Abstract
The measurement of the electrically evoked compound action potential (ECAP) in cochlear implant (CI) patients is widely used to provide evidence of a functioning electrode-nerve interface, to confirm proper location of the electrode array and to program the sound processor. In patients with an auditory brainstem implant (ABI), a likewise versatile measurement would be desirable. The ECAP measurement paradigm “Alternating Polarity” was utilized to record responses via the implanted ABI electrode array placed on the cochlear nucleus. Emphasizing on the different location of stimulation and recording, these responses are called local evoked potentials (LEP). LEP measurements were conducted during the clinical routine in 16 ABI patients (12 children and 4 adults), corresponding to 191 electrode contacts. A retrospective analysis of these data revealed, that LEP responses were observed in 64.9% of all measured electrode contacts. LEP responses predicted auditory perception with a sensitivity of 90.5%. False-positive rate was 33.7%. Objective LEP thresholds were highly significantly (p < 0.001) correlated both to behavioral thresholds (Pearson’s r = 0.697) and behavioral most comfortable levels (r = 0.840). Therefore, LEP measurements have the potential to support fitting in ABI patients.
Highlights
An auditory brainstem implant (ABI) was used to restore hearing after tumor resection in patients with neurofibromatosis type 2 (NF2) [1]
Comparable to evoked compound action potential (ECAP) measurements in cochlear implant (CI) patients, biphasic, charge-balanced stimuli were delivered with increasing current to one electrode contact of the ABI array
Besides shorter latencies of the P peaks, truncated N peaks, and much higher voltage, these local evoked potentials (LEP) responses look similar to ECAP responses
Summary
An auditory brainstem implant (ABI) was used to restore hearing after tumor resection in patients with neurofibromatosis type 2 (NF2) [1]. Patients with congenital malformation of the inner ear or with cochlear nerve aplasia, in which case a cochlear implant (CI) would not provide sufficient hearing, have been benefitting from an ABI, too. Over one thousand of such devices have been implanted worldwide [2]. In order to cope with the age-related development of the auditory cortex, early implantation of deaf children is recommended [3]. Fitting the sound processor can be challenging, especially in the case of very young children or other patients, who cannot give sufficient feedback regarding.
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