Level Specific CE-Chirp® BAEP's: A new faster technique in neuromonitoring cochlear nerve during cerebello-pontine angle tumor surgery

Abstract

Abstract Background Level Specific (LS) CE-Chirp® Brainstem Auditory Evoked Potentials (BAEP's) are the most recent evolution of classical Click BAEP's, performed both in clinical studies and in intraoperative neuromonitoring (IONM) of acoustic pathways during several neurosurgical procedures. LS CE-Chirp® is a new group of acoustic stimuli, latter evolution of Broadband CE-Chirp®, designed by Claus Elberling to provide faster recording of larger amplitude BAEP's V waves in infants. While the original Broadband CE-Chirp® was conceived for optimal response amplitude of V wave at low and medium stimulation intensities, the LS CE-Chirp® provides clearer I–III–V waves at high intensities. Material and method We report a consecutive series of 31 cases in which the new LS CE-Chirp® BAEP's were performed during different skull base surgery procedures during the last 24 months: 25 vestibular schwannomas, 3 cerebello-pontine angle (CPA) meningiomas and 3 CPA epidermoid tumors. Results Using LS-CE-Chirp® BAEP's monitoring, neurosurgeon was alerted in 10–15 s about variation of conduction parameters of acoustic pathways. At the end of surgery, BAEP's were normal in 11 patients, showed deconstructed waves in 14, and elongated waves in 6. At a minimum clinical and BAEP's follow-up of 6 months, hearing function was preserved in 19 cases (61,3%). Conclusions We herein confirm that LS CE-Chirp® BAEP's provide a fast feedback to surgeons regarding acoustic pathways function, helping them during skull base tumor removal in the attempt to hearing preservation when it is socially useful in the preoperative evaluation.