title: Modelling encapsulation tissue around cochlear implant electrodes.
abstract: The objective of the study was to explore the effect of electrode encapsulation by fibrous scar tissue on electrical potential distributions and auditory nerve fibre excitation patterns. A finite element model in combination with an auditory nerve fibre model was used to predict changes in threshold currents and auditory nerve fibre excitation patterns. The model showed that electrical potentials at the target nerve fibres and the electrode contacts changed in the presence of encapsulation tissue. This led to changes in threshold currents and spread of excitation. The effect of electrode encapsulation on threshold currents and spread of excitation depended on the thickness of the perilymph layer separating the fibrous tissue encapsulation and the electrode array, nerve fibre survival status, electrode geometry and configuration, and array location. Model results suggested that arrays located close to the modiolus were most sensitive to threshold changes caused by electrode encapsulation (changes were between -0.26 and 2.41 dB), whereas encapsulation of an electrode array had less effect on threshold currents when the array was located in a lateral position in the scala tympani (changes were between -0.64 and 1.5 dB). For medially located arrays, changes in the spread of excitation varied between an increase of 0.21 mm and a decrease of 0.33 mm along the length of the basilar membrane, and an increase of 0.18 mm and a decrease of 0.66 mm along the length of the basilar membrane were calculated for laterally located arrays.
authors.affiliation: Department of Electrical, Electronic & Computer Engineering, University of Pretoria, Pretoria, South Africa. tania.hanekom@eng.up.ac.za
authors.forename: T
authors.initials: T
authors.lastname: Hanekom
mesh_terms: D002921:Cicatrix / Q000503:physiopathology; D003054:Cochlear Implants; D003056:Cochlear Nerve / Q000503:physiopathology; D004553:Electric Conductivity; D004567:Electrodes, Implanted; D020342:Finite Element Analysis; D006801:Humans; D008954:Models, Biological
references.citation: Hear Res. 1992 Dec;64(1):99-117
references.pmid: 1490906
references.citation: J Speech Hear Res. 1992 Oct;35(5):1126-30
references.pmid: 1447922
references.citation: Ear Hear. 2001 Aug;22(4):300-15
references.pmid: 11527037
references.citation: Ann Otol Rhinol Laryngol. 1991 Nov;100(11):914-21
references.pmid: 1746827
references.citation: Ear Hear. 2002 Jun;23(3):184-97
references.pmid: 12072611
references.citation: Hear Res. 1995 Jul;87(1-2):170-86
references.pmid: 8567435
references.citation: Ann Otol Rhinol Laryngol. 1978 Nov-Dec;87(6 Pt 2):1-39
references.pmid: 736424
references.citation: Hear Res. 1993 Mar;66(1):108-20
references.pmid: 8473242
references.citation: Ann Otol Rhinol Laryngol Suppl. 1982 Sep-Oct;98:3-8
references.pmid: 6814331
references.citation: Ann Otol Rhinol Laryngol Suppl. 1995 Sep;166:40-2
references.pmid: 7668722
references.citation: Otol Neurotol. 2001 Mar;22(2):195-9
references.pmid: 11300268
references.citation: Acta Otolaryngol. 1998 Jun;118(3):313-26
references.pmid: 9655204
references.citation: Acta Otolaryngol. 2001 Jan;121(2):216-9
references.pmid: 11349782
references.citation: Hear Res. 1996 May;95(1-2):33-48
references.pmid: 8793506
references.citation: Ann Biomed Eng. 1994 Jan-Feb;22(1):23-33
references.pmid: 8060024
references.citation: IEEE Trans Biomed Eng. 1985 Dec;32(12):1001-11
references.pmid: 4077078
references.citation: Biomaterials. 1994 Nov;15(14 ):1161-9
references.pmid: 7893919
references.citation: Hear Res. 1989 Dec;43(1):25-38
references.pmid: 2613564
references.citation: Clin Mater. 1992;9(1):49-68
references.pmid: 10149959
references.citation: Otolaryngol Head Neck Surg (1979). 1980 Mar-Apr;88(2):183-7
references.pmid: 6773014
references.citation: Am J Otol. 1994 Sep;15(5):644-51
references.pmid: 8572066
references.citation: Hear Res. 2000 Jun;144(1-2):175-86
references.pmid: 10831876
references.citation: Ciba Found Symp. 1970;:127-56
references.pmid: 4943822
references.citation: Hear Res. 2003 May;179(1-2):72-87
references.pmid: 12742240
references.citation: Ear Hear. 1995 Oct;16(5):439-49
references.pmid: 8654899
references.citation: Hear Res. 1997 Aug;110(1-2):119-34
references.pmid: 9282894
references.citation: Am J Otol. 1991 Jul;12(4):245-311
references.pmid: 1928309
references.citation: Hear Res. 1990 Dec;50(1-2):225-36
references.pmid: 2076974
references.citation: Hear Res. 2001 May;155(1-2):63-81
references.pmid: 11335077
references.citation: Clin Exp Pharmacol Physiol. 1996 Sep;23(9):766-76
references.pmid: 8911712
references.citation: Med Prog Technol. 1997;21 Suppl:13-23
references.pmid: 9413824
references.citation: Otol Neurotol. 2001 Jan;22(1):33-41
references.pmid: 11314713
references.citation: Ear Hear. 1992 Jun;13(3):200-9
references.pmid: 1397761
references.citation: Ann Otol Rhinol Laryngol Suppl. 1999 Apr;177:8-16
references.pmid: 10214794
references.citation: IEEE Trans Biomed Eng. 1981 Oct;28(10):721-5
references.pmid: 7319508
references.citation: Am J Otol. 1988 Jan;9(1):8-13
references.pmid: 3364540
references.citation: Acta Otolaryngol. 2002 Jun;122(4):363-9
references.pmid: 12125990