Clinical test results on patients with a novel electrical hearing prosthesis: the two-shank Auditory Midbrain Implant (AMI)

During 2017 to 2019, five deaf patients with neurofibromatosis type II (NF2) were implanted at Hannover Medical School with a novel central auditory prosthesis – the Auditory Midbrain Implant (AMI). The AMI was developed as an alternative to the Auditory Brainstem Implant (ABI) for patients with NF2 in whom an ABI does not provide hearing rehabilitation, for example due to damage to the cochlear nucleus.

The electrode array consists of two penetrating arrays (shanks) with a length of 5mm each and 11 electrode contacts. The two arrays are inserted in the midbrain in the inferior colliculus next to each other at a distance of about 1mm. The aim is to cover the central nucleus of the inferior colliculus (ICC) as completely as possible along its tonotopic gradient.

The two-shank AMI is a further development of a single-shank model, which has already been implanted in five patients during 2006 and 2008, but only resulted in limited hearing performance, probably due to insufficient temporal coding and suppression effects in the neurons.

Studies in animal models have shown that these suppression effects can be reduced by alternating stimulation in two electrode arrays in parallel in the same frequency layer in the ICC.

Results of speech tests as well as tests of pitch perception and measurements of suppression effects in patients with the two-shank AMI are shown. For example, a stable loudness at the shortest pulse intervals (17.5 µs) was observed in contrast to the single-shank AMI, which leads to stable auditory perceptions in the patients.

National Institutes of Health (U01DC013030)

Publication History

Article published online:
24 May 2022