Clin Exp Otorhinolaryngol.  2012 Dec;5(4):194-200. 10.3342/ceo.2012.5.4.194.

Long-Term Evolution of the Electrical Stimulation Levels for Cochlear Implant Patients

• Vargas JL
• Sainz M
• Roldan C
• Alvarez I
• de la Torre A

• KMID: 1489078
• DOI: http://doi.org/10.3342/ceo.2012.5.4.194

Abstract

OBJECTIVES
The stimulation levels programmed in cochlear implant systems are affected by an evolution since the first switch-on of the processor. This study was designed to evaluate the changes in stimulation levels over time and the relationship between post-implantation physiological changes and with the hearing experience provided by the continuous use of the cochlear implant.
METHODS
Sixty-two patients, ranging in age from 4 to 68 years at the moment of implantation participated in this study. All subjects were implanted with the 12 channels COMBI 40+ cochlear implant at San Cecilio University Hospital, Granada, Spain. Hearing loss etiology and progression characteristics varied across subjects.
RESULTS
The analyzed programming maps show that the stimulation levels suffer a fast evolution during the first weeks after the first switch-on of the processor. Then, the evolution becomes slower and the programming parameters tend to be stable at about 6 months after the first switch-on. The evolution of the stimulation levels implies an increment of the electrical dynamic range, which is increased from 15.4 to 20.7 dB and improves the intensity resolution. A significant increment of the sensitivity to acoustic stimuli is also observed. For some patients, we have also observed transitory changes in the electrode impedances associated to secretory otitis media, which cause important changes in the programming maps.
CONCLUSION
We have studied the long-term evolution of the stimulation levels in cochlear implant patients. Our results show the importance of systematic measurements of the electrode impedances before the revision of the programming map. This report also highlights that the evolution of the programming maps is an important factor to be considered in order to determine an adequate calendar fitting of the cochlear implant processor.

Keyword

Cochlear implant; Electrical stimulation; Prosthesis adjustment; Bioelectrical impedance

MeSH Terms

Acoustics
Cochlear Implants
Electric Impedance
Electric Stimulation
Electrodes
Hearing
Hearing Loss
Humans
Otitis Media with Effusion
Prosthesis Fitting
Spain

Figure

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  Fig. 1 Evolution of the averaged stimulation levels after the first switch-on of the processor. The vertical bars represent the mean±standard deviation. Stabilization occurred after 6 months of implant use. THR, threshold; MCL, maximum comfortable level; nC, nano-Coulombs.

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  Fig. 2 Evolution of the hearing sensitivity obtained from aided open-field pure tone audiometry. The error bars represent averaged hearing sensitivity±standard deviation. Hearing sensitivity increased during the first 6 months of implant use, thereafter stabilization occurred.

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  Fig. 3 Evolution of the average electrode impedance. The vertical bars represent the mean±standard deviation. A reduction in the averaged impedances was observed during the first weeks. Although impedances tended to increase with the use of the cochlear implant, no statistically significant differences were found between months.

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  Fig. 4 Transitory alterations of the impedances (A) and the maximum comfortable level (MCL) levels (B) for the 4 patients affected by secretory otitis media. A high relationship between changes in the impedances and changes in the MCL levels can be observed. nC, nano-Coulombs.

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