Effects of cochlear nuclei electrical stimulation with surface brain stem implants in nonhuman primates.
OBJECTIVE
We undertook morphological evaluation of the cochlear nucleus complex (CNC) after implantation of a surface auditory brain stem implant (ABI).


METHODS
We used 14 nonhuman primates (Macaca fascicularis). They underwent translabyrinthine bilateral auditory deafferentation and simultaneous unilateral implantation of an ABI. In 6 cases the ABI was not activated, whereas it was activated in 8 cases. The ABI array consisted of 3 platinum disc electrodes mounted on a silicone pad with the back side covered with polyethylene terephthalate mesh, connected via a cable to an external stimulator in animals undergoing electrical stimulations.


RESULTS
All animals tolerated the procedures well. In both groups of animals, neuropathologic lesions or changes attributed to surgical trauma were found. The biotolerance of neural tissue to the materials used was adequate. The stimulation times ranged from 0 to 732 hours. Neuropathologic examination and stereological assessment revealed that the animals showed no signs of significant neural damage after CNC chronic stimulation if this took place within the safety limits. Time of stimulation did not seem to play a significant role in changes.


CONCLUSIONS
Besides surgical trauma, the most important factors responsible for CNC changes are the electrical stimulation parameters.
Manrique
Manuel
M
Departamento de Otorrinolaringología, Clínica Universitaria, Universidad de Navarra, Avda Pío XII No. 36, 31008 Pamplona, Spain.
Cervera-Paz
Francisco Javier
FJ
Insausti
Ana M
AM
Nevison
Barry
B
D000818:Animals; D038262:Auditory Brain Stem Implants; D001933:Brain Stem / Q000473:pathology; D002452:Cell Count; D017626:Cochlear Nucleus / Q000473:pathology*; D004558:Electric Stimulation; D008252:Macaca fascicularis; D008297:Male; D009474:Neurons / Q000473:pathology