Continuous dynamic mapping to avoid accidental injury of the facial nerve during surgery for large vestibular schwannomas

Abstract Background Cerebellopontine angle (CPA) surgery carries the risk of lesioning the facial nerve. The goal of preserving the integrity of the facial nerve is usually pursued with intermittent electrical stimulation using a handheld probe that is alternated with the resection. We report our experience with continuous electrical stimulation delivered via the ultrasonic aspirator (UA) used for the resection of a series of vestibular schwannomas. Methods A total of 17 patients with vestibular schwannomas, operated on between 2010 and 2018, were included in this study. A constant-current stimulator was coupled to the UA used for the resection, delivering square-wave pulses throughout the resection. The muscle responses from upper and lower face muscles triggered by the electrical stimulation were displayed continuously on multichannel neurophysiologic equipment. The careful titration of the electrical stimulation delivered through the UA while tapering the current intensity with the progression of the resection was used as the main strategy. Results All operations were performed successfully, and facial nerve conduction was maintained in all patients except one, in whom a permanent lesion of the facial nerve followed a miscommunication to the neurosurgeon. Conclusion The coupling of the electrical stimulation to the UA provided the neurosurgeon with an efficient and cost-effective tool and allowed a safe resection. Positive responses were obtained from the facial muscles with low current intensity (lowest intensity: 0.1 mA). The availability of a resection tool paired with a stimulator allowed the surgeon to improve the surgical workflow because fewer interruptions were necessary to stimulate the facial nerve via a handheld probe.

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Sensitivity and Negative Predictive Value of Motor Evoked Potentials of the Facial Nerve

Journal of Neurological Surgery Part A Central European Neurosurgery ◽

10.1055/s-0040-1719026 ◽

2021 ◽

Author(s):

Nicolas Bovo ◽

Shahan Momjian ◽

Renato Gondar ◽

Philippe Bijlenga ◽

Karl Schaller ◽

...

Keyword(s):

Facial Nerve ◽

Evoked Potentials ◽

Negative Predictive Value ◽

Patient Group ◽

Vestibular Schwannoma ◽

Predictive Value ◽

Cerebellopontine Angle ◽

Motor Evoked Potentials ◽

Vestibular Schwannomas ◽

Predictive Values

Abstract Objective The objective of this study was to determine the performance of the standard alarm criterion of motor evoked potentials (MEPs) of the facial nerve in surgeries performed for resections of vestibular schwannomas or of other lesions of the cerebellopontine angle. Methods This retrospective study included 33 patients (16 with vestibular schwannomas and 17 with other lesions) who underwent the resection surgery with transcranial MEPs of the facial nerve. A reproducible 50% decrease in MEP amplitude, resistant to a 10% increase in stimulation intensity, was applied as the alarm criterion during surgery. Facial muscular function was clinically evaluated with the House–Brackmann score (HBS), pre- and postsurgery at 3 months. Results In the patient group with vestibular schwannoma, postoperatively, the highest sensitivity and negative predictive values were found for a 30% decrease in MEP amplitude, that is, a criterion stricter than the 50% decrease in MEP amplitude criterion, prone to trigger more warnings, used intraoperatively. With this new criterion, the sensitivity would be 88.9% and the negative predictive value would be 85.7%. In the patient group with other lesions of the cerebellopontine angle, the highest sensitivity and negative predictive values were found equally for 50, 60, or 70% decrease in MEP amplitude. With these criteria, the sensitivities and the negative predictive values would be 100.0%. Conclusion Different alarm criteria were found for surgeries for vestibular schwannomas and for other lesions of the cerebellopontine angle. The study consolidates the stricter alarm criterion, that is, a criterion prone to trigger early warnings, as found previously by others for vestibular schwannoma surgeries (30% decrease in MEP amplitude).

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The Anatomical Location and Course of the Facial Nerve in Vestibular Schwannomas : A Study of 163 Surgically Treated Cases

Journal of Korean Neurosurgical Society ◽

10.3340/jkns.2007.42.6.450 ◽

2007 ◽

Vol 42 (6) ◽

pp. 450 ◽

Cited By ~ 8

Author(s):

Chae Wan Bae ◽

Young Hyun Cho ◽

Seok Ho Hong ◽

Jeong Hoon Kim ◽

Jung-kyo Lee ◽

...

Keyword(s):

Facial Nerve ◽

Vestibular Schwannomas ◽

Anatomical Location

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Preservation of Hearing and Facial Nerve Function with the Microsurgical Excision of Large Vestibular Schwannomas: Experience with the Retrosigmoid Approach

Cureus ◽

10.7759/cureus.3684 ◽

2018 ◽

Author(s):

Muhammad Shaheryar Ahmed Rajput ◽

Ahmad Nawaz Ahmad ◽

Asif Ali Arain ◽

Mohammad Adeel ◽

Saeed Akram ◽

...

Keyword(s):

Facial Nerve ◽

Retrosigmoid Approach ◽

Vestibular Schwannomas ◽

Nerve Function ◽

Facial Nerve Function

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Continuous Dynamic Mapping of the Corticospinal Tract in Motor Eloquent Tumor Surgery: Our Experience and Evaluation of the Method

Acta Medica Academica ◽

10.5644/ama2006-124.308 ◽

2021 ◽

Vol 49 (1, 2, 3) ◽

pp. 63

Author(s):

Andrej Porčnik ◽

Jure Pešak ◽

Tilen Žele ◽

Blaž Koritnik ◽

Zoran Rodi ◽

...

Keyword(s):

Corticospinal Tract ◽

Cortical Stimulation ◽

Gross Total Resection ◽

Motor Deficit ◽

Total Resection ◽

Direct Cortical Stimulation ◽

Dynamic Mapping ◽

Combined Use ◽

Eloquent Tumor ◽

Continuous Dynamic

Objective. The aim of this article is to present our experience with continuous dynamic mapping (CDM) of the corticospinal tract (CST) when removing tumors in motor eloquent regions.Methods. We studied 44 patients with a brain tumor adjacent to the CST where CDM was used. The mapping probe was integrated at the tip of the suction device. Thresholds for eliciting MEPs were recorded. In all patients, along with CDM, MEPs to direct cortical stimulation were also monitored throughout the operation. Motor function was assessed preoperatively, after the procedure and on discharge.Results. In the series, there were 37 patients with gliomas, six with brain metastasis, and one with cavernoma. The threshold to elicit MEPs in CDM was >20 mA in 17 cases, 16–20 mA in six cases, 11–15 mA in six cases, 6–10 mA in nine cases and 2–5 mA in six cases. MEPs to direct cortical stimulation were preserved in all patients. In three cases a new temporary motor deficit was noted. No new permanent motor deficit occurred. Gross total resection was reached in 57% of cases.Conclusions. From our experience, the combined use of CDM and MEPs to direct cortical stimulation improves the safety of surgery in the proximity of the CST, and at the same time offers the possibility of higher rates of gross total resection.

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Translabyrinthine microsurgical resection of small vestibular schwannomas

Journal of Neurosurgery ◽

10.3171/2017.2.jns162287 ◽

2018 ◽

Vol 129 (1) ◽

pp. 128-136 ◽

Cited By ~ 12

Author(s):

Marc S. Schwartz ◽

Gregory P. Lekovic ◽

Mia E. Miller ◽

William H. Slattery ◽

Eric P. Wilkinson

Keyword(s):

Facial Nerve ◽

Vestibular Schwannoma ◽

Sinus Thrombosis ◽

Treatment Options ◽

Previous Treatment ◽

Cerebrospinal Fluid Leak ◽

Neurofibromatosis Type ◽

Additional Treatment ◽

Vestibular Schwannomas ◽

Tumor Control

OBJECTIVETranslabyrinthine resection is one of a number of treatment options available to patients with vestibular schwannomas. Though this procedure is hearing destructive, the authors have noted excellent clinical outcomes for patients with small tumors. The authors review their experience at a tertiary acoustic neuroma referral center in using the translabyrinthine approach to resect small vestibular schwannomas. All operations were performed by a surgical team consisting of a single neurosurgeon and 1 of 7 neurotologists.METHODSData from a prospectively maintained clinical database were extracted and reviewed. Consecutive patients with a preoperative diagnosis of vestibular schwannoma that had less than 1 cm of extension into the cerebellopontine angle, operated on between 2008 and 2013, were included. Patents with neurofibromatosis Type 2, previous treatment, or preexisting facial weakness were excluded. In total, 107 patients were identified, 74.7% of whom had poor hearing preoperatively.RESULTSPathologically, 6.5% of patients were found to have a tumor other than vestibular schwannoma. Excluding two malignancies, the tumor control rates were 98.7%, as defined by absence of radiographic disease, and 99.0%, as defined by no need for additional treatment. Facial nerve outcome was normal (House-Brackmann Grade I) in 97.2% of patients and good (House-Brackmann Grade I–II) in 99.1%. Complications were cerebrospinal fluid leak (4.7%) and sigmoid sinus thrombosis (0.9%), none of which led to long-term sequelae.CONCLUSIONSTranslabyrinthine resection of small vestibular schwannomas provides excellent results in terms of complication avoidance, tumor control, and facial nerve outcomes. This is a hearing-destructive operation that is advocated for selected patients.

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