A soft-surgery approach to minimize hearing damage caused by the insertion of a cochlear implant electrode: a guinea pig animal model.
OBJECTIVE
A "soft surgery" technique was applied, using various types of specifically designed dummy electrodes, to mimic cochlear implantation in a guinea pig model, and the degree of hearing-preservation/cochlear damage was assessed.


METHODS
Tricolor guinea pigs were divided into 3 groups: group A were implanted with electrodes without any contacts or wires (soft electrode), group B were implanted with electrodes having a metallic wire inside (stiff electrode), and group C underwent a cochleostomy procedure without implantation. Compound action potentials, in the range of 4 to 32 kHz, were used to assess electrophysiologic changes in the hearing function presurgery and postsurgery. Data were collected before surgery, at times t = 0 (immediately after surgery) and at 3, 7, 14, and 30 days.


RESULTS
At low frequencies (4-8 kHz), an immediate elevation of hearing threshold was observed in all 3 groups. Higher threshold shifts were more consistent for group B implanted with a stiff electrode, in comparison to the other 2 groups. Animals from group C presented a recovery from hearing loss, starting 3 days after surgery. At high frequencies (16-32 kHz), the elevation of hearing threshold was higher, as compared with the data from the low frequencies. Group C animals presented oscillatory threshold shifts twice, and the recovery to normal threshold values occurred approximately at t = 14 days.


CONCLUSIONS
The data suggest that cochleostomy is minimally harmful to the inner ear and that a soft electrode might better preserve the inner ear integrity than a rigid electrode.
*Bioacoustics Research Laboratory, University of Padua, Padua; †Department of Audiology, University of Ferrara, Ferrara; ‡Department of ENT and Head-Neck Surgery, Meran; §Department of Mathematical Sciences, Worcester Polytechnic Institute, Worcester, Massachusetts, U.S.A.; and ∥ENT Surgery, Department of Neurosciences, University of Padua, Padua, Italy.
Pietro
P
Giordano
Stavros
S
Hatzopoulos
Nadia
N
Giarbini
Silvano
S
Prosser
Joseph
J
Petruccelli
Edi
E
Simoni
Chiara
C
Faccioli
Laura
L
Astolfi
Alessandro
A
Martini
D000818:Animals; D003051:Cochlea / Q000601:surgery*; D019929:Cochlear Implantation / Q000009:adverse effects* / Q000379:methods*; D003054:Cochlear Implants; D004195:Disease Models, Animal; D006168:Guinea Pigs; D006309:Hearing; D034381:Hearing Loss / Q000209:etiology / Q000517:prevention & control* / Q000601:surgery; D008297:Male