Diagnostic Challenges and Imaging Considerations for Intraparotid Facial Nerve Schwannoma: A Case Report and Literature Review.

BACKGROUND A mass in the parotid gland usually indicates parotid gland neoplasia. Warthin tumors or pleomorphic adenomas are common differential diagnoses. Less frequently, other differential diagnoses and sites of origin are considered. Schwannomas are rare, benign tumors in the head and neck region. Even more rarely, these tumors occur in the intraparotid course of the facial nerve. In the following, we report about 2 patients in whom a mass in the right parotid gland was found incidentally during magnetic resonance imaging (MRI). CASE REPORT We reviewed data from the literature on intraparotid facial nerve schwannomas (IPFNS) and compared them with those from our cases. The focus was on data such as clinical history, clinical symptoms, electroneurography, and various imaging modalities, such as ultrasonography and MRI combined with diffusion-weighted imaging. CONCLUSIONS It is challenging to distinguish facial nerve schwannomas from other neoplasms. Patient's history, clinical symptoms, MRI examination with diffusion-weighted imaging, and high-resolution ultrasound imaging are decisive factors for diagnosis and should be performed when IPFNS is suspected. Diagnosis and therapy for IPFNS remain challenging. A wait-and-scan approach could be an option for patients with small tumors and good facial nerve function. On the other hand, patients with advanced tumors associated with limited facial nerve function can benefit from surgical approaches or stereotactic radiosurgery.

Intra-parotid facial nerve path by MRI tractography: radio-clinical comparison in parotid tumors.

PURPOSE: The objective of our study was to evaluate the ability of preoperative MRI tractography to visualize and predict the path of the facial nerve with respect to an intra-parotid mass. METHODS: We performed an observational bicentric study from June 2019 to August 2020. All patients older than 18 years old, treated for a parotid mass with surgical indication, without MRI contraindication and who agreed to participate in the study were enrolled prospectively. All patients underwent a cervico-facial MRI with tractographic analysis. Postprocessed tractography images of the intra-parotid facial nerve were analyzed by two expert radiologists in head and neck imaging. The intraoperative anatomical description of the facial nerve path and its relationship to the mass was performed by the surgeon during the operation, with no visibility on MRI examination results. A statistical study allowed for the description of the data collected as well as the measurement of inter-observer agreement and agreement between tractography and surgery using kappa coefficients. RESULTS: Fifty-two patients were included. The facial nerve trunk and its first two divisional branches were visualized via tractography in 93.5% of cases (n = 43). The upper distal branches were visualized in 51.1% of cases (n = 23), and the lower branches were visualized in 73.3% of cases (n = 33). Agreement with the location described per-operatively was on average 82.9% for the trunk, 74.15% for the temporal branch, and 75.21% for the cervico-facial branch. CONCLUSION: Fiber tractography analysis by MRI of the intra-parotid facial nerve appears to be a good test for predicting the path of the nerve over the parotid mass and could be an additional tool to guide the surgeon in the operative procedure.

Augmented reality presentation of the extracranial facial nerve: an innovation in parotid surgery.

Surgeons used to be unaware of the facial nerve's position during parotid surgery. Now, with special magnetic resonance imaging (MRI) sequences, it can be located and converted into a 3D model displayed on an augmented reality (AR) device for surgeons to study and manipulate. This study explores the accuracy and usefulness of the technique for the treatment of benign and malignant parotid tumours. A total of 20 patients with parotid tumours had 3-Tesla MRI scans, and their anatomical structures were segmented using Slicer software. The structures were imported into a Microsoft HoloLens 2® device, displayed in 3D, and shown to the patient for consent. Intraoperative video recording was used to record the position of the facial nerve in relation to the tumour. The predicted path of the nerve taken from the 3D model was combined with surgical observation and video recording in all cases. The imaging proved to have application in both benign and malignant disease. It also improved the process of informed patient consent. Three-dimensional MRI imaging of the facial nerve within the parotid gland and its display in a 3D model is an innovative technique for parotid surgery. Surgeons can now see the nerve's position and tailor their approach to each patient's tumour, providing personalised care. The technique eliminates the surgeon's blind spot and is a significant advantage in parotid surgery.

Predicting postoperative facial nerve paralysis by using intraoperative nerve monitoring during parotid surgery.

OBJECTIVES: To investigate a method for predicting postoperative facial nerve paralysis (POFNP) during parotid surgery using intraoperative nerve monitoring (IONM). METHODS: We assessed prediction for POFNP by using IONM, comparing between stimulation in the facial nerve trunk and each branch by using facial nerve monitoring. The amplitude response ratio (ARR) was calculated for the trunk/periphery. In addition, we then examined the correlation between ARR and time to recovery of paralyzed branches. RESULTS: 372 branches of 93 patients did not develop POFNP and were classified as group A. Among 20 patients who developed POFNP, 51 branches without POFNP were classified as group B, and 29 branches with POFNP were classified as group C. The ARR was approximately 1 in group A and B. but less than 0.5 in all branches in Group C. When the cut off value of ARR was set at 0.55, the sensitivity, specificity, and accuracy of POFNP diagnosis by ARR were 96.5%, 93.1%, and 96.8%, respectively. CONCLUSION: Using IONM during parotid surgery enables easy prediction of POFNP.

Superficial parotidectomy with or without great auricular nerve preservation. Is there a difference in postoperative sensory recovery rates and quality of life?

The clinical implications of great auricular nerve (GAN) preservation or sacrifice during parotid surgery have long been a topic of controversy. This study aimed to compare sensory recovery rates and quality of life (QoL) in patients who had undergone superficial parotidectomy and had their GAN preserved or sacrificed. Fifty patients were prospectively analysed, 28 with the GAN preserved, and 22 with it sacrificed. The primary outcomes were tactile sensitivity and QoL. The secondary outcomes were operating times and other complications. There was a gradual improvement in tactile sensitivity in both groups, which showed a statistically significant difference favouring the preserved group at 1, 3, 6, and 9 months postoperatively (p<0.05). There was no statistically significant difference in tactile sensation for both groups at 12 months postoperatively. The overall sensory recovery rates in the GAN preserved and sacrificed groups after 1, 3 ,6, 9 and 12 months were 42.8%, 42.8%, 57.1%, 57.1%, and 78.5%, and 0%, 0%, 13.6%, 27.3%, and 59.1%, respectively. According to the QoL assessment, there was a significant difference in mean (SD) loss of sensation scores (sacrificed group 0.86 (0.94) and preserved group 0.39 (0.62), p= 0.039). However, there were no statistical differences between the groups regarding other categories of the questionnaire. No significant difference was seen between groups regarding operating time and other complications. This study concluded that when evaluated objectively, sensory impairment ultimately lessened in severity in the second half of the first postoperative year. GAN preservation minimised sensation disturbance in long-term results, but overall QoL seemed to be unaffected following GAN preservation or sacrifice.

Impact of great auricular nerve sacrifice on sensory disturbance after parotidectomy.

PURPOSE: To investigate the association between great auricular nerve (GAN) sacrifice during parotidectomy and postoperative sensory disturbance. MATERIALS AND METHODS: Patients who underwent parotidectomy between November 2016 and May 2020 at a single academic institution were included in this retrospective chart review. Operative notes were reviewed to determine incidence of GAN sacrifice. Prevalence of patient-reported sensory complaints in the GAN distribution and time to spontaneous resolution of symptoms were assessed. RESULTS: Of 305 parotidectomy patients, 111 (36.4%) endorsed complaints of postoperative sensory disturbances in the GAN distribution typically characterized by numbness or shooting pains. GAN sacrifice was present in 9 (8.1%) of 111 patients who experienced sensory disturbances compared to 9 (4.6%) who reported no sensory disturbances (p > 0.05). Twenty-five patients (32.5%) experienced spontaneous resolution of symptoms at their most recent follow-up at a mean of 6.2 months after onset of symptoms. Of those that experienced a sensory disturbance, GAN preservation was not significantly associated with likelihood of spontaneous recovery (p > 0.05). CONCLUSIONS: We report the largest series to date of post-operative sensory disturbance in parotidectomy patients as it relates to intraoperative GAN sacrifice. Although the relationship between GAN sacrifice and the incidence of postoperative sensory disturbance and its subsequent resolution were not significant, we continue to advocate for GAN preservation to reduce incidence of postoperative sensory disturbances.

The Great Auricular Nerve Trigger Site: Anatomy, Compression Point Topography, and Treatment Options for Headache Pain.

BACKGROUND: Peripheral nerve decompression surgery can effectively address headache pain caused by compression of peripheral nerves of the head and neck. Despite decompression of known trigger sites, there are a subset of patients with trigger sites centered over the postauricular area coursing. The authors hypothesize that these patients experience primary or residual pain caused by compression of the great auricular nerve. METHODS: Anatomical dissections were carried out on 16 formalin-fixed cadaveric heads. Possible points of compression along fascia, muscle, and parotid gland were identified. Ultrasound technology was used to confirm these anatomical findings in a living volunteer. RESULTS: The authors' findings demonstrate that the possible points of compression for the great auricular nerve are at Erb's point (point 1), at the anterior border of the sternocleidomastoid muscle in the dense connective tissue before entry into the parotid gland (point 2), and within its intraparotid course (point 3). The mean topographic measurements were as follows: Erb's point to the mastoid process at 7.32 cm/7.35 (right/left), Erb's point to the angle of the mandible at 6.04 cm/5.89 cm (right/left), and the posterior aspect of the sternocleidomastoid muscle to the mastoid process at 3.88 cm/4.43 cm (right/left). All three possible points of compression could be identified using ultrasound. CONCLUSIONS: This study identified three possible points of compression of the great auricular nerve that could be decompressed with peripheral nerve decompression surgery: Erb's point (point 1), at the anterior border of the sternocleidomastoid muscle (point 2), and within its intraparotid course (point 3).

The external jugular vein axis: a new anatomical landmark for pre-operative prediction of the location of parotid gland tumours.

The relationships between parotid tumours and the facial nerve determine duration of surgical procedure and risks involved. As the division of the facial nerve is not visible using standard imaging techniques, other anatomical landmarks are used to determine the pre-operative location of tumours. This retrospective study aimed to evaluate reliability of the 'external jugular vein axis' compared with other landmarks generally used in imaging, such as the retromandibular vein, Conn's arc, the facial nerve line and the Utrecht line. Forty-eight pre-operative imaging exams of patients who underwent parotid benign tumour surgery between 2010 and 2016 were examined. We determined the location of tumour using the five markers. A pre-operative simulation was compared with the description given by the surgeon intraoperatively, in terms of sensitivity and specificity for each marker. External jugular vein axis and retromandibular vein are the most sensitive markers for locating suprafacial tumours (Se = 1). External jugular vein axis and Conn's arc are the most specific markers for locating suprafacial tumours (Spe = 0.92). External jugular vein axis is reproducible and present on all radiological sections, thereby overcoming any anatomical and nomenclature variations. This landmark appears to be the most representative marker of the dividing branches of the facial nerve.

Risk Factors of Postoperative Facial Palsy for Benign Parotid Tumors: Outcome of 1,018 Patients.

OBJECTIVE: The aim of this study was to evaluate the rate of postoperative facial palsy in benign parotid tumors, as well as its risk factors, pathology, and clinical results. STUDY DESIGN: Retrospective analysis. METHODS: We performed a retrospective analysis of data from patients whose initial operation for a benign parotid tumor had been performed in our department between 1999 and 2020. RESULTS: We included 1,018 patients in this study. The most common tumor observed was pleomorphic adenoma (614 patients), followed by Warthin tumor (234 patients). Fine-needle aspiration cytology and frozen section biopsy were used to identify the tumor histopathology. The overall rate of postoperative facial nerve palsy was 19.5%; the rate was significantly higher in patients with large-diameter tumors or deep lobe tumors. Postoperative facial palsy improved within 24 months of surgery in all cases. There were no cases with permanent facial palsy. CONCLUSIONS: Postoperative facial nerve palsy developed regularly after surgery to remove benign parotid tumors despite preservation of the nerve. Palsy rate was high in patients with large tumors or deep lobe tumors. Despite the high risk of facial palsy in these patients and the benign nature of the tumor, we recommend surgery rather than follow-up observation, as the risk of postoperative facial palsy may increase as the tumor grows. It is important to provide an accurate explanation on the risks of postoperative complications to all patients to obtain appropriate informed consent for surgery. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:E2857-E2864, 2021.

Long-Term Facial Nerve Outcome in Primary Parotid Cancer Surgery: A Population-Based Analysis.

OBJECTIVES/HYPOTHESIS: To determine immediate postoperative and long-term facial nerve dysfunction after parotid cancer surgery, risk factors, and the role of facial reanimation surgery. STUDY DESIGN: Population-based long-term analysis for all new primary parotid carcinoma cases in Thuringia from 1996 to 2019. METHODS: Data of the cancer registries of Thuringia, a federal state in Germany, were analyzed in combination with hospital-based data on facial function. RESULTS: About 477 patients (42.3% women; median age: 68 years) were included. It was observed that 6.7% had a preoperative facial nerve dysfunction, 11.7% received a radical parotidectomy, that is, that 5% had a normal preoperative facial function but needed radical surgery because of intraoperative detection of tumor infiltration into the facial nerve. About 10.2% received facial nerve reconstruction surgery. Immediate postoperative facial nerve dysfunction in the other patients was observed in 34.4% of the patients. Advanced T classification (odds ratio [OR] = 2.140; confidence interval [CI] = 1.268-3.611; P = .004) and neck dissection (OR = 2.012; CI = 1.027-3.940; P = .041) were independent risk factors for immediate postoperative facial nerve dysfunction. In addition, 22.0% showed no recovery during follow-up. Advanced T classification (OR = 2.177; CI = 1.147-4.133; P = .017) and postoperative radiotherapy (OR = 2.695; CI = 1.244-5.841; P = .012) were independent risk factors for permanent postoperative facial nerve dysfunction. CONCLUSION: Patients with primary parotid cancer are at high risk for long-term facial nerve dysfunction. It seems that the possibilities of facial reanimation surgery needs to be utilized even more effectively. LEVEL OF EVIDENCE: 3 Laryngoscope, 131:2694-2700, 2021.

First Bite Syndrome: What Neurologists Need to Know.

PURPOSE OF REVIEW: Though first bite syndrome is well known in surgical settings, it is not commonly included in the differential for sharp paroxysmal facial pain in the neurology literature. This paper will highlight the clinical features and relevant anatomy of first bite syndrome, with the goal of helping clinicians differentiate this from other similar facial pain disorders. RECENT FINDINGS: First bite syndrome is severe sharp or cramping pain in the parotid region occurring with the first bite of each meal and improving with subsequent bites. Pathophysiology has been attributed to imbalanced sympathetic/parasympathetic innervation of the parotid gland. This is seen most typically in the post-surgical setting following surgery in the parotid or parapharyngeal region, but neoplastic etiologies have also been reported. It is common for patients to present with concurrent great auricular neuropathy and/or Horner's syndrome. Evidence regarding treatment is limited to case reports/series, however, botulinum toxin injections and neuropathic medicines have been helpful in select cases. It is critical for clinicians to be able to differentiate first bite syndrome from other paroxysmal facial pain. To help with this, we have proposed diagnostic criteria for clinical assessment. Patients often improve gradually over time, but symptomatic treatment with botulinum toxin or neuropathic medicine may be required.

First Bite Syndrome: Presentation of a Patient Status-Post Right Carotid Endarterectomy.

First bite syndrome (FBS) is a sharp unilateral pain in the vicinity of the angle of the mandible after taking the first bite of a meal that presents typically after surgery in the area of the ipsilateral parapharyngeal space. It is not confirmed what the pathophysiology is that causes this pain, but the proposed mechanism is the iatrogenic damage of sympathetic fibers that extend from the superior cervical ganglion (SCG) to innervate the parotid gland. The presentation of this syndrome has been acknowledged in patients who have undergone head and neck tumor resections, but it has not been documented in the same thorough manner among vascular surgery cases in the parapharyngeal space, possibly because of a higher risk of development in other head and neck surgeries, or to under-reporting of cases. To date, only 5 cases of FBS status post carotid endarterectomy have been documented in the literature. Definitive treatment of FBS has not been established. Some studies have shown improvement with amitriptyline, and carbamazepine as well as botulinum toxin injections. We will present the case of a 75 year old male who developed first bite syndrome after a right carotid endarterectomy with efforts of raising awareness of a potential acute complication of carotid endarterectomy.

First Bite Syndrome Following Carotid Endarterectomy.

A 67-year-old man with a high position carotid plaque presented with severe pain in ipsilateral parotid region several days after carotid endarterectomy (CEA). The pain occurred at the first bite of each meal and resolved as further bite. We diagnosed the pain as first bite syndrome (FBS). FBS is infrequent but known as a complication associated with parapharyngeal space surgery. The pain is characterized by sharp pain in the parotid region associated with mastication. The cause is unclear but thought to the result from sympathetic denervation of the parotid gland, followed by parasympathetic nerve hypersensitivity. Only five cases associated with carotid endarterectomy (CEA) have been reported. We should be in mind that CEA for high position plaque is one of the risk factors to cause FBS associated with CEA. Neurologists and vascular surgeons as well as otolaryngologists should all be informed FBS as one of the complications after carotid endarterectomy.

Pefloxacin induced changes in serotonergic innervation and mast cell number in rat salivary glands.

Pefloxacin is a second-generation fluoroquinolone antibiotic. Besides its advantageous characteristics, side effects including the hypofunction of salivary glands, decreased saliva production, and peripheral neuropathy were observed during the administration of pefloxacin. The aim of this study was to investigate the changes in the number of serotonergic immunoreactive fibers and mast cells after pefloxacin treatment in the parotid and sublingual glands of rats to detect the possible neurotoxic effect of pefloxacin. The adult female rats were treated with intraperitoneal (i.p.) injection of pefloxacin for three or seven days (at a concentration of 20 mg/100g body weight) and the serotonergic innervation pattern along with the change in mast cell number were evaluated by using histochemistry and immunohistochemistry in the parotid and sublingual glands. We found that a three-day treatment significantly increased the number of immunoreactive serotonergic nerve fibers, but after a seven-day treatment the number of serotonin positive nerve fibers decreased almost to values of the control group. The alteration of mast cell number was parallel with the changes of the serotonin positive fibers during the treatment. These results suggest that pefloxacin treatment can modify the finely controlled communication between the immune- and the peripheral nervous systems, resulting neurogenic inflammatory process. The background of this process is the altered serotonergic innervation and the increased number of activated mast cells releasing different mediators for example histamine, which can finally lead to reduced number of serotonin positive nerve fibers after a seven-day treatment of pefloxacin leading to atrophy and hypofunction of the salivary glands.

Tympanic-mastoid and parotid schwannomas of the facial nerve: clinical presentation related to the anatomic site of origin.

Objective: To describe the clinical presentation of the facial nerve schwannomas according to the anatomical site of origin. Method: A retrospective study in which the clinical presentation, diagnostic protocol and treatment of facial nerve tumors in adults was evaluated. Results: We found 6 cases, 4 cases of tympanic-mastoid location at the spectrum of its possible clinical presentation: from symptomatic cases with facial paralysis, to an asymptomatic case in the tympanic portion found as intraoperative finding; and also found two cases located at the parotid gland, one with complete facial paralysis and one without facial palsy. Conclusions: For the diagnosis of intratemporal and parotid schwannomas of the facial nerve, a high clinical suspicion is required given its heterogeneous presentation; its clinical course depends on the segment of origin and expansion: more frequently asymptomatic at the tympanic horizontal portion and symptomatic at the mastoid vertical portion. These tumors must be assessed with imaging studies, incisional biopsy is not recommended. The treatment is surgical resection in symptomatic patients with facial paralysis greater than grade III of House-Brackmann, with immediate reconstruction of the nerve.

Objetivo: Describir la presentación clínica de los schwannomas del nervio facial de acuerdo con el sitio anatómico de origen. Método: Se realizó un estudio retrospectivo en el que se evaluó la presentación clínica, el protocolo diagnóstico y el tratamiento de tumores del nervio facial en adultos. Resultados: Se encontraron seis casos, cuatro de ellos de localización tímpano-mastoidea en los extremos de su posible presentación clínica: desde casos sintomáticos con parálisis facial, hasta un caso asintomático de la porción timpánica encontrado como hallazgo transoperatorio; y se encontraron dos casos de localización parotídea, uno con parálisis facial completa y otro sin parálisis facial. Conclusiones: Para el diagnóstico de tumores intratemporales y parotídeos del nervio facial se requiere una elevada sospecha clínica dado lo heterogéneo de su presentación; su curso clínico depende del segmento de origen y de su extensión: más frecuentemente son asintomáticos los de la porción timpánica y son sintomáticos los de la porción mastoidea. Estos tumores deben evaluarse con estudios de imagen; no se recomienda realizar biopsia incisional. El tratamiento es la resección quirúrgica en los casos sintomáticos con parálisis facial de grado IV o mayor de House-Brackmann, con reconstrucción inmediata del nervio.

Assessment of Intraoperative Nerve Monitoring Parameters Associated With Facial Nerve Outcome in Parotidectomy for Benign Disease.

Importance: Prior studies suggest that the use of facial nerve monitoring decreases the rate of immediate postoperative facial nerve weakness in parotid surgery, but published data are lacking on normative values for these parameters or cutoff values to prognosticate facial nerve outcomes. Objective: To identify intraoperative facial nerve monitoring parameters associated with postoperative weakness and to evaluate cutoff values for these parameters under which normal nerve function is more likely. Design, Setting, and Participants: This retrospective case series of 222 adult patients undergoing parotid surgery for benign disease performed with intraoperative nerve monitoring was conducted at an academic medical institution from September 13, 2004, to October 30, 2014. The data analysis was conducted from May 2018 to January 2019. Main Outcomes and Measures: The main outcome measure was facial nerve weakness. Receiver operating characteristic curves were generated to define optimal cut point to maximize the sensitivity and specificity of the stimulation threshold, mechanical events, and spasm events associated with facial nerve weakness. Results: Of 222 participants, 121 were women and 101 were men, with a mean (SD) age of 51 (16) years. The rate of temporary facial nerve paresis of any nerve branch was 45%, and the rate of permanent paralysis was 1.3%. The mean predissection threshold was 0.22 milliamperes (mA) (range, 0.1-0.6 mA) and the mean postdissection threshold was 0.24 mA (range, 0.08-1.0 mA). The average number of mechanical events was 9 (range, 0-66), and mean number of spontaneous spasm events was 1 (range, 0-12). Both the postdissection threshold (area under the curve [AUC], 0.69; 95% CI, 0.62-0.77) and the number of mechanical events (AUC, 0.58; 95% CI, 0.50-0.66) were associated with early postoperative facial nerve outcome. The number of spasm events was not associated with facial nerve outcome. The optimal cutoff value for the threshold was 0.25 mA, and the optimal cutoff for number of mechanical events was 8. If a threshold of greater than 0.25 mA was paired with more than 8 mechanical events, there was a 77% chance of postoperative nerve weakness. Conversely, if a threshold was 0.25 mA or less and there were 8 mechanical events or less, there was 69% chance of normal postoperative nerve function. No parameters were associated with permanent facial nerve injury. Conclusions and Relevance: Postdissection threshold and the number of mechanical events are associated with immediate postoperative facial nerve function. Accurate prediction of facial nerve function may provide anticipatory guidance to patients and may provide surgeons with intraoperative feedback allowing adjustment in operative techniques and perioperative management.

Long-term quality of life and sensory impact of great auricular nerve preservation in parotid surgery as measured with the Parotidectomy Outcome Inventory-8.

OBJECTIVES: This study aimed to evaluate sensory dysfunction resulting from great auricular nerve (GAN) sacrifice versus preservation in parotid surgery for benign lesions and its imact on long-term health-related quality of life (QOL). DESIGN: Retrospective. SETTING/MAIN OUTCOME MEASURES: Participants were divided into two groups (GAN and non-GAN), and both short-term (two postoperative weeks) and long-term (at least 5 years) QOL were assessed. The second item of the Parotidectomy Outcome Inventory-8 (POI-8) was used to analyse postoperative sensory loss. All items of the POI-8 questionnaire were used to determine health-related QOL.We used t test for dependent samples and Mann-Whitney U-test to compare patient groups PARTICIPANTS: A total of 137 patients (65 male and 72 female) enrolled in this study. Average age at the time of surgery was 53 years (±12.8). RESULTS: The GAN preservation group had significantly better sensation than the GAN sacrifice in short term (2.8 vs 2.1; P = 0.017). Both groups experienced improved sensation in the long term, and there was a trend towards better QOL in the GAN-preservation group. However, the difference in sensation was not statistically significant (1.7 vs 1.3; P = 0.145). Health-related QOL also increased in the long term (compared to short term) for both groups (7.6 ± 6.2 to 12 ± 7.6; P < 0.0001) postoperatively. GAN preservation did not significantly improve sensation in long term, nor did it increase health-related QOL postoperatively. CONCLUSION: Although GAN preservation was easily feasible, it only improved sensation in short term. We report a negative result: GAN preservation did not significantly improve sensation in long-term, nor did it increase health-related QOL postoperatively when compared to GAN sacrifice.

Distribution, nature, and origin of CXCL14-immunoreactive fibers in rat parotid gland.

The distribution and nature of CXCL14-immunoreactive nerve fibers in salivary glands, especially the parotid gland was immunohistochemically investigated. Furthermore, the origin of parotid CXCL14-immunoreactive nerve fibers was determined by retrograde tracing experiments. CXCL14-immunoreactive nerve fibers were localized in the parotid, submandibular, and sublingual glands, particularly in the parotid gland. Double staining using identical sections revealed that a subpopulation of cells neuropeptide Y (NPY)-containing fibers was immunopositive for CXCL14 in the parotid gland. In the peripheral regions of acinar cells, CXCL14-immunoreactive fibers tended to coexist with NPY; however, perivascular NPY-immunoreactive fibers tended to be immunonegative for CXCL14. Parotid CXCL14-immunoreactive fibers were immunopositive for tyrosine hydroxylase (TH) but immunonegative for choline acetyltransferase and vasoactive intestinal peptide (VIP). After injection of horseradish peroxidase-labeled wheat germ agglutinin (WGA-HRP) in the parotid gland, retrogradely labeled neurons were seen in the superior cervical ganglion (SCG) and otic ganglion. Some of the WGA-immunoreactive somata in the SCG were immunopositive for CXCL14; however, no doubly-labeled somata were noted in the otic ganglion. These results indicate that CXCL14-immunoreactive nerve fibers originate in the SCG, and are sympathetic in nature. The coexistence of CXCL14 with NPY/TH suggests that CXCL14 may be associated with NPY/TH functions as a neuromodulatory chemokine in the parotid gland. The localization of CXCL14 nerve fibers around the acinar cells of the parotid gland indicates its involvement in acinar cell function, but not vasoconstriction.