Neurosurgical Review. CE-Chirp ABR in cerebellopontine angle surgery neuromonitoring: technical assessment in four cases.

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1 CE-Chirp ABR in cerebellopontine angle surgery neuromonitoring: technical assessment in four cases. Journal: Neurosurgical Review Manuscript ID: Draft Manuscript Type: Case Report Date Submitted by the Author: n/a Complete List of Authors: Di Scipio, Ettore; San Filippo Neri, Dep. of Neurology - Neurophysiology Mastronardi, Luciano; Dep. of Neurosurgery, San Filippo Neri Hospital Keywords: CE Chirp,, ABR, BAEP s, intraoperative neuromonitoring, cochlear nerve, CPA surgery

2 Page of Neurosurgical Review 0 0 TITLE PAGE CE-Chirp ABR in cerebellopontine angle surgery neuromonitoring: technical assessment in four cases. Authors: Ettore Di Scipio, Luciano Mastronardi. Ettore Di Scipio, MD - Neurophysiopathology Unit - San Filippo Neri Hospital - Via Martinotti 0, Rome Italy. Luciano Mastronardi, MD, PhD Chief of Neurosurgery Dep. - San Filippo Neri Hospital - Via Martinotti 0, Rome Italy Corresponding Author: Luciano Mastronardi, MD, PhD Via Reno, 00, Roma mastro@tin.it Phone: +0 Fax: +0 KEYWORDS CE Chirp, ABR, BAEP s, intraoperative neuromonitoring, cochlear nerve, CPA surgery. Acknowledgments: We express our sincere thanks to Laura Conti, Director of Unit of Neurophysiopathology of San Filippo Neri Hospital in Rome and to Nicola Stiacci, LeDiSo Italia srl, via Panciatichi, Firenze, Italian distriboutor of Interacoustics Eclipse EP ABR system, for tireless, comprehensive support. Disclosures: There is no conflict of interest nor financial support.

3 Page of CE-Chirp ABR in cerebellopontine angle surgery neuromonitoring: technical assessment in four cases. Ettore Di Scipio, MD*; Luciano Mastronardi, MD *Neurophysiopathology Unit - San Filippo Neri Hospital - Via Martinotti 0, Rome - Italy 0 Director, Neurosurgery Unit - San Filippo Neri Hospital - Via Martinotti 0, Rome Italy Corrispondence to: mastro@tin.it ABSTRACT Background: Continuous monitoring of wave V of Auditory Brainstem Response (ABR), also called Brainstem Auditory Evoked Potential (BAEP s), is the most common method used in intraoperative neuromonitoring (IONM) functionality of cochlear nerve during surgery in 0 cerebellopontine angle (CPA). CE-Chirp ABR represent a recent development of classical ABR. CE-Chirp is a new acoustic stimulus used in newborns hearing testing, designed to provide enhanced neural synchronicity and faster detection of larger amplitude wave V. Methods: In four cases CE-Chirp ABR were performed during cerebellopontine angle (CPA) surgery. Results: CE-Chirp ABR represented a safe and effective method in neuromonitoring functionality of vestiboulocochlear nerve. Conclusions: A faster neuromonitoring feedback to surgical equipe was possible with CE-Chirp ABR. KEYWORDS CE Chirp, ABR, BAEP s, intraoperative neuromonitoring, cochlear nerve, CPA surgery. INTRODUCTION The aim of this technical report is to suggest the possible use of CE-Chirp ABR in intraoperative neuromonitoring during CPA surgery (CPA tumors, trigeminal neuralgia, hemifacial spasm). CE-Chirp acoustic stimulus, developed by Claus Elberling, has the same spectrum and the same calibration as a usual square wave click stimulus (Fig ). Acoustic energy from the CE-Chirp stimulus reaches all regions of the cochlea at approximately the same time []. The difference lies in the presentation timing of the low, mid and high frequency components of acoustic stimuli. This change in the stimulus presentation offsets the mechanics of the cochlea s traveling wave and results in an auditory brainstem response waveform of increased amplitude than the corresponding click ABR in normal hearing subjects []. METHOD Subjects talanffy, Direktor - Zentrum für Vaskuläre Neurochirurgie, International Neuroscience Institute - Hannover, Rudolf-Pichlmayr-Str

4 Page of Neurosurgical Review Four patients were examined (one male and three females, mean age years, range - ) during CPA surgery. The male patient had a mm (maximum diameter) vestibular schwannoma, with mild hypoacusia (AAO-HNS A). All females patients underwent surgery for trigeminal neuralgia. For all subjects, clinical and strumental examinations were performed to identify existing conditions that would preclude ABR testing. All patients underwent a previous screening for classical ABR and CE-Chirp ABR in outpatients 0 setting, in order to evaluate which was the best parameters (acoustic level and frequency of stimulation) giving clear and monitorable waves V. ABR s neuromonitoring: Both classical ABR and CE-Chirp ABR neuromonitoring were recorded with Interacoustics Eclipse EP ABR system. Classical ABR recording were performed in common way: Surface electrodes were placed at the vertex (Cz) and on each earlobe (A and A). 0 Filters bandwidth was Hz, khz. Two channels were used: : A Cz; : A Cz CE-Chirp ABR were recorded with the same channels scheme. Stimulation: Stimulation was performed by M E-A-RTone Gold A insert earphones, for both classical ABR and CE-Chirp ABR. Stimuli were presented with alternate polarity at, Hz for classical ABR and at, Hz for CE- Chirp ABR. Classical ABR can be performed, in neuromonitoring, at faster rates (usually at Hz) and CE-Chirp ABR can be recorded also at 0 Hz with no substantial changes in results. Nevertheless, in this study, the above presented rates of stimulation were used, in order to evitate possibly waves distortions. Sound pressure ranged between 0 to db nhl for classical ABR and to 0 db nhl for CE- Chirp ABR, choosing the sound pressure level giving the clearest wave V. Controlateral ears was masked by white noise at db nhl. Time analysis was 0 seconds per sweep. All patients had preoperative ABR and CE-Chirp ABR trials in holding area, after general anesthesia and before surgical procedure, in order to have a clear baseline result. The same presurgical parameters of stimulation were mantained during the CPA surgery. During the operation, on surgeon s demand, one or two series of acoustic stimuli for classical ABR were sent and, if potentials were stable, one or two series of 0-00 stimuli for CE- Chirp ABR were also performed, in order to evaluate which was the fastest and accurate neuromonitoring feedback to surgical equipe. RESULTS Classical ABR needed series of about 000 stimuli, in all patients, to evoke a clear and monitorable V-wave (Fig ). Using CE-Chirp ABR, a series of about 0 stimuli was sufficient, in all patients, talanffy, Direktor - Zentrum für Vaskuläre Neurochirurgie, International Neuroscience Institute - Hannover, Rudolf-Pichlmayr-Str

5 Page of to evoke a clear V-wave. For both classical ABR and CE-Chirp ABR more stimuli did not modify in a significative way morphology of V-waves. Sound pressure of db nhl evoked very clear V-waves in all patients using CE Chirp stimulation (Fig. ). 0 Classical ABR and CE-Chirp ABR monitoring showed stable V-waves morphology, at the same values of presurgical baseline, from the beginning to the end of surgery, in patients with trigeminal neuralgia. In the case with vestibular schwannoma, classical ABRs and CE-Chirp ABRs were stable until the direct approach to schwannoma. Then a sudden loss of classical ABR underwent. Also CE- Chirp ABR were not evocable after classical ABR loss. Controlateral classical ABR and CE- Chirp ABR were recordable after omolateral ABR loss. 0 DISCUSSION CE-Chirp ABR represent a safe method in neuromonitoring functionality of vestiboulocochlear nerve. In fact, CE-Chirp ABR was developed and used in newborns hearing testing by pediatric audiologists []. This first experiences confirmed that CE-Chirp ABR can evoke more clear and larger V-wave than classical ABR, especially with low-intensity stimuli []. This allows to obtain V-wave standing out clearly from baseline, without artifacts induced by overstimulation, even if with longer latency. Anyway, this last issue is not relevant in intraoperative neuromonitoring, being the changes in latency or the amplitude from baseline the most important parameters, as the patient acts as his own control []. CE-Chirp ABR V-wave also showed a more clear morphology, without shoulders in IV-V waves complex, common finding in classical ABR. This can allow an easiest detection of V-wave in doubtful cases. This study also confirmed that CE-Chirp ABR in neuromonitoring can be performed up to four times faster than classical ABR, because they need a reduced numbers of stimulations at the double frequency. This is very useful in intraoperative neuromonitoring. One of the problems reported from neurosurgeons in CPA surgery is the lack of fast alerts in neuromonitoring functionality of vestibulocochlear nerve with classical ABR. With CE-Chirp ABR neurophysiologyst can be able to inform neurosurgical equipe in -0 seconds about possible variations of V-wave parameters. Classical ABR and CE-Chirp ABR sudden loss in our patient with vestiboular schwannoma was likely due to lack of vascular supply by internal auditory artery or possible thermal damage. Persistence of controlateral ABR confirmed that loss was not imputable to tecnichal problems. CE-Chirp ABR are not so useful to detect others waves than wave V, because CE-Chirp stimulus was designed to enhance V-wave. CONCLUSIONS The present report provides the first description of usefulness of faster neuromonitoring of vestibulocochlear nerve during surgery in cerebellopontine angle using CE Chirp ABR. talanffy, Direktor - Zentrum für Vaskuläre Neurochirurgie, International Neuroscience Institute - Hannover, Rudolf-Pichlmayr-Str

6 Page of Neurosurgical Review Obviously, more systematic trials and studies are necessary to confirm this first experience. Implementation of CE Chirp stimuli in neuromonitoring equipment in the next future is desirable. Acknowledgments. 0 We express our sincere thanks to Laura Conti, Director of Unit of Neurophysiopathology of San Filippo Neri Hospital in Rome and to Nicola Stiacci, LeDiSo Italia srl, via Panciatichi, Firenze, Italian distriboutor of Interacoustics Eclipse EP ABR system, for tireless, comprehensive support. Conflict of interest There is no conflict of interest nor financial support. Figures 0 Fig : Click and CE-Chirp spectrum Fig : Classical ABR Fig : CE-Chirp ABR at different db. REFERENCES ) Aatif M. Usain F (00). A practical approach to neurophysiologic intraoperative monitoring 00 Demos Medical Publishing - New York ) Cebulla M, Lurz H, Shehata-Dieter W (0). Evaluaton of waveform, latency and amplitude values of chirp ABR in newborns. Int J Pediatr Otorhinolaryngol ():- ) Dau T, Wagner O, Mellert V, and Kollmeier B (000). Auditory Brainstem Responses with Optimized Chirp Signals Compensating Basilar Membrane Dispersion. J Acoust Soc Am 0:. ) Elberling C, Don M, Cebulla M and Sturzebecher E (00). Auditory steady-state responses to chirp stimuli based on coclea traveling delay. J Acoustic Soc Am, - ) Elberling C, Callo J, and Don M (00). Evaluating auditory brainstem responses to different chirp stimuli at three levels of stimulation J Acoustic Soc Am (). - talanffy, Direktor - Zentrum für Vaskuläre Neurochirurgie, International Neuroscience Institute - Hannover, Rudolf-Pichlmayr-Str

7 Page of 0 0 Fig : Click and CE-Chirp spectrum xmm (0 x 0 DPI)

8 Page of Neurosurgical Review 0 0 Fig : Classical ABR xmm (0 x 0 DPI)

9 Page of 0 0 Fig : CE-Chirp ABR at different db 0xmm (0 x 0 DPI)