Purpose: This review article provides the readers with an in-depth insight in understanding and interpreting various research literatures on the masseter vestibular evoked myogenic potentials(mVEMP). The article also ...Purpose: This review article provides the readers with an in-depth insight in understanding and interpreting various research literatures on the masseter vestibular evoked myogenic potentials(mVEMP). The article also reviews the contemporary researches involving the clinical applications of the mVEMP. Conclusions: Masseter VEMP is an evolving yet clinically promising neuro-otology test tool that has recently gained more research interest and is considered an additional tool to diagnose various vestibular disorders. Masseter VEMP assesses the functional integrity of the acoustic-masseteric and vestibulo-masseteric reflex pathways. The mVEMP could be used as a complementary test to evaluate the same peripheral generator as the cervical VEMP but a different central pathway i.e., vestibulo-trigeminal pathway. Various research studies that have experimented on parameters such as the effect of different electrode montages(zygomatic vs mandibular configurations), stimulation rates, filter settings and stimuli used to evoke mVEMP have been discussed in this article that could assist in the optimization of a comprehensive clinical protocol. The latency and the amplitude of mVEMP waveforms serve as significant parameters in differentiating normals from those of the clinical populations. Along with the cVEMPs and oVEMPs, mVEMP might help diagnose brainstem lesions in REM Sleep behaviour disorders, Multiple Sclerosis and Parkinson's disease. However, further studies are required to probe in this area of research.展开更多
Orofacial muscle hypertonicity,characterized by excessive muscle tension in the facial and masticatory regions,can lead to significant functional impairment and aesthetic concerns.Botulinum toxin type A(BoNT-A),widely...Orofacial muscle hypertonicity,characterized by excessive muscle tension in the facial and masticatory regions,can lead to significant functional impairment and aesthetic concerns.Botulinum toxin type A(BoNT-A),widely known for its cosmetic applications,has emerged as a valuable therapeutic tool in dentistry and maxillofacial medicine.This review explores the pharmacological mechanisms,anatomical considerations,and clinical applications of BoNT-A in the treatment of functional disorders such as bruxism,masseter hypertrophy,temporomandibular joint dysfunction,and facial asymmetry.Emphasis is placed on precision-guided injection techniques,region-specific dosing trends,and formulation-specific performance.Adverse effects,although generally mild and self-limiting,are preventable through anatomical expertise and individualized protocols.Preliminary clinical observations and recent East Asian data suggest variations in the response patterns and optimal dosing strategies.This review also highlights the current gaps,including the need for long-term safety data,standardized training for dental practitioners,and comparative evaluations with non-pharmacological therapies.BoNT-A is a minimally invasive interdisciplinary approach for restoring oral function and facial harmony,supporting its integration into modern dental practice.展开更多
Objective: To compare the functional outcomes of patients who had parotid masseter fascia reserved and unreserved flap elevating scheme in parotidectomy, especially the morbidity of Frey's syndrome. Methods: Twent...Objective: To compare the functional outcomes of patients who had parotid masseter fascia reserved and unreserved flap elevating scheme in parotidectomy, especially the morbidity of Frey's syndrome. Methods: Twenty-three patients (group A) had parotid masseter fascia reserved in the parotidectomy, 32 patients (group B) had parotid masseter fascia unreserved in the operation. Compare the morbidity of gustatory sweating syndrome of the two groups. Results: Follow-up after 6 months to 2.5 years, gustatory sweating syndrome occurred in 4 patients of group A (17%), 17 patients in group B (57%). Conclusion: Reservation technic of the parotid masseter fascial in parotidectomy could prevent regeneration of parasympathetic nerve and thus prevent Frey's syndrome post-operation.展开更多
Introduction:The masseter vestibular evoked myogenic potential(mVEMP)is a bilaterally generated,electromyographically(EMG)-mediated response innervated by the trigeminal nerve.The purpose of the present investigation ...Introduction:The masseter vestibular evoked myogenic potential(mVEMP)is a bilaterally generated,electromyographically(EMG)-mediated response innervated by the trigeminal nerve.The purpose of the present investigation was to 1)determine whether subjects could accurately achieve and maintain a range of EMG target levels,2)to examine the effects of varied EMG levels on the latencies and amplitudes of the mVEMP,and 3)to investigate the degree of side-to-side asymmetry and any effects of EMG activation.Methods:Subjects were nine neurologically and otologically normal young adults.A high-intensity tone burst was presented monaurally while subjects were seated upright and asked to match a range of EMG target levels by clenching their teeth.Recordings were made from the ipsilateral and contralateral masseter muscles referenced to the ear being monaurally stimulated.Results:We found that the tonic EMG target had no effect on mVEMP latency.Additionally,although mVEMP amplitudes“scaled”to the EMG target,there was a tendency for the subjects’EMG level to“undershoot”the EMG target levels greater than 50 mV.While some individuals did generate differences in EMG activation between sides,there were no significant differences on average EMG activation between sides.Further,while average corrected amplitude asymmetry was similar across EMG targets,some individuals demonstrated large,corrected amplitude asymmetry ratios.Conclusions:The results of this investigation suggest that,as with cVEMP recordings,the underlying EMG activation may vary between subjects and could impact mVEMP amplitudes,yet could be mitigated by amplitude correction techniques.Further it is important to be aware that even young normal subjects have difficulty maintaining large,tonic EMG activity during the mVEMP recording.展开更多
Objective： To investigate the masseter inhibitory tension-type headache （TTH）. Methods： MIR was studied in 21 sex matched to the study cohort. Median age of patients was reflex （MIR） and its eventual changes in ...Objective： To investigate the masseter inhibitory tension-type headache （TTH）. Methods： MIR was studied in 21 sex matched to the study cohort. Median age of patients was reflex （MIR） and its eventual changes in patients with episodic patients with episodic TTH and 30 healthy subjects, with age and 17.0 years （ranged 16-49 years）, median duration of disease 12 months （1-5 years）, and median frequency of headache 7.5 d per month. Results： The second period of suppression （$2） of MIR was reduced in intensity and duration in 10% of controls and 66.7% （confidence interval （CI） 45.3%-85%; P〈0.05） of patients with episodic TTH （X2=74.9; P〈0.001）. In 3 （14.3%） of patients with episodic TTH, S2 was completely absent. No significant correlation between the duration of disease and headache frequency was found. Conclusion： Our results confirm the link between episodic TTH and reduction or absence of S2. Teenage patients with episodic TTH may exhibit marked pathological changes in S2 in contrast to older individuals.展开更多
Both interposition nerve grafts and masseter nerve transfers have been successfully used for facial reanimation after irreversible injuries to the cranial portion of the facial nerve.However,no comparative study of th...Both interposition nerve grafts and masseter nerve transfers have been successfully used for facial reanimation after irreversible injuries to the cranial portion of the facial nerve.However,no comparative study of these two procedures has yet been reported.In this two-site,twoarm,retrospective case review study,32 patients were included.Of these,17 patients(eight men and nine women,mean age 42.1 years)underwent interposition nerve graft after tumor extirpation or trauma between 2003 and 2006 in the Ear Institute,School of Medicine,Shanghai Jiao Tong University,China,and 15 patients(six men and nine women,mean age 40.6 years)underwent masseter-to-facial nerve transfer after tumor extirpation or trauma between November 2010 and February 2016 in Shanghai Ninth People's Hospital,China.More patients achieved House-Brackmann III recovery after masseter nerve repair than interposition nerve graft repair(15/15 vs.12/17).The mean oral commissure excursion ratio was also higher in patients who underwent masseter nerve transfer than in patients subjected to an interposition nerve graft.These findings suggest that masseter nerve transfer results in strong oral commissure excursion,avoiding obvious synkinesis,while an interposition nerve graft provides better resting symmetry.This study was approved by the Institutional Ethics Committee,Shanghai Ninth People's Hospital,China(approval No.SH9 H-2019-T332-1)on December 12,2019.展开更多
Objective:To report vestibular evoked myogenic potentials from different recording sites(neck extensor or masseter muscles) in miniature pigs and rats.Methods:Potentials were recorded using 1000 Hz tone bursts from th...Objective:To report vestibular evoked myogenic potentials from different recording sites(neck extensor or masseter muscles) in miniature pigs and rats.Methods:Potentials were recorded using 1000 Hz tone bursts from the neck extensor muscle or masseter muscle in normal adult Bama miniature pigs and rats anesthetized with 3%pentobarbital sodium and Sumianxin Ⅱ.Results:At 80 dB SPL,the first positive wave(P wave) of VEMPs was recognizable in 58%of rats with a latency of 6.45±0.23 ms and an amplitude of 1.45±0.49 μV when recorded from the neck extensor muscle,and in 50%of rats with a latency of 6.38±0.34 ms and an amplitude of 1.57±0.35 μV when recorded from the masseter muscle.In miniature pigs,at the same stimulus intensity,P wave was recognizable in 58%of the animals with a latency of 7.65±0.64 ms and an amplitude of 1.66±0.34 μV when recorded from the neck extensor muscle,and in 50%of the animals with a latency of 7.65±0.64 ms and an amplitude of 0.31±0.28 μV when recorded from the masseter muscle.Conclusion:VEMP can be induced from both neck extensor and masseter muscles in the miniature pig and rat.For a given species,the site of recording affects P wave induction rate and amplitude but not latency.Consistency and repeatability analysis suggests that the masseter muscle is a better recording site in miniature pigs while the cervical extensor is a better recording site in rats.For a given recording site,both latency and amplitude of the P wave are slightly greater in miniature pigs than in rats.展开更多
AIM: To make an electrophysiological demonstration of a possible jaw muscle afferents-oculomotor neural pathway that was proposed by our previous works on rats, which substantiates an early "release hypothesis&qu...AIM: To make an electrophysiological demonstration of a possible jaw muscle afferents-oculomotor neural pathway that was proposed by our previous works on rats, which substantiates an early "release hypothesis" on pathogenesis of human Marcus Gunn Syndrome(MGS). METHODS: Extracellular unit discharge recording was applied and both orthodromic and spontaneous unitary firing were recorded in the oculomotor nucleus(III), and the complex of pre-oculomotor interstitial nucleus of Cajal and Darkschewitsch nucleus(INC/DN), following electric stimulation of the ipsilateral masseter nerve(MN) in rats. RESULTS: Extracellular orthodromic unit discharges, with latencies of 3.7±1.3 and 4.7±2.9 ms, were recorded unilaterally in the III, and the INC/DN neurons, respectively. Spontaneous unit discharges were also recorded mostly in the INC/DN and less frequently in the III. Train stimulation could prompt either facilitation or inhibition on those spontaneous unit discharges. The inhibition pattern of train stimulation on the spontaneous discharging was rather different in the III and INC/DN. A slow inhibitory pattern in which spontaneous firing rate decreased further and further following repeated train stimulation was observed in the III. While, some high spontaneous firing rate units, responding promptly to the train stimuli with a short-term inhibition and recovered quickly when stimuli are off, were recorded in the INC/DN. However, orthodromic unit discharge was not recorded in the III and INC/DN in a considerable number of experiment animals. CONCLUSION: A residual neuronal circuit might exist in mammals for the primitive jaw-eyelid reflex observed in amphibians, which might not be well-developed in all experimental mammals in current study. Nonetheless, this pathway can be still considered as a neuroanatomic substrate for development of MGS in some cases among all MGS with different kind of etiology.展开更多
Traumatic brain injury（TBI）represents a global pandemic and is currently a leading cause of injury related death worldwide.Unfortunately,those who survive initial injury often suffer devastating functional,social,an...Traumatic brain injury（TBI）represents a global pandemic and is currently a leading cause of injury related death worldwide.Unfortunately,those who survive initial injury often suffer devastating functional,social,and economic consequences.展开更多
BACKGROUND： Masseter muscle nerve is often injured in mandible osteotomy. What changes in food intake and masseter muscle will be brought after masseter muscle nerve injury？ OBJECTIVE： This study was designed to se...BACKGROUND： Masseter muscle nerve is often injured in mandible osteotomy. What changes in food intake and masseter muscle will be brought after masseter muscle nerve injury？ OBJECTIVE： This study was designed to selectively establish animal models of denervated masseter muscle and investigate the effects of severing masseter muscular nerve on masseter muscle and animal＇s food intake. DESIGN, TIME AND SETTING： A randomized controlled animal experiment was performed at the Laboratory Animal Center, Nanfang Hospital, Southern Medical University from September to November 2005. MATERIALS： A total of 50 healthy, adult, SPF-grade, New Zealand rabbits, of both genders, were used to develop an animal model of selectively denervated masseter muscle. METHODS： Five rabbits were randomly selected as normal controls. According to various mutilation methods, the remaining animals were randomly divided into 3 experimental groups, with 15 rabbits in each group： masseter muscular neural stem denervated, masseter muscular neural superior branch-denervated, and masseter muscular neural inferior brancb-denervated groups. Self-control comparison was performed on each animal. The right masseter muscle served as the experimental side, and the left masseter muscle served as the control side. In each group, 3 time points （2, 8, and 24 weeks post-surgery） were allotted for observation. MAIN OUTCOME MEASURES： At the pre-set time points, masseter muscular thickness was measured with a Logic 500 color Doppler ultrasonic diagnostic apparatus. Masseter muscle tissue was resected for hematoxylin eosin staining. Masseter muscular fiber diameter and area were measured with an optical microscope. Masseter muscle tissue was sectioned and nicotinamide adenine dinucleotide tetrazolium oxidoreductase （NADH-TR） and adenosine triphosphatase staining were performed. Following staining, the sections were quantitatively analyzed using an IBAS200 image analyzer. RESULTS： Post-surgery food intake： No abnormal food intake was found after surgery among the three groups. Intragroup comparison： In each experimental group, following denervation, masseter muscular thickness was decreased （P 〈 0.05） and masseter muscular fiber cross-section area was reduced in the experimental side compared to the control side （P 〈 0.05）. Inter-group comparison： There was a significant difference in masseter muscular thickness and masseter fiber cross-section area among the three experimental groups （P 〈 0.05）. There was no significant difference in masseter fiber type between the control side of the three experimental groups and the normal control group （P 〉 0.05）. CONCLUSION： Following various methods of masseter muscle denervation, masseter muscle thickness and masseter fiber cross-section area was reduced by varying degrees. Denervated masseter muscle did not influence food intake of experimental animals or alter masseter muscle fiber ratio.展开更多
The C-C method was adopted to analyze the nonlinear characteristics of masseter electromyography （EMG） signals and the chaotic degree by the largest Lyapunov exponent （LLE） of different genders and sides. First, t...The C-C method was adopted to analyze the nonlinear characteristics of masseter electromyography （EMG） signals and the chaotic degree by the largest Lyapunov exponent （LLE） of different genders and sides. First, the embedding dimension and the delay time were obtained through this method, then the phase space was reconstructed to resume the chaotie attractor and determine the LLE. The result shows that the trajectory of attractor is denser than Chen＇s attractor, and the LLE is positive, which means that not only the signal has the character of chaos, but also the chaotic degree of masseter EMG is relatively high. According to the value of the LLE, the chaotic degree of men＇s masseter EMG is higher than that of women＇s; when the dentition is normal, the chaotic degree of two sides is almost the same. Then, a conclusion can be deduced that if the LLE of both sides are in great difference, the unilateral mastication is likely to exist, which means that the nonlinear characteristics of masseter EMG can be applied to predict the unilateral mastication.展开更多
BACKGROUND Blink and masseter reflexes provide reliable,quantifiable data on the function of the central nervous system:Delayed latencies have been found in patients with neurocognitive disorder(ND)and type 2 diabetes...BACKGROUND Blink and masseter reflexes provide reliable,quantifiable data on the function of the central nervous system:Delayed latencies have been found in patients with neurocognitive disorder(ND)and type 2 diabetes mellitus(T2DM),but this has not been studied in patients with both pathologies.AIM To investigate if older adults with ND plus T2DM have prolonged latencies of blink and masseter-reflex and if they were associated with disease progression.METHODS This cross-sectional study included 227 older adults(>60 years)from Colima,Mexico.Neurocognitive disorder was identified by a neuropsychological battery test,and T2DM identified by medical history,fasting glucose,and glycosylated hemoglobin.Latencies in the early reflex(R1),ipsilateral late(R2),and contralateral late(R2c)components of the blink reflex were analyzed for all subjects,and 183 subjects were analyzed for latency of the masseter reflex.RESULTS In 20.7%of participants,ND was detected.In 37%,T2DM was detected.Latencies in R1,R2,and R2c were significantly prolonged for groups with ND plus T2DM,ND,and T2DM,compared with the control group(P<0.0001).The masseter reflex was only prolonged in older adults(regardless of T2DM status)with ND vs controls(P=0.030).In older adults with ND and without T2DM,the more the cognitive impairment progressed,the more prolonged latencies in R2 and R2c presented(P<0.01).CONCLUSION These findings suggest that blink and masseter reflexes could be used to evaluate possible changes in brainstem circuits in older adults with ND and T2DM.展开更多
Objective:To report detection of vestibular-evoked myogenic potentials (VEMPs) in the miniature pig. Methods:Potentials evoked by 1000 Hz tone bursts were recorded from neck extensor muscles and the masseter muscles i...Objective:To report detection of vestibular-evoked myogenic potentials (VEMPs) in the miniature pig. Methods:Potentials evoked by 1000 Hz tone bursts were recorded from neck extensor muscles and the masseter muscles in normal adult Bama miniature pigs anesthetized with 3%pentobarbital sodium and Carbachol II. Results:The latency of the first positive wave P from neck extensor muscles was 7.65 ± 0.64 ms, with an amplitude of 1.66 ± 0.34 uv and a rate of successful induction of 75%at 80 dB SPL. The latency of potentials evoked from the masseter muscles was 7.60 ± 0.78 ms, with an amplitude of 1.31 ± 0.28 uv and a rate successful induction of 66%at 80 dB SPL. Conclusion:The latencies and thresholds of VEMPs recorded from the neck extensor muscle and the masseter muscle appear to be comparable in normal adult Bama miniature pigs, although the amplitude recorded from the neck extensor muscle seems to be higher than that from the masseter muscle. However, because of their usually relatively superficial and easily accessible location, as well as their large volume and strong contractions, masseter muscles may be better target muscles for recording myogenic potentials.展开更多
This study aimed to develop a system to measure the flavor detection time for chewed solid and semi-solid foods. Twelve healthy young adults (seven males and five females) were asked to chew gummy candies with three d...This study aimed to develop a system to measure the flavor detection time for chewed solid and semi-solid foods. Twelve healthy young adults (seven males and five females) were asked to chew gummy candies with three different fruit flavors (grape, lemon, and pineapple) in a random order while their masseter activities were recorded by surface electromyograms on their habitual working and non-working sides. The participants were also asked to press a button as soon as possible with their preferred hand once they detected the flavor. The time interval between the start of chewing and the button press was measured;the start of chewing was defined as the start of a burst in the masseter electromyogram on the habitual working side. The average interval ranged from 2.82 s (lemon in males) to 4.63 s (grape in males);no significant differences were found between the three tested gummy candies or between the sexes of the participants. The present system can perform the measurements of the following two conventional measurement systems: 1) simple reaction time task for the taste and olfactory stimuli of fluids and vapors, respectively, and 2) time-intensity analysis of the flavor from solid and semi-solid foods, which does not generally consider the flavor detection time.展开更多
Few studies have evaluated the effects of activity patterns of the jaw closing muscles assessed by specific parameters on jaw opening in subsequent cycles during the chewing of food. The objective of this study was to...Few studies have evaluated the effects of activity patterns of the jaw closing muscles assessed by specific parameters on jaw opening in subsequent cycles during the chewing of food. The objective of this study was to quantitatively analyze the effect of the masseter (jaw closer) activity patterns on suprahyoid (jaw opener) activity during subsequent cycles. The assessments were performed while participants naturally chewed six test foods that differed in size dimensions and textural properties. Surface electromyograms of the masseter (on the habitual working side) and suprahyoid muscles were recorded in ten healthy young adults, each of whom randomly received one of the six test foods. The activity patterns were assessed using three parameters specifically developed for their quantification. Changes in suprahyoid activity during each of the subsequent chewing cycles were examined by three amplitudinal (minimum, maximum, and net values of the integrated suprahyoid electromyogram) parameters and one durational (active duration) parameter. The main finding was that two of the three activity pattern parameters had a statistically significant effect only on the three amplitudinal parameters in three of the six test foods. These results suggest that masseter activity patterns partially affect suprahyoid activity during subsequent chewing cycles and that the effect is food dependent. A possible neural mechanism responsible for this effect is presented.展开更多
This study analyzed the factors responsible for determining the flavor detection time for chewed semi-solid foods. Thirteen healthy young adults (eight males and five females) were asked to chew gummy candies with fiv...This study analyzed the factors responsible for determining the flavor detection time for chewed semi-solid foods. Thirteen healthy young adults (eight males and five females) were asked to chew gummy candies with five different fruit flavors (i.e., apple, grape, orange, pear, and strawberry) in a random order. The detection time to flavor was measured using an electromyography-based system, which was recently developed by the authors. Briefly, each participant was recorded with surface masseter electromyograms on both sides to determine the start of chewing. Each participant was asked to press a button as soon as possible with his/her preferred hand after detecting the flavor. The time elapsed between the start of chewing and the button press was measured. Two taste components, sugars and organic acids, of the gummy candies were chemically analyzed, and two major sugars and organic acid were individually detected. The odor intensity was also analyzed for the gummy candies. The average detection time significantly differed among the five gummy candies and among the participants. Simple regression analyses revealed that the intensity of the odors was significantly associated with the average time intervals, but the amounts of the two major sugars and the organic acids were not. The analysis yielded the following equation for the regression estimation:?? (y = the time interval, x = the intensity of odors). The results suggest that the intensity of odors of the gummy candies, not the taste components, is responsible for determining the flavor detection time.展开更多
The aim of this study was to quantify the relationships between four physiological parameters of masseter activity during chewing and properties related to the sizes and textures of the six representative test foods. ...The aim of this study was to quantify the relationships between four physiological parameters of masseter activity during chewing and properties related to the sizes and textures of the six representative test foods. The physiological parameters analyzed were the number of chewing cycles, chewing time, masseter amplitude, and cycle duration, which were obtained from masseter surface electromyography recorded in ten (seven male and three female) healthy, young participants. The six test foods differed in size dimensions (length, width, and height) and in textural properties (hardness, fracturability, and adhesiveness). The quantitative relationships were examined using linear regression. Nine statistically significant regression coefficients were found between the four physiological parameters and the textural properties, but not the height, of the test foods. From the regression coefficients, contributions of the food properties to the physiological parameters were estimated. Individual relationships between the physiological parameters and textural properties of the test foods are discussed in relation to their physiological implications.展开更多
This study examined the effects of the textural properties and chemical components of foods on masseter activity patterns. Ten healthy young participants (seven men and three women) were asked to chew four gummy candi...This study examined the effects of the textural properties and chemical components of foods on masseter activity patterns. Ten healthy young participants (seven men and three women) were asked to chew four gummy candies with different flavors while their masseter activities were recorded by a surface electromyogram. The masseter activity patterns during chewing were analyzed quantitatively using a TP technique, generating three TP values (T25, T50 and T75). The textural analysis included four representative properties, and six sugars and four organic acids were tested in the chemical analysis. The hierarchical cluster analysis classified the T25 and T75 values into four subclusters and classified the T50 values into three subclusters. Two T75 subclusters differed significantly in the combined amounts of the two predominant sugars (sucrose and maltose);however, these T75 subclusters did not differ in their organic acid contents or textural properties. Therefore, sucrose and maltose affect masseter activity patterns during chewing, particularly in the later stage of masseter activity.展开更多
We present the case of a 4 year old girl whose adenoidectomy had to be performed via an endoscopictrans oral approach due to the unexpected inability to fully open the mouth during the procedure. The patient had previ...We present the case of a 4 year old girl whose adenoidectomy had to be performed via an endoscopictrans oral approach due to the unexpected inability to fully open the mouth during the procedure. The patient had previously been taking Risperidone for behavioral symptoms associated with her autism. The jaw tone returned to normal following the procedure and there were no complications. An interaction between the Risperidone and the anesthetics were the likely cause of the trismus.展开更多
Background:Botulinum toxin type A injection,a noninvasive alternative method for treating masseteric hypertrophy,is inadequate for treating patients with a round lower face.This study aimed to investigate the operativ...Background:Botulinum toxin type A injection,a noninvasive alternative method for treating masseteric hypertrophy,is inadequate for treating patients with a round lower face.This study aimed to investigate the operative technique and clinical results of liposuction followed by botulinum toxin type A injections in patients with masseteric hypertrophy and excessive subcutaneous fat.Methods:Sixty-five patients(50 women and 15 men)were treated using this technique between May 2014 and January 2019.Their mean age was 26.3 years(range,18–35 years)and the mean follow-up period was 13 months(range,8–18 months).Results:All patients achieved slimmer lower cheeks with improved jaw definitions after the procedure.Among the 65 patients,61(94%)expressed satisfaction with the results and believed that the procedure produced their desired face shape.No major complications were observed.The effect of this combination treatment remained stable for 12 months after the procedure.Conclusion:The authors believe that liposuction followed by botulinum toxin type A injections is an effective technique for the treatment of masseteric hypertrophy and excessive subcutaneous fat.It is also a relatively simple and safe treatment approach.展开更多
文摘Purpose: This review article provides the readers with an in-depth insight in understanding and interpreting various research literatures on the masseter vestibular evoked myogenic potentials(mVEMP). The article also reviews the contemporary researches involving the clinical applications of the mVEMP. Conclusions: Masseter VEMP is an evolving yet clinically promising neuro-otology test tool that has recently gained more research interest and is considered an additional tool to diagnose various vestibular disorders. Masseter VEMP assesses the functional integrity of the acoustic-masseteric and vestibulo-masseteric reflex pathways. The mVEMP could be used as a complementary test to evaluate the same peripheral generator as the cervical VEMP but a different central pathway i.e., vestibulo-trigeminal pathway. Various research studies that have experimented on parameters such as the effect of different electrode montages(zygomatic vs mandibular configurations), stimulation rates, filter settings and stimuli used to evoke mVEMP have been discussed in this article that could assist in the optimization of a comprehensive clinical protocol. The latency and the amplitude of mVEMP waveforms serve as significant parameters in differentiating normals from those of the clinical populations. Along with the cVEMPs and oVEMPs, mVEMP might help diagnose brainstem lesions in REM Sleep behaviour disorders, Multiple Sclerosis and Parkinson's disease. However, further studies are required to probe in this area of research.
文摘Orofacial muscle hypertonicity,characterized by excessive muscle tension in the facial and masticatory regions,can lead to significant functional impairment and aesthetic concerns.Botulinum toxin type A(BoNT-A),widely known for its cosmetic applications,has emerged as a valuable therapeutic tool in dentistry and maxillofacial medicine.This review explores the pharmacological mechanisms,anatomical considerations,and clinical applications of BoNT-A in the treatment of functional disorders such as bruxism,masseter hypertrophy,temporomandibular joint dysfunction,and facial asymmetry.Emphasis is placed on precision-guided injection techniques,region-specific dosing trends,and formulation-specific performance.Adverse effects,although generally mild and self-limiting,are preventable through anatomical expertise and individualized protocols.Preliminary clinical observations and recent East Asian data suggest variations in the response patterns and optimal dosing strategies.This review also highlights the current gaps,including the need for long-term safety data,standardized training for dental practitioners,and comparative evaluations with non-pharmacological therapies.BoNT-A is a minimally invasive interdisciplinary approach for restoring oral function and facial harmony,supporting its integration into modern dental practice.
文摘Objective: To compare the functional outcomes of patients who had parotid masseter fascia reserved and unreserved flap elevating scheme in parotidectomy, especially the morbidity of Frey's syndrome. Methods: Twenty-three patients (group A) had parotid masseter fascia reserved in the parotidectomy, 32 patients (group B) had parotid masseter fascia unreserved in the operation. Compare the morbidity of gustatory sweating syndrome of the two groups. Results: Follow-up after 6 months to 2.5 years, gustatory sweating syndrome occurred in 4 patients of group A (17%), 17 patients in group B (57%). Conclusion: Reservation technic of the parotid masseter fascial in parotidectomy could prevent regeneration of parasympathetic nerve and thus prevent Frey's syndrome post-operation.
文摘Introduction:The masseter vestibular evoked myogenic potential(mVEMP)is a bilaterally generated,electromyographically(EMG)-mediated response innervated by the trigeminal nerve.The purpose of the present investigation was to 1)determine whether subjects could accurately achieve and maintain a range of EMG target levels,2)to examine the effects of varied EMG levels on the latencies and amplitudes of the mVEMP,and 3)to investigate the degree of side-to-side asymmetry and any effects of EMG activation.Methods:Subjects were nine neurologically and otologically normal young adults.A high-intensity tone burst was presented monaurally while subjects were seated upright and asked to match a range of EMG target levels by clenching their teeth.Recordings were made from the ipsilateral and contralateral masseter muscles referenced to the ear being monaurally stimulated.Results:We found that the tonic EMG target had no effect on mVEMP latency.Additionally,although mVEMP amplitudes“scaled”to the EMG target,there was a tendency for the subjects’EMG level to“undershoot”the EMG target levels greater than 50 mV.While some individuals did generate differences in EMG activation between sides,there were no significant differences on average EMG activation between sides.Further,while average corrected amplitude asymmetry was similar across EMG targets,some individuals demonstrated large,corrected amplitude asymmetry ratios.Conclusions:The results of this investigation suggest that,as with cVEMP recordings,the underlying EMG activation may vary between subjects and could impact mVEMP amplitudes,yet could be mitigated by amplitude correction techniques.Further it is important to be aware that even young normal subjects have difficulty maintaining large,tonic EMG activity during the mVEMP recording.
文摘Objective： To investigate the masseter inhibitory tension-type headache （TTH）. Methods： MIR was studied in 21 sex matched to the study cohort. Median age of patients was reflex （MIR） and its eventual changes in patients with episodic patients with episodic TTH and 30 healthy subjects, with age and 17.0 years （ranged 16-49 years）, median duration of disease 12 months （1-5 years）, and median frequency of headache 7.5 d per month. Results： The second period of suppression （$2） of MIR was reduced in intensity and duration in 10% of controls and 66.7% （confidence interval （CI） 45.3%-85%; P〈0.05） of patients with episodic TTH （X2=74.9; P〈0.001）. In 3 （14.3%） of patients with episodic TTH, S2 was completely absent. No significant correlation between the duration of disease and headache frequency was found. Conclusion： Our results confirm the link between episodic TTH and reduction or absence of S2. Teenage patients with episodic TTH may exhibit marked pathological changes in S2 in contrast to older individuals.
基金supported by Shanghai Municipal Commission of Health and Family Planning Program,China,No.201504253(to WW)Special Fund for Science and Technology Innovation by Shanghai Jiao Tong University,China,No.YG2016MS10(to WW)the National Natural Science Foundation of China,Nos.81570906(to HW)and 81371086(to ZYW)。
文摘Both interposition nerve grafts and masseter nerve transfers have been successfully used for facial reanimation after irreversible injuries to the cranial portion of the facial nerve.However,no comparative study of these two procedures has yet been reported.In this two-site,twoarm,retrospective case review study,32 patients were included.Of these,17 patients(eight men and nine women,mean age 42.1 years)underwent interposition nerve graft after tumor extirpation or trauma between 2003 and 2006 in the Ear Institute,School of Medicine,Shanghai Jiao Tong University,China,and 15 patients(six men and nine women,mean age 40.6 years)underwent masseter-to-facial nerve transfer after tumor extirpation or trauma between November 2010 and February 2016 in Shanghai Ninth People's Hospital,China.More patients achieved House-Brackmann III recovery after masseter nerve repair than interposition nerve graft repair(15/15 vs.12/17).The mean oral commissure excursion ratio was also higher in patients who underwent masseter nerve transfer than in patients subjected to an interposition nerve graft.These findings suggest that masseter nerve transfer results in strong oral commissure excursion,avoiding obvious synkinesis,while an interposition nerve graft provides better resting symmetry.This study was approved by the Institutional Ethics Committee,Shanghai Ninth People's Hospital,China(approval No.SH9 H-2019-T332-1)on December 12,2019.
基金supported by grants from the National Basic Research Program of China (973 Program)(#2012CB967900)National Natural Science Foundation of China (31300624,81470684)+3 种基金Postdoctoral Science Foundation of China (2015M571818)Six Major Categories of Talent (2014-WSN043,2011-WS-074)Innovation and Entrepreneurship Training Program for College Students in Jiangsu Province(201510313003Z,201510313003,KYLX14-1455)Clinic Medical Special Foundation of Jiangsu Province (b12014032)
文摘Objective:To report vestibular evoked myogenic potentials from different recording sites(neck extensor or masseter muscles) in miniature pigs and rats.Methods:Potentials were recorded using 1000 Hz tone bursts from the neck extensor muscle or masseter muscle in normal adult Bama miniature pigs and rats anesthetized with 3%pentobarbital sodium and Sumianxin Ⅱ.Results:At 80 dB SPL,the first positive wave(P wave) of VEMPs was recognizable in 58%of rats with a latency of 6.45±0.23 ms and an amplitude of 1.45±0.49 μV when recorded from the neck extensor muscle,and in 50%of rats with a latency of 6.38±0.34 ms and an amplitude of 1.57±0.35 μV when recorded from the masseter muscle.In miniature pigs,at the same stimulus intensity,P wave was recognizable in 58%of the animals with a latency of 7.65±0.64 ms and an amplitude of 1.66±0.34 μV when recorded from the neck extensor muscle,and in 50%of the animals with a latency of 7.65±0.64 ms and an amplitude of 0.31±0.28 μV when recorded from the masseter muscle.Conclusion:VEMP can be induced from both neck extensor and masseter muscles in the miniature pig and rat.For a given species,the site of recording affects P wave induction rate and amplitude but not latency.Consistency and repeatability analysis suggests that the masseter muscle is a better recording site in miniature pigs while the cervical extensor is a better recording site in rats.For a given recording site,both latency and amplitude of the P wave are slightly greater in miniature pigs than in rats.
基金Supported by Natural Sciences Research Funding from Shaanxi Province(No.2009K01-74)
文摘AIM: To make an electrophysiological demonstration of a possible jaw muscle afferents-oculomotor neural pathway that was proposed by our previous works on rats, which substantiates an early "release hypothesis" on pathogenesis of human Marcus Gunn Syndrome(MGS). METHODS: Extracellular unit discharge recording was applied and both orthodromic and spontaneous unitary firing were recorded in the oculomotor nucleus(III), and the complex of pre-oculomotor interstitial nucleus of Cajal and Darkschewitsch nucleus(INC/DN), following electric stimulation of the ipsilateral masseter nerve(MN) in rats. RESULTS: Extracellular orthodromic unit discharges, with latencies of 3.7±1.3 and 4.7±2.9 ms, were recorded unilaterally in the III, and the INC/DN neurons, respectively. Spontaneous unit discharges were also recorded mostly in the INC/DN and less frequently in the III. Train stimulation could prompt either facilitation or inhibition on those spontaneous unit discharges. The inhibition pattern of train stimulation on the spontaneous discharging was rather different in the III and INC/DN. A slow inhibitory pattern in which spontaneous firing rate decreased further and further following repeated train stimulation was observed in the III. While, some high spontaneous firing rate units, responding promptly to the train stimuli with a short-term inhibition and recovered quickly when stimuli are off, were recorded in the INC/DN. However, orthodromic unit discharge was not recorded in the III and INC/DN in a considerable number of experiment animals. CONCLUSION: A residual neuronal circuit might exist in mammals for the primitive jaw-eyelid reflex observed in amphibians, which might not be well-developed in all experimental mammals in current study. Nonetheless, this pathway can be still considered as a neuroanatomic substrate for development of MGS in some cases among all MGS with different kind of etiology.
文摘Traumatic brain injury（TBI）represents a global pandemic and is currently a leading cause of injury related death worldwide.Unfortunately,those who survive initial injury often suffer devastating functional,social,and economic consequences.
文摘BACKGROUND： Masseter muscle nerve is often injured in mandible osteotomy. What changes in food intake and masseter muscle will be brought after masseter muscle nerve injury？ OBJECTIVE： This study was designed to selectively establish animal models of denervated masseter muscle and investigate the effects of severing masseter muscular nerve on masseter muscle and animal＇s food intake. DESIGN, TIME AND SETTING： A randomized controlled animal experiment was performed at the Laboratory Animal Center, Nanfang Hospital, Southern Medical University from September to November 2005. MATERIALS： A total of 50 healthy, adult, SPF-grade, New Zealand rabbits, of both genders, were used to develop an animal model of selectively denervated masseter muscle. METHODS： Five rabbits were randomly selected as normal controls. According to various mutilation methods, the remaining animals were randomly divided into 3 experimental groups, with 15 rabbits in each group： masseter muscular neural stem denervated, masseter muscular neural superior branch-denervated, and masseter muscular neural inferior brancb-denervated groups. Self-control comparison was performed on each animal. The right masseter muscle served as the experimental side, and the left masseter muscle served as the control side. In each group, 3 time points （2, 8, and 24 weeks post-surgery） were allotted for observation. MAIN OUTCOME MEASURES： At the pre-set time points, masseter muscular thickness was measured with a Logic 500 color Doppler ultrasonic diagnostic apparatus. Masseter muscle tissue was resected for hematoxylin eosin staining. Masseter muscular fiber diameter and area were measured with an optical microscope. Masseter muscle tissue was sectioned and nicotinamide adenine dinucleotide tetrazolium oxidoreductase （NADH-TR） and adenosine triphosphatase staining were performed. Following staining, the sections were quantitatively analyzed using an IBAS200 image analyzer. RESULTS： Post-surgery food intake： No abnormal food intake was found after surgery among the three groups. Intragroup comparison： In each experimental group, following denervation, masseter muscular thickness was decreased （P 〈 0.05） and masseter muscular fiber cross-section area was reduced in the experimental side compared to the control side （P 〈 0.05）. Inter-group comparison： There was a significant difference in masseter muscular thickness and masseter fiber cross-section area among the three experimental groups （P 〈 0.05）. There was no significant difference in masseter fiber type between the control side of the three experimental groups and the normal control group （P 〉 0.05）. CONCLUSION： Following various methods of masseter muscle denervation, masseter muscle thickness and masseter fiber cross-section area was reduced by varying degrees. Denervated masseter muscle did not influence food intake of experimental animals or alter masseter muscle fiber ratio.
文摘The C-C method was adopted to analyze the nonlinear characteristics of masseter electromyography （EMG） signals and the chaotic degree by the largest Lyapunov exponent （LLE） of different genders and sides. First, the embedding dimension and the delay time were obtained through this method, then the phase space was reconstructed to resume the chaotie attractor and determine the LLE. The result shows that the trajectory of attractor is denser than Chen＇s attractor, and the LLE is positive, which means that not only the signal has the character of chaos, but also the chaotic degree of masseter EMG is relatively high. According to the value of the LLE, the chaotic degree of men＇s masseter EMG is higher than that of women＇s; when the dentition is normal, the chaotic degree of two sides is almost the same. Then, a conclusion can be deduced that if the LLE of both sides are in great difference, the unilateral mastication is likely to exist, which means that the nonlinear characteristics of masseter EMG can be applied to predict the unilateral mastication.
文摘BACKGROUND Blink and masseter reflexes provide reliable,quantifiable data on the function of the central nervous system:Delayed latencies have been found in patients with neurocognitive disorder(ND)and type 2 diabetes mellitus(T2DM),but this has not been studied in patients with both pathologies.AIM To investigate if older adults with ND plus T2DM have prolonged latencies of blink and masseter-reflex and if they were associated with disease progression.METHODS This cross-sectional study included 227 older adults(>60 years)from Colima,Mexico.Neurocognitive disorder was identified by a neuropsychological battery test,and T2DM identified by medical history,fasting glucose,and glycosylated hemoglobin.Latencies in the early reflex(R1),ipsilateral late(R2),and contralateral late(R2c)components of the blink reflex were analyzed for all subjects,and 183 subjects were analyzed for latency of the masseter reflex.RESULTS In 20.7%of participants,ND was detected.In 37%,T2DM was detected.Latencies in R1,R2,and R2c were significantly prolonged for groups with ND plus T2DM,ND,and T2DM,compared with the control group(P<0.0001).The masseter reflex was only prolonged in older adults(regardless of T2DM status)with ND vs controls(P=0.030).In older adults with ND and without T2DM,the more the cognitive impairment progressed,the more prolonged latencies in R2 and R2c presented(P<0.01).CONCLUSION These findings suggest that blink and masseter reflexes could be used to evaluate possible changes in brainstem circuits in older adults with ND and T2DM.
基金supported by grants from the National Basic Research Program of China (973 Program) (#2012CB967900)National Natural Science Foundation of China (31300624, 81470684)+3 种基金Postdoctoral Science Foundation of China(2015M571818)Six Major Categories Talent (2014-WSN043, 2011-WS-074)Innovation and Entrepreneurship Training Program for College Students in Jiangsu Province (201510313003Z, 201510313003, KYLX14-1455)Clinic Medical Special Foundation Of Jiangsu Province (b12014032)
文摘Objective:To report detection of vestibular-evoked myogenic potentials (VEMPs) in the miniature pig. Methods:Potentials evoked by 1000 Hz tone bursts were recorded from neck extensor muscles and the masseter muscles in normal adult Bama miniature pigs anesthetized with 3%pentobarbital sodium and Carbachol II. Results:The latency of the first positive wave P from neck extensor muscles was 7.65 ± 0.64 ms, with an amplitude of 1.66 ± 0.34 uv and a rate of successful induction of 75%at 80 dB SPL. The latency of potentials evoked from the masseter muscles was 7.60 ± 0.78 ms, with an amplitude of 1.31 ± 0.28 uv and a rate successful induction of 66%at 80 dB SPL. Conclusion:The latencies and thresholds of VEMPs recorded from the neck extensor muscle and the masseter muscle appear to be comparable in normal adult Bama miniature pigs, although the amplitude recorded from the neck extensor muscle seems to be higher than that from the masseter muscle. However, because of their usually relatively superficial and easily accessible location, as well as their large volume and strong contractions, masseter muscles may be better target muscles for recording myogenic potentials.
文摘This study aimed to develop a system to measure the flavor detection time for chewed solid and semi-solid foods. Twelve healthy young adults (seven males and five females) were asked to chew gummy candies with three different fruit flavors (grape, lemon, and pineapple) in a random order while their masseter activities were recorded by surface electromyograms on their habitual working and non-working sides. The participants were also asked to press a button as soon as possible with their preferred hand once they detected the flavor. The time interval between the start of chewing and the button press was measured;the start of chewing was defined as the start of a burst in the masseter electromyogram on the habitual working side. The average interval ranged from 2.82 s (lemon in males) to 4.63 s (grape in males);no significant differences were found between the three tested gummy candies or between the sexes of the participants. The present system can perform the measurements of the following two conventional measurement systems: 1) simple reaction time task for the taste and olfactory stimuli of fluids and vapors, respectively, and 2) time-intensity analysis of the flavor from solid and semi-solid foods, which does not generally consider the flavor detection time.
文摘Few studies have evaluated the effects of activity patterns of the jaw closing muscles assessed by specific parameters on jaw opening in subsequent cycles during the chewing of food. The objective of this study was to quantitatively analyze the effect of the masseter (jaw closer) activity patterns on suprahyoid (jaw opener) activity during subsequent cycles. The assessments were performed while participants naturally chewed six test foods that differed in size dimensions and textural properties. Surface electromyograms of the masseter (on the habitual working side) and suprahyoid muscles were recorded in ten healthy young adults, each of whom randomly received one of the six test foods. The activity patterns were assessed using three parameters specifically developed for their quantification. Changes in suprahyoid activity during each of the subsequent chewing cycles were examined by three amplitudinal (minimum, maximum, and net values of the integrated suprahyoid electromyogram) parameters and one durational (active duration) parameter. The main finding was that two of the three activity pattern parameters had a statistically significant effect only on the three amplitudinal parameters in three of the six test foods. These results suggest that masseter activity patterns partially affect suprahyoid activity during subsequent chewing cycles and that the effect is food dependent. A possible neural mechanism responsible for this effect is presented.
文摘This study analyzed the factors responsible for determining the flavor detection time for chewed semi-solid foods. Thirteen healthy young adults (eight males and five females) were asked to chew gummy candies with five different fruit flavors (i.e., apple, grape, orange, pear, and strawberry) in a random order. The detection time to flavor was measured using an electromyography-based system, which was recently developed by the authors. Briefly, each participant was recorded with surface masseter electromyograms on both sides to determine the start of chewing. Each participant was asked to press a button as soon as possible with his/her preferred hand after detecting the flavor. The time elapsed between the start of chewing and the button press was measured. Two taste components, sugars and organic acids, of the gummy candies were chemically analyzed, and two major sugars and organic acid were individually detected. The odor intensity was also analyzed for the gummy candies. The average detection time significantly differed among the five gummy candies and among the participants. Simple regression analyses revealed that the intensity of the odors was significantly associated with the average time intervals, but the amounts of the two major sugars and the organic acids were not. The analysis yielded the following equation for the regression estimation:?? (y = the time interval, x = the intensity of odors). The results suggest that the intensity of odors of the gummy candies, not the taste components, is responsible for determining the flavor detection time.
文摘The aim of this study was to quantify the relationships between four physiological parameters of masseter activity during chewing and properties related to the sizes and textures of the six representative test foods. The physiological parameters analyzed were the number of chewing cycles, chewing time, masseter amplitude, and cycle duration, which were obtained from masseter surface electromyography recorded in ten (seven male and three female) healthy, young participants. The six test foods differed in size dimensions (length, width, and height) and in textural properties (hardness, fracturability, and adhesiveness). The quantitative relationships were examined using linear regression. Nine statistically significant regression coefficients were found between the four physiological parameters and the textural properties, but not the height, of the test foods. From the regression coefficients, contributions of the food properties to the physiological parameters were estimated. Individual relationships between the physiological parameters and textural properties of the test foods are discussed in relation to their physiological implications.
文摘This study examined the effects of the textural properties and chemical components of foods on masseter activity patterns. Ten healthy young participants (seven men and three women) were asked to chew four gummy candies with different flavors while their masseter activities were recorded by a surface electromyogram. The masseter activity patterns during chewing were analyzed quantitatively using a TP technique, generating three TP values (T25, T50 and T75). The textural analysis included four representative properties, and six sugars and four organic acids were tested in the chemical analysis. The hierarchical cluster analysis classified the T25 and T75 values into four subclusters and classified the T50 values into three subclusters. Two T75 subclusters differed significantly in the combined amounts of the two predominant sugars (sucrose and maltose);however, these T75 subclusters did not differ in their organic acid contents or textural properties. Therefore, sucrose and maltose affect masseter activity patterns during chewing, particularly in the later stage of masseter activity.
文摘We present the case of a 4 year old girl whose adenoidectomy had to be performed via an endoscopictrans oral approach due to the unexpected inability to fully open the mouth during the procedure. The patient had previously been taking Risperidone for behavioral symptoms associated with her autism. The jaw tone returned to normal following the procedure and there were no complications. An interaction between the Risperidone and the anesthetics were the likely cause of the trismus.
基金the National Natural Science Foundation of China(grant no.81671964,2017/01–2020/12).
文摘Background:Botulinum toxin type A injection,a noninvasive alternative method for treating masseteric hypertrophy,is inadequate for treating patients with a round lower face.This study aimed to investigate the operative technique and clinical results of liposuction followed by botulinum toxin type A injections in patients with masseteric hypertrophy and excessive subcutaneous fat.Methods:Sixty-five patients(50 women and 15 men)were treated using this technique between May 2014 and January 2019.Their mean age was 26.3 years(range,18–35 years)and the mean follow-up period was 13 months(range,8–18 months).Results:All patients achieved slimmer lower cheeks with improved jaw definitions after the procedure.Among the 65 patients,61(94%)expressed satisfaction with the results and believed that the procedure produced their desired face shape.No major complications were observed.The effect of this combination treatment remained stable for 12 months after the procedure.Conclusion:The authors believe that liposuction followed by botulinum toxin type A injections is an effective technique for the treatment of masseteric hypertrophy and excessive subcutaneous fat.It is also a relatively simple and safe treatment approach.
