variation of the Digastric Muscle Anterior Belly Related to False Submandibular Triangle

A Rare Variation of the Digastric Muscle Anterior Belly Related to False Submandibular Triangle

Inhibition of Water-Evoked Swallowing During Noxious Mechanical Stimulation of Tongue in Anesthetized Rats.

Dysphagia is sometimes accompanied by pain. Because orofacial structures subserve mastication and swallowing, orofacial pain might impair both functions. Tongue biting can occur not only accidentally while eating but also in some pathological conditions. However, it remains unclear whether noxious mechanical stimulation of the tongue affects swallowing. To explore this question, we evaluated the effects of lingual pinch stimulation on the initiation of swallowing evoked by distilled water (DW) infusion with a flow rate of 5.0µL/s for 20s into the pharyngolaryngeal region in anesthetized rats. The swallowing reflex was identified by electromyographic (EMG) bursts in the suprahyoid muscles which include the anterior belly of the digastric muscle, mylohyoid and geniohyoid muscles, and laryngeal elevation by visual inspection. The number of DW-evoked swallows during pinch stimulation was significantly smaller than that in a control condition or during pressure stimulation. The onset latency of the first swallow during pinch stimulation was significantly longer than that in the control condition. DW-evoked swallowing was almost abolished following bilateral transection of the superior laryngeal nerve (SLN) compared with the control condition, suggesting that the SLN plays a crucial role in the initiation of DW-evoked swallowing. Finally, electrophysiological data indicated that some SLN-responsive neurons in the nucleus tractus solitarii (nTS) exhibited delayed latency from a single SLN stimulation during lingual pinch stimulation. These results suggest that noxious mechanical stimulation of the tongue inhibits the initiation of swallowing and modulates neuronal activity in the nTS.

Mylohyoid nerve revisited

The mylohyoid nerve is also called nerve to mylohyoid (muscle). This nerve is a branch from the inferior alveolar nerve, which is very familiar to our dentists due to the frequently used block anesthesia for mandibular tooth treatment. The motor fiber is known to be the main component of the nerve that is distributed in the my-lohyoid muscle and anterior belly of digastric muscle. In this review article, the following contents will be discussed: the naming story based on the etymology, the general route and main function of the nerve, the research related to the failure of inferior alveolar nerve block anesthesia, and finally other miscellaneous anatomical research results and their clinical significance.

Effects of visual input on changes in the bioelectrical activity of the cervical and masticatory muscles in myopic subjects.

The study aimed to analyze the changes within the bioelectrical activity of the cervical spine and masticatory muscles during the change of visual stimulus—open and closed eyes test. After applying the inclusion criteria, 50 subjects were included in the study, with visual impairment ranging from −0.5 to −5.75 Diopters. Four muscle pairs were analyzed: the anterior part of the temporalis muscle (TA), the superficial part of the masseter muscle (MM), the anterior belly of the digastric muscle (DA), and the middle part of the sternocleidomastoid muscle (SCM) belly during rest, teeth clenching, teeth clenching on dental cotton rollers, and active mouth opening. Statistical analysis showed a significant decrease in the bioelectrical activity during teeth clenching of all analyzed muscles during the closed eyes test. Significant decreases of electromyographic values were also observed during resting activity within TA muscles, during teeth clenching with dental cotton rollers within SCM and DA muscles, and during active mouth opening within the right masseter. Changing the visual stimulus from open eyes to closed eyes in people with myopia affects the bioelectrical activity of the masticatory and cervical spine muscles.

P.129 Radiofrequency rhizotomy for trigeminal neuralgia under general anaesthetic with intraoperative neuromonitoring

Background: Radiofrequency rhizotomy is an efficacious technique for treatment of trigeminal neuralgia that is classically performed with the patient awake. Previous studies have investigated methods for both anatomic and neurophysiologic optimization for nerve targeting. Methods: We performed a retrospective review of prospectively collected data on patients undergoing radiofrequency rhizotomy under a general anesthetic. Electrodes are placed in the temporalis, masseter and one of mylohyoid or anterior belly of digastric muscles. We then localize of the correct subdivision of the trigeminal nerve. The division of the trigeminal nerve with pain shows a muscle response, which is not present in normal subdivisions. Results: A total of 23 radiofrequency rhizotomies were performed under general anesthetic. Abnormal conduction reflexes were present in all cases, and dissipated after lesioning. Pre-operative BNI pain scores were 4.1 ± 0.3, which dropped to 1.8 ± 1.9 post-op (p=0.003). Number of pain medications (2.9 ± 0.6 v. 1.3 ± 1.3, p=0.007) and number of patients with opioid usage (78.7% v. 21.7%, p=0.007) both decreased after rhizotomy. Conclusions: Using a novel conduction pathway, we have successfully been able to monitor radiofrequency rhizotomy in patients operated on under a general anesthetic, with promising preliminary results. Further work is needed to better evaluate this intervention.

Reverse Facial-submental Artery Island Flap with Reinnervation of the Anterior Belly of the Digastric Muscle.

Reconstruction of the upper lateral lip subunit is challenging, and use of several classical local flaps have been previously reported. However, these methods have drawbacks such as visible scarring, anatomic distortion, and functional disability. To obtain satisfactory results, preservation of perioral function is important. We report a case of functional upper lip reconstruction after tumor resection using a reverse facial-submental artery island flap with a reinnervated anterior belly of the digastric muscle (ABDM) without sacrificing the perioral structure. A 73-year-old man presented with basal cell carcinoma on the left upper lip which was widely excised, including the orbicularis oris muscle. The remaining 4 cm × 3.5 cm defect was reconstructed using a reverse facial-submental artery island flap with ipsilateral ABDM. The motor nerve of the ABDM was sutured with the stump of the buccal branch of the ipsilateral facial nerve. The postoperative course was uneventful, and good functional and esthetic recovery were observed at 12-month follow-up. This procedure may be an alternative option for reconstruction of lateral upper lip defects.

Surface electromyography for evaluating patients with oromandibular dystonia

ABSTRACT Objective To investigate myoelectric signals of dystonic activities in oromandibular dystonia (OMD) subjects using surface electromyography (EMG). Methods Twelve OMD subjects were included in this study. Resting myoelectric activities of the superficial masseter, anterior temporalis, and anterior belly of the digastric muscle on both sides were monitored, and dystonic muscle contractions were recorded using surface EMG. Myoelectric signal amplitude, the type of muscle contraction, and contraction rate for phasic activities were evaluated. Results Surface EMG revealed that eight subjects had dystonic muscle activities in the phasic contraction pattern, three subjects had a tonic contraction pattern, and one subject had a mixed pattern. Synchronous contraction of dystonic muscles was frequently observed. Many of the monitored muscles showed high resting amplitudes. Conclusion Surface EMG detects abnormal muscle activities related to oromandibular dystonia. Surface EMG can serve as an objective method for diagnosing oromandibular dystonia.

Masticatory Muscle Thickness and Activity Correlates to Eyeball Length, Intraocular Pressure, Retinal and Choroidal Thickness in Healthy Women versus Women with Myopia.

This study aims to examine the correlations between masticatory and neck muscle thickness and activity versus eyeball length, retinal thickness, choroidal thickness, and intraocular pressure in healthy women versus women with myopia. The study group consisted of 21 women aged 24 years and a control group of 19 women (mean age 23 years). For bioelectrical activity analysis within the temporalis anterior, the superficial part of the masseter muscle, the middle part of the sternocleidomastoid muscle, and the anterior belly of the digastric muscle, an eight-channel BioEMG III electromyograph were used. An M-Turbo ultrasound machine was used to analyze masticatory and neck muscle thickness. The eyeball length was examined by IOL Master 500; choroidal and retinal thickness by Optovue Angiovue; and intraocular pressure by Tono-Pen XL. Refractive errors are related to differences in muscle thickness and electromyographic activity. Bioelectrical activity within the temporalis anterior seems to be associated with ocular length, retinal thickness, and choroidal thickness in women with myopia.

Cutaneous branch of the nerve to the mylohyoid muscle: Potential cause of postoperative sensory alteration in the submental area

BackgroundPrevious studies suggest that the nerve to the mylohyoid muscle could have a cutaneous branch. However, its clinical relevance has rarely been discussed because there is insufficient evidence for it. Our aim in this study was to investigate the anatomy of the cutaneous branch of the nerve to the mylohyoid muscle and extend the discussion to surgical management. MethodsTwenty sides from ten embalmed cadaveric heads were dissected to identify the cutaneous branch of the nerve to the mylohyoid muscle. The cutaneous branch was traced up to its termination. ResultsThe cutaneous branch was observed in 90% and classified into types I and II. In type I, the terminal trunk reached the anterior belly of the digastric muscle. In type II there were two types of terminal trunks, superior and inferior branches, which were identified on all sides. The number of the terminal trunk was one in 23.1% (type I; 6/26) and two in 76.9% (type II; 20/26). The terminal points of the cutaneous branch were all located within a 3 cm × 2 cm rectangular segment in the center of the submental area. ConclusionsWe propose a new dermatome including the nerve to the mylohyoid muscle in the center. Understanding the cutaneous branch of the nerve could help surgeons to prevent iatrogenic sensory loss of the submental area.