Impact of Placing a Modiolar Array and
Slim Straight Array in Opposite Ears of
the Same Pediatric Patient
Lisa R Park, AuD
Joseph Roche, MD
Holly FB Teagle, AuD
Jennifer Woodard, AuD
Craig Buchman, MD
University of North Carolina – Chapel Hill Ear and Hearing Center
Inherent differences
•  Smaller electrodes on the 422
resulting in higher impedance.
•  Electrodes further from nerve
resulting in higher T/C levels.
•  More fluid between electrode
and nerve resulting in higher
impedance fluctuation.
Exaggeration of electrode size and location differences,
courtesy of Cochlear Americas.
How this impacts the MAP
Subjects
Subject
Etiology/
Risk Factor
Stability
Age @ 1st CI/
Device
Age @ 2nd CI/
Device
Time between
surgeries
1
Unknown
Progressive
3.6 years Freedom CA
(AD)
4.9 years
CI422 (AS)
15 months
2
Unknown
Progressive
7.7 years
CI512 (AD)
10.3 years
CI422 (AS)
30 months
3
Unknown
Progressive
9.6 years
CI512 (AS)
11.7 years
CI422 (AD)
24 months
4
Unknown (ANSD)
Progressive
2.5 years Freedom CA
(AD)
6.7 years
CI422 (AS)
50 months
5
Unknown
Progressive
8.9 years Freedom CA
(AD)
10.2 years
CI422 (AS)
15 months
6
Connexin 26 & 30 mutations
Stable
0.8 years
CI422 (AD)
1.1 years Freedom CA
(AS)
3 months
7
Waardenburg
Stable
1.1 years Freedom CA
(AS)
2.8 years
CI422 (AD)
20 months
8
Connexin 26 mutation
Progressive
3.4 years Freedom CA
(AD)
5.1 years
CI422 (AS)
20 months
9
Prematurity complications
(ANSD)
Progressive
2.4 years Freedom CA
(AD)
7.6 years
CI422 (AS)
61 months
Change in residual hearing threshold
at 250 Hz
Change in residual hearing threshold
at 250 Hz
Number of Active Electrodes
Impedance Fluctuations
Impedance Fluctuations
Impedance Fluctuation Index (IFI)
2.5
IFI (kohm)
2.0
Contour Device
1.5
CI422
1.0
0.5
0.0
1
2
3
4
5
Subject
6
7
8
9
Impedance Averages
Charge Levels
Change in NRT Threshold
Charge Levels
NRT Threshold
Charge Levels
Power Levels and Battery Life
Recorded PBK Scores
Recorded PBK Scores
120
% words Correct
100
80
Slim Straight
60
Contour Advance
40
Binaural
20
0
1
2
3
4
5
Subjects
6
7
8
9
Summary
Significant Factors:
• 
• 
• 
422 has fewer active electrodes
at surgery and at 6 months. All
of the contour electrodes were
active at surgery and 6 months
NRT was lower at post op than
in the OR for both devices and
NRT for the Contour was
significantly lower than the 422.
Impedance values fluctuate
more and are higher in slim
straight devices than contour
advance devices.
Non-Significant Factors:
• 
• 
• 
• 
• 
T values, C values, or dynamic
range
The change in NRT threshold
from OR to postop
The change in residual hearing
at 250 Hz despite differences in
surgical approach.
Battery life or power levels.
Recorded PBK Scores