The assessment method of lip closure ability based on sEMG nonlinear onset detection algorithms.

OBJECTIVES: To overcome the limitations of traditional diagnosis of orbicularis oris muscle function in mouth-breathing patients, this study aims to propose a surface electromyographic (sEMG) based method for reliable and accurate quantitative assessment of lip closure ability. METHODS: A total of 21 volunteers (16 patients and 5 healthy subjects, aged 8-16) were included in the study. Three nonlinear onset detection algorithms - Teager-Kaiser Energy (TKE) operator, Sample Entropy (SampEn), and Fuzzy Entropy (FuzzyEn) - were compared for their ability to identify lip closure in sEMG signals. Lip Closure EMG Activity Index (LCEAI) was proposed based on the action segments detected by the best performing algorithm for the quantitative assessment of lip closure. RESULTS: The results indicated that FuzzyEn had the highest lip closure identification rate at 93.78 %, the lowest average onset delay of 47.50 ms, the lowest average endpoint delay of 73.10 ms, and the minimal time error of 111.61 ms, exhibiting superior performance. The calculation results of the LCEAI closely corresponded with the actual degree of lip closure in patients. CONCLUSIONS: The lip closure ability assessment method proposed in this study can provide a quantitative basis for the diagnosis of mouth breathing.

A Comparison Between Skeletal Class II and Class III Malocclusion Patients in Terms of the Masticatory Muscles' Activity: A Cross-Sectional Study.

Background This study aimed to determine if individuals with skeletal Class II and skeletal Class III malocclusions had different levels of masticatory muscle activity. Materials and methods This cross-sectional study, conducted at the University of Damascus, investigated the myoelectric activity of perioral muscles in patients with Class II and III malocclusions. The sample size of 60 patients was determined according to a prior sample size calculation. Patients were selected based on specific inclusion and exclusion criteria and divided into Class II and III groups. Electromyography was used to monitor the activity of various muscles, including the temporalis, masseter, orbicularis oris, buccinator, mentalis, and digastric muscles. Results The study found similar muscle activity within the same group in the temporalis, masseter, buccinator, digastric, and orbicularis oris muscles. No significant differences were observed between the Class II and III groups for several oral and perioral muscles (P > 0.05). However, the mean activity of the digastric muscle was significantly greater in the Class II group (P < 0.05), whereas the mean activity of the mentalis muscle was smaller in the Class II group (P < 0.05). Conclusions Perioral muscles influence facial complex development and jaw relationship, affecting orthodontic treatment. Digastric muscle activity is greater in Class II patients, while mental muscle activity is smaller in Class III patients. Further studies are needed for older age groups and other skeletal malocclusion types.

Long-term results of orbicularis oris muscle reconstruction in primary cleft lip repair using the "basket-weave method".

The basket-weave method is an orbicularis oris muscle reconstruction method used in primary unilateral cleft lip repair. We compared the long-term results of the basket-weave method with those of a conventional method. For primary unilateral cleft lip repair, we compared the long-term results of 7 cases in which the orbicularis oris muscle was reconstructed by use of the basket-weave method, and of 7 cases in which the reconstruction was performed by use of the conventional method. The average postoperative follow-up period was 12 years and 7 months for the basket-weave method, and 11 years and 9 months for the conventional method. Using photographs of the front and elevation angle views, we evaluated the results as good if the philtrum ridge was formed on the fissure side and was almost symmetrical in height; as fair if the philtrum ridge was lower than the normal side; and as poor if the philtrum ridge had disappeared. For the basket-weave method, the results were good in 6 cases (85.7%), fair in 1 case (14.3%), and poor in 0 cases. For the conventional method, the results were good in 2 cases (28.6%), fair in 4 cases (57.1%), and poor in 1 case (14.3%). A significant difference was found between the 2 groups (Mann-Whitney U test, P = 0.0417). The philtrum ridge shape could be reconstructed by use of the basket-weave method, which gave better results in the long-term than did the conventional method for orbicularis oris muscle reconstruction in primary unilateral cleft lip repair.

"Untying the knot": The primitive orofacial muscle architecture in the gorilla (Gorilla gorilla) as a key to the evolution of hominin facial movement.

The anatomical underpinnings of primate facial expressions are essential to exploring their evolution. Traditionally, it has been accepted that the primate face exhibits a "scala natura" morphocline, ranging from primitive to derived characteristics. At the primitive end, the face consists of undifferentiated muscular sheets, while at the derived end there is greater complexity with more muscles and insertion points. Among these, the role of the human modiolus ("knoten" in German) has been emphasized. Recent studies have challenged this view by revealing significant complexity in the faces of several non-human primates, thereby rejecting the linear notion of facial evolution. However, our knowledge of the facial architecture in gorillas, the second closest living relatives to modern humans, remains a significant gap in the literature. Here, we present new findings based on dissection and histological analysis of one gorilla craniofacial specimen, alongside 30 human hemifaces. Our results indicate that while the number and overall arrangement of facial muscles in the gorilla are comparable to those of chimpanzees and modern humans, several orofacial features distinguish the gorilla's anatomy from that of hominins. Among these are the absence of a modiolus, the continuity of muscular fibers over the region of the mouth corner, the flat (uncurving) sheet of the orbicularis oris muscle, and the insertion of direct labial tractors both anterior and posterior to it. Collectively, the anatomical characteristics observed in the gorilla suggest that the complex anatomy of the hominin face should be considered synapomorphic (shared-derived) within the Pan-Homo clade.

Evaluación cefalométrica y electromiográfica de niños y niñas con incompetencia labial y anomalías dentomaxilares / Cephalometric and electromyographic evaluation in children with lip incompetence and dentomaxillary anomalies

Objetivo: Describir las características craneofaciales, dentoalveolares, de tejido blando, vía aérea y el patrón de actividad muscular determinadas a través de los estudios cefalométricos y electromiográficos de individuos incompetentes labiales y con presencia de anomalías dentomaxilares de 7 a 12 años de edad. Materiales y método: Cuarenta y seis participantes con incompetencia labial fueron sometidos a una toma de radiografía lateral de perfil para el análisis cefalométrico. Para el estudio electromiográfico se consideró el patrón de actividad de los músculos Orbicular superior de los labios, orbicular inferior de los labios y temporal anterior en funciones: reposo, fonoarticulación, deglución, máximo apriete labial. Resultados: Se observó clase II esqueletal y molar, retrusión mandibular, biprotrusión incisal, biprotrusión labial, disminución de vía aérea superior. La mayor actividad muscular fue observada en máximo apriete labial. Conclusión: Los niños y niñas con incompetencia labial y anomalías dentomaxilares presentan alteraciones en las características craneofaciales, dentoalveolares, de tejido blando, vía aérea y actividad muscular determinadas a través de los estudios cefalométricos y electromiográficos.

Objective: To describe craniofacial, dentoalveolar, soft issue and airway features, and the muscular activity, determined through a cephalometric and electromyographic study in individuals with lip incompetence and dentomaxillary anomalies aged 7 to 12 years. Methods: Forty-six participants with lip incompetence underwent lateral profile radiography for cephalometric analysis. For the electromyographic study, the activity of the superior orbicularis oris, inferior orbicularis oris and anterior temporalis muscles was considered in the following functions: rest, speaking, swallowing, and reciprocal compression of the lips. Results: Skeletal and molar class II, mandibular retrusion, labial biprotrusion, incisal biprotrusion, and upper airway dysfunction were found. The highest muscular activity was observed in reciprocal compression of the lips. Conclusion: Children with lip incompetence and dentomaxillary anomalies have alterations in the craniofacial, dentoalveolar, soft issue, and airway features, and in the muscular activity , determined through a cephalometric and electromyographic study.

Relationship between EMG features and force in orbicularis oris muscle.

BACKGROUND: Lip incompetence resulting from mouth breathing is a common clinical manifestation, while there are no definite indicators of amplitude and intensity of muscle functional training in clinical practice, which leads to unsatisfactory training results. OBJECTIVE: The aim was to quantify the relationship between electromyography (EMG) and force in orbicularis oris muscle, so that the indicators of muscle functional training can be evaluated using EMG signals, so as to improve the training effects. METHODS: The EMG and the force signals of orbicularis oris muscle from 0% to 100% MVC within 5 s in twelve healthy subjects (six males and six females; age, 25 ± 2 years; mass, 60 ± 15 kg) were recorded simultaneously for three trials. Four EMG features consisting of RMS, WAMP, SampEn and FuzzyEn were analyzed. The regression analyses were performed using first-order and third-order polynomial model. RESULTS: There were high correlations between the four EMG features and muscle force with the two models. The third-order model yielded a higher coefficient of determination (R2) than the linear model (p< 0.001) and the result of FuzzyEn (R2: 0.884 ± 0.059) was the highest in the four features. CONCLUSION: The third-order model with FuzzyEn of EMG signals may be used to guide the muscle functional training.

The comparison of tone and viscoelastic properties of superior orbicularis oris muscle in multiple sclerosis patients to healthy individuals.

BACKGROUND: The orbicularis oris muscle is an important muscle for oral perception in mouth and swallowing rehabilitation. The muscle can be affected in patients with multiple sclerosis for many reasons. It is important to understand the quantitative changes in this muscle to determine the many problems associated with the cranio-facial region in multiple sclerosis. Therefore, this study aimed to compare the mechanical properties of the orbicularis oris muscle between MS patients and healthy individuals. METHODS: A total of 55 individuals (28 with multiple sclerosis and 27 healthy) who met the inclusion criteria were evaluated. The tone and viscoelastic properties (elasticity and stiffness) of the superior orbicularis oris muscle of both groups were evaluated bilaterally in the supine position with the MyotonPro® (Myoton AS, Estonia) device. The reference point of the muscle is accepted as the right and left paramedial philtrum dimple. RESULTS: It was observed that there was no difference in terms of stiffness values of the right and left orbicularis oris muscles of both groups (p>0.05). The tone and the elasticity of the muscle on both sides were higher in the HI group than MS group (p<0.05). CONCLUSION: We think that the orbicularis oris muscle has a central location in the facial region, and that this muscle may be the key muscle for the symptoms arising from many neurological mechanisms. The decrease in muscle tone and elasticity may be the beginning of the changes in MS patients. We believe that the data from this muscle will be useful for comparative studies.

Blefaroplastia inferior transcutánea con fijación muscular orbicular externa en pacientes con deformidades del párpado inferior / Transcutaneous lower blepharoplasty with external orbicularis oculi muscle fixation in patients with lower eyelid deformities

Objetivo: Describir el resultado de la técnica de fijación muscular orbicular externa en la Blefaroplastia inferior. Método: Se realizó una investigación descriptiva, prospectiva en pacientes que asistieron a la consulta de Cirugía Plástica del Hospital "Camilo Cienfuegos" entre enero 2018 a enero 2019, la muestra estuvo constituida por 43 pacientes. Para diagnosticarlos se utilizó la clasificación de Ginsbach, con criterios de exclusión el hábito de fumar. Se tuvo en cuenta variables como edad, sexo, deformidad palpebral inferior, complicaciones en el post operatorio a las 24 h y a los 30 días, y grado de satisfacción de los pacientes intervenidos. Se utilizaron métodos de revisión documental, observación, análisis y síntesis y empírico (encuesta), utilizadas para evaluar los resultados. La investigación se realizó siguiendo procedimientos éticos. Resultados: Mostraron que la mayor cantidad de pacientes estuvo en el grupo edad entre 46-50 años todos femeninos, el exceso de piel y las patas de gallina fueron las deformidades que predominaron. La complicación que se presentó fue el sangramiento posoperatorio resuelto en las primeras horas, 42 pacientes refirieron estar satisfechos. Conclusiones: La blefaroplastia es una técnica que se ha venido modificando junto a la necesidad de brindar procedimientos que ofrezcan seguridad y efectividad, en cuanto a la corrección de deformidades en el parpado inferior, con un adecuado tiempo de recuperación, resultados con menor riesgo de complicaciones(AU)

Objective: To describe the outcome of the external orbicularis oris muscle fixation technique in lower blepharoplasty. Methods: A descriptive, prospective research was conducted in patients who attended the Plastic Surgery consultation of the Hospital "Camilo Cienfuegos" from January 2018 to January 2019, the sample consisted of 43 patients. In order to diagnose them, the Ginsbach classification was used, with smoking as exclusion criteria. Variables such as age, gender, lower palpebral deformity, postoperative complications at 24 h and 30 days, and degree of satisfaction of the operated patients were taken into account. Documentary review, observation, analysis and synthesis and empirical (survey) methods were used to evaluate the results. The research was carried out following ethical procedures. Results: They showed that the greatest number of patients was in the age group between 46-50 years old, all of them female; excess skin and goose bumps were the predominant deformities. The complication that occurred was postoperative bleeding resolved in the first hours, 42 patients reported to be satisfied. Conclusions: Blepharoplasty is a technique that has been modified along with the need to provide procedures that offer safety and effectiveness, in terms of correction of deformities in the lower eyelid, with adequate recovery time, results with lower risk of complications(AU)

A Systematic Review of the Role of Mitochondria in Cleft Pathology: A Forgotten General?

ABSTRACT@#Orofacial clefts (OFC) are one of the most common birth defects that affects the lip, palate, or lip and palate of an infant. The deterioration of clefts is multifactorial involving multiple genes, various interactions from environmental factor and most forgotten, mitochondrial abnormality. The aim of this review is to highlight the importance of mitochondrial activity related to non-syndromic OFC deformity. Despite its important role in cells, the study on mitochondrial activity in cleft pathology was scarce and almost forgotten compared to other genetic investigations. This systematic review was completed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. The literature search was done via the following databases: Google Scholar, Pubmed and Scopus with a total of nine studies of mitochondrial abnormalities were included. We hypothesise that mitochondria play an important role in early craniofacial development. A decreased in its function or activity may result in cleft lip formation. Hence, we would like to shed light on the remarkable role of mitochondria activity in the pathogenesis of non-syndromic OFC.

Lateral spread response of different facial muscles during microvascular decompression in hemifacial spasm.

OBJECTIVE: Interpreting lateral spread response (LSR) during microvascular decompression (MVD) for hemifacial spasm (HFS) is difficult when LSRs observed in different muscles do not match. We aimed to analyze LSR patterns recorded in both the orbicularis oris (oris) and mentalis muscles and their relationships with clinical outcomes. METHODS: The data of 1288 HFS patients who underwent MVD between 2015 and 2018 were retrospectively reviewed. LSR was recorded in the oris and mentalis muscles through centrifugal stimulation of the temporal branch of the facial nerve after preoperative mapping. The disappearance of LSR following surgery, clinical outcomes, and the characteristics of LSR in oris were analyzed. RESULTS: After surgery, LSR remained in 100 (7.7%) and 279 (21.6%) of the mentalis and oris muscles, respectively. The postoperative outcome correlated with LSR disappearance in the mentalis, not with that in the oris. CONCLUSION: LSR patterns differed in each muscle and may not be correlated with clinical outcomes. LSR in the mentalis and oris muscles should be interpreted differently. SIGNIFICANCE: We describe a monitoring protocol characterized by preoperative facial nerve mapping, antidromic stimulation, and recording from multiple muscles. We analyze differences in LSRs in the mentalis and oris muscles and suggest technical points for interpretation.

Effect of Lip-seal Resistance Training on Lip-seal Strength in Young Adults.

Lip-seal strength is important for articulating bilabials, capturing food during eating, maintaining fluid within the oral cavity before swallowing, and achieving swallowing pressure. The objective of this study was to investigate the effect of lip-seal resistance training on lip-seal strength in young adults. The participants comprised 15 young healthy adults aged 26-34 years, all with complete dentition. Each was required to perform lip-seal resistance training 5 weekdays a week for 4 weeks with a commercially available instrument for that purpose. The instrument was placed on the midline, left corner, and right corner of the mouth, and pulled forward, leftward, and rightward, respectively. The participants were required to pull the training instrument forcefully while resisting by closing the lips together as strongly as possible until the instrument exited the lips. Lip-seal strength was measured at before and after training using a measurement device. Change in lip-seal strength between before and after training was analyzed using the Wilcoxon signed rank test. The mean lip-seal strength was 8.9±1.5 N before training and 10.4±1.8 N after. A significant difference was observed in lip-seal strength between before and after training (p=0.003), and the mean increase during the training period was 18.1±17.6%. The results showed that lip-seal resistance training for 4 weeks increased lip-seal strength in young adults. These findings suggest that training that involves pulling not only in a forward direction, but also in bilateral directions strongly stimulates the orbicularis oris muscle, resulting in an increase in lip-seal strength.

Congenital Cheek Fistula: A Rare Case of Developmental Abnormality in the Buccal Area.

A congenital cheek fistula is a rare malformation in the buccal area. Here, we report the case of a congenital cheek fistula in a 50-year-old woman who visited our clinic with complaints of swelling and pain in her left cheek. Physical examination revealed a small hole in the left corner of the mouth present since birth. She had no other congenital malformations in the maxillofacial region such as an accessory ear and cleft lip. Manual compression of the cheek mass induced serous discharge from the hole. Magnetic resonance imaging (MRI) showed a cystic lesion in the left cheek and a fistula within the orbicularis oris muscle that opened into the small hole. After immediate incision and drainage of the cyst, both the cyst and fistula were surgically resected. The cystic lesion was completely delineated from the boundary of the parotid gland. The orbicularis oris muscle was partially incised to remove the fistula and the surrounding scar tissue. Histopathological examination of the resected specimen revealed a cavity consisting of epithelium inside the fistula. The postoperative course was insignificant. No recurrence of the cyst was observed six months postoperatively. The operative and pathological findings demonstrated that the ectoderm-derived epithelial tissue was enclosed by the mesoderm-derived muscle tissue. The mixture of different germ layer-derived tissues suggested that the fistula was a type of congenital transverse facial cleft induced by malfusion of the mandibular and maxillary prominences during embryonic development. The differential diagnoses of the congenital cheek fistula included orocutaneous fistulas and salivary fistulas. MRI was useful in delineating the border between the lesion and the surrounding tissue.

Superior Orbicularis Oris Muscle Activity in Children Surgically Treated for Bilateral Complete Cleft Lip and Palate.

The aim of this cross-sectional study was to evaluate the electromyographic activity of the superior orbicularis oris muscle both in children surgically treated for bilateral complete cleft lip and palate (BCCLP) as well as in subjects without BCCLP. The study comprised 77 children aged 6.6 to 12.5 years. All the patients with clefts had previously undergone lip and palate surgery. The upper lip electromyographic (EMG) assessments were made with a DAB-Bluetooth device (Zebris Medical GmbH, Germany) at rest, while swallowing saliva, protruding lips and compressing lips. EMG measurements were also made when the subjects produced phonemes /p/, /b/, and /m/ with the vowel /a/. The Mann-Whitney U test was applied to statistically analyze the EMG values. Significantly higher median upper lip EMG activity under working conditions such as swallowing saliva, lip compression, and production of the phoneme /p/ with the vowel /a/ was observed in patients with BCCLP compared to those without a cleft. The results of the study showed that the upper lip muscle activity increases in children with BCCLP when swallowing saliva, compressing lips and during some speech movement tasks. This may be important in the aspect of the effect of surgical lip repair on the craniofacial growth.

Effective training duration and frequency for lip-seal training in older people using a self-training instrument.

OBJECTIVE: To determine the effects of the training duration and frequency on lip-seal strength (LSS) in older people. BACKGROUND: Lip-seal is important for speaking, eating and swallowing. LSS decreases after training ends; therefore, continuous training is essential. MATERIALS AND METHODS: Participants underwent the resistance training of LSS. Regarding training duration, eight women aged ≥65 years participated in a crossover study with trainings A (direction: 1, duration: 50 seconds) and B (directions: 3, duration: 3 minutes), daily for 4 weeks. Regarding training frequency, 40 women aged ≥65 years were divided into four groups based on frequency (everyday, every-other-day, once-a-week and control groups), and all groups excluding the control group performed training B for 4 weeks. LSS was measured at weeks 0, 2 and 4 using a digital strain gauge. Friedman's test was used, followed by Steel-Dwass test (α = 0.05). RESULTS: Regarding the effects of the training duration, significant differences in LSS were noted between weeks 0 and 4 for training B, but no difference was noted for training A. Regarding training frequency, significant differences were observed between weeks 0 and 2 or 4 in the everyday and once-a-week groups. Significant differences were observed in the every-other-day group between weeks 0 and 4 and no difference in the control group. For all groups, median LSS was higher in week 2 or 4 than that in week 0. CONCLUSION: Lip-seal training for 3 minutes per session everyday, every-other-day or once-a-week for 4 weeks increased LSS of older people.

Quantitative evaluation of elasticity of lower orbicularis oris muscle during the lip closing measurement using sonographic elastography.

BACKGROUND: Lip closing functions have never been evaluated from the viewpoint of elastic properties. OBJECTIVES: The purpose of the present study was to investigate the behavior of the lower orbicularis oris muscle during a button-pull exercise to measure lip closing force and quantitatively evaluate its elastic properties using sonographic elastography. METHODS: Appropriate compression loads for elastography were randomly measured on one of three types of acoustic couplers on three examiners. Compression tests were performed on three types of acoustic couplers within the appropriate compression load. Using the acoustic coupler with the lowest elastic modulus, the strain ratio of the lower orbicularis oris muscle during lip closing was measured, and elastography was performed on six males under tension loads of 0-8 N. RESULTS: The intraclass correlation coefficient (1, 3) for the tension load of 0 N was 0.81. Elastography showed that the strain ratio values increased significantly (p < 0.05) as the tension load increased. CONCLUSIONS: Combining the data obtained from lip closing test devices and sonographic elastography enabled the muscle performance to be evaluated objectively and accurately.

[Study on the matching feature of current parameters for inducing contraction of orbicularis oris muscle by artificial facial nerve in rabbit with peripheral facial paralysis].

Objective: To explore the optimal matching of the current parameters about artificial facial nerve (AFN) for inducing contraction of the orbicularis oris muscle (OOM) in rabbit with peripheral facial paralysis. Methods: According to the combinations of different stimulus parameters, at different time points, we used AFN to induce contraction of the affected side OOM of the paralyzed rabbit in waking state. We recorded the current amplitudes of the threshold stimulation and peak stimulation under each combination, then compared the total charge of the stimulus consumption under different combinations. Results: Compared the total stimulus charge consumption of the AFN threshold stimulation and that in the peak stimulation respectively under different stimulus frequency and pulse width matching combinations, we found that the frequency, the pulse width and the interaction of the frequency and pulse width among different groups could affect the total charge, the differences were statistically significant (P<0.05). Conclusions: When AFN stimulus frequency is 60 Hz and the stimulus pulse width is 100 µs, the output current intensity is relatively lowest and the total consumed charge is the lowest under the premise of effectively inducing the paralytic side OOM contraction. Thus we recommend this stimulus parametric combination as the optimal combination for meeting the low power consumption of AFN.

Long-term comparison study of philtral ridge morphology with two different techniques of philtral reconstruction.

Cleft lip and/or cleft palate are the most common congenital craniofacial anomalies. Philtral ridge morphology is an important aesthetic component of unilateral cleft lip (UCL) repair. To this end, we have developed two techniques of philtral ridge reconstruction: (1) asymmetric mattress muscle sutures, and (2) overlapping mattress muscle sutures. The objective of this retrospective cohort study was to compare their outcomes in UCL repairs. Group I patients (n=30) underwent UCL repair before August 2003, including philtral ridge reconstruction by asymmetric mattress muscle sutures. Group II patients (n=30) underwent UCL repair after August 2003, including philtral ridge reconstruction by overlapping mattress muscle sutures. Philtral morphology was evaluated by ultrasonographic and three-dimensional photographic measurements, examining cleft side philtral projection and philtral ridge symmetry. These demonstrated that group II patients had better philtral column symmetry and projection on the cleft side when compared to group I. Overlapping mattress muscle sutures produced better philtral morphology in UCL repairs than asymmetric mattress muscle sutures.

Orbicularis oris muscle reconstruction and cheiloplasty with Z-plasty in a patient with a transverse facial cleft.

BACKGROUND: Transverse facial clefts are Tessier's number 7 facial cleft among numbers 1-15 in Tessier's classification of craniofacial malformations, which varies from a simple widening oral commissure to a complete fissure extending towards the external ear. CASE PRESENTATION: In a patient with a transverse facial cleft, to functionally arrange the orbicularis oris muscle and form the oral commissure naturally, we performed a surgical procedure including orbicularis oris muscle reconstruction and cheiloplasty with Z-plasty. CONCLUSION: We achieved good results functionally and esthetically by orbicularis oris muscle reconstruction and cheiloplasty with Z-plasty. The surgical modality of our anatomical repair and 3 months follow-up results are presented.

[Study on the method of microelectrodes implantation of artificial facial nerve prosthesis in closed mouth of orbicularis oris muscle in monkeys with facial nerve paralysis].

Objective: To explore the optimal method of microelectrode implantation that can produce efficient mouth closure with microelectrode for orbicularis oris muscle (OOM) in rhesus monkeys with unilateral peripheral facial paralysis (UPFP) in order to provide basis for the research and development of artificial facial nerve prosthesis (AFNP). Methods: Right lateral peripheral facial paralysis model on four healthy rhesus monkeys (two males and two femles, aged 5-6 years, weighed 2.0-3.0 kg) were prepared. AFNP electric stimulation was used to induce closed-mouth reaction of the affected OOM with a one-way rectangular pulse, 50 Hz frequency and 0.2 ms pulse width in vitro. Around the affected lateral OOM, four stimulus electrodes implantation positions were selected at the upper lip (position A), the lower lip (position B), the connection with the corner of the mouth to the ipsilateral tragus (position C), and the horizontal line of the mouth angle (position D). According to the different implantation positions of three stimulation electrodes on the stimulation side of AFNP and the results of our previous study, six groups of microelectrode implantation methods were designed. In Group A, two microelectrodes were implanted at position A and one microelectrode was implanted at position B; in Group B, one microelectrode was implanted at position A, B and C respectively; in Group C, one microelectrode was implanted at position A and two microelectrodes were implanted at position B; in Group D, one microelectrode was implanted at position A, B and D respectively; in Group E, one microelectrode was implanted at position A, C and D respectively; in Group F, one microelectrode was implanted at position B, C and D respectively. The minimum stimulating current (threshold current) required for effective mouth closure were recorded. The threshold and peak current values were compared using one-way ANOVA and LSD-t multiple comparisons. Results: The microelectrodes of the AFNP stimulating side in Group E and F failed to induce a smooth mouth closure. The microelectrodes in A, B, C and D group induced smooth mouth closure. The threshold current value of OOM contraction on affected side in the Group A, B, C, and D were (1.35±0.05), (1.02±0.04), (1.40±0.04) and (1.10±0.02) mA, respectively (F=295.302, P<0.001), with the lowest value in Group B and there was significant difference between the current value in Group B and those in the other groups (all P<0.05). The peak current value of OOM contraction on affected side in the four groups were (3.95±0.02), (2.95±0.03), (3.99±0.05) and (3.51±0.01) mA, respectively (F=1 014.985, P<0.001). Group B showed the best lip-closure morphology observed with naked eyes. Conclusions: When three output microelectrode of the AFNP stimulated side are separately imbedded into the upper lip, the lower lip and the connection with the corner of the mouth to the ipsilateral tragus, AFNP can sufficiently induce closed-mouth reaction. These positions are suitable as priority options microelectrodes implantation positions for the microelectrodes of the AFNP stimulated side.