Synkinetic patients often fail to produce a satisfactory smile because of antagonistic action of a hypertonic depressor anguli oris muscle and concomitantly weak depressor labii inferioris muscle. ...This study investigated their neurovascular anatomy to partially explain this paradoxical depressor anguli oris hypertonicity and depressor labii inferioris hypotonicity and delineated consistent anatomical landmarks to assist in depressor anguli oris muscle injection and myectomy.
Ten hemifaces from five fresh human cadavers were dissected to delineate the neurovascular supply of the depressor anguli oris and depressor labii inferioris muscles in addition to the depressor anguli oris muscle relation to consistent anatomical landmarks.
The depressor anguli oris muscle received innervation from both lower buccal and marginal mandibular facial nerve branches, whereas the depressor labii inferioris muscle was solely innervated by marginal mandibular branches. The mandibular depressor anguli oris origin was on average 39 mm wide, and its medial and lateral borders were located 17 mm from the symphysis and 41 mm from the mandibular angle, respectively. The depressor anguli oris fibers consistently passed anterior to the first mandibular molar toward their insertion into the modiolus, which was located 10 mm lateral and 10 mm caudal to the oral commissure.
Depressor anguli oris muscle dual innervation versus depressor labii inferioris single innervation may explain why depressor anguli oris hypertonicity and depressor labii inferioris weakness are commonly observed concomitantly in synkinetic patients. Based on treatment goals, diagnostic percutaneous injection with lidocaine can be performed on the depressor anguli oris muscle along a cutaneous line from the modiolus to the mandibular first molar border, and an intraoral depressor anguli oris myectomy can be performed along that same transmucosal line.
Evolution of facial muscle anatomy in dogs Kaminski, Juliane; Waller, Bridget M.; Diogo, Rui ...
Proceedings of the National Academy of Sciences - PNAS,
07/2019, Letnik:
116, Številka:
29
Journal Article
Recenzirano
Odprti dostop
Domestication shaped wolves into dogs and transformed both their behavior and their anatomy. Here we show that, in only 33,000 y, domestication transformed the facial muscle anatomy of dogs ...specifically for facial communication with humans. Based on dissections of dog and wolf heads, we show that the levator anguli oculi medialis, a muscle responsible for raising the inner eyebrow intensely, is uniformly present in dogs but not in wolves. Behavioral data, collected from dogs and wolves, show that dogs produce the eyebrow movement significantly more often and with higher intensity than wolves do, with highest-intensity movements produced exclusively by dogs. Interestingly, this movement increases paedomorphism and resembles an expression that humans produce when sad, so its production in dogs may trigger a nurturing response in humans. We hypothesize that dogs with expressive eyebrows had a selection advantage and that “puppy dog eyes” are the result of selection based on humans’ preferences.
•Craniofacial muscles innervated by the facial nerve lack muscle spindles.•Proprioceptive acuity in the facial muscles is accurate.•Proprioception of facial muscles is provided by the trigeminal ...nerve.•Putative mechanoproteins are present in mammalian muscle spindles.•Facial muscles contain putative propioceptors supplied by mechanosensory nerves.
The human craniofacial muscles innervated by the facial nerve typically lack muscle spindles. However these muscles have proprioception that participates in the coordination of facial movements. A functional substitution of facial proprioceptors by cutaneous mechanoreceptors has been proposed but at present this alternative has not been demonstrated. Here we have investigated whether other kinds of sensory structures are present in two human facial muscles (zygomatic major and buccal). Human checks were removed from Spanish cadavers, and processed for immunohistochemical detection of nerve fibers (neurofilament proteins and S100 protein) and two putative mechanoproteins (acid-sensing ion channel 2 and transient receptor potential vanilloid 4) associated with mechanosensing. Nerves of different calibers were found in the connective septa and within the muscle itself. In all the muscles analysed, capsular corpuscle-like structures resembling elongated or round Ruffini-like corpuscles were observed. Moreover the axon profiles within these structures displayed immunoreactivity for both putative mechanoproteins. The present results demonstrate the presence of sensory structures in facial muscles that can substitute for typical muscle spindles as the source of facial proprioception.
BACKGROUND:Cosmetic treatment of the forehead using neuromodulators is challenging. To avoid adverse events, the underlying anatomy has to be understood and thoughtfully targeted. Clinical ...observations indicate that eyebrow ptosis can be avoided if neuromodulators are injected in the upper forehead, despite the frontalis muscle being the primary elevator.
METHODS:Twenty-seven healthy volunteers (11 men and 16 women) with a mean age of 37.5 ± 13.7 years (range, 22 to 73 years) and of diverse ethnicity (14 Caucasians, four African Americans, three Asians, and six of Middle Eastern descent) were enrolled. Skin displacement vector analyses were conducted on maximal frontalis muscle contraction to calculate magnitude and direction of forehead skin movement.
RESULTS:In 100 percent of investigated volunteers, a bidirectional movement of the forehead skin was observedthe skin of the lower forehead moved cranially, whereas the skin of the upper forehead moved caudally. Both movements converged at a horizontal forehead line termed the line of convergence, or C-line. The position of the C-line relative to the total height of the forehead was 60.9 ± 10.2 percent in men and 60.6 ± 9.6 percent in women (p = 0.941). Independent of sex, the C-line was located at the second horizontal forehead line when counting from superior to inferior (men, n = 2; women, n = 2). No difference across ethnicities was detected.
CONCLUSIONS:The identification of the C-line may potentially guide practitioners toward more predictable outcomes for forehead neuromodulator injections. Injections above the C-line could mitigate the risk of neuromodulator-induced brow ptosis.
The facial motor system CATTANEO, Luigi; PAVESI, Giovanni
Neuroscience and biobehavioral reviews,
2014, 2014-Jan, 2014-1-00, 20140101, Letnik:
38
Journal Article
Recenzirano
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.
Demand for less-invasive procedures for treating gummy smile, such as botulinum toxin A injections, has increased substantially over the years. Meanwhile, the optimal injection site for botulinum ...toxin A injection is debated. The authors aimed to investigate the efficacy of botulinum toxin A injection at the Yonsei point for treating gummy smile.
In this double-blind, single-site, randomized clinical trial, healthy participants with a gummy smile (anterior gingival exposure of ≥3.0 mm) were enrolled and randomized (1:1 ratio) into two groups. The experimental group was administered 6 U of botulinum toxin A at the Yonsei point (a single-site injection of 3 U to the right Yonsei point and 3 U to the left Yonsei point), and the control group received the same dose in the bilateral levator labii superioris alaeque nasi muscle sites. The patients were assessed at baseline and 4, 12, 24, and 48 weeks after the first injection using a digital vernier caliper.
A total of 49 participants were enrolled. Anterior and bilateral posterior gingival exposure were reduced at 4, 12, and 24 weeks ( P ≤ 0.05) and returned to baseline at 48 weeks in both groups; there was no difference between the groups at these time points. The increase in satisfaction among patients was significant, and few adverse events were observed.
Both the Yonsei point and the levator labii superioris alaeque nasi muscle site can be used as botulinum toxin A injection sites for treating gummy smile.
Therapeutic, I.
Forehead rhytides are a popular target for botulinum toxin injections, but neuromodulation of the frontalis can be fraught with complications because of its anatomic complexity and integral role in ...brow position and expressivity.
This article explores common forehead movement discrepancies that can occur after neuromodulation of the frontalis, as well as how to correct and prevent them.
A review of the literature was conducted and combined with clinical experience to examine underlying forehead anatomy, etiology and correction of forehead movement discrepancies, and important factors to consider before injecting the frontalis with botulinum toxin.
Variable anatomy from person to person necessitates an individualized treatment approach to achieve the best cosmetic results and prevent the occurrence of forehead movement discrepancies.
Summary
Patterning of craniofacial muscles overtly begins with the activation of lineage‐specific markers at precise, evolutionarily conserved locations within prechordal, lateral, and both ...unsegmented and somitic paraxial mesoderm populations. Although these initial programming events occur without influence of neural crest cells, the subsequent movements and differentiation stages of most head muscles are neural crest‐dependent. Incorporating both descriptive and experimental studies, this review examines each stage of myogenesis up through the formation of attachments to their skeletal partners. We present the similarities among developing muscle groups, including comparisons with trunk myogenesis, but emphasize the morphogenetic processes that are unique to each group and sometimes subsets of muscles within a group. These groups include branchial (pharyngeal) arches, which encompass both those with clear homologues in all vertebrate classes and those unique to one, for example, mammalian facial muscles, and also extraocular, laryngeal, tongue, and neck muscles. The presence of several distinct processes underlying neural crest:myoblast/myocyte interactions and behaviors is not surprising, given the wide range of both quantitative and qualitative variations in craniofacial muscle organization achieved during vertebrate evolution.
BACKGROUND:To address functional and smile dysfunction associated with post–facial paralysis synkinesis, the senior author (B.A.) has offered “modified selective neurectomy” of the lower division of ...the facial nerve as a long-term solution. This article examines technical considerations and outcomes of this procedure.
METHODS:A retrospective review was conducted of patients who underwent modified selective neurectomy of buccal and cervical branches of the facial nerve performed by a single surgeon over a 4½-year period. House-Brackmann facial grading scores, electronic clinician-graded facial function scale, and onabotulinumtoxinA (botulinum toxin type A) dosages were examined before and after the procedure.
RESULTS:Sixty-three patients underwent modified selective neurectomy between June 20, 2013, and August 12, 2017. There were no serious complications. The revision rate was 17 percent. Temporary oral incompetence was reported in seven patients (11 percent) postoperatively. A statistically significant improvement was achieved in electronic clinician-graded facial function scale analysis of nasolabial fold depth at rest, oral commissure movement with smile, nasolabial fold orientation with smile, nasolabial depth with smile, depressor labii inferioris lower lip movement, midfacial synkinesis, mentalis synkinesis, platysmal synkinesis, static score, dynamic score, synkinesis score, periocular score, lower face and neck score, and midface and smile score. There was a significant decrease in botulinum toxin type A dosage and House-Brackmann score after surgery.
CONCLUSION:Modified selective neurectomy of the buccal and cervical divisions of the facial nerve is an effective long-term treatment for smile dysfunction in patients with post–facial paralysis synkinesis.
CLINICAL QUESTION/LEVEL OF EVIDENCE:Therapeutic, IV.
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