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.

Promotion effect of TGF-ß-Zfp423-ApoD pathway on lip sensory recovery after nerve sacrifice caused by nerve collateral compensation.

Resection of oral and maxillofacial tumors is often accompanied by the inferior alveolar nerve neurectomy, resulting in abnormal sensation in lower lip. It is generally believed that spontaneous sensory recovery in this nerve injury is difficult. However, during our follow-up, patients with inferior alveolar nerve sacrifice showed different degrees of lower lip sensory recovery. In this study, a prospective cohort study was conducted to demonstrate this phenomenon and analyze the factors influencing sensory recovery. A mental nerve transection model of Thy1-YFP mice and tissue clearing technique were used to explore possible mechanisms in this process. Gene silencing and overexpression experiments were then conducted to detect the changes in cell morphology and molecular markers. In our follow-up, 75% of patients with unilateral inferior alveolar nerve neurectomy had complete sensory recovery of the lower lip 12 months postoperatively. Patients with younger age, malignant tumors, and preservation of ipsilateral buccal and lingual nerves had a shorter recovery time. The buccal nerve collateral sprouting compensation was observed in the lower lip tissue of Thy1-YFP mice. ApoD was demonstrated to be involved in axon growth and peripheral nerve sensory recovery in the animal model. TGF-ß inhibited the expression of STAT3 and the transcription of ApoD in Schwann cells through Zfp423. Overall, after sacrificing the inferior alveolar nerve, the collateral compensation of the ipsilateral buccal nerve could innervate the sensation. And this process was regulated by TGF-ß-Zfp423-ApoD pathway.

Lower Facial Nerve Nomenclature Clarification: Cervical Branch Controls Smile-Associated Lower Lip Depression and Dental Display.

OBJECTIVE: In head and neck ablative surgery, traditional teaching is that the key facial nerve branch to preserve along the plane of the lower border of the mandible is the marginal mandibular branch (MMb), which is considered to control all lower lip musculature. The depressor labii inferioris (DLI) is the muscle responsible for pleasing lower lip displacement and lower dental display during natural emotive smiling. STUDY DESIGN: To understand the structure/function relationships of the distal lower facial nerve branches and lower lip musculature. SETTING: In vivo extensive facial nerve dissections under general anesthesia. METHODS: Intraoperative mapping was performed in 60 cases, using branch stimulation and simultaneous movement videography. RESULTS: In nearly all cases, the MMb innervated the depressor anguli oris, lower orbicularis oris, and mentalis muscles. The nerve branches controlling DLI function were identified 2 ± 0.5 cm below the angle of the mandible, originating from a cervical branch, separately and inferior to MMb. In half of the cases, we identified at least 2 independent branches activating the DLI, both within the cervical region. CONCLUSION: An appreciation of this anatomical finding may help prevent lower lip weakness following neck surgery. Avoiding the functional and cosmetic consequences that accompany loss of DLI function would have a significant impact on the burden of potentially preventable sequelae that the head and neck surgical patient frequently carries.

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.

Effect of concentrated growth factor on lower lip hypoesthesia after osseous genioplasty: a prospective, split-mouth, double-blind randomized controlled trial.

Lower lip hypoesthesia is the most common complication following osseous genioplasty. Concentrated growth factor (CGF) has recently been shown to improve neural regeneration. The aim of this study was to evaluate the effect of concentrated growth factor on neurosensory recovery after osseous genioplasty. Patients who underwent osseous genioplasty between June 2017 and February 2020 were enrolled. CGF was applied to the mental nerve on one side. The treatment side was randomized, and the other side was considered as the control. Lower lip hypoesthesia was assessed preoperatively and postoperatively (1 week, 1, 3, 6, and 9 months) using the two-point discrimination test and a 10-point visual analogue scale (self-reported paresthesia). The assessor was blinded. Twenty-six female patients completed the study. At 1 and 3 months, both the mean two-point discrimination value and mean visual analogue scale score were significantly lower in the CGF group than in the control group (P < 0.001). At 3 months, the percentage of patients with lower lip hypoesthesia in the CGF group was significantly lower than that in the control group (P < 0.001). Both groups showed resolution of lower lip hypoesthesia at 6 months. Concentrated growth factor may accelerate the recovery of long-standing sensory nerve impairment following mental osteotomy.

Somatotopic organization of corticospinal/corticobulbar motor tracts in controls and patients with tumours: A combined fMRI-DTI study.

OBJECTIVES: To investigate the relative somatotopic organization of the motor corticospinal/corticobulbar foot, hand, lip and tongue fascicles by combining fMRI with DTI and to examine the influence of subjacent intrinsic tumours on these fascicles. METHODS: The study was approved by the local ethics committee. Seven male and three female volunteers (median age: 35 years) and one female and eight male patients with brain tumours (median age: 37 years) were scanned on a 1.5-T MRI scanner. fMRI data, analysed using SPM5, identified the motor task-driven fMRI grey matter activations of the hand, foot, lips and tongue as seed regions for probabilistic tractography. The relationship between the components of the CST was assessed and the distances between them were measured. A statistical comparison was performed comparing these distances in the group of healthy hemispheres with those of the group of non-affected hemispheres and healthy hemispheres. RESULTS: Hand fascicles were identified in all subjects (38/38, 100%), followed by foot (32/38, 84%), lip (31/38, 81%) and tongue fascicles (28/38, 74%). At superior levels, the hand fascicles were anterolateral to the foot fascicles in 77-93% of healthy hemispheres (HH), in 50-71% of non-affected patients' hemispheres (pH) and in 67-89% of affected PH. At inferior levels, the hand fascicles were either anteromedial in 46-45% of HH or anterior in 75% of non-affected PH and in 67-83% of affected PH. Tongue and lip fascicles overlapped in 25-45% of HH, in 10-20% of non-affected PH and in 15-25% of affected PH. No significant difference was found between the group of affected hemispheres and that of healthy and non-affected hemispheres. CONCLUSION: The somatotopy of the hand fascicles in relation to the foot fascicles was anterolateral in patients and volunteers at superior levels but anteromedial in volunteers and mostly anterior in patients at inferior levels. The lip and tongue fascicles generally overlapped. Intracranial tumours displaced the motor fascicles without affecting their relative somatotopy.

Evaluation of accuracy and sensory outcomes of mandibular reconstruction using computer-assisted surgical simulation.

PURPOSE: To introduce a modified protocol for mandibular reconstruction and evaluate the protocol using a standardized assessment method. METHOD: This retrospective study involved a case series of nine patients who underwent mandibular reconstruction between 2015 and 2017. The modular protocol comprised three novel modifications in terms of computer-assisted surgical simulation (CASS); surgical template (ST), and surgical procedure. The standardized postoperative evaluation consisted of operation time, part comparison analysis (PCA), facial symmetry, and mechanical quantitative sensory testing. RESULTS: The surgery successfully removed the affected mandible and preserved the inferior alveolar neurovascular bundle (IANB). PCA revealed that the mean error and standard deviation were 0.92 and 0.96 mm, respectively, for all mandibular surface sites. Follow-up results showed good facial symmetry, existence of sensation in lower lip, and no significant differences in pulp vitality between both sides (p = 0.181). Also, the results showed a reduction in the overall operating time. CONCLUSION: The modified mandibular reconstruction method used in this study could repair lateral mandibular defects and preserve the sensory function of the chin and lower lip.

Operative technique for benign submandibular gland mass without identifying the mandibular branch of the facial nerve.

OBJECTIVE: The marginal mandibular branch of the facial nerve must be protected during surgery for benign diseases of submandibular gland. Methods for protecting the marginal mandibular branch include the nerve identification method and the non-identification method. METHODS: We performed submandibular gland surgery in 138 patients with benign submandibular gland diseases using the non-identification method to preserve the marginal mandibular branch. In brief, the submandibular gland capsule is incised at the inferior border of the gland and detached along the gland parenchyma. The nerve is protected by this procedure without the need for identification. RESULTS: Among 138 patients who underwent this surgical procedure, only 7 patients developed transient paralysis of the lower lip. CONCLUSION: This method of resecting the submandibular gland without identifying the marginal mandibular branch is an effective procedure associated with a low incidence of transient paralysis. Moreover, no patient developed paralysis due to procedural errors.

Subjective perception of paraesthesia of the lower lip after bilateral sagittal split osteotomy at a district general hospital.

Our aim was to assess patients' perception of paraesthesia of the lower lip after bilateral sagittal split osteotomy (BSSO) at a district general hospital. Patients who had BSSO between August 2013 and August 2014 (n=46) were asked to score their perception of numbness between 0-10 (0=normal sensation. 10=complete loss of sensation/total numbness) one day postoperatively and then weekly for seven weeks, and at three months, 6 months, and one year. Data was collected on score sheets and by regular contact by telephone. Of the 46 operated on, 31 were female and 15 male. Data were available one year postoperatively for 43 patients. Ten of the 92 sides were reported as feeling normal on day 1 postoperatively, three-quarters as feeling normal at six months, and 79 at one year. On multivariate analysis there was no significant difference in postoperative sensation at one year between sides operated on by the registrar (left) and consultant (right) operated (p=0.76). Our results compared favourably with the limited data available in similarly designed studies.

Numbness of the lower lip does not adversely affect quality of life or patients' satisfaction after mandibular orthognathic surgery.

Measures of patient-reported quality of life (QoL) are increasingly being used to tailor services that are funded by Clinical Commissioning Groups (CCG) in England. Mandibular osteotomies may result in altered sensation of the lower lip, but we know of limited evidence about the resulting effect on QoL. The modified Bristol orthognathic patient outcomes questionnaire was given to patients who had mandibular osteotomies at the Queen Elizabeth Hospital, Birmingham, between March 2006 and April 2016. Questionnaires were collected at the final orthognathic postoperative appointment. The significance of the difference in QoL between those who had altered sensation of the lower lip and those who did not was compared using a two-tailed t test. During this period 170 patients had mandibular orthognathic operations. Completed questionnaires were received from 117 of those patients (69%) during this period, after a follow up of about six months. We found no significant difference between the perceived benefits of treatment between the 41 who had altered sensation and the 74 who did not (p=0.30). Only 5/41 who reported residual numbness six months postoperatively stated that they would not choose to have the same treatment again. In conclusion, orthognathic surgery results in an appreciable improvement in QoL and should continue to be funded by CCG in England. Contrary to the perception of some clinicians, those patients with residual numbness of the lip did not have significantly poorer QoL. Future interpretation of the data will be improved if they are collected both before and after the operation.

Effects of ageing on orofacial fine force control and its relationship with parallel change in sensory perception.

PURPOSE: Current theoretical models suggest the importance of a bidirectional relationship between sensation and production in the vocal tract to maintain lifelong speech skills. The purpose of this study was to assess age-related changes in orofacial skilled force production and to begin defining the orofacial perception-action relationship in healthy adults. METHOD: Low-level orofacial force control measures (reaction time, rise time, peak force, mean hold force (N) and force hold SD) were collected from 60 adults (19-84 years). Non-parametric Kruskal Wallis tests were performed to identify statistical differences between force and group demographics. Non-parametric Spearman's rank correlations were completed to compare force measures against previously published sensory data from the same cohort of participants. RESULT: Significant group differences in force control were found for age, sex, speech usage and smoking status. Significant correlational relationships were identified between labial vibrotactile thresholds and several low-level force control measures collected during step and ramp-and-hold conditions. CONCLUSION: These findings demonstrate age-related alterations in orofacial force production. Furthermore, correlational analysis suggests as vibrotactile detection thresholds increase, the ability to maintain low-level force control accuracy decreases. Possible clinical applications and treatment consequences of these findings for speech disorders in the ageing population are provided.

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.

Hypoesthesia associated with mandibular movement after sagittal split ramus osteotomy.

PURPOSE: This retrospective study investigated the relationship between the degree of neurosensory disturbance (NSD) and mandibular movement distance after sagittal split ramus osteotomy (SSRO) and assessed sensory recovery. METHODS: Lower lip hypoesthesia was evaluated at 1 week, 1 month, and 2 months after SSRO in 38 patients categorized according to the distance of mandibular movement: S group (0-7 mm; n = 17, 4 males and 13 females) and L group (7-14 mm; n = 21, 7 males, 14 females). Symptoms were evaluated by visual analog scale (VAS), tactile-threshold (SW) test, static 2-point discrimination (s-2PD) test, and current perception threshold (CPT) test. RESULTS: The two groups did not differ significantly in gender and age. The Aß fiber results of the CPT test differed significantly between the groups at 1 week and 1 month postsurgery (P < 0.05). There were no significant differences between the groups throughout the period in terms of VAS, SW, s-2PD, Aδ fiber, and C fiber of CPT. CONCLUSIONS: Post-SSRO, the incidence of NSD in terms of tactile sensation may be greater in the L group early postoperatively. This may assist surgeons in explaining postoperative hypoesthesia to patients preoperatively.

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.

Lengthening Temporalis Myoplasty: Virtual Animation-Assisted Technical Video.

Lengthening temporalis myoplasty is a well-established procedure for dynamic palliative reanimation of the lip in facial palsy sequelae. The particularity of this technique is that the entire temporal muscle is transferred from the coronoid process to the upper half of the lip without interposition of aponeurotic tissue. To date, no video describing the technique was available. This is the first video describing the entire procedure, from preoperative markings through postoperative rehabilitation. In the video presented herein, the authors craft virtual three-dimensional animations in addition to a live operation on a patient performed by Daniel Labbé, who first described this technique 20 years ago.

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 low dose of subperiosteal anaesthesia injection versus a high dose of infiltration anaesthesia to minimise the risk of nerve damage at implant placement: A randomised controlled trial.

PURPOSE: To evaluate whether a low-dose subperiosteal anaesthesia is effective in minimising risks of inferior alveolar nerve damage at implant placement when compared to high-dose infiltration anaesthesia. MATERIAL AND METHODS: One hundred and twenty patients requiring the placement of a single implant in order to replace a missing first mandibular were randomly allocated to two groups: group A (awake hemilip) subperiosteal crestal injection equal to 0.9 ml of articaine with 0.5% epinephrine and group B (numb hemilip) infiltration equal to 7.2 ml of articaine with 0.5% epinephrine in the vestibular fundus. Intraoperative sensory control using sensory tests was carried out in all patients. Outcome measures were neurological complications, intraoperative and postoperative visual analogue scale (VAS) scores for pain and swelling, and a questionnaire evaluating patient satisfaction. Patients were followed for 1 week postoperatively. RESULTS: There were no cases of nerve injury. Seven days after surgery the postoperative VAS score for pain and swelling was lower in group A in a statistically significant manner (difference = -3.41%; 95% CI: -5.57, -1.26; P = 0.002 and difference = -3.33%; 95% CI: -5.41, -1.25; P = 0.002, respectively). CONCLUSIONS: No nerve damage occurred using either anaesthesia types, therefore the choice of type of anaesthesia is a subjective clinical decision, however it may be preferable to use a low dose (0.9 ml) of subperiosteal anaesthesia, since it is unnecessary to deliver 7.2 ml of articaine to anaesthetise a single mandibular molar implant site.

Malignant peripheral nerve sheath tumor of the lower labial mucosa: case report and literature review.

Malignant peripheral nerve sheath tumor (MPNST) is an uncommon soft tissue sarcoma with a predilection for the extremities and trunk of adults, rarely occurring in the oral cavity. To date, 10 cases of MPNSTs affecting the lower labial mucosa have been reported in the English language literature. We describe an additional case of MPNST in the lower labial mucosa of a 67-year-old male patient, who exhibited a painful swelling with a history of 4 months of evolution. Microscopic examination showed dense plexiform fascicles of spindle cells with wavy atypical nuclei. Mitotic figures and nuclear pleomorphism were evident. Immunohistochemical analysis of tumor cells revealed positivity for S-100 protein, CD56, CD34, and neuron-specific enolase but was negative for neurofilament protein, glut-1, claudin-1, desmin, and smooth muscle actin. Ki-67 labeling was 20%. The final diagnosis was MPNST. The lesion was surgically removed with wide margins, with no signs of recurrence after 4 years of follow-up.

The use of piezoelectric surgery to lateralize the inferior alveolar nerve with simultaneous implant placement and immediate buccal cortical bone repositioning: a prospective clinical study.

A prospective study was conducted to assess a variation of inferior alveolar nerve (IAN) lateralization. This study included 13 patients. An osteotomy was made with a piezoelectric device, and the IAN bundle was moved buccally. Dental implants were then inserted medial to the nerve bundle, and the inner surface of the buccal cortical bone plate was shaped to reduce its thickness. Finally, the bone plate was repositioned to restore the original shape and contour of the mandible. Neurosensory examinations of the lower lip and chin were performed using three tests: light touch, pain, and two-point discrimination. Three months after surgery, the function of the IAN was judged to be completely restored at 11 of the 13 surgical sites. Differences in the tests comparing the operated and non-operated sides were not significant. No implants were lost, and all patients were satisfied with the result. Although IAN lateralization in conjunction with dental implant placement is rarely indicated, the use of a piezoelectric device to perform a buccal osteotomy with final repositioning of the buccal cortical plate over the bony defect contributes to the recovery of the contour and shape of the mandible, without impairment of IAN function.