Proefschrift_vd

further than a straight horizontal line [Briaire, 2008].

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 (

s) × amplitude (

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

van der Beek/Briaire/Frijns

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-

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 1.

Patient demographics

Number of patients

151

Average age, years

Range

17–86

Average duration of deafness, years

Range

0.1–60

Female/male ratio

94/57

Etiology

Progressive

117

Medication

Ménière

Meningitis

Otosclerosis

Trauma

Usher

Average monosyllabic word score at 1 year, % 57

Range

5–93

Implant type: CII/HiRes 90K (HiFocus 1/1 J electrode).

Subset of 132 subjects.

Table 2.

Number of implanted patients excluded from the study

Mentally handicapped

Non-Dutch speaker

Deceased, natural cause

Facial nerve stimulation

Incomplete insertion

Device failure

Total

d by:

versity

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