Feasibility of preservation of chorda tympani nerve during noninflammatory ear surgery: A systematic review

Accurate Segmentation and Tracking of Chorda Tympani in Endoscopic Middle Ear Surgery with Artificial Intelligence

Objective: We introduce a novel endoscopic middle ear surgery dataset specifically designed for evaluating deep learning (DL)-based semantic segmentation of chorda tympani. Methods: We curated a dataset comprising 8240 images from 25 patients, divided into a training set (20%, 1648 images), validation set (5%, 412 images), and test set (75%, 6180 images). We employed data enhancement techniques to expand the picture size of the training and validation sets by 5 times (training set: 8240 images, verification set: 2060 images). Subsequently, we employed a multistage transfer learning training method to establish, train, and validate various convolutional neural networks. Results: On the validation set of 2060 labeled images, our proposed network achieved good results, with the U-net exhibiting the highest effectiveness (mIOU = 0.8737, mPA = 0.9263). Furthermore, when applied to the test dataset of 6180 raw images and contrasted with the prediction of otologists, the overall performance of the U-net was excellent (accuracy = 0.911, precision = 0.9823, sensitivity = 0.8777, specificity = 0.9714). Conclusions: Our findings demonstrate that DL can be successfully employed for automatic segmentation of chorda tympani in endoscopic middle ear surgery, yielding high-performance results. This study validates the potential feasibility of future intelligent navigation technologies to assist in endoscopic middle ear surgery.

Automatic detection and segmentation of chorda tympani under microscopic vision in otosclerosis patients via convolutional neural networks

BACKGROUND

Artificial intelligence (AI) techniques, especially deep learning (DL) techniques, have shown promising results for various computer vision tasks in the field of surgery. However, AI-guided navigation during microscopic surgery for real-time surgical guidance and decision support is much more complex, and its efficacy has yet to be demonstrated. We propose a model dedicated to the evaluation of DL-based semantic segmentation of chorda tympani (CT) during microscopic surgery.

METHODS

Various convolutional neural networks were constructed, trained, and validated for semantic segmentation of CT. Our dataset has 5817 images annotated from 36 patients, which were further randomly split into the training set (90%, 5236 images) and validation set (10%, 581 images). In addition, 1500 raw images from 3 patients (500 images randomly selected per patient) were used to evaluate the network performance.

RESULTS

When evaluated on a validation set (581 images), our proposed CT detection networks achieved great performance, and the modified U-net performed best (mIOU = 0.892, mPA = 0.9427). Moreover, when applying U-net to predict the test set (1500 raw images from 3 patients), our methods also showed great overall performance (Accuracy = 0.976, Precision = 0.996, Sensitivity = 0.979, Specificity = 0.902).

CONCLUSIONS

This study suggests that DL can be used for the automated detection and segmentation of CT in patients with otosclerosis during microscopic surgery with a high degree of performance. Our research validated the potential feasibility for future vision-based navigation surgical assistance and autonomous surgery using AI.

Subjective and Objective Taste Change After Cochlear Implantation Systematic Review and Meta-Analysis

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.

Gustatory Function of Patients With and Without Cholesteatoma Undergoing Middle Ear Surgery

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.

Subjective and Objective Taste Change After Stapes Surgery Systematic Review and Meta-Analysis

INTRODUCTION

Iatrogenic injury to the chorda tympani (CT) is a well recognized, although potentially underestimated, consequence of stapes surgery. This study aims to review the currently available literature to determine the incidence and prognosis of taste disturbances in these patients.

DATA SOURCES

PubMed, Embase, and Cochrane Library databases.

METHODS

Databases were searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Search terms included (chorda tympani OR gustatory OR taste OR chemosensory OR dysgeusia OR nervus intermedius) AND (ear surgery OR middle ear OR stapes OR stapedectomy OR stapedotomy). Patients with prospective data collection including preoperative data were further divided by methodology into "objective" and "subjective" assessments of taste dysfunction. A systematic review was performed for all included studies, with meta-analysis using a random-effects model was used for those with comparable methodology and patient populations.

RESULTS

Initial search yielded 2,959 articles that were screened according to inclusion and exclusion criteria. Once duplicates were removed, seven studies were identified, representing 173 patients with subjective testing (all seven studies) and 146 with objective testing (five studies). Eighty of 173 patients (46.2%) noted a disturbance in taste at early follow-up, whereas as 26 of 173 (15.0%) noted long-term problems. Objective methodology and result reporting were heterogenous and not amenable to pooled meta-analysis for all studies included.

CONCLUSION

Changes in taste occur relatively frequently after stapedectomy. Surgeons should continue to counsel prospective patients as to the risks of both short- and long-term taste disturbances.

The impact of injury of the chorda tympani nerve during primary stapes surgery or cochlear implantation on taste function, quality of life and food preferences: A study protocol for a double-blind prospective prognostic association study

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.

Chorda tympani nerve course and feasibility of its preservation during atresiaplasty for congenital aural atresia

Objectives

The association between the chorda tympani nerve (CTN) and atresiaplasty has not been investigated. This study aimed to describe the course of the CTN observed during atresiaplasty for congenital aural atresia (CAA) and explore the feasibility of CTN preservation.

Methods

In this retrospective study, six consecutive patients who underwent atresiaplasty in a tertiary academic center were included. The course of the tympanic segment of the CTN and its preservation feasibility were evaluated. Atresiaplasty was performed using an anterior approach. The average Jahrsdoerfer score was 8.7 points (range, 8-9 points).

Results

The CTN was located in the atretic plate in all patients. It emerged from an average of 5.6 mm (range, 5.2-6.1) inferior to the incus buttress and crossed the middle ear in an anterior-superior direction. The distance between the neck of the malleus and the CTN varied in the absence of the malleus handle. However, when the malleus handle developed, the CTN passed between the incus and the malleus handle. The CTN was preserved in two of the six patients. They had a Jahrsdoerfer score of 9 and grade I microtia.

Conclusion

The CTN was located in the atretic plate, emerging from an average distance of 5.6 mm inferior to the incus buttress. The incus buttress might serve as a good anatomical landmark to identify and preserve the CTN. CTN preservation is feasible in atresiaplasty candidates with a Jahrsdoerfer score of 9 and auricular deformity of grade I.

Level of Evidence

4.

The Etiologies and Considerations of Dysgeusia: A Review of Literature

BACKGROUND

Dysgeusia is a prevalent qualitative gustatory impairment that may affect food intake and quality of life. The facial (VII), glossopharyngeal (IX), and vagus (X) nerves are the three cranial nerves responsible for sensing taste. Typically, dysgeusia is considered a general term for all taste disorders. In addition, dysgeusia may be a symptom of underlying systemic conditions such as diabetes mellitus, chronic kidney disease, respiratory infections, and nutritional deficiencies. Various subjective and objective diagnostic approaches are available to aid clinicians, each with its own set of benefits and drawbacks.

HIGHLIGHTS

Taste impairment can lead to a lack of enjoyment while eating, food aversion, and malnutrition, resulting in a decrease in the quality of life and loss of muscle mass. Therefore, the present review aims to address the probable etiologies, diagnostic aids, and management of dysgeusia. A broad search for studies was conducted using PubMed, Web of Science, Scopus, and Google Scholar. In addition, relevant studies found in the references of the selected articles were also studied.

CONCLUSION

Oral health care providers should be aware of the possible etiologies of dysgeusia, diagnostic tools, and treatment options. Accurate diagnosis of the cause of taste dysfunction has a significant impact on the management of taste impairment.

Taste impairment after endoscopic stapes surgery: Do anatomic variability of chorda tympani and surgical technique matter? : Post-operative dysgeusia after EStS

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 CO₂ laser could have a role in increasing the risk of post-operative dysgeusia after EStS.

Taste-strip gustometry in cochlear implanted patients

OBJECTIVE

Investigation of the gustatory function in a large cohort of cochlear implanted patients using lateralized taste-strip tests.

PATIENTS AND METHODS

One hundred and seven unilaterally or bilaterally profoundly hearing impaired or deaf patients who received cochlear implants (n = 113) were included in this study. Data on gustometry, subjective gustatory dysfunction, and the detailed surgical procedure were acquired retrospectively. Gustatory function, assessed using lateralized taste-strip tests, was performed the day before, 3 days after cochlear implantation, and on the day of the initial CI adjustment (39 days ±7.3 SD).

RESULTS

Averaged taste-strip scores of the cohort declined significantly from preoperatively 12.3 [11.8; 12.7] (mean [95% confidence intervals]) to 10.5 [9.7; 11.2] on the implanted side about 6 weeks after surgery. Patients with intraoperatively exposed and rerouted, or a severed, chorda tympani nerve (CTN) showed significantly reduced unilateral postoperative scores (10.1 [8.8; 11.4] and 9.3 [8.1; 10.5], respectively), when compared to not exposing or to leaving a bony layer over the CTN. Total taste-strip test scores showed a significant decline 6 weeks postoperatively in CI-patients expressing a subjective gustatory dysfunction (from 23.6 [21.4; 25.8] to 17.5 [14.2; 20.8]), as opposed to patients with a documented subjectively normal taste.

CONCLUSION

We consider postoperative gustatory dysfunction as a relevant side effect post cochlear implantation, at least within the first month. Taste-strip based gustometry is a suitable diagnostic tool to assess taste function in CI patients and is recommended to be performed routinely.

LEVEL OF EVIDENCE

3, retrospective, nonrandomized follow-up study.

Transcanal Endoscopic Management of Glomus Tympanicum: Multicentric Case Series

OBJECTIVE

The aim of this study was to report a multicentric surgical experience in the exclusive endoscopic management of glomus tympanicum (GT).

STUDY DESIGN

Retrospective case series review at two institutions.

SETTING

Tertiary referral centers.

PATIENTS

The study included 30 patients who underwent exclusive transcanal excision of GT between 2010 and 2017 at the two referral centers.

INTERVENTIONS

Exclusive endoscopic transcanal excision of GT type A1, A2, and B1 (modified Fisch-Mattox classification). All surgical procedures were performed by two senior surgeons (L.P.; M.B.).

MAIN OUTCOME MEASURES

For each procedure, intraoperative features of the disease, postoperative complications, and functional outcomes were evaluated. Recurrent or residual diseases were clinically and radiologically assessed during the follow-up period.

RESULTS

None of the patients treated with transcanal endoscopic approach (TEA) experienced intraoperative complications, nor required conversion to microscopic approach. Gross total resection (GTR) was obtained in 90% of the cases, while a near total resection was advocated when the residual pathology had a close relationship with the internal carotid artery. Mean hospitalization time was 1.6 (±0.8 SD) days and no postoperative complications were reported. No recurrences were reported in the GTR group after a mean follow-up period of 38.1 (±28.7 SD) months.

CONCLUSIONS

Middle ear paragangliomas with no mastoid involvement (Class A1, A2, and B1) can be safely managed by means of a transcanal endoscopic approach. Low rate of postoperative complications, short hospitalization, and high rate of gross total resection demonstrate that TEA is a safe and effective procedure.

Changes of taste perception after stapes surgery: a prospective cohort study

PURPOSE

Taste perception is often affected after stapes surgery despite effort to preserve chorda tympani nerve. The aim was to examine changes of particular taste qualities and their recovery after operation of otosclerosis.

MATERIALS AND METHODS

Taste function was prospectively investigated with a questionnaire and a taste strip test (TST) preoperatively, 3-5 days and 1 year after stapes surgery with the preservation of CTN.

RESULTS

In the early postoperative examination, 34/42 patients had a lower TST score, 7/42 decrease of taste in the questionnaire. One year after surgery, 11/42 patients had a lower TST score, 1/42 patients decrease of taste in the questionnaire. The most pronounced decrease in the TST score was in sweet (- 1.76 points, p < 0.001), followed by bitter (- 1.71 points, p < 0.001), salty (- 1.64 points, p < 0.001) and sour taste (- 1.33 points, p < 0.001). The sour taste had a significant lower alteration compared to others. Men had significantly pronounced alteration in salty taste compared to women. The complete recovery was proved in bitter taste. Better recovery in bitter taste was observed in patients younger than 45 years of age.

CONCLUSIONS

Gustatory changes after stapes surgery are mostly transient with different impairment and recovery rate for particular taste qualities. A sour taste seems to be relatively resistant to damage. The best recovery rate is in a bitter taste, especially in younger patients.

Radiological and surgical aspects of round window visibility during cochlear implantation: a retrospective analysis

Purpose

The round window approach has become the most preferred option for cochlear implant (CI) insertion, however, sometimes it may not be possible due to the (in)visibility of the round window membrane (RWM). We addressed the prevalence, consequences and indicators of difficult detection of the RWM in cochlear implant surgery.

Methods

This study retrospectively analysed the operative reports and preoperative high resolution axial-computed tomography (CT) scans of a consecutive cohort of patients who underwent a CI insertion. The main outcomes were surgical outcomes of the RW approach, and assessment of radiological markers.

Results

The operative reports showed that RWM insertion was feasible in 151 out of 153 patients. In 18% of the patients the RWM was difficult to visualize. All these patients had at least one intraoperative event. The chorda tympani nerve (CTN) or posterior canal wall was affected in 8% of the 153 patients and the fallopian canal in 6%. These patients had a facial-chorda tympani nerve distance on the CT scan that was considerably smaller than normal patients (1.5 mm vs 2.3 mm). In addition, a prediction line towards the anterolateral side of the RWM was found to be more prevalent in these patients’ CT scans (sensitivity 81%, specificity 63%).

Conclusion

The RW approach is feasible in almost all patients undergoing CI surgery. Difficult visualisation of the RWM seems to lead to at least one intraoperative event. Radiological measures showed that these patients had a smaller facial recess and a more anteriorly placed facial nerve, which can be used to better plan a safe insertion approach.

'Black Bone' magnetic resonance imaging as a novel technique to aid the pre-operative planning of posterior tympanotomy for cochlear implantation

Purpose: 'Black Bone' magnetic resonance imaging (BB MRI) is a novel sequence developed as an alternative to computed tomography (CT) for osseous imaging. We explored its potential utilisation in the pre-operative surgical planning of posterior tympanotomy for cochlear implantation through depiction of the mastoid facial nerve (mFN) canal and the posterior canaliculus of the chorda tympani (ChT), thus defining the facial recess. Methods: Twenty five adult patients were prospectively imaged with a dedicated BB MRI sequence. A consensus qualitative BB MRI 'visibility score' for the confidence of demonstration of the mFN canal and the posterior canaliculus of the ChT was recorded, as well as a 'corresponding score' to determine whether the neural structures on BB MRI corresponded to the paths of the nerves on a previous CT study. Results/discussion: The BB MRI sequence was able to clearly delineate the course of mFN in 100% of cases and that of ChT in 72%, with their courses corresponding to those depicted on CT in almost all cases. Maximum intensity projections with 7 mm slabs provided the optimal simultaneous demonstration of mFN, ChT and round window along the posterior tympanotomy surgical approach. Conclusion: The proposed BB MRI sequence reliably depicts mFN and ChT in the majority of cases, with a performance comparable to that of CT. It is proposed that it will be a useful adjunct to MRI protocols as part of cochlear implant assessment in those centres where CT is not routinely performed.

Hedgehog Signaling Regulates Taste Organs and Oral Sensation: Distinctive Roles in the Epithelium, Stroma, and Innervation

The Hedgehog (Hh) pathway has regulatory roles in maintaining and restoring lingual taste organs, the papillae and taste buds, and taste sensation. Taste buds and taste nerve responses are eliminated if Hh signaling is genetically suppressed or pharmacologically inhibited, but regeneration can occur if signaling is reactivated within the lingual epithelium. Whereas Hh pathway disruption alters taste sensation, tactile and cold responses remain intact, indicating that Hh signaling is modality-specific in regulation of tongue sensation. However, although Hh regulation is essential in taste, the basic biology of pathway controls is not fully understood. With recent demonstrations that sonic hedgehog (Shh) is within both taste buds and the innervating ganglion neurons/nerve fibers, it is compelling to consider Hh signaling throughout the tongue and taste organ cell and tissue compartments. Distinctive signaling centers and niches are reviewed in taste papilla epithelium, taste buds, basal lamina, fibroblasts and lamellipodia, lingual nerves, and sensory ganglia. Several new roles for the innervation in lingual Hh signaling are proposed. Hh signaling within the lingual epithelium and an intact innervation each is necessary, but only together are sufficient to sustain and restore taste buds. Importantly, patients who use Hh pathway inhibiting drugs confront an altered chemosensory world with loss of taste buds and taste responses, intact lingual touch and cold sensation, and taste recovery after drug discontinuation.