Proefschrift_vd_Beek

Table 1. Patient demographics Number of patients

151

lt cochlear im- ed either a CII lant with a Hi- d into the co- anted between enter. All im- only two sur- cluded in this 1. All subjects ually deafened eriod were not 2). contact sepa- asic pulses in contact, stim- its (CU), until xt, the current ovide a clearly Subsequently, icated that he/ was decreased level. Finally, troduced with the more basal anced Bionics ly, the proces- normal voice f the M-levels eported to be d to assess the but, if needed, rp) were sug- lity for the pa- y, the M-levels ning a smooth arp, the slope t accepted the ontal line [Bri- 31 of the sub- ionale to fit in n previous re- e to different the possibility he array in line ers of subjects. contacts were e shown at the m all subjects. ionics, the lev- ulse width (μs) r’s clinical fit- centage (10%) interrelation-

Average age, years

57

Range

17–86

Average duration of deafness, years

22

Range

0.1–60 94/57

Female/male ratio

Etiology

Progressive Medication Ménière Meningitis Otosclerosis

117

4 5 6 3

14

Trauma Usher

2 Average monosyllabic word score at 1 year, % 57 Range 5–93 1 Implant type: CII/HiRes 90K (HiFocus 1/1 J electrode). 1 Subset of 132 subjects.

further than a straight horizontal line [Briaire, 2008]. ship between T- and M-levels was expressed as a percentage (T-/ M-level ratio = T-level/M-level × 100). Although this does not pro- vide the DR in linear clinical units, the DR in decibels can easily be derived: DR (dB) = 20 log[100/(T-/M-level ratio)]. To assess intrasubject variation and to f ilitat the compari on with previously published data [Pfingst and Xu, 2004], the data were recalculated and expressed in decibels: I (dB) = 20 log[I (CU)/1,000 × 20.6 (CU)]. This, for instanc , enables the data to be seen more in line with data presented in Cochlear’s current levels, which are also on a logarithmic scale. In line with Pfingst et al. [2004], across-site mean (ASM) and across-site variance (ASV) were calculated in order to be able to analyze fitting levels both across as well as within subjects. Both T- and M-levels were deter- mined during regular clinical fi ting sessions, approximately 8 times during the first year. The T- andM-levels of the initial fitting (about 4 weeks after implantation) and the levels obtained at 1 year of cochlear implant use were used for this study. Speech Perception Speech discrimination scores were obtained during normal clinical follow-up at predetermined intervals. The data used for analysis in this study were the scores obtained after 1 year of fol- Table 2. Number of implanted patients excluded from the study Mentally handicapped 5 Non-Dutch speaker 1 Deceased, natural cause 3 Facial nerve stimulation 1 Incomplete insertion 2 Device failure 3 Total 15 For most subjects, 12 electrodes were active, but 31 of the subjects were fitted with less active electrodes. The rationale to fit in most cases with 12 active electrodes was based upon previous research [Frijns et al., 2003]. Missing data points due to different numbers of electrodes being active would prevent the possibility of effectively plotting percentiles or averages along the array in line graphs, as plotted data would be from varying numbers of subjects. Therefore, the data from two neighboring electrode contacts were averaged. This allowed level data along the array to be shown at the 8 electrode contact duos, each representing data from all subjects. In line with the convention used by Advanced Bionics, the levels are expressed on a linear scale in clinical units [pulse width ( μ s) × amplitude ( μ A) × 0.0128447]. In the manufacturer’s clinical fitting software (SoundWave), T-levels are set as a percentage (10%) of M-levels. Therefore, also in the present study, the interrelationship between Tand M-levels was expressed as a percentage (T-/ M-level ratio = T-level/M-level × 100). Although

5

97

van der Beek/Briaire/Frijns

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