Intraoperative cochlear nerve mapping with the mobile cochlear nerve compound action potential tracer in vestibular schwannoma surgery

Abstract

OBJECTIVE The authors describe the usefulness and limitations of the cochlear nerve compound action potential (CNAP) mobile tracer (MCT) that they developed to aid in cochlear nerve mapping during vestibular schwannoma surgery (VSS) for hearing preservation. METHODS This MCT device requires no more than 2 seconds for stable placement on the nerve to obtain the CNAP and thus is able to trace the cochlear nerve instantaneously. Simultaneous bipolar and monopolar recording is possible. The authors present the outcomes of 18 consecutive patients who underwent preoperative useful hearing (defined as class I or II of the Gardner-Robertson classification system) and underwent hearing-preservation VSS with the use of the MCT. Mapping was considered successful when it was possible to detect and trace the cochlear nerve. RESULTS Mapping of the cochlear nerve was successful in 13 of 18 patients (72.2%), and useful hearing was preserved in 11 patients (61.1%). Among 8 patients with large tumors (Koos grade 3 or 4), the rate of successful mapping was 62.5% (5 patients). The rate of hearing preservation in patients with large tumors was 50% (4 patients). CONCLUSIONS In addition to microsurgical presumption of the arrangement of each nerve, frequent probing on and around an unidentified nerve and comparison of each waveform are advisable with the use of both more sensitive monopolar and more location-specific bipolar MCT. MCT proved to be useful in cochlear nerve mapping and may consequently be helpful in hearing preservation. The authors discuss some limitations and problems with this device.

Gross-total versus near-total resection of large vestibular schwannomas. An institutional experience

“…In recent years, numerous studies have reported a significant decrease in the number of large VSs (Koos grade IV). The recent reported incidence is between 2% and 12.5% [ 10 , 16 , 28 ]. This is most likely due to an increase in early diagnoses [ 2 , 4 , 19 , 32 , 33 , 34 , 35 ].…”

“…The patients in our study were a retrospective sample who underwent operations on Koos grade IV VSs between January 2007 and December 2015 in the Department of Neurosurgery, Emergency County Hospital, Târgu Mureş, Romania. To quantify risk and predict the surgical outcome, we chose the Koos grading system, as previous research has proven its validity [ 4 , 26 , 27 , 28 ].…”

Letter: Postoperative Hearing Preservation in Patients Undergoing Retrosigmoid Craniotomy for Resection of Vestibular Schwannomas: A Systematic Review of 2034 Patients

“…Recently, intraoperative adjunctive with cochlear mapping with the mobile cochlear nerve compound action potential tracer in VS surgery has been also suggested 20 . While this device might be useful in cochlear nerve mapping and consequently help in hearing preservation, it has also several limitations.…”

Soft and stretchable organic bioelectronics for continuous intra-operative neurophysiological monitoring during microsurgery

“…Although new developments based on thin metal wires have been attempted 18,19 , none of the existing probes can maintain stable and reliable recording during routine neurosurgical manipulations, as they inevitably are subjected to tugging, displacing, and bending motions. To address the limitations of current CINM devices 14,18,19,22 , we developed a biomechanically compatible, suture-free, and individually reconfigurable CINM based on soft and stretchable organic bioelectronic devices (Fig. S1).…”

“…However, these far-field signals are typically weak, requiring long-time acquisition and summation to achieve discernable signal-to-noise ratios. As a result, far-field potential recording itself is insufficient to provide high-quality physiological monitoring in real time [14][15][16] . In addition, many tumor-bearing patients already have considerable pre-operative neurological symptoms, which further lower the source neural signals.…”