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What is it about?

Preoperative electrically auditory evoked potentials (= eAEP, i.e., eABR for brainstem, eAMLR for midbrain, and eALR for cortex) can be performed under local anesthesia, achieving subjective sensation and hearing in patients having a functional auditory nerve. For intraoperative eAEP, we stimulate the auditory nerve with an intra-cochlear test electrode like a cochlear implant (= CI) and stimulate basally when using an extra-cochlear electrode. These measurements aim to confirm preoperative findings (e.g. uncertain preoperative eABR) or intraoperative decisions (e.g. vestibular schwannoma resection).

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Why is it important?

Preoperative eAEP can be performed with the trans-tympanic stimulation electrode and a neurological EP system for recording the responses. In addition, eAEP under local anesthesia allows for preoperative diagnostics of subjective sensation. For intraoperative eAEP, the intra-cochlear auditory nerve test system (= ANTS) system is preferable showing similar results to the gold standard CI-eABR (i.e., eABR using a CI for stimulation). The eAMLR can be used only preoperatively in case of ambiguous EABR or for extended analysis of the auditory pathway. Results: During preoperative eAEP in local anesthesia, an eABR is essential. eAMLR and eALR are optional. The subjective sensation can be recorded in parallel. A reliable response often avoids eAEP under general anesthesia. eAEP under general anesthesia should be performed as rarely as possible preoperatively to avoid unnecessary intraoperative eAEP, performed usually directly before cochlear implantation. Extra-cochlear stimulation avoids mechanical trauma and possible intra-cochlear infections. However, intra-cochlear stimulation is usually recommended due to larger response amplitudes; in fact, the ANTS electrode provides more stable monitoring.

Perspectives

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eAEP can be diagnostically useful preoperatively and intraoperatively with the concept presented here. Since not all clinics are familiar with these methods, a learning curve may be necessary.

Dr. rer. biol. hum. Daniel Polterauer
Ludwig-Maximilians-Universitat Munchen

Read the Original

This page is a summary of: Applications of pre- and intraoperative eAEP like eABR in cochlear implant candidacy, Current Directions in Biomedical Engineering, December 2024, De Gruyter,
DOI: 10.1515/cdbme-2024-2123.
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