Chorda Tympani Research Articles

The Sensory Auricular Branch of the Facial Nerve and its Relationship to Landmarks of the Facial Recess.

Delineate the anatomic relationship of the sensory auricular branch (SAB) of the facial nerve to other structures of the facial recess. Ten adult cadaveric temporal bones were randomly selected and dissected under operative microscopy. Linear and angular measurements were obtained for the following parameters: (1) the distance from the tip of the short process of the incus to the point of convergence of the SAB and the main trunk of the facial nerve; (2) the distance from the point of convergence of the SAB and the main trunk of the facial nerve to the chorda tympani (CT) division from the main trunk; (3) the distance from the bifurcation of the CT and facial nerve to the crossover point of the SAB/CT; (4) the angle at which the SAB merges with the main trunk (Y°), and (5) the angle at which the CT divides off the main trunk (X°). The mean distance from the tip of the short process of the incus to the SAB takeoff was 8.7 ± 1.83 mm (range 6-13 mm). The mean distance from the SAB to the CT division from the main trunk was 5.9 ± 2.41 mm (range 3-10 mm). The mean angle at which the SAB merged with the main trunk of the facial nerve was 38.5 ± 12.63° (range 25°-68°). The mean CT-main trunk angle was 16 ± 4.24° (range 8°-21°). The branching point of the SAB from the facial nerve approximately bisected the facial recess. Recognizing the SAB and knowing its relationships to surrounding anatomy provides a useful adjunctive landmark for the identification of the main trunk of the facial nerve's mastoid segment. 4.

Chorda tympani injury during endoscopic versus microscopic stapes surgery: a randomized controlled clinical trial

ObjectivesThe aim of this study was to compare the incidence of chorda tympani nerve (CTN) injury between endoscopic and microscopic stapes surgery.MethodsThis 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.ResultsThe 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).ConclusionAltered 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.

The Impact of the Location of Chorda Tymapni Nerve Origin on the Round Window Accessibility During Pediatric Cochlear Implantation: A Radioclinical Assessment.

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). It was a prospective observational case-series study. The included CI surgeries were performed at tertiary referral institutions from November 2018 to August 2021. We included 146 pediatric patients who were candidates for CI. 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. We correlated the preoperative radiologic CF-SM length with the intraoperative RW accessibility. 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. 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.

The pre-chorda and post-chorda tympani approach in endoscopic stapes surgery based on the chorda tympani nerve classification.

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. 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. 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. 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.

Validation of the radiological detection of the chorda-facial angle: impact on the round window accessibility during pediatric cochlear implantation

ObjectivesThe 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.MethodsIt 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.ResultsThe 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 accuracyConclusionsOur 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.

Comparison of endoscopic and microscopic methods in stapedotomy: a retrospective analysis.

The goal of the present study was to compare the audiologic results, complications, and advantages/disadvantages of endoscopic and microscopic stapedotomy. Patients who experienced stapedotomy surgery in the Ear Nose Throat Clinic (ENT) of Selcuk University Faculty of Medicine between September 2011 and January 2018 were included in the study. The data of all patients were analyzed and divided into two groups. Those who underwent endoscopic stapedotomy were included in group I, and patients who underwent microscopic stapedotomy formed group II. Surgical findings, complications, and operation times were compared for the two groups. Air and bone conduction thresholds were evaluated at the frequencies of 500, 1000, 2000, and 4000Hz pre- and postoperatively at 1, 3, and 6months, and the mean (± SD) air-bone gap value was recorded. While the mean pre- and postoperative air-bone gaps were 34.38 ± 7.47dB (23-53dB) and 9.69 ± 4.43dB (0-19dB), respectively, in group I, 34.32 ± 7.57dB (23-6dB) and 9.62 ± 4.25dB (2-23dB) were the respective means calculated in group II (p < 0.05). When the mean postoperative air-bone gap was compared, there was no statistically significant difference between the two groups (p = 0.774). The mean operative times for groups I and II were 57.22 ± 4.37min and 63.70 ± 7.34min, respectively (p < 0.001). The requirement for chorda tympani nerve manipulation and scutum curettage was significantly less in group I compared to group II (p = 0.003). Postoperative dysgeusia and postoperative pain were found to be higher in group II than group I, but they were not statistically significant (p > 0.05). Endoscopic stapedotomy displayed similar audiological results, shorter operation times, and similar complication rates, as well as being a less invasive surgery, compared to the microscopic approach.

Variation and protection of the chorda tympani nerve in endoscopic ear surgery.

ObjectiveTo observe and summarize variations of the chorda tympani nerve to effectively protect it during surgery.MethodsSurgical videos of patients undergoing endoscopic ear surgery in the past 3 years were retrospectively observed to identify chorda tympani nerve variations.ResultsIn total, 237 cases were reviewed. The tympanic sulcus or annulus was the boundary between the posterior wall of the external auditory canal and chordal eminence (CE). The chorda tympani nerve was divided into three types: type I, the periannular segment was located medial to the CE and covered by the bony eminence (32.5%); type II, the periannular segment was located inferior to the CE, and the nerve did or did not contact the bony edge of the CE (62.0%); and type III, the periannular segment was located lateral to the CE and medial to the tympanic annulus, and the iter chorda posterius was located in the tympanic sulcus (5.5%). The rate of injury to the chorda tympani nerve was 2.5% of 237 cases. The location of the iter chorda posterius on preoperative computed tomography was highly reliable for prediction of type I and III nerves. Secondary exposure of the posterior canaliculus might occur in patients with external auditory canal cholesteatoma, who were specifically included in this study.ConclusionCE‐based classification of the chorda tympani nerve can concisely describe variations of the chorda tympani nerve and provide guidance for neuroprotection during endoscopic ear surgery. Patients with external auditory canal cholesteatoma may have secondary exposure of the posterior canaliculus.Level of EvidenceNA.

Consequences of Stapes Surgery on Tongue Morphological Characteristics in Narrow Band Imaging, Gustatory Function and General Sensation: A Prospective Tertiary Center Study

(1) Background: Chorda tympani (CT) manipulation during stapes surgery affects its functions. We hypothesized that this alters tongue morphology and sensory functions. (2) Methods: Patients undergoing stapes surgery were tested 1 day preoperatively, 1 and 6 months postoperatively. Narrow band imaging contact endoscopy (NBI) was used to determine the number of fungiform papillae (Npapillae) and the total score of blood vessel morphology (NBItotal). The taste was tested with taste strips. General sensation was tested with a static two-point discrimination. Tests were performed on ipsilateral and contralateral side of the tongue. (3) Results: 52 otosclerosis patients were included in the study. There was a statistically significant decrease of NBItotal (p = 0.005), Npapillae (p = 0.009), sensation of sweet (p = 0.003), salty (p = 0.035), sour (p = 0.036), and bitter taste (p = 0.013) within the test side during the follow-up. A statistically significant impact on presence of dysgeusia for sweet was found 1 month postoperatively (p &lt; 0.005). Postoperative decrease in two-point discrimination score did not reach a statistical significance (p = 0.056). (4) Conclusions: CT manipulation affects fungiform papillae density, vascular patterns and taste sensation. The general sensation of the tongue is not influenced by CT manipulation.

Complete and incomplete lower motor neuron facial palsy in post-COVID-19 mucormycosis

Purpose:To study facial nerve palsy (FNP) in post-COVID-19-mucormycosis patients and its ocular complications, report different presentations of FNP in such patients, and propose its etiopathogenesis based on presentation and clinico-radiologic localization.Methods:A prospective cohort study was carried out in patients of post-COVID-19-mucormycosis who presented at our tertiary center, over a period of 3 months. Motor and sensory examination of the facial nerve was done to diagnose FNP and localize the lesion clinically. Slit-lamp examination was done for grading corneal involvement. MRI brain, orbit, and paranasal sinuses (PNS) with contrast were studied to find involvement along the facial nerve. It was assessed whether this site of lesion corresponded with clinical localization. Data were analyzed using the percentage of total cases and Fisher’s test.Results:A total of 300 patients with post-COVID-19 mucormycosis were examined, of which 30 (10%) patients were found to have FNP. All were lower motor neuron (LMN) type and were associated with corneal complications. The most common site clinically was distal to the chorda tympani (66.66%) and radiologically was infratemporal (IT) fossa (63.4%). The clinical localization significantly correlated with the radiological findings (P = 0.012). Twenty percent of patients showed incomplete involvement of facial musclesConclusion:FNP was found to be of LMN type. The most common site of insult was IT fossa. There was a good clinico-radiological correspondence of lesions. Isolated lesions were also found along the peripheral nerve course, presenting as incomplete facial palsy. Recognition of FNP in post-COVID-19 mucormycosis, in all its variable forms, is important to manage corneal complications.

Step-by-Step Stapedotomy through Transcanal Exclusive Endoscopic Approach.

In recent years there has been an increasing trend in the use of the endoscope to treat a variety of middle ear pathologies, including otosclerosis. Several studies comparing traditional microscopic and endoscopic stapes surgery have reported similar hearing results and an overall low rate of complications. The endoscope has unraveled its full potential in demanding settings of stapes surgery, such as unfavorable anatomy of the oval window niche or revision cases. Reduced manipulation of the chorda tympani and low rate of post-operative dysgeusia are further benefits to mention for endoscopic stapes surgery. Being a one-handed technique, management of bleeding, positioning, and crimping of the prosthesis may be challenging for novice endoscopic surgeons, so some training in endoscopic ear surgery is recommended before performing endoscopic stapedotomy. The problem of sharing the surgical field between the endoscope and the operating instruments could be easily overcome if proper instruments positioning is understood. One-handed bleeding control in the narrow space of the ear canal may represent an issue during the elevation of the tympano-meatal flap, possibly discouraging the surgeon since the preliminary steps of surgery. Following appropriate technique to raise the flap and the collaboration with the anesthesiology team in keeping the blood pressure low guarantee an adequate bleeding control in most cases. The aim of this article is to describe the entire surgical procedure of a transcanal exclusive endoscopic stapedotomy, from operating room set up and patient positioning to post-operative care. A step-by-step description of the surgical maneuvers with technical hints is reported, to guide the surgeon across the procedure and allow any ear surgeon to perform stapes surgery endoscopically.

Anatomy of the sphenoidal spine and its implications in endoscopic endonasal surgery of the infratemporal fossa.

The sphenoidal spine protrudes from the roof of the infratemporal fossa (ITF). This study aims to assess the anatomic relationships among the sphenoidal spine and other structures within the ITF from the perspective of an endoscopic endonasal access (EEA), and to explore the implications of these relationships. An EEA to the ITF was completed on six cadaveric specimens (12 sides). The anatomical relationships among the sphenoidal spine and adjacent structures were explored and associated distances from each other were measured using a navigation system. The foramen spinosum is located anterosuperior to the sphenoidal spine, whereas the chorda tympani courses caudal and medial to the sphenoidal spine and the Eustachian tube and parapharyngeal internal carotid artery (pICA) are at its posterior aspect. Two virtual vertical planes, at the anterior and posterior aspects of the sphenoidal spine, respectively, correspond to the posterior trunk of V3 and middle meningeal artery, and the stylopharyngeal aponeurosis. The average length of sphenoidal spine was 8.5 ± 2.43 mm, and the distance from distal apex of the sphenoidal spine to the foramen ovale, foramen spinosum, and pICA were 10.82 ± 0.83 mm, 6.42 ± 0.52 mm, and 5.02 ± 0.54 mm, respectively. The sphenoidal spine is a meaningful landmark for endonasal approaches to the ITF. Measurements and conceptualization of vertical planes prior and posterior to the sphenoidal spine are beneficial to better appreciate the anatomic relationships in the ITF.

Role of the endoscope in cochlear implantation: A systematic review.

To review the role of the endoscope in cochlear implantation (CI). MEDLINE, ScienceDirect, Google Scholar and the Cochrane Library databases, as well as other sources, were searched by two independent reviewers. Studies including patients undergoing either exclusively endoscopic or endoscopically assisted CI were eligible for inclusion. Endoscopic CI approaches and postoperative complications were the primary outcomes. Secondary endpoints included the degree of round window (RW) microscopic visualisation according to St Thomas' Hospital classification and type of cochleostomy for electrode insertion in the scala tympani (ST). Fourteen studies met the inclusion criteria comprising 191 endoscopic or endoscopically assisted CI cases. The endoscope was used for better visualisation of the RW across all included studies, facilitated the insertion of the electrode in the ST and spared a mastoidectomy in a number of cases. No facial nerve palsy was reported in any of the studies. The most common complication was external auditory canal/tympanic membrane tear followed by chorda tympani injury. The microscopic CI approach is still the gold standard. The endoscope facilitates the recognition of the RW area and leads to successful and safe implantation, particularly in difficult anatomical scenarios, ear malformations and advanced otosclerosis. Endoscopically assisted CI procedures offer the opportunity to avoid a posterior tympanotomy and reduce the risk of facial nerve injury. To date, the lack of long-term data does not permit the widespread adoption of completely endoscopic CI procedures without a mastoidectomy.

Supplementation effects of a kokumi substance, γ-Glu-Val-Gly, on the ingestion of basic taste solutions in rats

In addition to the well-accepted taste receptors corresponding to the 6 basic taste qualities, sweet, salty, sour, bitter, umami, and fatty, another type of taste receptor, calcium-sensing receptor (CaSR), is located in taste bud cells. CaSR is called the kokumi receptor because its agonists induce koku (or kokumi), a Japanese word meaning the enhancement of flavor characteristics, such as thickness, mouthfulness, and continuity. Kokumi is an important factor in enhancing food palatability. γ-Glu-Val-Gly (EVG) is the most potent agonist of CaSR, which induces a strong kokumi flavor. However, no behavioral studies have been documented in animals using EVG. Here, we show that EVG at low concentrations that do not elicit a taste of its own enhances preferences for umami, fat, and sweet taste solutions in rats. An increased preference for inosine monophosphate (IMP) and Intralipos was the most dominant effect. NPS-2143, an antagonist of CaSR, abolished the additive effect of EVG on IMP and Intralipos solutions. These effects of EVG on taste stimuli are thought to occur in the oral cavity, because the effects of EVG were confirmed in a brief exposure test. The additive effects on IMP and Intralipos remained after the transection of the chorda tympani, indicating that these effects also occur in the palate and/or posterior part of the tongue. Moreover, the additive effects of EVG were verified in electrophysiological taste nerve responses. These results may partially provide the underlying mechanisms for EVG to induce kokumi flavor in humans.

TOTAL ENDOSCOPIC STAPES SURGERY. OUR TECHNIQUE AND EXPERIENCE OF 45 CASES

Objective: To assess the hearing results of transcanal endoscopic stapedotomy&#x0D; Study Design: Descriptive study.&#x0D; Place and Duration of Study: Pakistan Naval Ship Hafeez Islamabad Pakistan, from Jun 2016 to Jun 2020.&#x0D; Methodology: All patients with surgically confirmed otosclerosis were included in the study. All patients were operated with 0-degree 3mm, 14cm rigid endoscope under general anesthesia. Preoperative and post operative air bone gap was noted along with demographic data, middle ear anomalies (persistent stapedial artery, dehiscent facial nerve, anteriorly placed facial nerve, floating foot plate) and injury to chorda tympani. Postoperative air bone gap (A-B Gap) was documented 12 weeks after surgery. All patients were followed up for 6-12 months&#x0D; Results: Mean age of patients was, 37 years and standard deviation was 12.34 (range 27-52 years). Out of total 45 cases 13 were males (29%) and 32 females (71.%). Four (8.8%) patients had dehiscent facial canal and 1 (2.2%) patient had persistent stapedial artery. Average preoperative A-B gap was 35 db and Average Postoperative A-B Gap was 7 db. Chorda tympani was preserved in all cases. One patient (2.2%) complained of altered taste which resolved after 3 months. Four patients had Postoperative vertigo that lasted 2 days on average.&#x0D; Conclusion: Endoscopic trans canal Stapes surgery is scarless safe effective procedure demonstrable hearing benefits in all patients with minimum complications. The Technique is single handed and has steep learning curve.

Cochlear Implant Complications in Children and Adults: Retrospective Analysis of 148 Cases.

ObjectiveThis study aimed to establish and discuss the intraoperative and postoperative complications affecting patients who underwent cochlear implant (CI) surgery from the Cochlear Implant Program of King Abdulaziz University Hospital (KAUH), Jeddah, Saudi Arabia.MethodsA retrospective study was conducted by reviewing the medical records of 148 patients who underwent cochlear implantation at KAUH between 1999 and 2019. Postoperative complications were classified into minor and major complications. Minor complications resolved with minimal or no treatment. Major complications required additional surgery or hospitalization.ResultsComplications occurred in 28 (18.9%) patients. Minor complications occurred in 17 (11.5%) patients, which included otitis media (2%), facial palsy (1.4%), wound infection (1.4%), vertigo (1.4%), intraoperative cerebrospinal fluid (CSF) gusher (1.4%), tinnitus (1.4%), facial stimulation (1.4%), hematoma (0.7%), and chorda tympani nerve injury (0.7%). Major complications occurred in 11 (7.4%) patients. These included flap dehiscence/infection (2%), device failure (1.4%), device migration (1.4%), mastoiditis (1.4%), electrode damage during insertion (0.7%), and misplaced electrodes (0.7%).ConclusionThis study reported a low rate of surgical complications associated with CI, and most have been managed successfully without further complications. Our results prove that CI is a safe and reliable procedure, with a low complications rate when performed by experienced surgeons.

The posterior ligament of the incus (“white dot”): A reliable surgical landmark for the facial recess

ObjectiveThere 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 methodsAfter 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. ResultsThe 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. ConclusionsThe 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.

Probing the multimodal fungiform papilla: complex peripheral nerve endings of chorda tympani taste and mechanosensitive fibers before and after Hedgehog pathway inhibition

The fungiform papilla (FP) is a gustatory and somatosensory structure incorporating chorda tympani (CT) nerve fibers that innervate taste buds (TB) and also contain somatosensory endings for touch and temperature. Hedgehog (HH) pathway inhibition eliminates TB, but CT innervation remains in the FP. Importantly, after HH inhibition, CT neurophysiological responses to taste stimuli are eliminated, but tactile responses remain. To examine CT fibers that respond to tactile stimuli in the absence of TB, we used Phox2b-Cre; Rosa26LSL−TdTomato reporter mice to selectively label CT fibers with TdTomato. Normally CT fibers project in a compact bundle directly into TB, but after HH pathway inhibition, CT fibers reorganize and expand just under the FP epithelium where TB were. This widened expanse of CT fibers coexpresses Synapsin-1, β-tubulin, S100, and neurofilaments. Further, GAP43 expression in these fibers suggests they are actively remodeling. Interestingly, CT fibers have complex terminals within the apical FP epithelium and in perigemmal locations in the FP apex. These extragemmal fibers remain after HH pathway inhibition. To identify tactile end organs in FP, we used a K20 antibody to label Merkel cells. In control mice, K20 was expressed in TB cells and at the base of epithelial ridges outside of FP. After HH pathway inhibition, K20 + cells remained in epithelial ridges but were eliminated in the apical FP without TB. These data suggest that the complex, extragemmal nerve endings within and disbursed under the apical FP are the mechanosensitive nerve endings of the CT that remain after HH pathway inhibition.

Transcanal Endoscopic Ear Surgery for Advanced External Auditory Canal Cholesteatoma in Naim Stage III and IV

To report the clinical characteristics and treatment outcomes, as well as endoscopic-assisted ear surgery techniques used in patients with advanced external auditory canal cholesteatoma (EACC). Retrospective case series. University hospital. From October 2014 to September 2017, adult patients (age > 18) with advanced EACC (Naim's classification: stage III or IV) who underwent transcanal endoscopic ear surgery (TEES) were enrolled. The presenting features, extent of the lesion, and reconstruction techniques used were assessed. The healing time which was defined as the time required to develop a dry, re-epithelialized, and self-cleaning external auditory canal, was compared between stage III and IV. Twenty-three patients were included. EACC was categorized as stage III in 11 ears and stage IV in 12 ears. Cholesteatoma involved the mastoid (30%), middle ear (26%), chorda tympani (22%), temporomandibular joint, antrum, and facial nerve (17% for each). In 96% of patients, a dry and self-cleaning external auditory canal (EAC) was maintained after a mean follow-up of 15 months. The median healing time was 8 weeks in stage III, which was significantly shorter than the 12 weeks required for stage IV (p < 0.05). There was no significant difference in the median healing time between TEES and the canal wall up mastoidectomy for stage IV EACC (14 weeks) performed by the same surgeon over the same period (p > 0.05). TEES is a feasible and safe technique for the exposure and eradication of advanced EACC. Some critical endoscopic techniques for resecting disease and reconstructing the defect in the EAC and middle ear should be mastered before performing this operation.

Accessing the Stapedius Muscle Via Novel Surgical Retrofacial Approach: A Cadaveric Feasibility Study.

Despite the complete embodiment of the stapedius muscle (SM) into the pyramidal eminence, it is possible to safely gain access to the SM belly via a retrofacial approach. This presents a novel approach to directly measure the electrically evoked stapedius reflex threshold (eSRT). Objective fitting of maximum comfortable loudness levels for cochlear implant users can improve the benefit introduced by the device. Sensing SM activity via direct surgical access represents a potential tool for objective eSRT fitting. Eighteen human temporal bones (TBs) were used. Micro-computed tomography was performed for six TBs. Standard computed tomography for six TBs. Manual 3D-segmentation of the relevant middle and inner ear anatomy was performed on 12 TBs. Mastoidectomy and posterior tympanotomy allowed the access to middle ear of all 18 the TBs. Once identified the mastoidal segment of the facial nerve (FN), the retrofacial access to the SM was drilled. The total access rate was 72.2%. Only in the first three cases the posterior semi-circular canal was hit. The SM access was identified posterior to the FN at a 4 ± 0.78 mm distance from the stapes' head, almost halfway to the chorda tympani's branching point along the FN direction. The drilling depth to access the SM posterior to the external surface of FN on average was 2 ± 0.30 mm. The exposure took on average of 5 to 8 minutes. The retrofacial approach seems to offer a feasible and reproducible access to the SM belly opening an avenue to electromyographic sensing of eSRT.

Improved visualization of the chorda tympani nerve using ultra-high-resolution computed tomography.

BackgroundRecognition of the anatomical course of the chorda tympani nerve (CTN) is important for preventing iatrogenic injuries during middle-ear surgery.PurposeThis study aims to compare visualization of the CTN using two computed tomography (CT) methods: conventional high-resolution CT (C-HRCT) and ultra‐high-resolution CT (U-HRCT).Materials and methodsWe performed a retrospective visual assessment of 59 CTNs in normal temporal bones of 54 consecutive patients who underwent both C-HRCT and U-HRCT. After dividing CTN into three anatomical segments (posterior canaliculus, tympanic segment, and anterior canaliculus), two neuroradiologists scored the visualizations on a four-point scale.ResultsOn C-HRCT, the visual scores of the posterior canaliculus, tympanic segment, and anterior canaliculus were 3.5 ± 0.7, 1.6 ± 0.6, and 3.1 ± 0.7, respectively. The respective values were significantly higher in all segments on U-HRCT: 3.9 ± 0.2, 2.4 ± 0.6, 3.5 ± 0.6 (p < 0.01). Although the difference in scores between methods was greatest for the tympanic segment, the visual score on U-HRCT was lower for the tympanic segment than for the anterior and posterior segments (p < 0.01).ConclusionUltra‐high-resolution CT provides superior visualization of the CTN, especially the tympanic segment.