The functional anatomy of the muscles of facial expression in humans with and without cleft lip and palate. A contribution to refine muscle reconstruction in primary cheilo- and rhinoplasties in patients with uni- and bilateral complete CLP

Three-dimensional Analysis of Maxillary Morphology in Infants with Unilateral Cleft Lip and Palate

OBJECTIVE

To three-dimensionally (3D) analyze the maxillary morphology of infants with unilateral cleft lip and palate (UCLP) and preliminarily classify the alveolar arch to assist in personalization of sequence therapy.

DESIGN

Retrospective study.

SETTING

Patients with UCLP referred to outpatients' clinic.

PARTICIPANTS

84 nonsyndromic infants with complete UCLP were recruited (58 boys, 26 girls, mean age 29.48 days).

MAIN OUTCOME MEASURE

Morphometric analysis was conducted on 3D maxillary models. Principal component analysis (PCA) and cluster analysis were combined to classify maxillary phenotypes preliminarily. The Wilcoxon Signed Rank test and the Kruskal-Wallis test were used to compare differences between variables. A P value less than .05 was considered statistically significant.

RESULTS

The maxilla was divided into three types: narrow, homogenous and broad, accounting for 9.52%, 23.81% and 66.67% respectively. The alveolar cleft site (median value) was located in 61% of the total length of the alveolar arch. In the comparison of anterior and total alveolar lengths, the non-cleft side had longer alveolar bone than the affected side, a difference of approximately 2 mm. Pairwise comparisons of variables describing alveolar symmetry revealed significant differences in all subjects; whereas type C had poorer arch symmetry than types A and B, mainly in terms of anterior and overall symmetry.

CONCLUSIONS

In infants with UCLP, the maxillary alveolar arch was inherently asymmetrical with partially bone missing (about 2 mm). Significant differences in alveolar bone morphology and symmetry exist between different types of infants, with individuals with broad clefts (type C, the largest proportion) having the worst maxillary development.

Cleft lip, alveolus and palate: Defect or dislocation malformation? Importance of adopting a physiological concept for surgical repair in achieving optimal outcomes in LMICs. Part 1: Physiological processes in facial development

The conventional surgical procedures for the closure of cleft-lip and palate are based on proven plastic-surgical procedures from tumour surgery or traumatology. These flap surgeries take little account of the fact that the treatment of such malformations takes place during the time of a child's increased growth and is known to lead to pronounced scarring and skeletal growth disorders. It is therefore imperative to develop modified surgical procedures based on physiological growth processes. These physiological procedures must include the reconstruction of all facial structures such as orofacial, palatal and pharyngeal muscles, complete nose, upper jaw and palate. Transfer of this know how to low resource LMIC and training is essential if optimal outcomes are to be achieved.

Anatomical networks reveal the musculoskeletal modularity of the human head

Mosaic evolution is a key mechanism that promotes robustness and evolvability in living beings. For the human head, to have a modular organization would imply that each phenotypic module could grow and function semi-independently. Delimiting the boundaries of head modules, and even assessing their existence, is essential to understand human evolution. Here we provide the first study of the human head using anatomical network analysis (AnNA), offering the most complete overview of the modularity of the head to date. Our analysis integrates the many biological dependences that tie hard and soft tissues together, arising as a consequence of development, growth, stresses and loads, and motion. We created an anatomical network model of the human head, where nodes represent anatomical units and links represent their physical articulations. The analysis of the human head network uncovers the presence of 10 musculoskeletal modules, deep-rooted in these biological dependences, of developmental and evolutionary significance. In sum, this study uncovers new anatomical and functional modules of the human head using a novel quantitative method that enables a more comprehensive understanding of the evolutionary anatomy of our lineage, including the evolution of facial expression and facial asymmetry.

Beyond the functional matrix hypothesis: a network null model of human skull growth for the formation of bone articulations

Craniofacial sutures and synchondroses form the boundaries among bones in the human skull, providing functional, developmental and evolutionary information. Bone articulations in the skull arise due to interactions between genetic regulatory mechanisms and epigenetic factors such as functional matrices (soft tissues and cranial cavities), which mediate bone growth. These matrices are largely acknowledged for their influence on shaping the bones of the skull; however, it is not fully understood to what extent functional matrices mediate the formation of bone articulations. Aiming to identify whether or not functional matrices are key developmental factors guiding the formation of bone articulations, we have built a network null model of the skull that simulates unconstrained bone growth. This null model predicts bone articulations that arise due to a process of bone growth that is uniform in rate, direction and timing. By comparing predicted articulations with the actual bone articulations of the human skull, we have identified which boundaries specifically need the presence of functional matrices for their formation. We show that functional matrices are necessary to connect facial bones, whereas an unconstrained bone growth is sufficient to connect non-facial bones. This finding challenges the role of the brain in the formation of boundaries between bones in the braincase without neglecting its effect on skull shape. Ultimately, our null model suggests where to look for modified developmental mechanisms promoting changes in bone growth patterns that could affect the development and evolution of the head skeleton.

Electrophysiological method to examine muscle fiber architecture in the upper lip in cleft-lip patients

OBJECTIVES

The upper lip's musculature comprises several muscle fiber groups with different spatial orientations for various lip movements. In the past, it has not been possible to describe these various groups and their motor units in detail with traditional methods of electromyography (EMG). The purpose of this investigation was to create a viable method for studying the architecture of upper-lip muscle fibers in patients with surgically closed cleft lip by refining the design of a flexible electrode array for multichannel EMG.

METHODS

Calibrated perioral photographs of 36 adult subjects were used to determine the basic geometry of an electrode array for use on different facial shapes. A total of 256 chloride silver electrodes, 1 mm in diameter, were distributed over this geometry to form a grid with interelectrode distances of 2.5 mm. Technical implementation of the electrode array was based on a modified technique used for flexible printed circuit boards. A double-sided adhesive tape with perforations was used to apply the array to the skin in the upper-lip area. Surface EMG signals were recorded while the subjects were performing various lip movements and exerting specific lip forces. The latter were recorded with a specially developed transducer.

RESULTS

Despite an extremely dense grid of electrodes associated with downsized contacts, the electrode array could be precisely applied to the perforated adhesive tape. The electrode array remained firmly attached to the skin even during extensive lip movements. The recorded EMG signals offered high baseline stability and a strong signal-to-noise ratio, thus, allowing us to extract individual motor unit action potentials (MUAPs). Spatiotemporal tracking of MUAPs succeeded in demonstrating the course of muscle fibers belonging to individual motor units. Pilot measurements taken on subjects with surgically closed unilateral cleft lip revealed an asymmetric distribution of muscle activity surrounding the closed cleft-lip segments.

CONCLUSION

Our refined noninvasive electrophysiological method is capable of providing detailed information about muscle fiber architecture and the position, size, and organization of motor units in the lip area. It is thus feasible to conduct further studies to analyze differences in muscle morphology and motor control between surgically treated cleft-lip patients and noncleft individuals.

The facial motor system

Facial movements support a variety of functions in human behavior. They participate in automatic somatic and visceral motor programs, they are essential in producing communicative displays of affective states and they are also subject to voluntary control. The multiplicity of functions of facial muscles, compared to limb muscles, is reflected in the heterogeneity of their anatomical and histological characteristics that goes well beyond the conventional classification in single facial muscles. Such parcellation in different functional muscular units is maintained throughout the central representation of facial movements from the brainstem up to the neocortex. Facial movements peculiarly lack a conventional proprioceptive feedback system, which is only in part vicariated by cutaneous or auditory afferents. Facial motor activity is the main marker of endogenous affective states and of the affective valence of external stimuli. At the cortical level, a complex network of specialized motor areas supports voluntary facial movements and, differently from upper limb movements, in such network there does not seem to be a prime actor in the primary motor cortex.

Dorsorostral snout muscles in the rat subserve coordinated movement for whisking and sniffing

Histochemical examination of the dorsorostral quadrant of the rat snout revealed superficial and deep muscles that are involved in whisking, sniffing, and airflow control. The part of M. nasolabialis profundus that acts as an intrinsic (follicular) muscle to facilitate protraction and translation of the vibrissae is described. An intraturbinate and selected rostral-most nasal muscles that can influence major routs of inspiratory airflow and rhinarial touch through their control of nostril configuration, atrioturbinate and rhinarium position, were revealed.

Secondary palatal closure in rats in association with relative maternofetal levels of folic acid, vitamin B12, and homocysteine

Animal experiments are used in embryological and teratological studies of matters relevant to humans. In gravid rats, a decrease in the levels of folic acid and vitamin B12 was observed in maternal blood and in amniotic fluid. At the time of secondary palatal closure (14th day of pregnancy), the folic acid level of the amniotic fluid was 73% lower than that of the maternal blood. A drop in vitamin B12 in conjunction with an increase in amniotic homocysteine levels is seen as a risk factor for malformation of the palate. The understanding of causes of cleft generation could lead to a prophylactic treatment approach.

Morphofunctional changes of orofacial muscles in patients with unilateral or bilateral cleft lip, alveolus and palate

The facial musculature is part of a biocybernetic feedback system within the stomatognathic system, the continuity of which is disturbed by clefts of the lip, jaw, and palate (cheilognathopalatoschisis). This results in topographic, fine-structural and functional alterations of the facial musculature. In two heads with unilateral clefts and two heads with bilateral clefts, the facial musculature was dissected and the M. orbicularis oris macroscopically and topographically examined. We found changes in the attachment of the M. orbicularis oris. The modiolus, which is coresponsible for the proper topographic relation of the M. obicularis oris to the other facial muscles, was unchanged. Further, we examined the vascular system of the muscle, which likewise adapts to the altered situation. Lip/jaw/palatal clefts result in anatomically functional and fine-structural alterations of the M. orbicularis oris, while the rest of the facial musculature remains unchanged.