Gochlear implants from model to patients
Briaire, J.J.
Citation
Briaire, J. J. (2008, November 11). Gochlear implants from model to patients. Retrieved from https://hdl.handle.net/1887/13251
Version: Corrected Publisher’s Version
License: Licence agreement concerning inclusion of doctoral thesis in the Institutional Repository of the University of Leiden
Downloaded from: https://hdl.handle.net/1887/13251
Note: To cite this publication please use the final published version (if applicable).
COCHLEAR IMPLANTS
FROM MODEL TO PATIENTS
COCHLEAR IMPLANTS
FROM MODEL TO PATIENTS
PROEFSCHRIFT
ter verkrijging van
de graad van Doctor aan de Universiteit Leiden,
op gezag van de Rector Magnificus prof.mr. P.F. van der Heijden, volgens besluit van College voor Promoties
te verdedigen op dinsdag 11 November 2008 te klokke 11:15 uur
Jeroen Johannes Briaire
door geboren te Nootdorpin 1974
Promotiecommissie Promotor:
Referent:
Overige leden:
Prof.Dr.Ir. J.H.M. Frijns
Prof.Dr. J. Wouters ( KU Leuven) Prof.Dr. P. van Dijk (UMC Groningen) Prof.Dr. J.G. van Dijk
Dr. W. Soede
Dr. B. van Zanten (UMC Utrecht)
ISBN 978-90-9023555-4
The printing of this thesis was financially sponsored by: Advanced Bionics, Stichting Atze Spoor Fonds, Med-El and Veenhuis Medical Audio B.V.
Aan Saskia, Pascal en Lianne
Contents
1 Introduction 13
1.1 The first bursts of electric sound . . . 16
1.2 Industry comes into play . . . 21
1.3 Different CI devices . . . 23
1.4 Overview of the present study . . . 23
2 Integrated Use of Volume Conduction and Neural Models to Sim- ulate the Response to Cochlear Implants 27 2.1 Introduction . . . 29
2.2 Electrical volume conduction in the cochlea . . . 31
2.3 Simulating the auditory nerve fibre responses . . . 36
2.4 Results . . . 38
2.4.1 Potential distributions due to intra-cochlear electrodes . 38 2.4.2 Model validation: the dependence of the neural responses on the electrode position . . . 40
2.4.3 Applications . . . 46
2.5 Conclusions and future directions . . . 49
2.A The generalised SEF auditory nerve fibre model . . . 51
3 3D Mesh Generation to Solve the Electrical Volume Conduction
Problem in the Implanted Inner Ear. 55
7
3.1 Introduction . . . 57
3.2 Numerical method selection . . . 59
3.2.1 Lumped parameter models . . . 60
3.2.2 Finite element method (FEM) . . . 61
3.2.3 Finite difference method (FDM) . . . 61
3.2.4 Boundary element method (BEM) . . . 62
3.3 A 3D cochlea mesh . . . 64
3.4 Constructing meshes of implants and the surrounding area . . 66
3.5 Calculated potential distributions . . . 71
3.6 Discussion and Conclusions . . . 73
4 Field Patterns in a 3D Tapered Spiral Model of the Electrically Stim- ulated Cochlea 77 4.1 Introduction . . . 79
4.2 Materials and Methods . . . 81
4.2.1 Numerical method to calculate the potential distribution in the cochlea . . . 81
4.2.2 Models of the cochlea . . . 82
4.3 Results . . . 88
4.3.1 Potential and current distributions in the cochlea . . . . 88
4.3.2 Neural responses . . . 95
4.4 Discussion . . . 97
4.5 Acknowledgements . . . 102
5 The Importance of Human Cochlear Anatomy for the Results with Modiolus Hugging Multi-Channel Cochlear Implants 103 5.1 Introduction . . . 105
5.2 Materials and Methods . . . 108
5.2.1 Three-dimensional volume conduction model of the hu- man and guinea pig cochlea . . . 108
8
5.2.2 Simulated electrode configurations . . . 111
5.2.3 Calculating the neural responses . . . 113
5.3 Results . . . 114
5.4 Discussion and Conclusions . . . 118
5.5 Acknowledgement . . . 124
6 Initial evaluation of the Clarion CII cochlear implant: Speech per- ception and neural response imaging 125 6.1 Introduction . . . 127
6.2 Patients, Materials and Methods . . . 128
6.2.1 The Clarion CII Cochlear Implant . . . 128
6.2.2 Patient Demographics and Follow-Up . . . 130
6.2.3 Neural Response Imaging . . . 133
6.3 Results . . . 134
6.3.1 Speech Perception in Quiet and in Background Noise . 136 6.3.2 Neural Responses . . . 140
6.4 Discussion and Conclusions . . . 145
6.5 Acknowledgement . . . 152
7 The relative value of predictive factors of cochlear implant perfor- mance depends on follow-up time 153 7.1 Introduction . . . 156
7.2 Materials and Methods . . . 157
7.2.1 Participants . . . 157
7.2.2 Profile fitting method . . . 161
7.2.3 Statistical Analysis . . . 162
7.3 Results . . . 163
7.3.1 Group comparisons . . . 163
7.3.2 Bivariate regression analyses . . . 166
9
7.3.3 Multiple regression analysis . . . 170
7.4 Discussion . . . 174
7.5 Conclusions . . . 177
7.6 Acknowledgement . . . 178
8 Unraveling the Electrically Evoked Compound Action Potential 179 8.1 Introduction . . . 181
8.2 Materials and methods . . . 184
8.2.1 The forward problem: simulating neural excitation in the human cochlea . . . 184
8.2.2 The backward problem: calculation of the compound ac- tion potential . . . 187
8.2.3 The use of an artifact rejection scheme . . . 188
8.3 Results . . . 190
8.4 Discussion . . . 200
8.5 Acknowledgement . . . 207
9 The consequences of neural degeneration regarding optimal coch- lear implant position in scala tympani: A model approach 209 9.1 Introduction . . . 211
9.2 Materials and Methods . . . 214
9.3 Results . . . 218
9.4 Discussion . . . 224
9.5 Acknowledgment . . . 229
10 Concept and initial testing of a new, basally perimodiolar elec- trode design 231 10.1 Introduction . . . 233
10.2 Materials and methods . . . 234
10.3 Results . . . 236
10
10.4 Discussion . . . 236
10.5 Acknowledgment . . . 237
11 The model as a clinical tool: General discussion and future per- spectives 239 11.1 Tuning the implant . . . 241
11.2 The individual patient’s cochlear model . . . 241
11.3 Objective measures . . . 242
11.4 Keeping up the pace . . . 244
11.5 The future of cochlear implants . . . 244
Bibliography 249
Summary 269
Samenvatting 275
Curriculum vitae 281
11
