Article
An Evaluation of Two Different eCAP Measures of Spatial Selectivity
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Authors
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J. Briaire
- ENT department, Leiden University Medical Centre, Leiden, The Netherlands
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F.B. van der Beek
- ENT department, Leiden University Medical Centre, Leiden, The Netherlands
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J.H.M. Frijns
- ENT department, Leiden University Medical Centre, Leiden, The Netherlands
| Published: | May 31, 2005 |
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Outline
Text
Introduction
Spatial selectivity measurements give an indication of the width of the excitation area, which is generally considered to be a determinant of the optimal number of electrodes that can be used in the patient's speech program. This study investigates the information included in two different paradigms used to obtain the selectivity curve.
Materials and Methods
In 25 patients with a HiFocus-CII the selectivity is measured with both scanning (shifting the recording contact) and sMP3 method (shifting the probe electrode) on three electrodes along the array (apical, middle and basal) and at various currents strengths. The selectivity is determined by the width of the curve at 60% of the response amplitude.
Results
In most cases (>80%) the scanning method produced broader curves then the sMP3 method. The sMP3 curves in the middle of the array were very asymmetric; approximately 85% of the curves are broader on the apical side. Analysis showed that this does not automatically mean that the excitation area is asymmetric; it could also indicate symmetric excitation areas but changing selectivity along the cochlea. The sMP3 method shows an improved selectivity with current reduction in 70% of the cases, the scanning method only shows this effect for the majority of the patients at the basal contact.
Conclusions
The selectivity method (sMP3) indicates a better selectivity and an improved selectivity with reduced current, indicating that this is the most reliable method of the two.
