Anatomical considerations and surgical manipulation of the rhomboid lip in microvascular decompression for hemifacial spasm.

BACKGROUND: In microvascular decompression (MVD) procedures for hemifacial spasm (HFS), surgeons often encounter a rhomboid lip which may obscure the root exit zone (REZ) of the facial nerve. This study aims to explore the anatomical variations of rhomboid lips and their surgical implications to improve safety and effectiveness in MVD surgeries. METHODS: A retrospective analysis was conducted on 111 patients treated for HFS between April 2021 and March 2023. The presence of a rhomboid lip was assessed through operative video records, and its characteristics, dissection methods, and impact on nerve decompression outcomes were further examined. Preoperative magnetic resonance imaging (MRI) scans were reviewed for detectability of the rhomboid lip. RESULTS: Rhomboid lips were identified in 33% of the patients undergoing MVD, with a higher prevalence in females and predominantly on the left side. Two distinct types of rhomboid lips were observed: membranous and cystic variations. The membranous type was noted for its smaller size and position ventral to the choroid plexus. In contrast, the cystic variation was distinguished by its larger size and a thin membrane that envelops the choroid plexus. Preoperative MRI successfully identified rhomboid lips in only 21% of the patients who were later confirmed to have them in the surgical procedures. Surgical approaches primarily involved incisions on the dorsal wall and along the glossopharyngeal nerve root, with only limited need for extensive dissection from lower cranial nerves. Immediate spasm relief was observed in 97% of the patients. One case exhibited a lower cranial nerve deficit accompanied by brainstem infarction, which was caused by the dissection from the lower cranial nerves. CONCLUSIONS: Recognizing the two variations of the rhomboid lip and understanding their anatomical structures are essential for reducing lower cranial nerve injuries and ensuring effective nerve decompression.

Mentalis nerve branches supplying the lower lip revisited: a study of human fetuses and donated elderly cadavers.

PURPOSE: Little information is known about the mentalis nerve course from the lower lip approximation margin (free margin) to the upper lip. Likewise, no difference in nerve distribution has been observed between the cutaneous and mucosal parts of the lip. Therefore, this study reexamined mentalis nerve morphology. METHODS: For macroscopic observations, three fresh cadavers were dissected (one male and two females; aged 78-93). We also evaluated histological sections obtained from five donated elderly cadavers (two males and three females, aged 82-96 years) and 15 human fetuses (11-40 weeks or crown-rump length 80-372 mm). Immunohistochemical analysis for S100 protein and tyrosine hydroxylase was performed. RESULTS: In both fetuses and adult cadavers, one to three nerve branches ran upward in the submucosal tissue from the mental foramen. Near the free margin of the lip, some branches passed through the orbicularis oris muscle layer toward the lip skin, whereas others followed a reversed J-shaped course along the free margin. Nerve twigs ran in parallel beneath the mucosa, whereas wavy nerve twigs attached to the basal lamina of the lip epidermis. The difference in nerve endings abruptly occurred at the skin-mucosal junction. Tyrosine hydroxylase-positive sympathetic nerve twigs surrounded arteries and formed a branch composed of S100-negative unmyelinated fibers. CONCLUSION: The lower lip skin was innervated by a perforating branch passing through the orbicularis oris muscle, that was different from the lip mucosa. A sudden change in the nerve ending configuration at the mucocutaneous junction seemed to develop postnatally.

Neuropathic Pain in Lower Lip after Guided Tissue Regeneration: A Case Report.

Post-traumatic trigeminal neuropathic pain is mainly caused by the extraction of third molars or the placement of dental implants. This report describes the treatment of neuropathic pain arising after guided tissue regeneration (GTR). The patient was a 55-year-old woman who had to undergo GTR due to severe periodontitis in the distal aspect of the right mandibular second molar. Postoperatively, the patient had been prescribed mecobalamin for hypesthesia and allodynia in the right lower lip. No improvement was observed in these symptoms after 4 months, however, so she was referred to our Orofacial Pain Center. Preoperative and postoperative cone-beam computed tomography revealed a cyst-like lesion (radiolucent area) close to the right mandibular second molar and canal. Although the results of quantitative sensory examination were normal, rubbing the right lower lip with a cotton swab elicited mechanical allodynia. The diagnosis was post-traumatic trigeminal neuropathic pain for which the patient was given pregabalin and Neurotropin®. The symptoms improved within approximately 32 weeks, with the medication being terminated at 64 weeks. Although hypoesthesia due to nerve injury may suddenly go into remission, allodynia is often intractable. If symptoms show no improvement after 3 months, possible nerve injury should be investigated. Additionally, the distal root of the mandibular molar may be close to the inferior alveolar nerve, necessitating appropriate diagnostic imaging of the operative field. If the lesion or distal root is close to the inferior alveolar nerve, postoperative hypesthesia or neuropathic pain may occur, even without direct trauma.

Review of Risk Assessment of Major Anatomical Variations in Clinical Dentistry: Accessory Foramina of the Mandible.

Most of the studies of the mandible's anatomical variations have presented the authors' speculations, and only a limited number has provided evidence that demonstrated the actual complications injury to the variant structures caused. To our knowledge, no study has evaluated the risks associated with these variant anatomical structures' injury. We reviewed articles that described clinical cases of the injury to, and anatomical studies of, three anatomical variants of the mandible-the accessory mental, lingual, and retromolar foramina-with which dentists are relatively familiar and that are mentioned often in the context of implant and third molar surgeries, to describe risk assessment methods with which to evaluate potential complications preoperatively. Only a limited number of the clinical reports of injury to the mandible's accessory foramina were available. The potential severe complication of injury of the accessory mental foramen (AMF) is sensory disturbance of the lower lip. Risk of neurosensory disturbance of lower lip can be assessed by AMF/MF ratio and positional relations to the MF. Potential severe complication of injury of the lingual foramen is bleeding and hemorrhage in the oral cavity's floor. Risk of bleeding can be assessed by diameter and positional relation between the mental spine/mylohyoid line. A risk assessment of the retromolar foramen could not be made because of inadequate data. We hope the risk assessments suggested will encourage dentists to predict intraoperative/postoperative complications caused by damaging the mandible's accessory foramina. Clin. Anat. 32:672-677, 2019. © 2019 Wiley Periodicals, Inc.

Functional and Quantitative MRI Mapping of Somatomotor Representations of Human Supralaryngeal Vocal Tract.

Speech articulation requires precise control of and coordination between the effectors of the vocal tract (e.g., lips, tongue, soft palate, and larynx). However, it is unclear how the cortex represents movements of and contact between these effectors during speech, or how these cortical responses relate to inter-regional anatomical borders. Here, we used phase-encoded fMRI to map somatomotor representations of speech articulations. Phonetically trained participants produced speech phones, progressing from front (bilabial) to back (glottal) place of articulation. Maps of cortical myelin proxies (R1 = 1/T1) further allowed us to situate functional maps with respect to anatomical borders of motor and somatosensory regions. Across participants, we found a consistent topological map of place of articulation, spanning the central sulcus and primary motor and somatosensory areas, that moved from lateral to inferior as place of articulation progressed from front to back. Phones produced at velar and glottal places of articulation activated the inferior aspect of the central sulcus, but with considerable across-subject variability. R1 maps for a subset of participants revealed that articulator maps extended posteriorly into secondary somatosensory regions. These results show consistent topological organization of cortical representations of the vocal apparatus in the context of speech behavior.

Digital Relief of the Mental Foramen for a CAD/CAM-Fabricated Mandibular Denture.

Relief of the intaglio surface of a denture base is conventionally performed using thin wax and soft metal foil attached to the master cast. The following report highlights a new relief procedure for the mental foramen using a CT double scan technique on the CAD/CAM dentures fabricated for the patient with paresthesia of the left lower lip and chin during mastication.

Reevaluation of reflex responses of the human masseter muscle to electrical lip stimulation.

We examined the reflex response of the human masseter muscle to electrical stimulation of the lip using both single motor unit and surface electromyogram based methods. Using the classical analysis methods, reflex response to mild electrical stimuli generated two distinct short-lasting inhibitions. This pattern may reflect the development of combinations of short- and long-latency inhibitory postsynaptic potentials as a result of the mildly painful electrical lip stimulation. However, this pattern appearing in the classical analysis methods may have developed as a consequence of earlier responses and may not be genuine. This study examined the genuineness of these responses using both the classical analysis methods and the discharge rate method to uncover the realistic postsynaptic potentials in human trigeminal motor nucleus. Using the discharge rate method, we found that the electrical lip stimulation only generated a long-lasting single or compound inhibitory response that is followed by late, long-lasting excitation. These findings have important implications on the redrawing of the neuronal pathways of the trigeminal nerve that are frequently used to judge neuromuscular disorders of the trigeminal region.NEW & NOTEWORTHY We examined the human masseter reflex response to electrical stimulation of lower lip to uncover realistic postsynaptic potentials in the trigeminal motor nucleus. We found that the stimulation generates a long-lasting single or compound inhibitory response that is followed by a late, long-lasting excitation. These findings have important implications on the redrawing of the neuronal pathways of the trigeminal nerve that are frequently used to judge neuromuscular disorders of the trigeminal region.

Intraoral Observation of the Mentalis and Incisivus Labii Inferioris Muscles.

The mentalis (MT) and the incisivus labii inferioris (ILI), which are accessory muscles of the orbicularis oris (OO) muscle, form an intertwined and three-dimensionally related complex. The purpose of this study is to clarify the relationship between the MT, ILI, and OO muscles via intraoral dissection. Twenty-two sides from 11 fresh adult Caucasian cadaveric heads were used, and the MT, ILI, and OO dissected under the surgical microscope. Next, measurements of the bony attachment were carried out on another 12 sides. The fibers of the MT were separated into 2 parts: a superior and an inferior part with the former coursing anteromedially and joining the inferior part of the OO. The latter coursed anteroinferiorly to the skin of the chin. The ILI traveled anterolaterally and joined the inferior part of the OO. Inferior labial branches of the mental nerves ran on the OO. There was a significant difference (P = 0.0001) between specimens that were edentulous or had severe periodontitis with regard to the distance from the alveolar ridge to the upper side of the quadrangle when compared with specimens with mild periodontitis. However, there was no significant difference (P > 0.05) between specimens that were edentulous or had severe periodontitis specimens with mild periodontitis with regard to the distance from the inferior border of the mandible to the lower side of the quadrangle. We believe that the observations of this study could help surgeons better understand the anatomy of the chin and minimize complications following surgical and other invasive procedures in this area.

Relationship Between the Quantity of Nerve Exposure During Bilateral Sagittal Split Osteotomy Surgery and Sensitive Recovery.

AIM AND OBJECTIVES: The purpose of this study was to evaluate how different exposures of the V3 nerves during orthognathic surgery impact neurosensory disturbances. METHODS: The study included 127 patients who underwent either bilateral sagittal split osteotomy (BSSO) or BSSO with maxillary le Fort 1. They were divided into 6 groups, identified by the quantity of V3 nerve exposure. All patients were examined in a pre-op period and again after 1, 3, 6 months post-op. The standardized tests used were to clarify the objective and subjective neurosensory status of the exposed nerve. Neurosensory evaluation included; a pin prick test, the 2 points discriminator, light touch, warm and cold tests, and blunt discrimination. They were all done bilaterally on the lower lip area. RESULTS: In only 2 patients the nerve was damaged during surgery and thus they were not included in this study. In 10.2% of patients there was no nerve exposure, 25.2% had longitudinal vestibular segment nerve exposed, 22.8% had the longitudinal upper-vestibular segment exposed, 20.5% had the longitudinal lower-vestibular segment exposed, 14.2% had the longitudinal upper-lower-vestibular segment exposed, and in 7.1% of patients the nerve was totally exposed. Given the estimated time of 1 month there was 100% recovery in patients whose nerve was unexposed. Considering the other patients, the authors had a variable number of patients who did not recover completely. CONCLUSION: The authors estimate a correlation between the recovery time and the quantity of the exposed nerve. There is a high incidence of neurosensory disturbance in the lower lip and chin after BSSO and intraoperative quantity of nerve exposure.

Left dorsal speech stream components and their contribution to phonological processing.

Models propose an auditory-motor mapping via a left-hemispheric dorsal speech-processing stream, yet its detailed contributions to speech perception and production are unclear. Using fMRI-navigated repetitive transcranial magnetic stimulation (rTMS), we virtually lesioned left dorsal stream components in healthy human subjects and probed the consequences on speech-related facilitation of articulatory motor cortex (M1) excitability, as indexed by increases in motor-evoked potential (MEP) amplitude of a lip muscle, and on speech processing performance in phonological tests. Speech-related MEP facilitation was disrupted by rTMS of the posterior superior temporal sulcus (pSTS), the sylvian parieto-temporal region (SPT), and by double-knock-out but not individual lesioning of pars opercularis of the inferior frontal gyrus (pIFG) and the dorsal premotor cortex (dPMC), and not by rTMS of the ventral speech-processing stream or an occipital control site. RTMS of the dorsal stream but not of the ventral stream or the occipital control site caused deficits specifically in the processing of fast transients of the acoustic speech signal. Performance of syllable and pseudoword repetition correlated with speech-related MEP facilitation, and this relation was abolished with rTMS of pSTS, SPT, and pIFG. Findings provide direct evidence that auditory-motor mapping in the left dorsal stream causes reliable and specific speech-related MEP facilitation in left articulatory M1. The left dorsal stream targets the articulatory M1 through pSTS and SPT constituting essential posterior input regions and parallel via frontal pathways through pIFG and dPMC. Finally, engagement of the left dorsal stream is necessary for processing of fast transients in the auditory signal.

The effect of speech distortion on the excitability of articulatory motor cortex.

It has become increasingly evident that human motor circuits are active during speech perception. However, the conditions under which the motor system modulates speech perception are not clear. Two prominent accounts make distinct predictions for how listening to speech engages speech motor representations. The first account suggests that the motor system is most strongly activated when observing familiar actions (Pickering and Garrod, 2013). Conversely, Wilson and Knoblich's account asserts that motor excitability is greatest when observing less familiar, ambiguous actions (Wilson and Knoblich, 2005). We investigated these predictions using transcranial magnetic stimulation (TMS). Stimulation of the lip and hand representations in the left primary motor cortex elicited motor evoked potentials (MEPs) indexing the excitability of the underlying motor representation. MEPs for lip, but not for hand, were larger during perception of distorted speech produced using a tongue depressor, relative to naturally produced speech. Additional somatotopic facilitation yielded significantly larger MEPs during perception of lip-articulated distorted speech sounds relative to distorted tongue-articulated sounds. Critically, there was a positive correlation between MEP size and the perception of distorted speech sounds. These findings were consistent with predictions made by Wilson & Knoblich (Wilson and Knoblich, 2005), and provide direct evidence of increased motor excitability when speech perception is difficult.

Dissociating Contributions of the Motor Cortex to Speech Perception and Response Bias by Using Transcranial Magnetic Stimulation.

Recent studies using repetitive transcranial magnetic stimulation (TMS) have demonstrated that disruptions of the articulatory motor cortex impair performance in demanding speech perception tasks. These findings have been interpreted as support for the idea that the motor cortex is critically involved in speech perception. However, the validity of this interpretation has been called into question, because it is unknown whether the TMS-induced disruptions in the motor cortex affect speech perception or rather response bias. In the present TMS study, we addressed this question by using signal detection theory to calculate sensitivity (i.e., d') and response bias (i.e., criterion c). We used repetitive TMS to temporarily disrupt the lip or hand representation in the left motor cortex. Participants discriminated pairs of sounds from a "ba"-"da" continuum before TMS, immediately after TMS (i.e., during the period of motor disruption), and after a 30-min break. We found that the sensitivity for between-category pairs was reduced during the disruption of the lip representation. In contrast, disruption of the hand representation temporarily reduced response bias. This double dissociation indicates that the hand motor cortex contributes to response bias during demanding discrimination tasks, whereas the articulatory motor cortex contributes to perception of speech sounds.

Causal Influence of Articulatory Motor Cortex on Comprehending Single Spoken Words: TMS Evidence.

Classic wisdom had been that motor and premotor cortex contribute to motor execution but not to higher cognition and language comprehension. In contrast, mounting evidence from neuroimaging, patient research, and transcranial magnetic stimulation (TMS) suggest sensorimotor interaction and, specifically, that the articulatory motor cortex is important for classifying meaningless speech sounds into phonemic categories. However, whether these findings speak to the comprehension issue is unclear, because language comprehension does not require explicit phonemic classification and previous results may therefore relate to factors alien to semantic understanding. We here used the standard psycholinguistic test of spoken word comprehension, the word-to-picture-matching task, and concordant TMS to articulatory motor cortex. TMS pulses were applied to primary motor cortex controlling either the lips or the tongue as subjects heard critical word stimuli starting with bilabial lip-related or alveolar tongue-related stop consonants (e.g., "pool" or "tool"). A significant cross-over interaction showed that articulatory motor cortex stimulation delayed comprehension responses for phonologically incongruent words relative to congruous ones (i.e., lip area TMS delayed "tool" relative to "pool" responses). As local TMS to articulatory motor areas differentially delays the comprehension of phonologically incongruous spoken words, we conclude that motor systems can take a causal role in semantic comprehension and, hence, higher cognition.

Nerve Sharing Between the Lingual and Mental Nerve to Restore Lower Lip Sensation After Segmental Resection of the Mandible.

This report demonstrates a successful new procedure for reconstructing the inferior alveolar nerve by transplanting the great auricular nerve (GAN) between the mental nerve and the remaining submandibular ganglion to achieve nerve sharing of the lingual nerve. A 59-year-old woman with discomfort in the left mandibular retromolar region and ipsilateral neck was referred to our hospital by a local dentist. Physical examination showed mild swelling and redness at the left mandibular retromolar region. The histologic diagnosis showed central mucoepidermoid carcinoma of the jaw. With the patient under general anesthesia, segmental resection of the mandible followed by level 1 selective neck dissection was performed. The resected mandible was reconstructed with a titanium plate. The submandibular incision was extended to the lower edge of the tragus for harvesting of the GAN. The GAN was grafted, and an epineural neurorrhaphy was carried out with the mental nerve, as well as the submandibular ganglion, under a microscope. After the operation, submental sensation was evaluated with a Semmes-Weinstein pressure esthesiometer. The Semmes-Weinstein pressure esthesiometer test showed a loss of perception at the third week after surgery. Within 12 months, nerve sensation was substantially improved and the patient was free from discomfort.

A Cadaveric Study of the Communication Patterns Between the Buccal Trunks of the Facial Nerve and the Infraorbital Nerve in the Midface.

Most nerve communications reported in the literature were found between the terminal branches. This study aimed to clarify and classify patterns of proximal communications between the buccal branches (BN) of the facial nerve and the infraorbital nerve (ION).The superficial musculoaponeurotic system protects any communication sites from conventional dissections. Based on this limitation, the soft tissues of each face were peeled off the facial skull and the facial turn-down flap specimens were dissected from the periosteal view. Dissection was performed in 40 hemifaces to classify the communications in the sublevator space. Communication site was measured from the ala of nose.A double communication was the most common type found in 62.5% of hemifaces. Triple and single communications existed in 25% and 10% of 40 hemiface specimens, respectively. One hemiface had no communication. The most common type of communication occurred between the lower trunk of the BN of the facial nerve and the lateral labial (fourth) branch of the ION (70% in 40 hemifaces). Communication site was deep to the levator labii superioris muscle at 16.2 mm from the nasal ala. Communications between the motor and the sensory nerves in the midface may be important to increase nerve endurance and to compensate functional loss from injury.Proximal communications between the main trunks of the facial nerve and the ION in the midface exist in every face. This implies some specific functions in normal individuals. Awareness of these nerves is essential in surgical procedure in the midface.

Cortical reorganization after macroreplantation at the upper extremity: a magnetoencephalographic study.

With the development of microsurgical techniques, replantation has become a feasible alternative to stump treatment after the amputation of an extremity. It is known that amputation often induces phantom limb pain and cortical reorganization within the corresponding somatosensory areas. However, whether replantation reduces the risk of comparable persisting pain phenomena as well as reorganization of the primary somatosensory cortex is still widely unknown. Therefore, the present study aimed to investigate the potential development of persistent pain and cortical reorganization of the hand and lip areas within the sensory cortex by means of magnetoencephalographic dipole analyses after replantation of a traumatically amputated upper limb proximal to the radiocarpal joint. Cortical reorganization was investigated in 13 patients with limb replantation using air puff stimulation of the phalanges of both thumbs and both corners of the lower lip. Displacement of the centre of gravity of lip and thumb representations and increased cortical activity were found in the limb and face areas of the primary somatosensory cortex contralateral to the replanted arm when compared to the ipsilateral hemisphere. Thus, cortical reorganization in the primary somatosensory cortex also occurs after replantation of the upper extremity. Patients' reports of pain in the replanted body part were negatively correlated with the amount of cortical reorganization, i.e. the more pain the patients reported, the less reorganization of the subjects' hand representation within the primary somatosensory cortex was observed. Longitudinal studies in patients after macroreplantation are necessary to assess whether the observed reorganization in the primary somatosensory cortex is a result of changes within the representation of the replanted arm and/or neighbouring representations and to assess the relationship between the development of persistent pain and reorganization.

Lip Forces and Chewing Efficiency in Children with Peripheral Facial Paralysis.

Peripheral facial paralysis is accompanied by facial motor disorders and also, by oral dysfunctions. The aim of this study was to evaluate the lip forces and chewing efficiency in a group of children with peripheral facial paralysis. The degree of peripheral facial paralysis in the study group (n 11) was assessed using the House-Brackmann scale. The control group consisted of 21 children without facial nerve impairment. To assess lip forces, acrylic vestibular plates of three sizes were used: large (LVP), medium (MVP) and small (SVP). The lip force was recorded with a force transducer coupled with the data acquisition system. Masticatory efficiency was evaluated by the ability to mix two differently colored chewing gums. The images were processed with Adobe Photoshop CS3 (Delaware Corporation, San Jose, California, United States) and the number of pixels was quantified with the Image J software (DHHS/NIH/NIMH/RSB, Maryland, United States). For statistical analysis, the following statistical analysis were used: Pearson or Spearman correlation coefficient, multiple linear regression analysis, multiple logistic regression analysis, and optimal cutoff values for muscular dysfunction. There were statistically significant differences between lip forces in the following three groups: p=0.01 (LVP), p=0.01 (MVP), and p=0.008 (SVP). The cutoff values of lip forces in the study group were as follows: 7.08 N (LVP), 4.89 N (MVP), and 4.24 N (SVP). There were no statistically significant differences between the masticatory efficiency in the two groups (p=0.25). Lip forces were dependent on the degree of peripheral facial paralysis and age, but not on gender. In peripheral facial paralysis in children, a significant decrease of lip forces, but not masticatory efficiency, occurs.

Inferior Alveolar Nerve Injury in Trauma-Induced Mandible Fractures.

PURPOSE: This prospective observational cohort study sought to determine the prevalence of inferior alveolar nerve (IAN) injury after mandibular fractures before and after treatment and to elucidate factors associated with the incidence of post-treatment IAN injury and time to normalization of sensation. MATERIALS AND METHODS: Consenting patients with mandibular fractures (excluding dentoalveolar, pathologic, previous fractures, or mandibular surgery) were prospectively evaluated for subjective neurosensory disturbance (NSD) and underwent neurosensory testing before treatment and then 1 week, 1.5, 3, 6, and 12 months after treatment. RESULTS: Eighty patients (men, 83.8%; mean age, 30.0 yr; standard deviation, 12.6 yr) with 123 mandibular sides (43 bilateral) were studied. Injury etiology included assault (33.8%), falls (31.3%), motor vehicle accidents (25.0%), and sports injuries (6.3%). Half the fractures (49.6%) involved the IAN-bearing posterior mandible; all condylar fractures (13.0%) had no NSD. Treatment included open reduction and internal fixation (ORIF; 74.8%), closed reduction and fixation (22.0%), or no treatment (3.3%). Overall prevalence of IAN injury was 33.7% (95% confidence interval [CI], 24.8-42.6) before treatment and 53.8% (95% CI, 46.0-61.6) after treatment. In the IAN-bearing mandible, the prevalence was 56.2% (95% CI, 43.2-69.2) before treatment and 72.9% (95% CI, 63.0-82.7) after treatment. In contrast, this prevalence in the non-IAN-bearing mandible was 12.6% (95% CI, 4.1-21.1) before treatment and 31.6% (95% CI, 20.0-43.3) after treatment. Factors associated with the development of post-treatment IAN injury included fracture site and gap distance (a 1-mm increase was associated with a 27% increase in odds of post-treatment sensory alteration). Time to normalization after treatment was associated with type of treatment (ORIF inhibited normalization) and fracture site (IAN-bearing sites took longer to normalize). CONCLUSION: IAN injury was 4 times more likely in IAN-bearing posterior mandibular fractures (56.2%) than in non-IAN-bearing anterior mandibular fractures (12.6%). After treatment, IAN injury prevalence (in 12 months) was higher (72.9% in posterior mandible, 31.6% in anterior mandible).

A Technique for Preoperative Identification of the Facial Nerve Mandibular Branch Using a Nerve Stimulator.

We established the method of preoperative identification to facial nerve marginal mandibular branch (FNMB) identification using a nerve stimulator with bipolar probe for upper-neck surgery. The bipolar electrode is placed on the region while patients were awake; the patient should be in the same position and posture as during the surgery, with the neck skin stretched. A nerve course is confirmed by observing the movement of the lower lip. In this study, 5 upper-neck surgeries were conducted. Preoperative analysis revealed that 4 of the 5 cases had 2 branches of FNMB, and 1 with 3 branches. All FNMB immediately confirmed preoperatively were identified during surgery. We performed this method in much surgery including the surgery of the upper neck. It was easy to identify the facial nerve by this method and came to be able to do it precisely, and an operative time was shortened. We concluded that the preoperative FNMB identification using a nerve stimulator is most useful and benefit for upper-neck surgery patients and lead to avoid lower lip paralysis.

Resolution of Implant-Induced Neurosensory Disturbance: A Procedural Failure.

PURPOSE: This case report describes the improvement of a patient's neurosensory symptoms after the removal of a mandibular implant within 24 hours of initial placement. After 1 year, neurosensory symptoms resolved, and a different sized dental implant was successfully placed at the same surgical site. MATERIALS AND METHODS: A 45-year-old woman experienced neurosensory disturbance along the inferior alveolar mandibular nerve after a dental implant surgery. A panoramic radiograph, obtained within 24 hours of implant placement, suggested a possible case of implant intrusion into the inferior alveolar nerve canal. After thorough evaluation, the implant was removed within 24 hours of initial placement, and the patient was followed up for 1 year. The neurosensory functions of the patient's chin and lower lip regions were assessed before implant removal, and 1 month and 1 year after the removal of the implant. RESULTS: Almost complete resolution of altered sensation occurred 1 year after implant removal. A second, shorter implant was placed at the same site with no subsequent symptoms of impaired sensation. CONCLUSION: This report highlights the plausible placement of a different size dental implant in the same area of previous-implant-induced nerve injury. The authors report that a lack of postoperative radiograph by the surgeon was considered to be a procedural failure.