Development of a feline model for preclinical research of a new translabyrinthine auditory nerve implant

Cochlear implants are among the most successful neural prosthetic devices to date but exhibit poor frequency selectivity and the inability to consistently activate apical (low frequency) spiral ganglion neurons. These issues can limit hearing performance in many cochlear implant patients, especially for understanding speech in noisy environments and in perceiving or appreciating more complex inputs such as music and multiple talkers. For cochlear implants, electrical current must pass through the bony wall of the cochlea, leading to widespread activation of auditory nerve fibers. Cochlear implants also cannot be implanted in some individuals with an obstruction or severe malformations of the cochlea. Alternatively, intraneural stimulation delivered via an auditory nerve implant could provide direct contact with neural fibers and thus reduce unwanted current spread. More confined current during stimulation can increase selectivity of frequency fiber activation. Furthermore, devices such as the Utah Slanted Electrode Array can provide access to the full cross section of the auditory nerve, including low frequency fibers that are difficult to reach using a cochlear implant. However, further scientific and preclinical research of these Utah Slanted Electrode Array devices is limited by the lack of a chronic large animal model for the auditory nerve implant, especially one that leverages an appropriate surgical approach relevant for human translation. This paper presents a newly developed transbullar translabyrinthine surgical approach for implanting the auditory nerve implant into the cat auditory nerve. In our first of a series of studies, we demonstrate a surgical approach in non-recovery experiments that enables implantation of the auditory nerve implant into the auditory nerve, without damaging the device and enabling effective activation of the auditory nerve fibers, as measured by electrode impedances and electrically evoked auditory brainstem responses. These positive results motivate performing future chronic cat studies to assess the long-term stability and function of these auditory nerve implant devices, as well as development of novel stimulation strategies that can be translated to human patients.

Middle Ear Cholesteatoma and Vestibular Schwannoma Resection Followed by Cochlear Implant: Surgical Challenges and Audiological Outcomes

(1) Background: The occurrence of vestibular schwannoma (VS) associated with cholesteatoma is rare. A hearing impairment is one of the most significant issues in such cases. Moreover, the presence of middle and inner ear pathologies combined may represent a surgical challenge. No studies have described a combined surgical approach for these coexisting conditions (VS and cholesteatoma), nor the hearing rehabilitation outcomes of using cochlear implants for these patients. (2) Case Report: This paper is on a female patient who underwent simultaneous surgical treatments for VS and middle ear cholesteatoma in the right ear followed by a cochlear implant, describing the technique and the audiological results. (3) Conclusions: The surgical approach was successful and enabled the resection of lesions with the auditory nerve and cochlea preservation. Cochlear implantation in the right ear showed positive postoperative results, with an improvement in the results with the CI in silent and noisy environments.

Two-Stage Surgical Management for Acutely Presented Large Vestibular Schwannomas: Report of Two Cases

The surgical management of vestibular schwannomas should be based on their presentation, neuro-imaging findings, surgeons' expertise, and logistics. Multi-stage surgery can be beneficial for large-sized lesions with acute presentations. Herein, we highlighted the indications for two cases managed initially through the retrosigmoid and, subsequently, translabyrinthine approaches. The first case presented with acute balance and gait issues and a long history of hearing loss and blurred vision. Neuroimaging findings revealed a cerebellopontine angle lesion, resembling a vestibular schwannoma, with significant brainstem compression and hydrocephalus. Due to the rapidly deteriorating clinical status and large-sized tumor, we first proceeded with urgent decompression via a retrosigmoid approach, followed by gross total resection via a translabyrinthine approach two weeks later. The second case presented with gradually worsening dizziness and hemifacial numbness accompanied by acute onset severe headaches and hearing loss. Neuroimaging findings showed a large cerebellopontine angle lesion suggestive of a vestibular schwannoma with acute intratumoral hemorrhage. Given the acute clinical deterioration and large size of the tumor, we performed urgent decompression with a retrosigmoid approach followed by gross total resection through a translabyrinthine approach a week later. Post-surgery, both patients showed excellent recovery. When managing acutely presented large-sized vestibular schwannomas, immediate surgical decompression is vital to avoid permanent neurological deficits.

A Rare Case of Pleomorphic Adenoma in the Internal Auditory Canal

Pleomorphic adenoma is a common tumor of the salivary gland tumor, but it is rare in the ear. To the authors' knowledge, this patient is the first reported case of pleomorphic adenoma arising in the internal auditory canal. There have been few documents reporting the manifestations and the therapy strategy of this disease. This study clearly demonstrated the experience in treating pleomorphic adenoma, including the characteristics of the clinical manifestation, the key procedures of surgery, and key points of the diagnosis. The translabyrinthine approach under the microscope performed to remove this tumor is a good option for resecting this type of tumor.

Early Outcomes of Simultaneous Translabyrinthine Resection and Cochlear Implantation

OBJECTIVES/HYPOTHESIS

Hearing rehabilitation after translabyrinthine resection of a vestibular schwannoma (VS) has largely been based on the transfer of acoustic stimulus to the contralateral ear, typically through a contralateral routing of signal hearing aid or bone-anchored hearing aid (BAHA). Cochlear implant, either as a subsequent surgery or simultaneously, has become a more common treatment option; however, there is still relatively limited data available on its success. The purpose of this study is to evaluate the early outcomes of simultaneous cochlear implantation in patients with sporadic VS undergoing translabyrinthine resection.

STUDY DESIGN

Prospective, nonrandomized study.

METHODS

A prospective study of nonrandomized patients was completed at a tertiary care neurotology center. Audiologic outcomes, primarily based on AzBIO in quiet and background noise, as well as consonant-nucleus-consonant (CNC) testing of the affected ears were utilized. Tinnitus, dizziness, and spatial hearing questionnaries were also completed. Audiologic outcomes and questionnaires were compared between the pre- and postoperative groups.

RESULTS

Ten patients were included in the study with 3 month follow-up data. There was statistically significant improvement in AzBO with +10 and +5 signal to noise ratio and in quiet, as well as in CNC testing (P < .05). There was a significant improvement in Tinnitus Handicap Inventory between the two groups.

CONCLUSIONS

Simultaneous cochlear implantation is a viable treatment for hearing loss after translabyrinthine approach to VS. These patients have improved hearing in background noise and tinnitus compared to their preoperative state. Further prognostic data are required to determine which patients are the best candidates.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E2312-E2317, 2021.

An investigation of life quality of patients after two different acoustic neuroma resections

Background: Patients may suffer postoperative facial nerve injury, hearing loss, or other postoperative complications after the operation, which seriously affect their postoperative life quality. Aims/objectives: To investigate the differences in QOL (quality of life) of patients with acoustic neuroma resection by the translabyrinthine or retrosigmoid approach. Material and methods: Patients with acoustic neuroma resection in our department were enrolled in this experimental study, among which fifty patients underwent the translabyrinthine approach resection, the other 50 patients underwent the retrosigmoid approach resection. Different scores by the SF-36 scale between these two groups of patients one month after discharge were then analyzed. Results: Scores of patients undergoing the retrosigmoid approach were higher in the three dimensions of Social Functioning, Role-emotional and Mental Health than those of patients undergoing the translabyrinthine approach with statistical significance. However, scores of patients undergoing the translabyrinthine approach were higher in the two dimensions of Body Pain and Vitality than those of the patients undergoing the retrosigmoid approach. Conclusions and significance: The results indicated that individual nursing interventions for different patients are necessary to improve the QOL of patients after hospitalization. Moreover, the operated patients with translabyrinthine approach were more advantage than patients with retrosigmoid approach.

Microsurgical Gross Total Resection of a Large Residual/Recurrent Vestibular Schwannoma via Translabyrinthine Approach

Although, gross total resection in large vestibular schwannomas is an ideal goal, subtotal resection is frequently performed due to lack of expertise, concerns for facial palsy, or overuse of stereotactic radiation. In this video, we present a 31-year-old man with a 7-year history of tinnitus, dizziness, and hearing loss. The patient had a subtotal resection of a 2.5 cm right-sided vestibular schwannoma via retrosigmoid craniotomy at an outside hospital. He was referred for further surgical resection due to the increased size of the tumor on surveillance magnetic resonance imagings (MRIs) and worsening symptoms. MRI showed a residual/recurrent large schwannoma with extension to the full length of the internal acoustic canal and brain stem compression. He underwent microsurgical gross total resection via a translabyrinthine approach. The facial nerve was preserved and stimulated with 0.15 mA at the brainstem entry zone. He awoke with House–Brackmann grade III facial function, with an otherwise uneventful postoperative course. In this video, microsurgical techniques and important resection steps for this residual/recurrent vestibular schwannoma are demonstrated, and nuances for microsurgical technique are discussed.

The link to the video can be found at: https://youtu.be/a0ZxE41Tqzw .

Hearing Preservation After Translabyrinthine Vestibular Schwannoma Excision: Audiometry and Electrocochleography Results

OBJECTIVES

To describe a case of inadvertent hearing preservation following a classical translabyrinthine resection of a vestibular schwannoma of the internal auditory canal in an otherwise healthy patient.

METHODS

Herein, we describe the case of an otherwise healthy patient who underwent resection of an intracanalicular vestibular schwannoma via a translabyrinthine approach. Furthermore, as part of an ongoing study aimed at characterizing hearing changes due to intraoperative events, cochlear hair cell and nerve activity were monitored using electrocochleography throughout surgery. Unexpectedly, the patient maintained serviceable hearing following surgery. As a result, we are able to provide electrophysiologic evidence of cochlear hair cell activity at various stages of this surgery.

RESULTS

Hair cell responses across tested frequencies were detectable prior to and following completion of the translabyrinthine procedure. Neural integrity of the auditory division of cranial nerve VIII was maintained throughout. Lastly, postoperative audiometric testing supported the patient's subjective assertion of serviceable hearing in the surgical ear.

CONCLUSION

Our results suggest that some degree of hair cell and neural integrity can be maintained throughout the course of the translabyrinthine approach, and if preservation of the auditory division of cranial nerve VIII is feasible, a functional amount of hearing preservation is attainable.

Revision Surgery for Vestibular Schwannomas

Objectives  To describe clinical outcomes of patients undergoing revision surgery for vestibular schwannomas. Design  Retrospective case series. Setting  Tertiary private neurotologic practice. Participants  Patients who underwent revision surgeries for recurrent/residual vestibular schwannomas between 1985 and 2015. Main Outcome Measures  Degree of resection, facial nerve function, cerebrospinal fluid (CSF) leak. Results  A total of 234 patients underwent 250 revision surgeries for recurrent/residual vestibular schwannomas. Of these, 86 carried a diagnosis of neurofibromatosis type 2 (NF2). The mean number of prior surgeries was 1.26, and 197 (85%) prior surgeries had been performed elsewhere. The average age at surgery was 43. The most common approach employed at the time of revision surgery was translabyrinthine (87%), followed by transcochlear (6%), middle fossa (5%), and retrosigmoid (2%). Gross total resection was achieved in 212 revision surgeries (85%). Preoperative House-Brackmann facial nerve function was similar in non-NF2 and NF2 groups (mean: 2.7). Mean postoperative facial nerve function at last follow-up was 3.8 in the non-NF2 group and 3.9 in the NF2 group. History of radiation and the extent of resection were not associated with differences in facial nerve function preoperatively or postoperatively. CSF leaks occurred after 21 surgeries (8%), and six (2%) patients required reoperation. Conclusions  This is the largest series of revision surgery for vestibular schwannomas to date. Our preferred approach is the translabyrinthine craniotomy, which can be readily modified to include the transcochlear approach for improved access. CSF leak rate slightly exceeds that of primary surgery, and gross total resection is achievable in the vast majority of patients.

Cadaveric Testing of Robot-Assisted Access to the Internal Auditory Canal for Vestibular Schwannoma Removal

HYPOTHESIS

An image-guided robotic system can safely perform the bulk removal of bone during the translabyrinthine approach to vestibular schwannoma (VS).

BACKGROUND

The translabyrinthine approach to VS removal involves extensive manual milling in the temporal bone to gain access to the internal auditory canal (IAC) for tumor resection. This bone removal is time consuming and challenging due to the presence of vital anatomy (e.g., facial nerve) embedded within the temporal bone. A robotic system can use preoperative imaging and segmentations to guide a surgical drill to remove a prescribed volume of bone, thereby preserving the surgeon for the more delicate work of opening the IAC and resecting the tumor.

METHODS

Fresh human cadaver heads were used in the experiments. For each trial, the desired bone resection volume was planned on a preoperative computed tomography (CT) image, the steps in the proposed clinical workflow were undertaken, and the robot was programmed to mill the specified volume. A postoperative CT scan was acquired for evaluation of the accuracy of the milled cavity and examination of vital anatomy.

RESULTS

In all experimental trials, the facial nerve and chorda tympani were preserved. The root mean squared surface accuracy of the milled cavities ranged from 0.23 to 0.65 mm and the milling time ranged from 32.7 to 57.0 minute.

CONCLUSION

This work shows feasibility of using a robot-assisted approach for VS removal surgery. Further testing and system improvements are necessary to enable clinical translation of this technology.

Simultaneous Translabyrinthine Tumor Removal and Cochlear Implantation in Vestibular Schwannoma Patients

Refinement of surgical techniques has allowed hearing preservation after tumor resection to be prioritized. Moreover, restoration of hearing after tumor removal can be attempted in patients with bilateral vestibular schwannomas or those with a schwannoma in the only-hearing ear. Cochlear implantation (CI) has emerged as a proper method of acoustic rehabilitation, provided that the cochlear nerve remains intact. Studies of electrical promontory stimulation in patients after vestibular schwannoma resection have demonstrated favorable results. We describe herein two cases of hearing rehabilitation via CI implemented at the time of vestibular schwannoma resection. Tumors were totally removed, and cochlear implant electrodes were successfully inserted in both cases. Also, post operative CI-aided hearing showed improved results.