Patterns of coordinated lower facial muscle function and their importance in facial reanimation

Comparison of Facial Muscle Activation Patterns Between Healthy and Bell's Palsy Subjects Using High-Density Surface Electromyography

Facial muscle activities are essential for the appearance and communication of human beings. Therefore, exploring the activation patterns of facial muscles can help understand facial neuromuscular disorders such as Bell’s palsy. Given the irregular shape of the facial muscles as well as their different locations, it should be difficult to detect the activities of whole facial muscles with a few electrodes. In this study, a high-density surface electromyogram (HD sEMG) system with 90 electrodes was used to record EMG signals of facial muscles in both healthy and Bell’s palsy subjects when they did different facial movements. The electrodes were arranged in rectangular arrays covering the forehead and cheek regions of the face. The muscle activation patterns were shown on maps, which were constructed from the Root Mean Square (RMS) values of all the 90-channel EMG recordings. The experimental results showed that the activation patterns of facial muscles were distinct during doing different facial movements and the activated muscle regions could be clearly observed. Moreover, two features of the activation patterns, 2D correlation coefficient (corr2) and Centre of Gravity (CG) were extracted to quantify the spatial symmetry and the location of activated muscle regions respectively. Furthermore, the deviation of activated muscle regions on the paralyzed side of a face compared to the healthy side was quantified by calculating the distance between two sides of CGs. The results revealed that corr2 of the activated facial muscle region (classified into forehead region and cheek region) in Bell’s palsy subjects was significantly (p < 0.05) lower than that in healthy subjects, while CG distance of activated facial region in Bell’s palsy subjects was significantly (p < 0.05) higher than that in healthy subjects. The correlation between corr2 of these regions and Bell’s palsy [assessed by the Facial Nerve Grading Scale (FNGS) 2.0] was also significant (p < 0.05) in Bell’s palsy subjects. The spatial information on activated muscle regions may be useful in the diagnosis and treatment of Bell’s palsy in the future.

Facial Muscle Activity Patterns in Clarinet Players: A Key to Understanding Facial Muscle Physiology and Dysfunction in Musicians

OBJECTIVES

Facial muscle activity is crucial to controlling musical performance in wind instrument playing. Facial muscle dysfunctions are common in wind instrument players, dramatically affecting their professional musical activity and potentially leading to disabling symptoms.The aim of this pilot study on a cohort of healthy clarinetists was to use surface electromyography to identify the facial muscle activity patterns involved in stabilizing the mouthpiece, controlling emission and articulation during musical tasks in physiological conditions, also comparing muscle activity between less and more experienced clarinetists (students vs postgraduates/professionals).

METHODS

Surface electromyographic measures of the sternocleidomastoid, masseter, mentalis, mylohyoid and buccinator muscles were obtained from eight healthy clarinet players (four students and four postgraduates/professionals) performing two standardized musical tasks.

RESULTS

Overall, mean IEMG activity was significantly lower for the sternocleidomastoid than for the other muscles (P = .000), and for the mouthpiece-stabilizing muscles (masseter and mentalis) than for those directly involved in controlling emission and articulation (buccinator and mylohyoid muscles) (P = .000).Regardless of the musical task, the mean IEMG values were significantly higher in the students for the masseter (P = .0007), buccinator (P = .0001) and mylohyoid (0.000), while they were significantly higher in the postgraduates/professionals for the mentalis (P = .000). No significant differences emerged between the two groups for the sternocleidomastoid (P = .207).

CONCLUSIONS

These preliminary data reflect a significantly higher overall facial muscle activity in the less-experienced group, potentially resulting in an overload, whereas the more expert players had more optimized muscle activity patterns.

Perceptual and instrumental assessments of orofacial muscle tone in dysarthric and normal speakers

Clinical assessment of orofacial muscle tone is of interest for differential diagnosis of the dysarthrias, but standardized procedures and normative data are lacking. In this study, perceptual ratings of tone were compared with instrumental measures of tissue stiffness for facial, lingual, and masticatory muscles in 70 individuals with dysarthria. Perceptual and instrumental tone data were discordant and failed to discriminate between five dysarthria types. These results raised concerns about the validity of Myoton-3 stiffness measures in the orofacial muscles. Therefore, a second study evaluated contracted and relaxed orofacial muscles in 10 neurotypical adults. Results for the cheek, masseter, and lateral tongue surface followed predictions, with significantly higher tissue stiffness during contraction. In contradiction, stiffness measures from the superior surface of the tongue were lower during contraction. Superior-to-inferior tongue thickness was notably increased during contraction. A third study revealed that tissue thickness up to ~10 mm significantly affected Myoton-3 measures. Altered tissue thickness due to neuromuscular conditions like spasticity and atrophy may have undermined the detection of group differences in the original sample of dysarthric speakers. These experiments underscore the challenges of assessing orofacial muscle tone and identify considerations for quantification of tone-related differences across dysarthria groups in future studies.

An anatomical study of the risorius in Asians and its insertion at the modiolus

PURPOSE

Detailed explanations of the insertion, interaction patterns, and arrangement of the risorius muscle fibers at the modiolus have still not been clearly shown. The aim of this study is to clarify the arrangement of the risorius muscle by means of topographic examination, and to evaluate the anatomical variations in its attachments and pattern of shape to other perioral muscles, and eventually to understand the various features of the facial animation of Asians.

MATERIALS AND METHODS

Eighty embalmed Korean and Thai adult hemifaces from cadavers of both genders were dissected in this study. Detailed dissection at the modiolus revealed the insertion of the risorius muscle in relation to its attachments and fiber interaction forms.

RESULTS

When categorized into three common anatomical types--zygomaticus risorius (ZR), platysma risorius (PR), and triangularis risorius (TR). PR was most common with 45 % (36 cases) frequency. Risorius muscle also inserted into the modiolus in three distinct layers in relation to the depressor anguli oris: superficial, flush, and deep. Superficial attachment was most commonly found with 56.3 % (45 cases) frequency.

CONCLUSIONS

These results will provide critical information for future planning and performing of reconstructive, reanimation, and cosmetic surgical procedures for cases such as developmental defect, facial trauma, facial muscle paralysis, and restoring the natural personal appearances.

Somatotopic Organization of Perioral Musculature Innervation within the Pig Facial Motor Nucleus

The orbicularis oris and buccinator muscles of mammals form an important subset of the facial musculature, the perioral muscles. In many taxa, these muscles form a robust muscular hydrostat capable of highly manipulative fine motor movements, likely accompanied by a specialized pattern of innervation. We conducted a retrograde nerve-tracing study of cranial nerve (CN) VII in pigs (Sus scrofa) to: (1) map the motor neuron pool distributions of the superior and inferior orbicularis oris, and the buccinator, to test the hypothesis that perioral muscle motor neuron pools exhibit a somatotopic organization within the facial motor nucleus; and (2) test the hypothesis that portions of the superior orbicularis oris (SOO) motor neuron pool also exhibit a somatotopic organization, reflecting a potential compartmentalization of function of the rostral, middle, and caudal segments of this muscle. Cresyl violet histological staining showed that the pig facial motor nucleus was comprised of 7 well-defined subnuclei. Neuroanatomical tracers injected into these perioral muscles transported to the motor neuron pools of the lateral 4 of the 7 subnuclei of the facial motor nucleus. The motor neuron pools of the perioral muscles were generally segregated from motoneurons innervating other facial muscles of the rostrum. However, motor neuron pools were not confined to single nuclei but instead spanned across 3-4 subnuclei. Perioral muscle motor neuron pools overlapped but were organized somatotopically. Motor neuron pools of portions of the SOO overlapped greatly with each other but exhibited a crude somatotopy within the SOO motor neuron pool. The large and somatotopically organized SOO motor neuron pool in pigs suggests that the upper lip might be more richly innervated than the other perioral muscles and functionally divided.

Variability of the midfacial muscles: analysis of 50 hemifacial cadaver dissections

The region of the midface represents a challenging area to both reconstructive and aesthetic surgeons. An anatomic study was performed that attempted to identify patterns and variations of the muscular anatomy. The goals of this study were twofold: to identify patterns and variability of the midfacial muscles that might impact on reconstructive efforts and to attempt to correlate this anatomy with features of the overlying soft tissues, specifically the nasolabial crease. Fifty hemifacial cadaver dissections were performed. The information collected was assembled into a large data base, and statistical significance was analyzed using Fisher's exact probability test. Results demonstrated that, although a great degree of variability exists with respect to the midfacial muscles, seven distinct patterns of these muscles did emerge. The most common pattern was the presence of a levator alae nasi, levator labii superioris, and zygomaticus major, which occurred in 44 percent of specimens. Specimens that possessed a risorius, zygomaticus minor, or both, were relatively uncommon. The consistent presence of the levators suggests adding a superior vector to recreate a smile in facial reanimation surgery. Two important anatomic variations were noted. A bifid zygomaticus major was found to be present in 34 percent of individuals. Because the inferior bundle had a dermocutaneous insertion, this anomaly may represent the anatomic correlate of a cheek "dimple." A second anomaly noted was the lateral cheek crease, which appeared to be associated with a cutaneous attachment from the underlying platysma muscle. However, no correlation could be found for facial muscle pattern and the overlying nasolabial crease structure. This lack of correlation may indicate that the facial muscles alone do not dictate the structure of the nasolabial crease and that other dynamic factors are involved in determining this feature of the aging face.

Potential of surface laser scanning to measure facial movement

Linear and area measurements on the surface contour of the face have been recorded in a variety of chosen facial postures using surface laser scanning techniques on healthy volunteers. Subjects were scanned before and after active and voluntary (against resistance) movements. Quantitative measurements of changes in these lengths and areas were made by computer integration to provide an impression of the changes that accompany facial expression. Lip movements were found to be associated with dimensional changes at all facial locations tested, imposed by the action of the underlying muscles. The system has a potential value for dynamic monitoring of facial movement.