Review

Authors: Lauren M Bylsma, Asmir Gračanin, Ad J J M Vingerhoets...

The production of emotional tears appears to be uniquely present in Homo sapiens. Despite the ubiquity of this human behavior, research is only just beginning to uncover the neurobiologic underpinnings of human emotional crying. In this article, we review the current state of the literature investigating the neurobiologic aspects of this uniquely human behavior, including the neuroanatomical, neurochemical, and psychophysiologic findings. To set the context for this review, we first provide a brief overview of the evolutionary background and functions of tearful crying. Despite an accumulating understanding of the neurobiology of human emotional crying, the primary sources of information are currently from animal studies and observations in neurologic patients suffering from pathologic crying. Currently, most of the research on the neurobiology of crying in humans has focused on autonomic physiologic processes underlying tearful crying, which may yield essential clues regarding the neural substrates of the production of crying behavior and its effects on the crier. Further challenges in elucidating the neurobiology of crying involve the complexity of crying behavior, which includes vocalizations, tear production, the involvement of facial musculature, subjective emotional experience, emotion regulatory behaviors, and social behaviors. Future research is needed to comprehensively characterize the neurobiology of this intriguing and complex human behavior.

Topics: Animals; Brain; Crying; Emotions; Facial Muscles; Humans; Lacrimal Apparatus; Neural Pathways; Tears

PubMed: 29687400
DOI: 10.1007/s10286-018-0526-y

Authors: Natalia Kaczorowska, Kamil Kaczorowski, Joanna Laskowska...

Down syndrome (DS) is the most often diagnosed chromosomal disorder in newborns. The incidence is 1:792 live births. The article describes the irregularities and characteristics found in trisomy 21, which greatly affect the functioning of the stomatognathic system. The most significant disorders include the following: false macroglossia, muscular hypotonia and gothic palate. These abnormalities affect articulation, breathing, food intake, and swallowing. We analyzed the morphological characteristics of the craniofacial region in children with DS based on the current literature review. The following databases were used for the analysis: MEDLINE (via PubMed), Scopus, Infona, and Dentistry & Oral Sciences Source. In the course of the study, 199 pieces of literature were analyzed; the analysis also included 18 articles on children and adults with DS. It also took into account the structure of the palate, dental and skeletal defects, size of the tongue, muscular hypotonia, and temporomandibular joint dysfunction. Down syndrome is still a current subject of research. Although macroglossia, hypotonia, malocclusion, and temporomandibular joint abnormalities are not features exclusive to DS, numerous dysfunctions and parafunctions as well as retarded psychomotor development greatly complicate the treatment. Therefore, interdisciplinary treatment of patients with trisomy 21 and early treatment in the first months of life with the use of the Castillo-Morales plate are very important, as they ensure better adaptation to the subsequently used apparatus and reduce the risk of disorders of the stomatognathic system.

Topics: Down Syndrome; Facial Muscles; Humans; Infant; Infant, Newborn; Macroglossia; Muscle Hypotonia; Tongue; Trisomy

PubMed: 31778604
DOI: 10.17219/acem/112785

Review

Authors: Gi-Woong Hong, Soo-Bin Kim, Soo Yeon Park...

The pathogenesis of marionette lines involves a complex interplay of anatomical, physiological, and age-related factors leading to the development of wrinkles around the oral commissures. This exploration delves into the distinct anatomical predispositions observed among different ethnicities, emphasizing the role of compact modiolus structures and muscle compositions. Notably, individuals of East Asian descent exhibit inherent facial structures that predispose them to pronounced sagging around the oral commissures during aging. The emergence of distinct facial lines, such as the commissural line and the melolabial fold, contributes to the formation of marionette lines. This specific wrinkle pattern, resembling a marionette puppet's mouth contours, is influenced by various factors like bone resorption, gravitational forces, fat compartment variations, muscle compression, ligament tethering, and skin aging. Treatment strategies for marionette lines encompass diverse interventions, including filler injections, botulinum neurotoxin, surgeries targeting fat reduction, thread lifting, and volumizing fillers. These approaches aim to address the underlying causes and mitigate the appearance of marionette lines. Botulinum neurotoxin injections, for instance, weaken specific facial muscles, reducing downward strain and aiding in tissue retraction. Anatomical considerations during procedures are crucial to avoid nerve or vascular damage. Delicate manipulation and precise entry points are essential to prevent inadvertent injuries, particularly concerning blood vessels like the facial artery and nerves like the mental nerve. Technical guidelines for procedures targeting marionette lines involve specific techniques like cogged thread reverse methods and volumizing thread placements. Attention to entry points, tissue engagement, and the direction of threads is crucial for effective treatment outcomes, minimizing complications, and ensuring patient safety.

Topics: Humans; Cosmetic Techniques; Face; Facial Muscles; Lip; Botulinum Toxins; Skin Aging

PubMed: 38572585
DOI: 10.1111/srt.13676

Randomized Controlled Trial

Authors: Stephanie Santiago, Abraham M Joshua, Akshatha Nayak...

The purpose of the study was to assess the effects of a novel technique involving facial stretching of the unaffected side along with a structured exercise for the affected side on facial symmetry and facial functions as compared to conventional exercise. A hospital-based parallel-group randomized trial was completed among patients with acute Bell's palsy in Mangalore, India. Participants were randomized to receive facial stretching and a structured exercise program (experimental group) or the conventional exercise regimen (conventional group). Primary outcomes were facial symmetry and voluntary movement; assessed by the Sunnybrook Facial Grading System (SFGS). Both regimens were given for 3 weeks, with baseline, 10th day, and 20th day assessments. Out of 31 participants screened, 24 were eligible and 12 participants each were assigned to experimental and conventional groups. Change scores revealed greater improvement in the SFGS score (p = 0.002) for the experimental group participants. Facial stretching and structured exercise program exhibited promising results in enhancing facial symmetry and function in acute Bell's palsy when compared to conventional exercise regimen.

Topics: Humans; Bell Palsy; Male; Female; Adult; Exercise Therapy; Muscle Stretching Exercises; Treatment Outcome; Middle Aged; Single-Blind Method; Face; Facial Muscles; Young Adult

PubMed: 38858464
DOI: 10.1038/s41598-024-64046-z

Authors: Ronald Sahyouni, Khodayar Goshtasbi, Alessandro Presacco...

OBJECTIVES

Facial paralysis is a debilitating condition with substantial functional and psychological consequences. This feline-model study evaluates whether facial muscles can be selectively activated in acute and chronic implantation of 16-channel multichannel cuff electrodes (MCE).

METHODS

Two cats underwent acute terminal MCE implantation experiments, 2 underwent chronic MCE implantation in uninjured facial nerves (FN) and tested for 6 months, and 2 underwent chronic MCE implantation experiments after FN transection injury and tested for 3 months. The MCE were wrapped around the main trunk of the skeletonized FN, and data collection consisted of EMG thresholds, amplitudes, and selectivity of muscle activation.

RESULTS

In acute experimentation, activation of specific channels (ie, channels 1-3 and 6-8) resulted in selective activation of , whereas activation of other channels (ie, channels 4, 5, or 8) led to selective activation of with higher EMG amplitudes. MCE implantation yielded stable and selective facial muscle activation EMG thresholds and amplitudes up to a 5-month period. Modest selective muscle activation was furthermore obtained after a complete transection-reapproximating nerve injury after a 3-month recovery period and implantation reoperation. Chronic implantation of MCE did not lead to fibrosis on histology. Field steering was achieved to activate distinct facial muscles by sending simultaneous subthreshold currents to multiple channels, thus theoretically protecting against nerve damage from chronic electrical stimulation.

CONCLUSION

Our proof-of-concept results show the ability of an MCE, supplemented with field steering, to provide a degree of selective facial muscle stimulation in a feline model, even following nerve regeneration after FN injury.

LEVEL OF EVIDENCE

N/A.

Topics: Animals; Cats; Disease Models, Animal; Electric Stimulation Therapy; Electrodes, Implanted; Electromyography; Facial Muscles; Facial Nerve Injuries; Facial Paralysis; Female; Muscle Contraction

PubMed: 34096343
DOI: 10.1177/00034894211023218

Authors: K Madisen Omstead, Jade Williams, Seth M Weinberg...

Muscle spindles are sensory receptors in skeletal muscle that provide information on muscle length and velocity of contraction. Previous studies noted that facial muscles lack muscle spindles, but recent reports indicate that the human platysma muscle and "buccal" muscles contain spindles. Mammalian facial muscles are active in social communication, vibrissa movement, and vocalizations, including human speech. Given these functions, we hypothesized that facial muscles contain muscle spindles, and we predicted that humans would have the greatest number, given the role our lips play in speech. We examined previously sectioned and stained (with H&E and trichrome stains) orbicularis oris (upper fibers) and zygomaticus (major) muscles across a broad phylogenetic range of mammalian species, spanning a wide distribution of body size and ecological niche, to assess the presence of muscle spindles. We also stained several sections with Sirius red to highlight the muscle spindle capsule. Our results indicate that mammalian facial muscles contain muscle spindles, supporting our hypothesis. Contrary to our prediction, though, humans (and other primates) had the lowest number of muscle spindles. We instead found that the carnivoran sample and the horse sample had the greatest number of spindles. Larger body size and nocturnality were also associated with a greater number of spindles. These results must be viewed with caution, though, as our sample size was small and there are critical mammalian taxa missing. Future work should use an expanded phylogenetic range of mammalian species to ascertain the role that phylogeny plays in muscle spindle presence and count.

Topics: Humans; Animals; Horses; Facial Muscles; Muscle Spindles; Phylogeny; Muscle, Skeletal; Mammals

PubMed: 36799659
DOI: 10.1002/ar.25172

Authors: Vlad Tereshenko, Dominik C Dotzauer, Matthias Luft...

The surgical redirection of efferent neural input to a denervated muscle via a nerve transfer can reestablish neuromuscular control after nerve injuries. The role of autonomic nerve fibers during the process of muscular reinnervation remains largely unknown. Here, we investigated the neurobiological mechanisms behind the spontaneous functional recovery of denervated facial muscles in male rodents. Recovered facial muscles demonstrated an abundance of cholinergic axonal endings establishing functional neuromuscular junctions. The parasympathetic source of the neuronal input was confirmed to be in the pterygopalatine ganglion. Furthermore, the autonomically reinnervated facial muscles underwent a muscle fiber change to a purely intermediate muscle fiber population myosin heavy chain type IIa. Finally, electrophysiological tests revealed that the postganglionic parasympathetic fibers travel to the facial muscles via the sensory infraorbital nerve. Our findings demonstrated expanded neuromuscular plasticity of denervated striated muscles enabling functional recovery via alien autonomic fibers. These findings may further explain the underlying mechanisms of sensory protection implemented to prevent atrophy of a denervated muscle. Nerve injuries represent significant morbidity and disability for patients. Rewiring motor nerve fibers to other target muscles has shown to be a successful approach in the restoration of motor function. This demonstrates the remarkable capacity of the CNS to adapt to the needs of the neuromuscular system. Yet, the capability of skeletal muscles being reinnervated by nonmotor axons remains largely unknown. Here, we show that under deprivation of original efferent input, the neuromuscular system can undergo functional and morphologic remodeling via autonomic nerve fibers. This may explain neurobiological mechanisms of the sensory protection phenomenon, which is because of parasympathetic reinnervation.

Topics: Humans; Male; Facial Muscles; Muscle Fibers, Skeletal; Muscle, Skeletal; Neurons; Autonomic Pathways; Nerve Regeneration; Muscle Denervation

PubMed: 36216502
DOI: 10.1523/JNEUROSCI.0670-22.2022

Authors: Tanja S H Wingenbach, Beatriz Ribeiro, Caroline Nakao...

Stimulating CT-afferents by forearm caresses produces the subjective experience of pleasantness in the receiver and modulates subjective evaluations of viewed affective images. Receiving touch from another person includes the social element of another person's presence, which has been found to influence affective image evaluations without involving touch. The current study investigated whether these modulations translate to facial muscle responses associated with positive and negative affect across touch-involving and mere presence conditions. Female participants ( = 40, (age) = 22.4,  = 5.3) watched affective images (neutral, positive, negative) while facial electromyography was recorded (sites: zygomaticus, corrugator). Results from ANOVAs showed that providing touch to another person or oneself modulated zygomaticus site responses when viewing positive images. Providing CT-afferent stimulating touch (i.e., forearm caresses) to another person or oneself dampened the positive affective facial muscle response to positive affective images. Providing touch to another person generally increased corrugator facial muscle activity related to negative affect. Receiving touch did not modulate affective facial muscle responses during the viewing of affective images but may have effects on later cognitive processes. Together, previously reported social and touch modulations of subjective evaluations of affective images do not translate to facial muscle responses during affective image viewing, which were differentially modulated.

Topics: Humans; Female; Young Adult; Adult; Touch; Facial Muscles; Touch Perception; Emotions; Face; Electromyography

PubMed: 37712676
DOI: 10.1080/02699931.2023.2258588

Authors: Wataru Sato, Takanori Kochiyama

There is ample evidence that electromyography (EMG) signals from the corrugator supercilii and zygomatic major muscles can provide valuable information for the assessment of subjective emotional experiences. Although previous research suggested that facial EMG data could be affected by crosstalk from adjacent facial muscles, it remains unproven whether such crosstalk occurs and, if so, how it can be reduced. To investigate this, we instructed participants ( = 29) to perform the facial actions of frowning, smiling, chewing, and speaking, in isolation and combination. During these actions, we measured facial EMG signals from the corrugator supercilii, zygomatic major, masseter, and suprahyoid muscles. We performed an independent component analysis (ICA) of the EMG data and removed crosstalk components. Speaking and chewing induced EMG activity in the masseter and suprahyoid muscles, as well as the zygomatic major muscle. The ICA-reconstructed EMG signals reduced the effects of speaking and chewing on zygomatic major activity, compared with the original signals. These data suggest that: (1) mouth actions could induce crosstalk in zygomatic major EMG signals, and (2) ICA can reduce the effects of such crosstalk.

Topics: Humans; Electromyography; Facial Expression; Face; Emotions; Facial Muscles

PubMed: 36904924
DOI: 10.3390/s23052720

Review

Authors: O Laccourreye, R K Orosco, F Rubin...

GOAL

To document the role of the styloglossus muscle (SG) in head and neck oncology and at the time of surgical treatment and mandibular preservation surgery for squamous cell carcinoma of the lateral oropharynx (SCCLO).

METHOD

Based on a search conducted within the Pubmed, Embase, and Cochrane databases, using the key words SG muscle, parapharyngeal space and oropharynx, the authors discuss the embryology, physiology, anatomy and radiology of this muscle as well as its role in the oncologic staging surgery of SCCLO.

RESULTS

The most specific radiologic exam to evaluate the involvement of SG muscle in SCCLO is magnetic resonance imaging (MRI). According to the eigth international staging classification systems, radiologic invasion of the SG muscle, at the time of MRI, leads to reclassify as T4a many tumors considered as T1-3 at the time of clinical and/or on computerized tomography evaluation. This must lead to extreme care when comparing oncologic results from series published prior and after the MRI era. When transoral resection of the SG muscle is advocated for SCCLO, one must know that this maneuver brings numerous arterial and venous structures within the operative field. If difficulties to achieve safe margins of resection and/or to control bleeding are encountered, a simple trans cervical maneuver described herein is most useful.

CONCLUSION

The importance of the SG muscle should be emphasized as a touchstone for staging and surgeon's guide to mandibular preservation surgery of SCCLO. The various approaches allowing the control of this muscle and its vascular environment must be taught at the time of initial training.

Topics: Anatomic Landmarks; Carcinoma, Squamous Cell; Facial Muscles; Humans; Oropharyngeal Neoplasms

PubMed: 30341015
DOI: 10.1016/j.anorl.2017.11.012