Nerve to the zygomaticus major muscle: An anatomical study and surgical application to smile reconstruction.

Smile reconstruction using the branches that supply the zygomaticus major muscle as a motor source is an established procedure in facial reanimation surgery for facial paralysis. However, the anatomy of the nerve to the muscle remains unclear. Therefore, we herein examined the topographical anatomy of the nerve to the zygomaticus major muscle to obtain more detailed information on donor nerve anatomy. Preserved cadaver dissection was performed under a microscope on 13 hemifaces of 8 specimens. The branches that innervate the zygomaticus major muscle and their peripheral routes medial to the muscle were traced and examined. A median of four (ranges 2-4) branches innervated the zygomaticus major muscle. The proximal two branches (near the muscle origin) arose from the zygomatic branch, the second of which was the major branch. The distal branches (near the oral commissure) arose from the buccal branch or zygomaticobuccal plexus. The vertical distance from the caudal margin of the zygomatic arch to the major branch intersecting point was 19 ± 4.0 mm, while the horizontal distance parallel to the Frankfort plane was 29 ± 5.2 mm. The proximal two branches innervating the zygomaticus major muscle were detected in the majority of specimens. The anatomical findings obtained herein on the nerve to the zygomaticus major muscle will allow for more reliable donor selection in facial reanimation surgery.

New anatomical insights of the superficial branch of the zygomaticotemporal nerve for treating temporal migraines: An anatomical study.

The zygomaticotemporal nerve is known to contribute to temporal migraines; however, its precise anatomy remains unknown. The potential accessory branches of the zygomaticotemporal nerve may be considered a cause of continued temporal migraines after surgical procedures. In this study, we defined the novel superficial branch of the zygomaticotemporal nerve (sZTN) and investigated its anatomical course, distribution, and clinical implications. Twenty-two hemifaces from 11 fixed Korean cadavers (six males, five females; mean age, 78.3 years) were used in this study. The piercing points of the sZTN through the deep and superficial layers of the deep temporal fascia, and the superficial temporal fascia were defined as P1, P2, and P3, respectively. The distance of each point from the zygomatic tubercle was measured using an image analysis software. The sZTN ascended between the bone and the temporalis after emerging from the zygomaticotemporal foramen. It then pierced the deep temporal fascia without penetrating the temporalis. After then, it pierced the superficial layer of the deep temporal fascia and turned superiorly toward the upper posterior temple. When the sZTN passed through the superficial temporal fascia, it intersected with the superficial temporal artery in every case. The novel findings of the sZTN may help in the treatment of intractable temporal migraines refractory to injection or surgical procedure. Based on our findings, targeting the sZTN may be applied as an alternative treatment strategy for patients who do not show significant improvement with treatment targeted to trigger sites.

Pretreatment with High Mobility Group Box-1 Monoclonal Antibody Prevents the Onset of Trigeminal Neuropathy in Mice with a Distal Infraorbital Nerve Chronic Constriction Injury.

Persistent pain following orofacial surgery is not uncommon. High mobility group box 1 (HMGB1), an alarmin, is released by peripheral immune cells following nerve injury and could be related to pain associated with trigeminal nerve injury. Distal infraorbital nerve chronic constriction injury (dIoN-CCI) evokes pain-related behaviors including increased facial grooming and hyper-responsiveness to acetone (cutaneous cooling) after dIoN-CCI surgery in mice. In addition, dIoN-CCI mice developed conditioned place preference to mirogabalin, suggesting increased neuropathic pain-related aversion. Treatment of the infraorbital nerve with neutralizing antibody HMGB1 (anti-HMGB1 nAb) before dIoN-CCI prevented both facial grooming and hyper-responsiveness to cooling. Pretreatment with anti-HMGB1 nAb also blocked immune cell activation associated with trigeminal nerve injury including the accumulation of macrophage around the injured IoN and increased microglia activation in the ipsilateral spinal trigeminal nucleus caudalis. The current findings demonstrated that blocking of HMGB1 prior to nerve injury prevents the onset of pain-related behaviors, possibly through blocking the activation of immune cells associated with the nerve injury, both within the CNS and on peripheral nerves. The current findings further suggest that blocking HMGB1 before tissue injury could be a novel strategy to prevent the induction of chronic pain following orofacial surgeries.

A Pilot Study to Assess the Sialendoscopy-Assisted Transfacial Approach in Parotid Gland Sialolithiasis.

INTRODUCTION: Twenty percent of the total lithiasis that affect a major salivary gland will be found in the parotid gland. An exclusive sialoendoscopic approach has achieved success rates close to 80%. In a significant percentage of these remaining cases, combined transfacial approaches assisted by sialendoscopy are presented as an option to be taken into account. PATIENTS AND METHODS: A prospective analysis of cases treated by combined transfacial approach assisted by sialendoscopy for lithiasis of the parotid gland and the impact of the facial nerve stimulator used during surgery. RESULTS: Five patients were included; all of them operated satisfactorily. In 4 of them, the approach proposed by McGurk and modified by Capaccio was used, and in 1 of them, the approach proposed by Nahlieli was used. We suffered a complication in just case due to the appearance of postoperative sialocele. CONCLUSION: According to our results and those previously published, the transfacial approach assisted by sialendoscopy can be considered a useful technique. Proper planning ensures an optimal result in the treatment of parotid gland lithiasis. The use of facial nerve stimulator guarantees extra security when working near to a branch of the facial nerve is suspected.

Advance in Functional Restoration of Injured Nerve with Low Level Laser and its Utilization in the Dental and Maxillofacial Region.

The inferior alveolar nerve and facial nerve are the two most important nerves in the dental and maxillofacial region. The injury to them is one of the major postoperative complications after alveolar surgery and orthognathic surgery. However, recovering the nerve function after injury takes a long time and the recovery effect tends to be unsatisfactory. In recent years, an intensively investigated technique, low level laser which has been applying in assisting the recovery of nerve function, has been gradually proved to be effective in clinically treating postoperative nerve injury. In this article we review in terms of the mechanisms involved in low level laser-assisted functional restoration of nerve injury and its clinical application in the recovery of nerve function in the dental and maxillofacial area as well.

Automatic Facial Paralysis Assessment via Computational Image Analysis.

Facial paralysis (FP) is a loss of facial movement due to nerve damage. Most existing diagnosis systems of FP are subjective, e.g., the House-Brackmann (HB) grading system, which highly depends on the skilled clinicians and lacks an automatic quantitative assessment. In this paper, we propose an efficient yet objective facial paralysis assessment approach via automatic computational image analysis. First, the facial blood flow of FP patients is measured by the technique of laser speckle contrast imaging to generate both RGB color images and blood flow images. Second, with an improved segmentation approach, the patient's face is divided into concerned regions to extract facial blood flow distribution characteristics. Finally, three HB score classifiers are employed to quantify the severity of FP patients. The proposed method has been validated on 80 FP patients, and quantitative results demonstrate that our method, achieving an accuracy of 97.14%, outperforms the state-of-the-art systems. Experimental evaluations also show that the proposed approach could yield objective and quantitative FP diagnosis results, which agree with those obtained by an experienced clinician.

Multimodal mapping of the face connectome.

Face processing supports our ability to recognize friend from foe, form tribes and understand the emotional implications of changes in facial musculature. This skill relies on a distributed network of brain regions, but how these regions interact is poorly understood. Here we integrate anatomical and functional connectivity measurements with behavioural assays to create a global model of the face connectome. We dissect key features, such as the network topology and fibre composition. We propose a neurocognitive model with three core streams; face processing along these streams occurs in a parallel and reciprocal manner. Although long-range fibre paths are important, the face network is dominated by short-range fibres. Finally, we provide evidence that the well-known right lateralization of face processing arises from imbalanced intra- and interhemispheric connections. In summary, the face network relies on dynamic communication across highly structured fibre tracts, enabling coherent face processing that underpins behaviour and cognition.

Location of the infraorbital foramen with reference to soft tissue landmarks for regional nerve blocks during midface surgery.

PURPOSE: An infraorbital nerve (ION) block is widely used to accomplish regional anesthesia during surgical procedures involving the midface region. This study aimed to elucidate the exact location of the infraorbital foramen (IOF) in relation to clinically useful soft-tissue landmarks for achieving an effective ION block. METHODS: Forty-three hemifaces from 23 embalmed Korean cadavers were dissected. The lateral canthus, peak of Cupid's bow, medial limbus, and midline were used as reference points. The distances from the IOF to the midline and the lateral canthus were measured. RESULTS: The IOF was located approximately 25 mm below the lateral canthus and 27 mm lateral to the midline. In all cases, the IOF was situated within 9.0 mm of the crossing point of the oblique line connecting the lateral canthus to the peak of Cupid's bow and the vertical line through the medial limbus. CONCLUSION: Considering the spread of an anesthetic agent, injecting it into the crossing point of the oblique line through the lateral canthus to the peak of Cupid's bow and the vertical line through the medial limbus would successfully block the ION in most patients.

Surgical Anatomy of the Marginal Mandibular Nerve: A Systematic Review and Meta-Analysis.

The high number of marginal mandibular nerve (MMN) anatomical variants have a well-known clinical significance due to the risk of nerve injury in several surgical procedures. The aim of this study was to find and systematize the available anatomical data concerning this nerve. The PubMed and Scopus databases were investigated in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. All studies reporting extractable data on the origin, course, splitting, anastomosis and relationship of the MMN with the mandible or the facial vessels were included. We included 28 studies analyzing 1861 halves. The MMN had one (PP = 35% 95% CI:18-54%), two (PP =35% 95% CI:18-54%), three (PP = 18% 95% CI:0-35%), or four branches (PP = 2% 95% CI:0-8%). Anastomosis with the great auricular nerve, transverse cervical nerve, mental nerve, and other branches of the facial nerve were defined. The origin of the MMN in relation to the parotid and the mandible was variable. The MMN nearly always crossed the anterior facial vein laterally (PP = 38% 95% CI:9-72% if single, PP = 57% 95% CI:22-90% when multiple); its relation with other vessels was less constant. At least one branch of the MMN was found below the inferior border of the mandible (IBM), with a PP of 39% (95% CI:30-50%). The MMN has high anatomical variability and it is more often represented by one or two branches; its origin is frequently described at the parotid apex and above the IBM, although in its course at least one branch often runs below the IBM. Its most frequent anastomosis is with the buccal branch of the facial nerve. Clin. Anat., 33:739-750, 2020. © 2019 Wiley Periodicals, Inc.

Facial Sensory Restoration After Trigeminal Sensory Rhizotomy by Collateral Sprouting From the Occipital Nerves.

BACKGROUND AND IMPORTANCE: Lesioning procedures are effective for trigeminal neuralgia (TN), but late pain recurrence associated with sensory recovery is common. We report a case of recurrence of type 1A TN and recovery of facial sensory function after trigeminal rhizotomy associated with collateral sprouting from upper cervical spinal nerves. CLINICAL PRESENTATION: A 41-yr-old woman presented 2 yr after open left trigeminal sensory rhizotomy for TN with pain-free anesthesia in the entire left trigeminal nerve distribution. Over 18 mo, she developed gradual recovery of facial sensation migrating anteromedially from the occipital region, eventually extending to the midpupillary line across the distribution of all trigeminal nerve branches. She reported recurrence of her triggered lancinating TN pain isolated to the area of recovered sensation with no pain in anesthetic areas. Nerve ultrasound demonstrated enlargement of ipsilateral greater and lesser occipital nerves, and occipital nerve block restored facial anesthesia and resolved her pain, indicating that recovered facial sensation was provided exclusively by the upper cervical spinal nerves. She underwent C2/C3 ganglionectomy, and ganglia were observed to be hypertrophic. Postoperatively, trigeminal anesthesia was restored with complete resolution of pain that persisted at 12-mo follow-up. CONCLUSION: This is the first documented case of a spinal nerve innervating a cranial dermatome by collateral sprouting after cranial nerve injury. The fact that typical TN pain can occur even when sensation is mediated by spinal nerves suggests that the disorder can be centrally mediated and late failure after lesioning procedures may result from maladaptive reinnervation.

Will Repeated Ablative Er:YAG Laser Treatment Sessions Cause Facial Skin Sensitivity? Results of a 12-Month, Prospective, Randomized Split-Face Study.

Whether multiple laser irradiations affect skin sensitivity is still elusive. We aimed to investigate if repeated ablative erbium:yttrium-aluminum-garnet (Er:YAG) laser therapy could cause or increase skin sensitivity in the treatment areas. Nineteen healthy females received three sessions of a randomized, split-face, Er:YAG laser treatment in a scanning ablative mode (MicroLaserPeel™), with a 6-mm spot size, 8-µm ablative depths, and 30% of pulse overlap first. The next round was conducted in the fractional mode (ProFractional™) at depths ranging from 100 to 150 µm, with one pass by at coverage of 11% in the coagulation mode. Objective biophysical parameters, including transepidermal water loss (TEWL), skin glossiness, epidermal and dermal thickness and density, sensory nerve current perception threshold (CPT), and local blood flow, were measured before and after treatment. Quantitative evaluation of the Er:YAG laser treatment's effect on skin sensitivity is presented. Seventeen volunteers completed a follow-up of 12 months. On days 1 and 3, skin TEWL and epidermal thickness increased, while glossiness decreased. On day 7, there was no significant difference in the skin barrier function between the treated and the control side. Similarly, there was no significant difference in CPT values or local microvascular blood flow between sides at any time point before or after treatment, except that the local microvascular blood flow on the treated side was higher on the first day post-treatment. Er:YAG laser treatment does not influence skin sensitivity in healthy subjects in a long-term follow-up.

Role of cutaneous and proprioceptive inputs in sensorimotor integration and plasticity occurring in the facial primary motor cortex.

KEY POINTS: Previous studies investigating the effects of somatosensory afferent inputs on cortical excitability and neural plasticity often used transcranial magnetic stimulation (TMS) of hand motor cortex (M1) as a model, but in this model it is difficult to separate out the relative contribution of cutaneous and muscle afferent input to each effect. In the face, cutaneous and muscle afferents are segregated in the trigeminal and facial nerves, respectively. We studied their relative contribution to corticobulbar excitability and neural plasticity in the depressor anguli oris M1. Stimulation of trigeminal afferents induced short-latency (SAI) but not long-latency (LAI) afferent inhibition of face M1, while facial nerve stimulation evoked LAI but not SAI. Plasticity induction was observed only after a paired associative stimulation protocol using the facial nerve. Physiological differences in effects of cutaneous and muscle afferent inputs on face M1 excitability suggest they play separate functional roles in behaviour. ABSTRACT: The lack of conventional muscle spindles in face muscles raises the question of how sensory input from the face is used to control muscle activation. In 16 healthy volunteers, we probed sensorimotor interactions in face motor cortex (fM1) using short-afferent inhibition (SAI), long-afferent inhibition (LAI) and LTP-like plasticity following paired associative stimulation (PAS) in the depressor anguli oris muscle (DAO). Stimulation of low threshold afferents in the trigeminal nerve produced a clear SAI (P < 0.05) when the interval between trigeminal stimulation and transcranial magnetic stimulation (TMS) of fM1 was 15-30 ms. However, there was no evidence for LAI at longer intervals of 100-200 ms, nor was there any effect of PAS. In contrast, facial nerve stimulation produced significant LAI (P < 0.05) as well as significant facilitation 10-30 minutes after PAS (P < 0.05). Given that the facial nerve is a pure motor nerve, we presume that the afferent fibres responsible were those activated by the evoked muscle twitch. The F-wave in DAO was unaffected during both LAI and SAI, consistent with their presumed cortical origin. We hypothesize that, in fM1, SAI is evoked by activity in low threshold, presumably cutaneous afferents, whereas LAI and PAS require activity in (higher threshold) afferents activated by the muscle twitch evoked by electrical stimulation of the facial nerve. Cutaneous inputs may exert a paucisynaptic inhibitory effect on fM1, while proprioceptive information is likely to target inhibitory and excitatory polysynaptic circuits involved in LAI and PAS. Such information may be relevant to the physiopathology of several disorders involving the cranio-facial system.

THE ANATOMY OF OROFACIAL INNERVATION.

The whole human body receives rich sensory innervation with only one exception and that is the brain tissue. The orofacial region is hence no exception. The head region consequently receives a rich network of sensory nerves making it special because the two types of sensory fibres, visceral and somatic overlap, especially in the pharynx. Also, different pain syndromes that affect this region are rather specific in comparison to their presentation in other body regions. With this review article we wanted to show the detailed anatomy of the peripheral sensory pathways, because of its importance in everyday body functions (eating, drinking, speech) as well as the importance it has in pathological conditions (pain syndromes), in diagnostics and regional analgesia and anaesthesia.

Orofacial Movements Involve Parallel Corticobulbar Projections from Motor Cortex to Trigeminal Premotor Nuclei.

How do neurons in orofacial motor cortex (MCtx) orchestrate behaviors? We show that focal activation of MCtx corticobulbar neurons evokes behaviorally relevant concurrent movements of the forelimb, jaw, nose, and vibrissae. The projections from different locations in MCtx form gradients of boutons across premotor nuclei spinal trigeminal pars oralis (SpVO) and interpolaris rostralis (SpVIr). Furthermore, retrograde viral tracing from muscles that control orofacial actions shows that these premotor nuclei segregate their outputs. In the most dramatic case, both SpVO and SpVIr are premotor to forelimb and vibrissa muscles, while only SpVO is premotor to jaw muscles. Functional confirmation of the superimposed control by MCtx was obtained through selective optogenetic activation of corticobulbar neurons on the basis of their preferential projections to SpVO versus SpVIr. We conclude that neighboring projection neurons in orofacial MCtx form parallel pathways to distinct pools of trigeminal premotor neurons that coordinate motor actions into a behavior.

Relationship of the lobular branch of the great auricular nerve to the tympanoparotid fascia: Spatial anatomy for salvage during face and neck lift.

To enable selection of a safer suspension site to use in face and neck lifting procedures, the spatial relationship between the tympanoparotid fascia and the great auricular nerve should be clarified. In this study, we aimed to elucidate the position of the tympanoparotid fascia and the pathway of the lobular branch of the great auricular nerve traversing the tympanoparotid fascia. Twenty hemifaces from non-preserved bequeathed Korean cadavers (5 males, 7 females; mean age, 77.0 years) were dissected to determine the great auricular nerve distribution close to the tympanoparotid fascia of clinical significance for face and neck lift procedures. We observed the tympanoparotid fascia in all specimens (20 hemifaces). The tympanoparotid fascia was located anteriorly between the tragus and intertragic notch. Regarding the spatial relationship between the tympanoparotid fascia and the great auricular nerve, we found the sensory nerve entering the tympanoparotid fascia in all specimens (100%), and the depth from the skin was approximately 4.5 mm; in 65% of the specimens, the lobular branch was found to run close to the tympanoparotid fascia before going into the earlobe. Provided with relatively safer surface mapping to access the tympanoparotid fascia free of the lobular branch of the great auricular nerve, surgeons may better protect the lobular branch by anchoring the SMAS-platysma flap and thread to the deeper superior and anterior portions of the expected tympanoparotid fascia.

Automated objective and marker-free facial grading using photographs of patients with facial palsy.

PURPOSE: An automated, objective, fast and simple classification system for the grading of facial palsy (FP) is lacking. METHODS: An observational single center study was performed. 4572 photographs of 233 patients with unilateral peripheral FP were subjectively rated and automatically analyzed applying a machine learning approach including Supervised Descent Method. This allowed an automated grading of all photographs according to House-Brackmann grading scale (HB), Sunnybrook grading system (SB), and Stennert index (SI). RESULTS: Median time to first assessment was 6 days after onset. At first examination, the median objective HB, total SB, and total SI were grade 3, 45, and 5, respectively. The best correlation between subjective and objective grading was seen for SB and SI movement score (r = 0.746; r = 0.732, respectively). No agreement was found between subjective and objective HB grading [Test for symmetry 80.61, df = 15, p < 0.001, weighted kappa = - 0.0105; 95% confidence interval (CI) = - 0.0542 to 0.0331; p = 0.6541]. Also no agreement was found between subjective and objective total SI (test for symmetry 166.37, df = 55, p < 0.001) although there was a nonzero weighted kappa = 0.2670; CI 0.2154-0.3186; p < 0.0001). Based on a multinomial logistic regression the probability for higher scores was higher for subjective compared to objective SI (OR 1.608; CI 1.202-2.150; p = 0.0014). The best agreement was seen between subjective and objective SB (ICC = 0.34645). CONCLUSIONS: Automated Sunnybrook grading delivered with fair agreement fast and objective global and regional data on facial motor function for use in clinical routine and clinical trials.