Effects of cochlear nuclei electrical stimulation with surface brain stem implants in nonhuman primates

Area of Science:

• Neuroscience
• Biomaterials Science
• Auditory Prosthetics

Background:

• The cochlear nucleus complex (CNC) is a critical relay in the auditory pathway.
• Auditory brain stem implants (ABI) offer a potential solution for hearing restoration in cases of auditory nerve damage.
• Understanding the morphological effects of ABI implantation and stimulation on the CNC is crucial for device safety and efficacy.

Purpose of the Study:

• To evaluate the morphological changes in the cochlear nucleus complex (CNC) following the implantation of a surface auditory brain stem implant (ABI).
• To assess the neuropathological effects of chronic electrical stimulation via the ABI on the CNC in a nonhuman primate model.

Main Methods:

• Morphological evaluation of the CNC in 14 nonhuman primates (Macaca fascicularis) after translabyrinthine bilateral auditory deafferentation and unilateral ABI implantation.
• Comparison between ABI-implanted animals with and without electrical stimulation (n=6 and n=8, respectively).
• Neuropathologic examination and stereological assessment of neural tissue response to ABI materials and electrical stimulation.

Main Results:

• All surgical procedures were well-tolerated, with adequate biotolerance of neural tissue to ABI materials.
• Neuropathologic lesions were observed, primarily attributed to surgical trauma.
• Chronic CNC stimulation within safety limits did not result in significant neural damage, irrespective of stimulation duration.

Conclusions:

• Surgical trauma is an inherent factor causing changes in the CNC post-ABI implantation.
• Electrical stimulation parameters, rather than duration, are the primary determinants of CNC changes during chronic ABI use.
• Safe stimulation parameters are essential for minimizing neuropathological effects in the CNC.