Letter to the Editor: Save the nerve

MRI surveillance after translabyrinthine vestibular schwannoma resection and cochlear implantation: is it feasible?

PURPOSE

Cochlear implantation in patients with vestibular schwannomas is of increasing importance and interest. Two remaining challenges are the assessment of conduction of the cochlear nerve and the possibility of postoperative surveillance with magnetic resonance imaging. The aim of the current study was to assess follow-up imaging and determine the visibility of the internal auditory canal after vestibular schwannoma resection and cochlear implantation as well as in patients with persistent vestibular schwannomas and cochlear implants in place. Visibility of the internal auditory canal, cerebellopontine angle, and labyrinth were evaluated and graded.

METHODS

For this retrospective study, 15 MR examinations of 13 patients after translabyrinthine vestibular schwannoma resection and ipsilateral cochlear implantation were included. All patients had been implanted with an MED-EL cochlear implant. Magnetic resonance imaging was carried out on a 1.5T device. All patients were prepped according to the manufacturer's recommendations.

RESULTS

All 15 examinations were carried out without any adverse event during imaging, such as pain, magnet dislocation, or malfunction. The internal auditory canal and the cerebellopontine angle were sufficiently visible in all cases to allow for vestibular schwannoma follow-up.

CONCLUSION

Magnetic resonance imaging surveillance of the internal auditory canal following vestibular schwannoma resection and cochlear implantation is feasible and safe with modern implants with a 1.5T magnetic resonance imaging device using metal artifact reduction sequences. Necessary follow-up imaging should not be a contraindication for cochlear implantation in patients with vestibular schwannomas.

A consensus definition of supratotal resection for anatomically distinct primary glioblastoma: an AANS/CNS Section on Tumors survey of neurosurgical oncologists

INTRODUCTION

Supratotal resection (SpTR) of glioblastoma may be associated with improved survival, but published results have varied in part from lack of consensus on the definition and appropriate use of SpTR. A previous small survey of neurosurgical oncologists with expertise performing SpTR found resection 1-2 cm beyond contrast enhancement was an acceptable definition and glioblastoma involving the right frontal and bilateral anterior temporal lobes were considered most amenable to SpTR. The general neurosurgical oncology community has not yet confirmed the practicality of this definition.

METHODS

Seventy-six neurosurgical oncology members of the AANS/CNS Tumor Section were surveyed, representing 34.0% of the 223 members who were administered the survey. Participants were presented with 11 definitions of SpTR and rated each definition's appropriateness. Participants additionally reviewed magnetic resonance imaging for 10 anatomically distinct glioblastomas and assessed the tumor location's eloquence, perceived equipoise of enrolling patients in a randomized trial comparing gross total to SpTR, and their personal treatment plans.

RESULTS

Most neurosurgeons surveyed agree that gross total plus resection of some non-contrast enhancement (n = 57, 80.3%) or resection 1-2 cm beyond contrast enhancement (n = 52, 73.2%) are appropriate definitions for SpTR. Cases were divided into three anatomically distinct groups by perceived equipoise between gross total and SpTR. The best clinical trial candidates were thought to be right anterior temporal (n = 58, 76.3%) and right frontal (n = 55, 73.3%) glioblastomas.

CONCLUSION

Support exists among neurosurgical oncologists with varying familiarity performing SpTR to adopt the proposed consensus definition of SpTR of glioblastoma and to potentially investigate the utility of SpTR to treat right anterior temporal and right frontal glioblastomas in a clinical trial. A smaller proportion of general neurosurgical oncologists than SpTR experts would personally treat a left anterior temporal glioblastoma with SpTR.

Medial Acoustic Tumors: Special Considerations: 2-Dimensional Operative Video

Medial acoustic tumors are a rare distinct type of vestibular schwannoma having distinguished clinical and radiological features.1 Originating medially in the cerebellopontine angle without extending into the lateral internal auditory meatus, they are frequently giant in size at presentation in younger patients with a relatively preserved hearing, while they have other neurological deficits from cerebellar or brainstem compression and associated hydrocephalus. Imaging typically shows a cystic tumor with local mass effect and an internal auditory canal filled with cerebrospinal fluid.1,2 Surgical resection of theses schwannoma is particularly challenging not only due to their size and hypervascularity, but also given their particular arachnoidal rearrangement inducing marked adherence to the brainstem and facial nerve.2  The treatment is surgical resection, despite, however, their giant size hearing preservation should be sought and is attainable.1-5 Transmastoid approach with squeletonization and reflection of the transverse sigmoid sinus provides lateral exposure avoiding cerebellar retraction.6 In this report, we demonstrate the specific surgical considerations applied to the resection of a giant medial acoustic tumor in a 40-yr-old patient presenting with ataxia, vertigo, facial paresthesia, and intact hearing. The patient agreed to the surgery and photography.  Image at 1:44 © Ossama Al-Mefty, used with permission; Image at 8:21 from Dunn et al,2 used with permission from JNSPG.

"Save the Nerve": Technical Nuances for Hearing Preservation and Restoration in Vestibular Schwannoma Surgery: 2-Dimensional Operative Video

Hearing loss is a significant disability that inflects dysfunction and affects the patient quality of life. Consequently, hearing preservation and the potential of hearing restoration are prized quests in the management of vestibular schwannoma.1 Although small intracanalicular vestibular schwannomas are commonly observed, progressive hearing loss occurs despite the absence of tumor growth; hence, surgical resection can be performed with the sole aim of hearing preservation in well-informed and eager patients. Hearing preservation by surgical resection has proven to be durable.1-4 In this group of patients, we concur with Yamakami et al2 that vascularized meatal flap to reconstruct the canal helps prevent scarring of the cochlear nerve and provides cerebrospinal fluid (CSF) bathing to the cochlear nerve, yielding better long-term hearing preservation.  With larger tumors and more severe hearing loss at presentation, microsurgical resection should aim at preserving the cochlear nerve, a goal frequently achievable, which offers the potential for hearing restoration with cochlear implants.3 The results of cochlear implants in restoration of severe hearing loss have been to say the least most impressive.5 We demonstrate these 2 frequently encountered clinical situations with 2 surgical videos showing specific surgical tenets, including intra-arachnoidal dissection, medial to lateral manipulation of the tumor, preservation of the labyrinthine artery, as well as reconstruction of the internal auditory canal.2,3,6,7 The patients consented to the surgery and to the publication of their picture in a surgical video.  Illustration in video © 1997 O. Al-Mefty. Used with permission. All rights reserved.

Long-term outcome after Gamma Knife radiosurgery for acoustic neuroma of all Koos grades: a single-center study

OBJECTIVE

The authors present long-term follow-up data on patients treated with Gamma Knife radiosurgery (GKRS) for acoustic neuroma.

METHODS

Six hundred eighteen patients were radiosurgically treated for acoustic neuroma between 1992 and 2016 at the Department of Neurosurgery, Medical University Vienna. Patients with neurofibromatosis and patients treated too recently to attain 1 year of follow-up were excluded from this retrospective study. Thus, data on 557 patients with spontaneous acoustic neuroma of any Koos grade are presented, as are long-term follow-up data on 426 patients with a minimum follow-up of 2 years. Patients were assessed according to the Gardner-Robertson (GR) hearing scale and the House-Brackmann facial nerve function scale, both prior to GKRS and at the times of follow-up.

RESULTS

Four hundred fifty-two patients (81%) were treated with radiosurgery alone and 105 patients (19%) with combined microsurgery-radiosurgery. While the combined treatment was especially favored before 2002, the percentage of cases treated with radiosurgery alone has significantly increased since then. The overall complication rate after GKRS was low and has declined significantly in the last decade. The risk of developing hydrocephalus after GKRS increased with tumor size. One case (0.2%) of malignant transformation after GKRS was diagnosed. Radiological tumor control rates of 92%, 91%, and 91% at 5, 10, and 15 years after GKRS, regardless of the Koos grade or pretreatment, were observed. The overall tumor control rate without the need for additional treatment was even higher at 98%. At the last follow-up, functional hearing was preserved in 55% of patients who had been classified with GR hearing class I or II prior to GKRS. Hearing preservation rates of 53%, 34%, and 34% at 5, 10, and 15 years after GKRS were observed. The multivariate regression model revealed that the GR hearing class prior to GKRS and the median dose to the cochlea were independent predictors of the GR class at follow-up.

CONCLUSIONS

In small to medium-sized spontaneous acoustic neuromas, radiosurgery should be recognized as the primary treatment at an early stage. Although minimizing the cochlear dose seems beneficial for hearing preservation, the authors, like others before, do not recommend undertreating intracanalicular tumors in favor of low cochlear doses. For larger acoustic neuromas, radiosurgery remains a reliable management option with tumor control rates similar to those for smaller acoustic neuromas; however, careful patient selection and counseling are recommended given the higher risk of side effects. Microsurgery must be considered in acoustic neuromas with significant brainstem compression or hydrocephalus.

Simultaneous cochlear implantation as a therapeutic option in vestibular schwannoma surgery: case report

Hearing loss is the most common symptom of vestibular schwannomas (VSs). The management of these lesions includes observation, radiosurgery, and microsurgical resection. Hearing preservation and rehabilitation are the major challenges after the tumor treatment. A 43-year-old man with previous left-sided profound hearing loss and tinnitus presented with a 2-mm left-sided intracanalicular VS. The decision was made to perform a simultaneous cochlear implantation (CI) and microsurgical resection of the tumor. The patient did well postoperatively, with significant improvement of tinnitus, sound localization, and speech recognition in noise. Previous reports of simultaneous CI and VS resection in patients with neurofibromatosis type 2 and sporadic VS in the only hearing ear have been described. The role of CI in patients with VS and normal contralateral hearing has been recently described, showing positive outcomes due to the binaural benefits. Tinnitus also can be treated by the implantation of the cochlear device. The simultaneous microsurgical removal of VS and implantation of a cochlear device is a feasible approach in patients with unilateral hearing loss and severe tinnitus.