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Competing Interests: The authors disclose no conflicts of interest.

Introduction: There is a paucity of data reporting the rate of chorda tympani nerve injury during cochlear implantation (CI) surgery. To better provide clarity to patients and surgeons regarding the risk of taste change, we performed a systematic review and meta-analysis of prospective studies examining taste change after CI., Data Sources: PubMed, Embase, and Cochrane Library databases were queried., Methods: Databases were queried according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Search terms included "(chorda tympani OR gustatory OR taste OR chemosensory OR dysgeusia OR nervus intermedius) AND (cochlea OR cochlear implant OR cochlear implantation)." Prospective studies were included and further divided into "objective" and "subjective" assessments of taste dysfunction. A systematic review was performed for all studies. A random-effects model was used to compare studies with similar methods and patient demographics., Results: The initial database query yielded 2,437 articles, which were screened according to inclusion and exclusion criteria. Nine appropriate studies were identified, including 442 total patients-254 with subjective assessment and 271 with objective assessment of gustation. Seventeen of 144 patients (11.8%) reported short-term taste change (incidence = 0.09 [0.02-0.16], 95% confidence interval with pooled data). Twenty-six of 265 patients (9.8%) reported long-term taste change (incidence = 0.07 [0.01-0.13]). Objective results were heterogenous and therefore not amenable to pooled meta-analysis., Conclusions: Taste change from chorda tympani nerve injury is a likely underrecognized complication of CI and may be the most common adverse consequence of CI surgery. Surgeons should counsel prospective patients on this potential complication and that the risk of taste change may persist longer than the immediate postoperative period., Competing Interests: The authors disclose no conflicts of interest., (Copyright © 2023, Otology & Neurotology, Inc.)

Objective: To compare measured and perceived taste function before and after surgery of patients with chronic otitis media with cholesteatoma (OMCC) to patients without cholesteatoma (patients with chronic suppurative otitis media [CSOM] and patients with lateral skull base lesions [LSB])., Methods: This prospective cohort study included 29 patients undergoing surgery for unilateral OMCC. The chorda tympani nerve (CTN) was resected in 8 of these patients. Fourteen patients undergoing surgery for unilateral CSOM and 5 patients undergoing surgery for unilateral LSB (with CTN resection) served as the comparison group. Taste function was measured using taste strips on both sides of the tongue before surgery, 2 weeks postoperatively and 3 months postoperatively. The affected side of the tongue was compared to the unaffected side. A questionnaire on taste perception was completed at each visit., Results: Preoperatively, cholesteatoma patients showed higher taste strip scores than non-cholesteatoma patients, indicating a larger difference between the healthy and affected sides of the tongue. Despite this difference in measured taste function few cholesteatoma patients reported taste alteration before surgery (3/29 [10.3%]). Postoperatively, patients with CTN resection (OMCC patients with CTN resection and LSB patients) showed a decreased measured taste function. Subjectively, only approximately 20% of these patients reported taste alteration 3 months postoperatively., Conclusions: Before surgery, cholesteatoma patients displayed an impaired measured taste function compared to patients without cholesteatoma (CSOM, LSB). Subjectively this was often unnoticed. After surgery, despite removal of the CTN and consequent reduction of measured taste function, few patients reported taste alteration and subjective taste perception was seen to be improving. In regards to middle ear surgery, perceived taste function does not seem to reflect measured gustatory function.

Intrinsic facial nerve tumors are rare lesions. Among the different histology types, schwannomas is the most frequently reported in literature. Other histological types of facial nerve tumors are hemangiomas, meningiomas, and neurofibromas. Chorda tympani schwannomas (CTSs) are extremely rare entities and are considered as an independent subgroup of facial nerve schwannomas because of their clinical characteristics. The aim of this report is to present the clinical and radiological features and the management of a CTS in a 27-year-old male presenting with conductive hearing loss.

Background: The chorda tympani nerve (CTN) is a mixed nerve, which carries sensory and parasympathetic fibres. The sensory component supplies the taste sensation of the anterior two-thirds of the ipsilateral side of the tongue. During middle ear surgery the CTN is exposed and frequently stretched or sacrificed, because it lacks a bony covering as it passes through the middle ear. Injury may cause hypogeusia, ageusia or altered taste sensation of the ipsilateral side of the tongue. To date, there is no consensus regarding which type of CTN injury (sacrificing or stretching), during middle ear surgery, leads to the least burden for the patient., Methods: A double-blind prospective prognostic association study was designed in a single medical centre in the Netherlands to determine the effect of CTN injury on postoperative taste disturbance and quality of life. 154 patients, who will undergo primary stapes surgery or cochlear implantation will be included. The taste sensation, food preferences and quality of life of these patients will be evaluated preoperatively and at one week, six weeks and six months postoperatively using the Taste Strip Test, Electrogustometry, supplementary questionnaire on taste disturbance, Macronutrient and Taste Preference Ranking Task, Appetite, Hunger and Sensory Perception questionnaire and Questionnaire of Olfactory Disorders to assess the association of these outcomes with CTN injury. Evaluation of olfactory function will only take place preoperatively and at one week postoperatively using the Sniffin' Sticks. The patient and outcome assessor are blinded to the presence or absence of CTN injury., Discussion: This study is the first to validate and quantify the effect of chorda tympani nerve injury on taste function. The findings of this study may lead to evidence-based proof of the effect of chorda tympani injury on taste function with consequences for surgical strategies., Trial Registration: Netherlands Trial Register NL9791. Registered on 10 October 2021., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Blijleven et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objective: We evaluated chorda tympani nerve (CTN) and postoperative taste dysfunction according to anomaly severity and intraoperative CTN status., Study Design: Prospective observational study., Setting: Tertiary referral center, Samsung medical center hospital., Patients: Thirty-one patients who underwent atresioplasty by a single surgeon in a tertiary referral center were enrolled., Interventions: Therapeutic surgery., Main Outcome Measures: Preoperative Schuknecht type and Jahrsdoerfer score and intraoperative CTN status were recorded, and a postoperative questionnaire was administered to evaluate taste function., Results: A significant difference was found among intact, cut, and unidentified groups in terms of Schuknecht type ( p = 0.000) and Jahrsdoerfer score (9.28 ± 1.11, 8.80 ± 0.83, 8.10 ± 0.93, p = 0.028). CTN was observed in Schuknecht type B, and not in type C ( p = 0.000), and was more likely to be observed as Jahrsdoerfer score increased ( p = 0.012). Taste disturbance tended to last longer in adult patients than in children. A significant difference was observed in the incidence of taste change between cut and intact CTN groups ( p = 0.018)., Conclusion: CTN was not identified during surgery in patients with Schuknecht type C anomalies, and there was no change in taste after surgery. Meanwhile, CTN was observed in all patients with Schuknecht type B anomalies, and CTN injury occurred in 41.67%. Therefore, CTN presence can be predicted by severity of anomaly, and patients with type B anomalies should be informed of the risk of CTN injury before surgery., Competing Interests: Conflict of interest: The authors disclose no conflicts of interest., (Copyright © 2023, Otology & Neurotology, Inc.)

Objectives: The aim of this study was to compare the incidence of chorda tympani nerve (CTN) injury between endoscopic and microscopic stapes surgery., Methods: This randomized controlled clinical trial included 88 patients who were randomly divided into two groups: endoscopic stapedotomy group (n = 44) and microscopic stapedotomy group (n = 44). The incidence of chorda tympani nerve (CTN) injury after surgery was determined by both subjective taste testing and chemical taste tests, before and after surgery. The results were compared between the two groups., Results: The total number of patients who were identified as having CTN affection (based on the chemical testing) was 16 out of 88 (18.2%). The incidence was significantly lower in the endoscopic group (n = 2) than the microscopic group (n = 14) (p = 0.019)., Conclusion: Altered taste as a result of iatrogenic CTN injury can affect the patients' quality of life. Endoscopic ear surgery offers better visualization, less need for extensive manipulation of the chorda tympani, and consequently decreased incidence of CTN injury., (© 2022. The Author(s).)

Objectives: The facial recess, an essential landmark for the posterior tympanotomy approach, is limited by the facial nerve and the chorda tympani, with a complicated relationship. This study tried to find the most appropriate radiological method to evaluate the chorda-facial angle (CFA). We also checked the effect of this angle on the round window accessibility during cochlear implantation., Methods: It was a retrospective study that included cochlear implant surgeries of 237 pediatric patients, from September 2016 to April 2021. Two physicians evaluated the CFA in the para-sagittal cut of the preoperative HRCT. The round window accessibility was assessed in the unedited surgery videos., Results: The CFA ranged from 21° to 35° with a mean of 27.14 ± 3.5°. It was detected in all cases with a high agreement between the two CT reviewers' measurements. The CFA differed significantly between the accessible group and the group with difficult accessibility (p value < 0.001). Spearman's correlation coefficient revealed a strong correlation between the CFA and the intraoperative round accessibility. 25.5° was the best cutoff point; below this angle, difficult accessibility into the RW was expected, with high sensitivity, specificity, and accuracy CONCLUSIONS: Our study on a relatively large number of cases provided a precise, valid, reliable, and applicable method to evaluate the CFA in the HRCT scan. We found a significant-close relation between the CFA and the round window accessibility; the difficulty increased with a need for posterior tympanotomy modification when the angle decreased., Key Points: • Radiological detection of the chorda-facial angle was always problematic, without a previous straightforward method in the literature. • We used the para-sagittal cut of the high-resolution CT scans to evaluate the CFA. This cut was beneficial to seeing the chorda tympani nerve in every examined case. There was a high agreement between the two CT reviewers' measurements. • Preoperative evaluation of the CFA in the HRCT accurately predicted the round window accessibility. Patients with CFA less than 25.5 ° were expected to have difficult accessibility into the round window during cochlear implantation., (© 2022. The Author(s).)

Purpose: In most stapes surgeries, the posterior ear canal is enlarged and a piston is inserted posterior to the chorda tympani nerve (post-chorda tympani approach; Post C). Although reports vary, some indicate that more than 60% of the patients experience lingual symptoms following surgery. Endoscopic surgery may permit an anterior approach to the nerve (pre-chorda tympani approach; Pre C). Herein, we propose a suitable approach for endoscopic stapes surgery based on the classification of the chorda tympani nerve., Methods: We retrospectively reviewed the medical records of 23 patients who underwent endoscopic stapes surgery at our institution between 2019 and 2021. The nerve classification previously reported, the modified nerve classification (attached long type is divided into Category 1: lenticular process is visible with 0° endoscope and Category 2: not visible), selected approach (Pre C or Post C), use of a 30° endoscope, and manipulation of the nerve (number of contacts and traction, with or without suction, with or without malposition or extension and amputation, and damage score) were evaluated., Results: The damage score was significantly lower in the Pre C group (p < 0.05); however, using this approach for all cases is not desirable owing to the high risk of damage to the nerve during posterior malpositioning., Conclusion: The Post C should be used for the detached and attached long 1 types, while the Pre C with a 30° endoscope should be used for the attached long 2, attached short, ultrashort, and external auditory canal types., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Competing Interests: The authors disclose no conflicts of interest.

Background: To visualize the course of the tympanic segment of chorda tympani nerve (CTN) using ultra-high-resolution computed tomography., Methods: A hundred and fourteen ears with no evident otologic pathologies were included. The tympanic segment of CTN was divided into 4 portions as follows: periannular, posteromalleal, malleal, and anteromalleal. The length of the periannular portion running along the tympanic annulus was recorded. Four points of interest (the beginning and end of the posteromalleal and anteromalleal portions) were selected to perform distance measurements relative to the tip of the malleus manubrium. Differences in lengths and distances were compared in terms of ear sides and sexes., Results: The length of the periannular portion was 2.49 ± 1.16 mm. The beginning of the posteromalleal portion was located more laterally on the right side than on the left side (mean: 4.09 mm vs. 3.92 mm;, P = 0.016). The end of the posteromalleal portion was located more inferiorly on the right (mean: 2.11 mm vs. 2.26 mm; P = 0.018). The beginning of the anteromalleal portion on the right was located more laterally than that on the left (mean: 2.60 mm vs. 2.45 mm; P = 0.027). The start and end of the anteromalleal portion were more posteriorly located in women than in men (both Ps < 0.001)., Conclusions: The course of the tympanic segment of normal CTN was comprehensively visualized by ultra-high-resolution computed tomography. Preoperative evaluation of the tympanic segment of CTN might be helpful in avoiding iatrogenic injury during middle ear surgery., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objectives: This study assessed the impact of the location of the chorda tympani nerve (CTN) origin on the round window (RW) accessibility during pediatric cochlear implantation (CI). We also tried to validate the radiologic method to measure the length between the origin of the CTN from the facial nerve to the stylomastoid foramen (CF-SM)., Study Design: It was a prospective observational case-series study., Settings: The included CI surgeries were performed at tertiary referral institutions from November 2018 to August 2021., Subjects: We included 146 pediatric patients who were candidates for CI., Intervention: We measured the CF-SM length in the parasagittal cut of the preoperative high-resolution computed tomography. We also classified the intraoperative RW according to the accessibility through the ordinary posterior tympanotomy approach into accessible or inaccessible., Main Outcome Measure: We correlated the preoperative radiologic CF-SM length with the intraoperative RW accessibility., Results: The radiologic CF-SM length ranged from 2.9 to 7.4 mm with a mean of 4.9 ± 1.03 mm. The RW was accessible in 107 patients and inaccessible in 39 patients. Spearman's correlation coefficient revealed a significant relationship between the location of CTN origin and the RW accessibility as the p value was less than 0.0001., Conclusions: We found a precise method to measure the CF-SM length in the parasagittal cut of the high-resolution computed tomography. We also found a significant impact of the location of the CTN origin on intraoperative RW accessibility. The radiologic CF-SM length of more than 5.4 mm had a powerful prediction capability of the RW inaccessibility., Competing Interests: The authors disclose no conflicts of interest., (Copyright © 2022, Otology & Neurotology, Inc.)

A petrous bone cholesteatoma (PBC) is a rare epidermoid cyst of the petrous portion of the temporal bone. The main treatment is subtotal petrosectomy (SP), which generally involves sacrificing the chorda tympani. We report a case of extensive supralabyrinthine PBC in an elderly patient undergoing hemodialysis that was treated by SP with anatomical preservation of the chorda tympani. To the best of our knowledge, preservation of the chorda tympani during SP has not been previously reported. For maintenance of postoperative taste and appetite, preservation of the chorda tympani is a meaningful maneuver whenever possible.

Introduction: Preserving maximal quality of life is an important factor in middle ear surgery according to current standards. Taste disturbance is a common postoperative complication, which can be explained with the risk of injury due to the localisation of chorda tympani. The knowledge about this complication is mandatory for optimal surgical decision-making and for patient education as well. Objective: Investigation of early postoperative taste disturbances, to clarify the differences between the impact of different surgical interventions, and the impact of nerve manipulation. Methods: 15 stapes surgeries and 28 tympanoplasties were investigated. Patients answered subjective questionnaires before surgery and on the first postoperative day. Visual analogue scale (VAS) was used to measure the degree of disturbances (0-10). Degree of nerve manipulation was classified into 5 groups. Results: No significant differences between the impact of stapes surgeries and tympanoplasties could be found (9, 9.1; p = 0.861). In groups '0', '1' and '2', the VAS scores were 10, 9.26, and 8.5. Between the groups no manipulation (0) and significant manipulation without macroscopic injury (2), the difference was significant (10, 8.5; p = 0.039). In the stapes surgery group, no severe taste disturbance (VAS<5) was found. Discussion: In the case of adequate microscopic surgical technique, the rate of postoperative taste disturbances is relatively low. Conclusions: The rate of postoperative taste disturbance could be kept at a low level while the continuity of the chorda tympani could be preserved in the majority of cases. The postoperative morbidity rate is primarily influenced by the degree of nerve manipulation and not by the type of surgery.

Chorda tympani schwannoma is a very rare tumor, with only 12 reported cases in the English literature. There are few reports on the diagnosis of chorda tympani schwannoma, and it is easily misdiagnosed. At present, surgery is recognized as a treatment for chorda tympani schwannoma. We describe the clinical course of a patient presenting with a chorda tympani schwannoma treated with surgical resection using a transcanal endoscopic approach, and the results after this treatment were satisfactory. Therefore, we accordingly advocate the minimally invasive method of transcanal endoscopic resection to maximize intraoperative visualization and reduce postoperative morbidity for middle ear tumors.

Purpose: To investigate how the anatomical configuration of the oval window region (OWR) influences the management of the chorda tympani (ChT) and the curetting of adjacent bony structures, in a setting of patients undergoing endoscopic stapes surgery (EStS); to assess the incidence of early and late post-operative dysgeusia and to identify anatomical and surgical factors influencing taste function after EStS., Methods: Surgical video recordings of 48 patients undergoing EStS for otosclerosis between January 2019 and July 2020 were retrospectively revised, to classify the anatomical variability of selected middle ear structures and the management strategies for the ChT. Clinical records of included patients were reviewed for subjective early and late post-operative taste impairment using a 5-point Likert-scale., Results: The most common configuration of the OWR was type III. The extension of the bony curettage resulted inversely proportional to the exposure of the OWR. The long-term rate of preserved post-operative taste function was 85%. Displacement of the ChT was necessary in 43/48 cases (90%), mostly medially (36/48, 75%)., Conclusion: Bone curetting during EStS does not correlate with post-operative taste impairment. Despite 100% ChT preservation rate, dysgeusia may occur in a minority of patients, with no apparent relationship to anatomical variability or intraoperative management of the ChT. The use of CO 2 laser could have a role in increasing the risk of post-operative dysgeusia after EStS., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Cholesteatoma often presents with persistent otorrhoea, conductive hearing loss or vestibular dysfunction. Rarely, cholesteatoma can cause dysgeusia if the lesion invades into the chorda tympani nerve. This paper presents an individual with cholesteatoma whose dysgeusia resolved following a mastoidectomy in which the chorda tympani was sacrificed. The current literature was reviewed for explanations behind this phenomenon., Case Report: A previously fit 57-year-old man presented with a 3-month history of persistent otorrhoea and the complaint of a metallic taste in the mouth, and was diagnosed with cholesteatoma. The patient underwent radical mastoidectomy and the chorda tympani nerve was sacrificed. On post-operative review, he reported complete resolution of dysgeusia., Conclusion: The sense of taste is mediated by a complex neural network. It is possible that once the diseased chorda tympani is transected, compensation arises from other parts of the network. Sectioning of the chorda tympani could lead to a beneficial outcome in selected patients.

Objective: There is a void in the literature describing reliable surgical landmarks that aid in the dissection of the facial recess in the absence of skeletonizing the mastoid segment of the facial nerve. The posterior ligament of the incus is a readily distinguishable "white dot" along the incus buttress that has been used to guide dissection in a safe and efficient manner. The goal of our study is to describe a surgical approach that utilizes this surgical landmark to drill the facial recess and to take anatomical measurements demonstrating the safety and reliability of this approach., Materials and Methods: After cortical mastoidectomies were performed in 10 cadaveric temporal bones, the white dot was identified at the junction of short process of the incus and the incus buttress. Using the white dot for anatomical reference, a 2 mm diamond drill bit was used to open the facial recess without first identifying the facial nerve or chorda tympani nerve. After photographs were taken, the facial and chorda tympani nerves were definitively identified and skeletonized to delineate the confines of the facial recess. Photographs were once again acquired in a consistent manner for comparison. Finally, calibrated anatomic measurements were acquired from the 10 distinct image sets., Results: The facial recess was successfully drilled in 10 temporal bones using the posterior ligament as a surgical landmark without injury to the chorda tympani or facial nerve. The median angle taken from the axis of the short process of the incus to the facial nerve - chorda tympani junction was 139.2° (IQR 136.8-141). At the widest point in the facial recess, median distances anterior and posterior to an imaginary line connecting the white dot to the facial nerve - chorda tympani junction were 1.6 mm (IQR 1.5-1.7) and 1.6 mm (IQR 1.6-1.7; p = 0.57), indicating at this point, the white dot reference reliably bisects the facial recess width. Similarly, at the level of the round window niche, median anterior and posterior distances from an imaginary line connecting the white dot to the facial nerve - chorda tympani junction were 1.1 mm (IQR 1.1-1.3) and 1.3 mm (IQR 1.1-1.7; p = 0.07), respectively, once again demonstrating the white dot reliably bisecting the facial recess., Conclusions: The white dot, representing the posterior ligament of the incus, is a reliable surgical landmark that aids in safe and efficient drilling of the facial recess without first skeletonizing the facial nerve., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Hypothesis: A transcanal endoscopic approach enables visualization of the variable course of the chorda tympani inside the middle ear., Background: The chorda tympani is the longest intrapetrous branch of the facial nerve. Despite having been investigated in several studies, a description of its tympanic tract from an endoscopic point of view is lacking in the literature., Methods: We performed transcanal endoscopic dissections of 44 human cadaveric head and ear specimens. The entry point of the chorda tympani into the middle ear was classified into four categories according to its location, and as covered or dehiscent according to its appearance. The chordal eminence (CE) was defined as absent, shallow, intermediate, prominent, or fused, based on its shape and extension. The relationship of the chorda tympani to adjacent bony and ligamental structures was assessed., Results: The tympanic tract of the chorda tympani was divided into three portions. The periannular segment was dehiscent in 54.5% of specimens, with type II being the most frequent entry point configuration (52.3%). In the interossicular segment, the nerve consistently passed lateral to the incus and medial to the malleus. The course of the intrapetrous segment was independent from the conformation of the tensor fold and supratubal recess., Conclusion: The transcanal endoscopic approach allows a detailed description of tympanic segment of the chorda tympani. Novel anatomic classifications of the chorda tympani and CE are proposed herein to highlight their possible surgical implications during otologic procedures., Competing Interests: The authors disclose no conflicts of interest., (Copyright © 2021, Otology & Neurotology, Inc.)

Objectives: To determine the ability of preoperative computed tomography (CT) to predict the variable surgical anatomy of the chorda tympani nerve (CTN) based on endoscopic tympanotomy., Study Design: Retrospective case review., Setting: Tertiary referral center., Patients: We identified 192 ears of 162 patients who underwent transcanal endoscopic ear surgery from August 2013 to June 2018. Patients with middle ear malformations, revision surgeries, myringoplasty, and cholesteatoma involving the CTN were excluded., Interventions: An intraoperative endoscopic image depicting the chorda tympani was selected for each patient and classified into one of five types. Preoperative CT images were analyzed to match the pictorial classification., Main Outcome Measures: The visible tympanic segment of the chorda tympani was classified into the following five types: external auditory canal (EAC), detached, attached long, attached short, and ultrashort., Results: A total of 128 ears from 101 patients ranging in age from 2 to 81 years were enrolled. The EAC, detached, attached long, attached short, and ultrashort types of CTN were found in 7 (5.5%), 6 (4.7%), 84 (65.6%), 18 (14.0%), and 13 (10.2%) patients, respectively. The presence of the EAC type could be predicted by preoperative CT while the other four types could be predicted by binning into two groups, with a sensitivity of 0.61 and specificity of 0.72., Conclusion: The variable anatomy of the chorda tympani nerve can be classified into five major groups based on endoscopic tympanotomy., Competing Interests: The authors disclose no conflicts of interest., (Copyright © 2020, Otology & Neurotology, Inc.)

Background: The posterior tympanum approach of cochlear implantation is easy to damage the facial nerve and cord tympanic nerve. Therefore, we need to improve the safety of cochlear implantation., Objectives: To discuss the safety and feasibility of active and adequate transparent exposure of the facial nerve and chorda tympani nerve during the surgery., Methods: A retrospective analysis was performed on all 945 patients who underwent cochlear implantation from January 2011 to September 2017. All patients have been followed up for 14 months to 5 years postoperatively and postoperative complications have been observed., Results: All 945 patients received artificial cochlear implantation. The facial nerves of 76 cases were above the horizontal semicircular canal plane, while narrow facial recess was observed in 44 cases. Serious chorda tympani nerve variation was found in 1 case. No facial paralysis and facial nerve irritation and abnormal taste occurred after operation., Conclusions: Cochlear implantation with initiative and adequate exposure of facial nerve and the chorda tympani nerve can improve the safety of the cochlear implant surgery. Our study provide a safe and effective method for clinical cochlear implantation to reduce facial nerve and tympanic cord nerve injury.

The study is aimed to assess the scope of endoscopic stapedotomy in overcoming technical challenges faced during conventional stapedotomy using operating microscope. Sixty-four patients with clinical and audiological diagnosis of otosclerosis were randomly assigned into one of the 2 groups-one underwent conventional stapedotomy using operating microscope, while the other group underwent endoscopic stapedotomy, the operating surgeon being the same for both groups, for all cases. The 2 groups were observed in terms of extent of the postero-superior canal bone curettage/drilling, chorda tympani repositioning, visualization of footplate area, surgical time from first incision to ear packing, post-operative morbidity in terms of post-operative pain, vertigo, hearing outcome, and changes in taste sensation. It was observed that irrespective of the width of the external auditory canal, endoscopic approach offered better access to the footplate area requiring lesser bone removal and chorda tympani repositioning. The operating time, post-operative pain, and changes in taste sensation were significantly less in the endoscopic group. However, no difference was noted in terms of the post-operative hearing outcome and incidence of vertigo. Endoscopic stapedotomy has clear advantages in terms of the technicality and accessibility to the working area as well as faster recovery.

The current prevalence of obesity has been linked to the consumption of highly palatable foods and may be mediated by a dysregulated or hyposensitive orosensory perception of dietary fat, thereby contributing to the susceptibility to develop obesity. The goal of the current study was to investigate the role of lingual taste input in obesity-prone (OP, Osborne-Mendel) and obesity-resistant (OR, S5B/Pl) rats on the consumption of a high-fat diet (HFD). Density of fungiform papillae was assessed as a marker of general orosensory input. To determine if orosensory afferent input mediates dietary fat intake, surgical transection of the chorda tympani and glossopharyngeal nerves (GLX/CTX) was performed in OP and OR rats and HFD caloric intake and body weight were measured. Fungiform papillae density was lower in OP rats, compared with OR rats. GLX/CTX decreased orosensory input in both OP and OR rats, as measured by an increase in the intake of a bitter, quinine solution. Consumption of low-fat diet was not altered by GLX/CTX in OP and OR rats; however, GLX/CTX decreased HFD intake in OR, without altering HFD intake in OP rats. Overall, these data suggest that inhibition of orosensory input in OP rats do not decrease fat intake, thereby supporting that idea that hyposensitive and/or dysregulated orosensory perception of highly palatable foods contribute to the susceptibility to develop obesity., (© The Author(s) 2020. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Objectives: To ascertain the feasibility of endoscopic (4 mm) stapedotomy, and compare intra- and post-operative variations with microscopic stapedotomies., Methods: Forty otosclerosis patients were scheduled for microscopic or endoscopic stapedotomy. Intra-operative variables compared were: incision, canalplasty, canal wall curettage for ossicular assessment, chorda tympani manipulation, ability to perform stapes footplate perforation before its supra-structure removal, and operative time. Post-operative variables compared were ear pain and hearing improvement., Results: Of the 20 microscopy patients, 4 required endaural incision and canalplasty because of canal overhangs, and 7 required canal wall curettage for ossicular assessment. None of the 20 endoscopy patients required these procedures. Chorda tympani was manipulated in 13 and 6 patients in the microscopy and endoscopy groups respectively, while the stapes footplate could be perforated in 5 and 11 patients respectively. Mean operative time was 50.25 and 76.05 minutes in the microscopy and endoscopy groups respectively. In the endoscopy group, mean air-bone gap was 37.12 and 10.73 dB pre- and post-operation respectively; in the microscopy group, these values were 35.95 and 13.81 dB., Conclusion: Endoscopic stapedotomy has comparable hearing outcomes. Sinonasal endoscope serves as a better tool for: minimal incision, canalplasty avoidance, less chorda tympani mobilisation, and stapes footplate perforation ability.

Objectives: The aim of study was to evaluate the subjective changes of taste and salivation after middle ear surgery according to chorda tympani nerve (CTN) injury., Study Design: Prospective cohort study., Setting: Tertiary referral center., Patients: We enrolled 180 patients older than 13 years old who received middle ear surgery., Interventions: The patients were classified into cut, manipulated, and intact groups according to intraoperative assessments of the CTN. The patients responded taste and salivation surveys preoperatively, and 1, 3, and 6 months postoperatively., Main Outcome Measures: We analyzed results of questionnaires including disturbance rates, severity and character to evaluate taste and salivation functions., Results: Taste disturbance rate was significantly improved in all groups during follow-up (p < 0.05). The incidence of taste disturbance did not differ significantly between the three groups at each follow-up (p > 0.05). The taste disturbance score improved gradually in the cut and intact groups (p < 0.001), but not in the manipulated group (p = 0.067). Among the patients with taste disturbance, hypoguesia was most common symptom. Incidence of salivation disturbance did not differ between the three groups (p = 0.298). However, this symptom improved significantly only in the intact group (p < 0.001). The taste and salivation disturbance rate was not different between patients with and without chronic otitis media at 3 and 6 months, and both groups showed significant improvement., Conclusions: Prevalence of taste and salivation disturbance was similar between three groups until 6 months. However, taste disturbance did not improve in the manipulated group and salivation disturbance improved only in the intact group.

Microglia are critical for developmental pruning and immune response to injury, and are implicated in facilitating neural plasticity. The rodent gustatory system is highly plastic, particularly during development, and outcomes following nerve injury are more severe in developing animals. The mechanisms underlying developmental plasticity in the taste system are largely unknown, making microglia an attractive candidate. To better elucidate microglia's role in the taste system, we examined these cells in the rostral nucleus of the solitary tract (rNTS) during normal development and following transection of the chorda tympani taste nerve (CTX). Rats aged 5, 10, 25, or 50days received unilateral CTX or no surgery and were sacrificed four days later. Brain tissue was stained for Iba1 or CD68, and both the density and morphology of microglia were assessed on the intact and transected sides of the rNTS. We found that the intact rNTS of neonatal rats (9-14days) shows a high density of microglia, most of which appear reactive. By 29days of age, microglia density significantly decreased to levels not significantly different from adults and microglia morphology had matured, with most cells appearing ramified. CD68-negative microglia density increased following CTX and was most pronounced for juvenile and adult rats. Our results show that microglia density is highest during times of normal gustatory afferent pruning. Furthermore, the quantity of the microglia response is higher in the mature system than in neonates. These findings link increased microglia presence with instances of normal developmental and injury induced alterations in the rNTS., (Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The aim of this study was to elucidate the relationship between the gustatory function and average number of taste buds per fungiform papilla (FP) in humans. Systemically healthy volunteers (n = 211), pre-operative patients with chronic otitis media (n = 79), and postoperative patients, with or without a chorda tympani nerve (CTN) severed during middle ear surgery (n = 63), were included. Confocal laser scanning microscopy was employed to observe fungiform taste buds because it allows many FP to be observed non-invasively in a short period of time. Taste buds in an average of 10 FP in the midlateral region of the tongue were counted. In total, 3,849 FP were observed in 353 subjects. The gustatory function was measured by electrogustometry (EGM). An inverse relationship was found between the gustatory function and average number of fungiform taste buds per papilla. The healthy volunteers showed a lower EGM threshold (better gustatory function) and had more taste buds than did the patients with otitis media, and the patients with otitis media showed a lower EGM threshold and had more taste buds than did postoperative patients, reflecting the severity of damage to the CTN. It was concluded that the confocal laser scanning microscope is a very useful tool for using to observe a large number of taste buds non-invasively., (© 2017 Eur J Oral Sci.)

Background: A transection of the chorda tympani results in loss of spatial gustatory function on the ipsilateral tongue. Most patients do not notice anymore this alteration. The cause is unclear. Do adjacent gustatory areas become more sensitive or is the gustatory perception rather independent of the size of stimulated area?, Methods: 51 patients with proven unilateral transection of the chorda tympani and 51 healthy subjects were tested for gustatory recognition thresholds. The methods used were the "three-drops-choice-technique" by Henkin to evaluate the whole mouth taste (global taste examination) and the "spatial taste test" to evaluate the local gustatory function on 4 areas of the tongue. The taste solutions were sweet, sour, salty and bitter with increasing concentrations., Results: The global gustatory function of the patients and of the control group did not differ in either the 4 taste qualities but the composite score was increased within the group of patients. Most patients did not realize that. The spatial taste examination showed reduction of taste perception on 3 of the 4 gustatory areas of the tongue in the patients. The decreased gustatory function on the area of the transected chorda remained unchanged over time. The taste attenuation on the ipsilateral back area and the contralateral front area improved over time., Conclusion: Transection of chorda tympani also leads to an attenuation of spatial gustatory function in adjacent areas. Therefore, adjacent areas cannot be taken as reference. Instead, taste function has to be compared to the results of healthy probands., (© Georg Thieme Verlag KG Stuttgart · New York.)

Objective: This study was conducted to examine if taste over load with oral capsaicin improves the adverse behavioural effects induced by partial aberration of oral sensory relays to brain with bilateral transections of the lingual and chorda tympani nerves., Design: Male Sprague-Dawley rats received daily 1 ml of 0.02% capsaicin or water drop by drop into the oral cavity following the bilateral transections of the lingual and chorda tympani nerves. Rats were subjected to ambulatory activity, elevated plus maze and forced swim tests after 11th, 14th and 17th daily administration of capsaicin or water, respectively. The basal and stress-induced plasma corticosterone levels were examined after the end of behavioural tests., Results: Ambulatory counts, distance travelled, centre zone activities and rearing were increased, and rostral grooming decreased, during the activity test in capsaicin treated rats. Behavioural scores of capsaicin rats during elevated plus maze test did not differ from control rats. Immobility during the swim test was decreased in capsaicin rats with near significance (P = 0.0547). Repeated oral capsaicin increased both the basal level and stress-induced elevation of plasma corticosterone in rats with bilateral transections of the lingual and chorda tympani nerves., Discussion: It is concluded that repeated oral administration of capsaicin reduces anxiety-like behaviours in rats that received bilateral transections of the lingual and chorda tympani nerves, and that the increased corticosterone response, possibly modulating the hippocampal neural plasticity, may be implicated in the anxiolytic efficacy of oral capsaicin., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

We conducted a study to assess the use of the chorda tympani nerve in reconstruction of the ossicular chain. We retrospectively examined the medical records of 141 patients (154 ears) who had undergone middle ear surgery with 12 months of follow-up. The study population was made up of 58 males and 83 females, aged 9 to 83 years (mean: 45). These patients were divided into three groups based on the specific type of surgery they had undergone: in 35 patients, the chorda tympani nerve was used to spring and press the auricular bone prosthesis (CTN group); in 67 patients, the tympanic membrane was used to spring and press the auricular bone prosthesis (TM group); and in 39 patients, a gelatin sponge was used to support the auricular bone prosthesis (GS group). We compared pre- and postoperative air-bone gaps (ABGs) in each group, as well as the differences between these gaps among the three groups. We found significant differences between the pre- and postoperative ABGs in all three groups (all p < 0.01). These differences were also compared between the CTN and TM groups (t = 0.41; p > 0.05), between the CTN and GS groups (t = 2.07; p < 0.05), and between the TM and GS groups (t = 2.51; p < 0.05). In the CTN group, 1 patient experienced temporary postoperative hypogeusia, and another developed a mild case of delayed facial paralysis; both patients recovered within 2 weeks. We conclude that the chorda tympani nerve can be used to repair the ossicular chain to improve hearing without causing taste and facial nerve dysfunction and without the need for a second operation.

The peripheral taste system of the adult rodent is highly resilient against damage, with morphological, behavioral, and functional recovery evident after regeneration of a transected nerve. If chorda tympani transection (CTX) occurs at early postnatal ages however, the nerve fails to regenerate and effects on tongue morphology and behavior are more severe and longer-lasting compared to adult denervation. To examine whether neonatal CTX induces functional changes in intact nerves, whole-nerve electrophysiology was performed on the glossopharyngeal (GL) and chorda tympani (CT) nerves of adult rats that received CTX at P10. Attenuation of NaCl-elicited GL responses were observed in CTX rats 2 months after surgery, with bilateral denervation causing the largest decreases in responses. When assessed 1 year after neonatal CTX, amiloride-sensitive responses to NaCl in the contralateral CT increased while amiloride-insensitive responses decreased. Responses to other tastants were consistent with control animals. This is the first evidence of long-term functional changes to the peripheral taste system after injury in rats fed a normal diet. This study further characterizes the developing peripheral taste system as highly susceptible to change following neural injury., (© The Author 2014. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Objectives/hypothesis: Due to its anatomical features, the chorda tympani nerve (CTN) is sometimes sacrificed during middle ear surgery, resulting in taste dysfunction. We examined the effect of placing an artificial nerve conduit, a polyglycolic acid (PGA)-collagen tube, across the gap in the section of the resected chorda tympani nerve (CTN) running through the tympanic cavity., Methods: The CTN was reconstructed with a PGA-collagen tube in three patients with taste disturbance who underwent CTN resection. To evaluate the effect of the reconstruction procedure on the patients' gustatory function, we measured the patients' electrogustometry (EGM) thresholds. The patients were followed-up for at least two years., Results: Gustatory function was completely restored in all of the patients after the reconstruction. The patients' EGM thresholds exhibited early improvements within one to two weeks and had returned to their normal ranges within three months. They subsequently remained stable throughout the two-year follow-up period. In a patient who underwent a second surgical procedure, it was found that the PGA-collagen tube used in the first surgical procedure had been absorbed and replaced by new CTN fibers with blood vessels on their surfaces., Conclusion: These results suggest that reconstruction of the CTN with an artificial nerve conduit, a PGA-collagen tube, allows functional and morphological regeneration of the nerve and facilitates the recovery of taste function. PGA-collagen tubes might be useful for repairing CTNs that are resected during middle ear surgery. Further research is required to confirm these preliminary results although this is the first report to describe the successful regeneration of a nerve running through an aerial space.

The incidence of chronic oral pain such as burning mouth syndrome is greater in peri-menopausal females, and was postulated to be associated with gustatory nerve damage. We investigated whether bilateral transection of the chorda tympani, with or without accompanying ovariectomy, affected oral capsaicin avoidance in rats. Female rats had restricted access to 2 bottles, 1 bottle containing capsaicin (concentration range: 0.33-33 μM/L) and the other vehicle. Percent volume of capsaicin consumption and lick counts were measured. The concentration series was tested before and 0.5, 3, 6, 9, and 12 months after the following surgical procedures: (a) bilateral transection of the chorda tympani (CTx); (b) ovariectomy (OVx); (3) CTx plus OVx; or (4) sham CT surgery. Before surgery there was a concentration-dependent decrease in licks and volume of capsaicin consumed, with a threshold between 0.1 and 0.3 ppm. The majority of drink licks occurred during the first 9 minutes of access. Over the 12-month test period, the CTx group did not exhibit reduced capsaicin consumption, and consumed significantly more capsaicin at 6 and 9 months postsurgery. Rats in the OVx group consistently consumed significantly less capsaicin and exhibited significantly higher counts of capsaicin-evoked Fos-like immunoreactivity in the dorsomedial trigeminal subnucleus caudalis (Vc) compared to all other treatment groups. That CTx, with or without OVx, did not enhance capsaicin avoidance indicates that damage to the gustatory system does not disinhibit trigeminal nociceptive transmission., (Copyright © 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.)

Objective: To establish clinical tests for measurement of trigeminal sensitivity on the human tongue and objectively assess changes in oral trigeminal sensitivity and taste ability after chorda tympani nerve (CTN) injury., Study Design: Prospective study., Setting: University hospital., Patients: One-hundred and twenty-six patients with unilateral middle ear diseases who underwent primary middle ear surgery., Main Outcomes and Measures: Trigeminal sensation was measured each operated side as well as nonoperated side both before and 14 days after surgery using 3 kinds of tests: Semmes-Weinstein sensory test (SW test), 2-point discrimination test, and the electrostimulator test. Taste function was assessed with electrogustometry (EGM) similarly., Results: The patients which the CTN was not touched (n = 6) showed no differences between preoperative and postoperative thresholds in any tests. In the patients with sectioned CTN (n=30), postoperative thresholds on the operated side were significantly higher than preoperative thresholds on the electrostimulator test, 2-point discrimination test, and EGM. In the patients with manipulated but not sectioned CTN (n = 90), postoperative thresholds were significantly higher than preoperative thresholds on the electrostimulator test and EGM. The patients with manipulated but not sectioned CTN and abnormal EGM postoperative thresholds (n = 48) showed that postoperative thresholds were significantly higher than preoperative thresholds in all tests., Conclusion: These findings suggest that the electrostimulator test was most useful to objectively assess small changes of trigeminal sensation among the 3 tests. The finding that trigeminal sensitivity of the tongue deteriorated on the operated side after CTN injury suggests that CTN function affected both taste sensation and trigeminal sensation of the tongue.

Facial nerve (FN) macrodehiscence, in contrast to microdehiscence, generally occurs as a result of chronic otitis media and is rarely seen congenitally. A patient with normal hearing who had no history of ear disease or ear operation came to the clinic with recurrent facial paralysis (FP) and frequent blockage of the external ear canal with epithelial debris complaints. In the explorative ear surgery, we observed that the posterior wall of the external ear canal or tympanic ring was absent, a large external ear cavity was covered with a thin skin, the FN was under the skin, and the tympanic-mastoid segment of the FN and chorda tympani extending to the stylomastoid foramen was completely open. FP episodes were associated with the unprotected FN.To prevent an attack of FP, and to self-clean the external ears, mastoid obliteration surgery was performed, and the mastoid segment of the FN was covered with a conchal cartilage graft. This case was diagnosed as congenital aplasia of the external ear canal due to the tympanic bone aplasia-mastoid bone hypoplasia, and the dehiscence of the mastoid-tympanic segment of the FN, and as a cause of recurrent FP, has never to date been identified.

Objective: To investigate the effect of hyalinized chorda tympani nerve canal in mastoid segment to landmark facial nerve in middle ear surgery by means of observing the location relationship between hyalinized chorda tympani nerve canal and facial nerve., Method: 118 cases of cholesteatoma otitis media in our hospital undergoing tympanoplasty from 2008 to 2011 were retrospectively analyzed. In all the cases, the position of horizontal semicircular and fossa incus as well as the hyalinized chorda tympani nerve canal were used for landmark the height of facial ridge and vertical segment of facial nerve., Result: The chorda tympani nerve of 99 patients were higher than the vertical segment of the facial nerve which were not exposed, and the vertical segment of the facial nerve in 9 patients, which were exposed, were 1-2 mm lower and 2-3 mm ahead or backward than the chorda tympani nerve. The horizontal semicircular and fossa incus were broken in 9 patients, of whom the vertical segments of the facial nerve were 1-2 mm lower and 2-3 mm ahead or backward than the chorda tympani nerve. The chorda tympani nerve of 1 patient were lower than the exposed vertical segment of facial nerve., Conclusion: The hyalinized chorda tympani nerve canal in mastoid segment can landmark the positon of facial ridge, and it would be the complement to the traditional method of landmarking vertical segment of facial nerve, especially for those whose horizontal semicircular canal and fossa incus had been broken.

Objective: A manipulation of chorda tympani nerve (CTN) is frequently necessary during the surgical therapy of stapedial ankylosis. The aim of this study was to re-assess the taste function before and after stapes surgery in patients with unilateral stapes ankylosis., Methods: Eighteen patients (14 female and 4 male) with unilateral stapedial ankylosis were included. Taste and olfactory function were measured preoperatively, 3 days and 3 months after surgery by questionnaire, chemical taste test, electrogustometry, and Sniffin'Sticks. The patients who reported deterioration in taste and revealed pathological taste test results were re-investigated 8-12 months after surgery. Postoperatively 11 patients were treated intravenously for 3 days for inner ear protection with 1g of cortisone. The gustatory and olfactory results were compared with age and sex specific normative data., Results: A significant transient decrease of gustatory measurement values was found on the ipsilateral two thirds of the anterior tongue. 12 out of 17 patients whose CTN was slightly manipulated during stapes surgery reported tongue sensations, such as numbness or gustatory blindness of the ipsilateral tongue side. The measures of chemical taste test significantly decrease in lateralized taste test on the ipsilateral side and in whole mouth testing. There was no significant increase of the EGM measures at the ipslateral tongue. In 11 of 12 patients with symptoms, complaints recovered within one year after surgery completely. The factor "cortisone" did not have a significant effect on the taste test results after surgery., Conclusion: In conclusion, even after minor CTN manipulation the rate of postoperative taste disorders or tongue symptoms after stapes surgery is high. The symptoms appear to be transient. Therefore CTN should be preserved in stapes surgery after mild trauma of the CTN. Transient taste alteration should be mentioned prior to stapes surgery., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Objective: To report the way for searching the chorda tympani nerve and the significance for preserving the chorda tympani nerve during canal-wall-down mastoidectomy and tympanoplasty surgery., Method: Sixty-six cases with chronic suppurative otitis media underwent canal-wall-down mastoidectomy and tympanoplasty surgery. According to the marker of the short crus of incus, the posterior wall of auditory canal was lowered and crista of the chorda tympani nerve was found through tracing the facial nerve contour. The chorda tympani nerve was preserved after clearing the surrounding tissue., Result: Among the 66 cases, 24 cases had middle ear cholesteatoma, 42 cases had granulation in middle ear. The cholesteatoma and granulation on the surface of the chorda tympani nerve were cleared thoroughly. No neurotmesis or obvious change of taste occurred after operation., Conclusion: Canal-wall-down mastoidectomy and tympanoplasty surgery preserving chorda tympani nerve integrality may preserve the structure and function of the chorda tympani nerve, reduce the risk of ossicle extrusion above the head of stapes and serve as a frame for transplanting fascia.

Objective: To determine the immediate and long-term taste effects of chorda tympani nerve sacrifice in patients undergoing open cavity mastoidectomy., Design, Setting and Participants: A retrospective, questionnaire survey of patients receiving follow up and aural toilet following open cavity mastoidectomy, over a four-month period. The questionnaire assessed taste disturbance, both immediately post-operative and current. Available surgical records were reviewed for chorda tympani references., Results: Of 57 patients, six had undergone surgery to both ears. Of those who could recall (37/57), 24.3 per cent were aware of taste disturbance immediately after surgery, while 8.7 per cent reported current disturbance (median post-operative interval, 28.5 years; range, one month to 67 years). No bilateral surgery patients were aware of taste disturbance., Conclusion: Mastoidectomy consent procedure emphasises the risk of hearing loss and facial nerve injury, yet in open cavity surgery chorda tympani division is almost inevitable. Reassuringly, most post-operative taste disturbance resolves, and most patients are not aware of long-term disturbance. However, a small percentage suffer ongoing taste disturbance; this could be significant for professional chefs and wine-tasters. The risk of taste disturbance should be addressed in the consent procedure.

Objective: To review the currently available literature on iatrogenic injury of the adult chorda tympani., Design: Systematic literature review., Method: Five electronic databases and one search engine were used to access available English language literature on the chorda tympani, focusing on iatrogenic injury., Results: The chorda tympani is most often injured during middle-ear surgery, after which at least 15-22 per cent of patients experience symptoms, mostly changes in taste and dryness of the mouth. Numerous factors influence whether injury to the chorda tympani causes symptoms, including the extent of injury, type of surgery, age of the patient, anatomical variables and subjective adaptation. Although most patients experience gradual symptomatic recovery, complaints can be persistent and troublesome., Conclusion: Care should be taken to preserve the chorda tympani during middle-ear surgery, and to warn patients pre-operatively about this potential complication. This is particularly important if surgery is bilateral.

Objectives: The aim of this study was to evaluate the mean number of regenerated fungiform taste buds per papilla and perform light and electron microscopic observation of taste buds in patients with recovered taste function after severing the chorda tympani nerve during middle ear surgery., Methods: We performed a biopsy on the fungiform papillae (FP) in the midlateral region of the dorsal surface of the tongue from 5 control volunteers (33 total FP) and from 7 and 5 patients with and without taste recovery (34 and 29 FP, respectively) 3 years 6 months to 18 years after surgery. The specimens were observed by light and transmission electron microscopy. The taste function was evaluated by electrogustometry., Results: The mean number of taste buds in the FP of patients with completely recovered taste function was significantly smaller (1.9 +/- 1.4 per papilla; p < 0.01) than that of the control subjects (3.8 +/- 2.2 per papilla). By transmission electron microscopy, 4 distinct types of cell (type I, II, III, and basal cells) were identified in the regenerated taste buds. Nerve fibers and nerve terminals were also found in the taste buds., Conclusions: It was clarified that taste buds containing taste cells and nerve endings do regenerate in the FP of patients with recovered taste function.

This study was undertaken to assess dysgeusia in patients who have undergone middle ear surgery for chronic suppurative otitis media (CSOM) when the surgeon's practice was to cleanly divide the chorda tympani without prior manipulation, if it in any way hindered operative access or the aims of surgery. We wanted to determine whether lower rates of taste disturbance might be obtained by early, clean division of the nerve. We followed 110 patients prospectively and asked them to complete a postoperative dysgeusia questionnaire 1 year after surgery. The "cut nerve" group included 81 patients, and the "uncut nerve" group included 29 patients. In the uncut group, the nerve was untouched or underwent minimal handling. In the cut nerve group, 68% of patients had no taste disturbance after surgery; 4% of patients in this group had ongoing symptoms at 1 year postoperatively. In the uncut nerve group, 67% were asymptomatic, while 11% had ongoing taste disturbance at 1 year. Statistical analysis of symptoms beyond 1 year showed a mean difference of 7%, but this is not statistically significant (p = 0.38). These results suggest that early division of the chorda tympani without prior manipulation in patients with chronic suppurative otitis media does not result in higher rates of taste disturbance than in patients with uncut nerves. Indeed rates of taste disturbance in our cut group were lower than in the uncut group, and lower than or comparable to those seen in other studies.

Objective: To evaluate the relationship between the length of nerve gap defects, incidence of nerve regeneration, and recovery of gustatory function after severing the chorda tympani nerve (CTN)., Study Design: Retrospective study., Setting: University hospital., Patients: Eighty-eight consecutive patients whose CTNs were severed during primary surgery and who underwent secondary surgery were included. Proximal and distal stumps of severed nerves were readapted or approximated during surgery., Intervention: Therapeutic., Main Outcome Measures: Before and after surgery, the taste function was periodically evaluated using electrogustometry. Nerve gaps were classified into 4 groups: readaptation (Group 1), 1 to 3 mm (Group 2), 4 to 6 mm (Group 3), and more than 7 mm (Group 4)., Results: Regenerated nerves in the tympanic segment were detected in 36 (41%) of the 88 patients during secondary surgery. The incidence of nerve regeneration was 100% (10/10) in Group 1, 45% (10/22) in Group 2, 47% (9/19) in Group 3, and 19% (7/37) in Group 4. There was a significant difference between the length of nerve gap defects and incidence of nerve regeneration (p < 0.001). In the 36 patients with a regenerated CTN, the incidence of gustatory function recovery was 60% (6/10) in Group 1, 50% (5/10) in Group 2, 56% (5/9) in Group 3, and 43% (3/7) in Group 4. There was no significant difference between the length of nerve gap defects and incidence of taste function recovery., Conclusion: Reconstruction of a severed CTN is very important for regeneration. However, the regenerated CTN in the tympanic segment does not always reinnervate the fungiform papillae.

Purpose: To investigate the feasibility of parotid duct transposition after tympanic neurectomy to treat severe keratoconjunctivitis sicca (KCS) in rabbits., Methods: Thirty rabbits were divided into three groups in experiment 1. One eye was operated on, and the contralateral eye served as the control. In the KCS group, the lacrimal gland, harderian gland, and nictitating membrane were removed. In the group with parotid duct transposition (DT), the parotid duct was transposed into the lower conjunctival fornix. In the group with parotid duct transposition after tympanic neurectomy (DTTN), the tympanic nerve was resected in addition to parotid duct transposition. Schirmer test was performed and density of corneal staining was determined monthly after surgery, and goblet cell density was measured at postoperative month 3. In experiment 2, the tympanic nerve was resected on one side in 12 rabbits. Both sides of the parotid gland were resected for histopathology at intervals of 2 months to 1 year after surgery., Results: Tear secretion from operated eyes at rest increased significantly after surgery in the treatment groups compared with the KCS group. Tear secretion from operated eyes after chewing was significantly lower in the DTTN than in the DT group. The corneal staining scores were higher in the operated than in the control eyes of the three groups, without significant difference among the operated eyes. Parotid gland atrophy on the operated side occurred at postoperative month 4 and recovered to normal 1 year after surgery., Conclusions: Parotid duct transposition after tympanic neurectomy could effectively reduce gustatory epiphora but may be insufficient to promote ocular surface health.

The chorda tympani nerve (CTN) is the last collateral branch of the facial nerve in its third intraosseous portion just over the stylomastoid foramen. After a curved course against the medial aspect of the tympanum where it is likely to be injured in middle ear surgery, CTN reaches the lingual nerve in the infratemporal fossa. Knowledge of CTN topographic anatomy is not easily achieved by the students because of the deep location of this thin structure. The aim of this study was to assess the spatial relationships of the CTN in the infratemporal fossa. Therefore, ten nerves were dissected in five fresh cadavers. All the nerves were catheterized with a 3/0 wire. After a meticulous repositioning of surrounding structures, standard X-ray and CT scan examinations were performed with multiplanar acquisitions and three-dimensional surface rendering reconstructions. Ventral projection of the CTN corresponded to the middle of the maxillary sinus. Lateral landmark was the mandibular condyle. The CTN was present and unique in all the dissections. The average length of the nerve, as measured on CT scans, was 31.8 mm (29-34, standard deviation of 1.62); the anastomosis of the CTN to the lingual nerve was located at a mean 24.9 mm below the skull base (24-27, standard deviation of 0.99), approximately in the same horizontal plane as the lower part of the mandibular notch. The acute angle opened dorsally and cranially between CTN and LN measured mean 63.2° (60-65, standard deviation of 1.67). Three-dimensional volumetric reconstructions using surface rendering technique provided realistic educational support at the students' disposal.