Endoscopic Anatomy of the Chorda Tympani: Systematic Dissection, Novel Anatomic Classification, and Surgical Implications

Features and management of a schwannoma of the chorda tympani and review of the literature

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.

Recurrence of conductive hearing loss after stapes surgery: a narrative review

Among the functional failures of stapes surgery is recurrent conductive hearing loss, which can occur after a variable period of hearing improvement, from days/months up to many years after surgery. The most common cause of recurrent conductive hearing loss is prosthesis displacement, while fibrous adhesions or stapedotomy hole/oval window re-obliteration due to otosclerosis, occur less frequently. High resolution computed tomography plays an important role in the identification of the cause of hearing loss recurrence. Parallel to this, intra-operative exploration of the middle ear is crucial to confirm the cause of failure and address its treatment, possibly restoring hearing. While generally worse than after primary surgery, hearing outcomes after revision stapes surgery have improved thanks to advancements in pre-operative assessment, intra-operative view and technical refinements.

The utility and safety of diode laser in endoscopic stapes surgery

Objective

The advantages of laser stapedotomy are less trauma and more precise and minimally invasive techniques; however, the potential risk of overheating from the laser combined with the endoscope tip must be considered. This study aimed to assess the efficacy and safety of diode lasers for endoscopic stapes surgery.

Methods

A retrospective review of 56 patients with otosclerosis who underwent primary endoscopic stapedotomy with a diode laser from 2017 to 2020 was conducted. Demographic data, intraoperative findings, preoperative and postoperative audiological assessments, and postoperative complications were analyzed.

Results

There was no statistically significant difference between the preoperative and postoperative bone conduction thresholds. The mean postoperative air-bone gap (ABG) improved significantly compared to the preoperative ABG (4.07 vs. 35.43 dB, p < .001). The postoperative ABG closure within 10 dB at 6 and 12 months was achieved in 87.50% and 91.07% of patients, respectively. The postoperative pain scores at 4 and 24 h were 2.55 and 0.39, respectively. Immediate postoperative vertigo was reported in 12.50% of patients, with 100% complete recovery 2 months after surgery. The chorda tympani nerve was preserved in all the cases. Postoperative taste disturbances at 2 and 12 months were observed in 17.86% and 1.79% of patients, respectively.

Conclusion

The diode laser in endoscopic stapedotomy is a safe and effective technique that provides satisfactory hearing outcomes. Temporary taste disturbances during the early postoperative period are a concern. The handheld diode laser delivery system is suitable for an endoscopic approach and is an alternative armamentarium for the treatment of otosclerosis. Level of evidence: IV.

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

PURPOSE

The goal of the present study was to compare the audiologic results, complications, and advantages/disadvantages of endoscopic and microscopic stapedotomy.

METHODS

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 4000 Hz pre- and postoperatively at 1, 3, and 6 months, and the mean (± SD) air-bone gap value was recorded.

RESULTS

While the mean pre- and postoperative air-bone gaps were 34.38 ± 7.47 dB (23-53 dB) and 9.69 ± 4.43 dB (0-19 dB), respectively, in group I, 34.32 ± 7.57 dB (23-6 dB) and 9.62 ± 4.25 dB (2-23 dB) 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 ± 4.37 min and 63.70 ± 7.34 min, 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).

CONCLUSION

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.

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.

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

Objective

Methods

Results

Conclusion

Level of Evidence

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.