Minimally invasive transcochlear approach for future optogenetic manipulation of spiral ganglion neurons

Hearing restoration in profoundly hearing-impaired patients by electrical cochlear implants (CI) enables open speech comprehension in most cases. Frequency and intensity resolution of electrical CIs are limited by wide current spread in tissue, stimulating a large subset of spiral ganglion neurons (SGN) simultaneously. Focused stimulation by light could enhance the number of separate stimulation channels, activate smaller subsets SGNs and thus increase frequency and intensity resolution of CIs. Therefor, optogenetically modified light-sensitive SGNs are required.

Specific optogenetic modification of SGNs by an adeno-associated viral transfer (AAV), shown by preliminary work of optogenetic cochlear stimulation in adult rodents, required an intramodiolar injection into the auditory nerve. In regard to a future clinical translation of optogenetic cochlear stimulation, the current study established a minimally invasive transcochlear approach to SGNs in the human temporal bone. The promontory was microscopically exposed by a transmeatal approach in six different human temporal bone specimens. Minimally invasive access to SGNs could be established via the cochlear apex, demonstrated by radiologic cross-section examinations.

This study provides a minimally invasive transmeatal transcochlear surgical approach to the apical cochlear modiolus in the human temporal bone, which enables an aimed local application of AAVs for future optogenetic modification of SGNs.

Publication History

Publication Date:
23 April 2019 (online)