Download Comparison of Pseudobinaural Hearing to Real Binaural Hearing

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Comparison of Pseudobinaural Hearing to
Real Binaural Hearing Rehabilitation After
Cochlear Implantation in Patients With Unilateral
Deafness and Tinnitus
*Susan Arndt, *Antje Aschendorff, *Roland Laszig, *Rainer Beck,
*Christian Schild, *Stefanie Kroeger, †Gabriele Ihorst, and *Thomas Wesarg
*Department of OtorhinolaryngologyYHead and Neck Surgery, and ÞClinical Trials Centre (ZKS),
University Medical Center Freiburg, Freiburg, Germany
Objective: Up to now, treatment modalities of unilateral deafness consist of no treatment, conventional contralateral routing
of signal (CROS), or Bone-Anchored Hearing Aid (BAHA)
hearing aid. Cochlear implantation makes a new treatment
modality available for patients with single-sided deafness. The
aim of this study is to evaluate the use of unilateral electrical
stimulation with normal hearing on the contralateral side after a
period of 6 months compared with the preoperative unaided
situation, conventional CROS, or BAHA hearing aids.
Study Design: Prospective design.
Setting: Tertiary referral center; cochlear implant (CI) program.
Patients: Eleven adult subjects with unilateral deafness of
various causes were enrolled in the study. Only those patients
were included in whom therapy with CROS hearing aid or
BAHA was not successful and in whom the auditory nerve
was found to be intact and the cochlea patent for cochlear
implantation.
Intervention: All subjects were fitted in random order with a
BAHA Intenso mounted on the softband/tension clamp or with a
CROS hearing aid. After test periods with both devices, the
subjects received a CI.
Main Outcome Measures: The Hochmair-Schulz-Moser sentence test and the Oldenburg sentence test were used to test
speech comprehension in 3 presentation configurations in the
unaided situation, with conventional CROS and BAHA hearing
aids before cochlear implantation as well as after 6 months with
CI. Localization was assessed using an array of 7 speakers at
head level in a frontal semicircle. Subjective improvement in
daily life was evaluated using the Speech, Spatial and Qualities
of Hearing Scale, the Health Utilities Index 3 and the International Outcome Inventory for Hearing Aids questionnaires.
Tinnitus distress was measured with a tinnitus scale before and
after CI implantation.
Results: The results show significant improvement in localization ability as well as in speech comprehension in most presentation configurations with the CI. Especially, there is no
negative effect on speech comprehension if the noise is presented to the CI ear and speech to the normal hearing ear. With
the CI, the summation and squelch effects are not significant,
but a significant combined head shadow effect is seen. Speech,
Spatial and Qualities of Hearing results show an overall benefit
of wearing the CI compared with the other treatment options.
The tinnitus scale revealed a positive effect of CI stimulation in
cases of preoperative tinnitus.
Conclusion: The results in these patients suggest that cochlear
implantation improves hearing abilities in people with singlesided deafness and is superior to the alternative treatment
options. The use of the CI does not interfere with speech
understanding in the normal hearing ear. Our data suggest that
the binaural integration of electric and acoustic stimulation is
possible even with unilateral normal hearing. Key Words:
BAHAVCochlear implantVCROS hearing aidVLocalizationV
Speech comprehensionVUnilateral sensorineural hearing loss.
Otol Neurotol 00:00Y00, 2010.
The impairments caused by unilateral deafness have
been studied by many researchers since the mid 20th
century (1Y3). Patients report difficulties in sound loca-
lization and with speech comprehension when the speaker
is talking on the deaf side, especially in a noisy environment. The advantages of binaural hearing over the
unilateral situation have been shown by several research
groups (4Y7). Three effects are responsible for the
advantages of binaural hearing. The 2 effects suggesting
true binaural processing of auditory information arriving
at each ear are binaural summation and binaural squelch.
Address correspondence and reprint requests to Susan Arndt, M.D.,
Department of OtorhinolaryngologyYHead and Neck Surgery, University Medical Center Freiburg, Killianstrasse 5, D-79106 Freiburg,
Germany; E-mail: [email protected]
1
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2
S. ARNDT ET AL.
Although the head shadow effect is not based on binaural
sound processing, it is a consequence of hearing on both
sides, which permits the subject to take advantage of
2 different signal-to-noise ratios, subsequently leading to
improved speech comprehension. Up to now, treatment
modalities of unilateral deafness consist of no treatment,
contralateral routing of signal (CROS) treatment with
CROS hearing aids and the Bone-Anchored Hearing Aid
(BAHA) treatment based on bone conduction. The last 2
methods do not allow for real binaural hearing because
the brain only receives and processes auditory input from
one side. However, for patients deafened because of
cochlear ossification, or after acoustic neuroma surgery in
which the auditory nerve function is compromised, conventional treatment with BAHA or CROS hearing aid
represents the therapy of choice.
A single-center trial to investigate the potential clinical application of unilateral electrical stimulation with
cochlear implantation in patients with single-sided deafness and tinnitus was assessed and approved by the ethics
committee of the University of Freiburg (No. 69/2009/
Arndt). The effect of electrical stimulation of the implanted side with normal hearing on the other side was
evaluated after a period of 6 months and compared with
the unaided situation, with BAHA and conventional
CROS hearing aids. The data presented in this article
reflect the results of speech comprehension in noise,
sound localization ability, and subjective self-assessment
of the patients.
MATERIALS AND METHODS
Subjects/Study Design
Eleven adult German native speakers with acquired unilateral
deafness were enrolled in the study (Table 1). The mean duration of deafness was 25 months. They presented with a puretone average of more than 70 dB HL and a word score on
the Freiburg monosyllabic word test of maximum 30% at 70 dB
SPL. The hearing on the better ear was limited to pure-tone
average at maximum 30 dB HL in air conduction and a minimum word score of 80% in the Freiburg word test at 65 dB SPL.
Only those patients were included in whom therapy with CROS
hearing aid or BAHA was not successful and in whom the
auditory nerve was found to be intact and the cochlea patent
for cochlear implantation. Another selection criterion was a
TABLE 1.
Subjects
1
2
3
4
5
6
7
8
9
10
11
short duration of deafness with a maximum of approximately
10 years. Before cochlear implantation, all subjects were informed about the implications involved in the study and granted
written informed consent. In particular, the information included
the known risks of cochlear implant (CI) surgery, such as facial
nerve paralysis and loss of taste. Additionally, the patients were
informed about the postoperative rehabilitation time. The anticipated benefit is improvement of speech comprehension in
noise and improvement of sound localization. All subjects
received the Nucleus Freedom Implant (CI24RE; Cochlear Ltd.,
Lane Cove, Australia) and use the Nucleus Freedom speech
processor.
Repeated single subject measures were performed for each
subject, with each subject serving as his/her own control.
Objective and subjective data of speech comprehension and
localization were obtained to compare performance for the unaided condition and the aided conditions with BAHA, CROS, or
CI. Subsequently, all subjects were fitted in random order with a
BAHA Intenso mounted on the headband or with CROS hearing
aid (Phonak Una M). After test periods with both devices, the
subjects received a CI. Speech comprehension in noise and
localization abilities were measured 3 weeks after fitting of each
device and 6 months after the first fitting of CI.
Tests
Speech comprehension tests were conducted in a soundtreated chamber via 2 of 3 loudspeakers, at an angle of +45-, 0-,
and j45- 1 m away from the subject_s head. The 3 presentation
setups S0-N0-, S+45-Nj45-, and Sj45-N+45- were used for
testing speech comprehension in background noise. In relation
to the side of the subject_s deaf ear, these presentation setups are
the configurations S0N0 (speech and noise from the front),
SnhNssd (speech from the normal hearing side/noise from the
unilateral deaf side), and SssdNnh (speech from the unilateral
deaf side/noise from the normal hearing side). Speech comprehension in noise was assessed using the Hochmair-SchulzMoser (HSM) sentence test (8) and the Oldenburg sentence test
(OLSA) (9,10). Speech and background noise were presented
at 65 dB SPL with a fixed signal-to-noise ratio (SNR) of 0 dB
using the HSM test. Two lists of 20 sentences were used, and
speech comprehension was scored as percentage correct word
score. Speech comprehension in noise with the OLSA was
tested using an adaptive procedure in the unaided and the aided
condition with CI. The background noise was presented at
65 dB SPL, and the speech level of each sentence was adaptively adjusted depending on the subjects_ response to each test
item to obtain the SNR at which the percent correct word score
is 50% (critical SNR). Two lists of 30 sentences were used,
Patient demographics
Age at surgery, yr
Duration of
deafness, mo
Cause
Deaf side
Pure-tone average of the
good ear, mean dB HL
Pure-tone average of the
poor ear, mean dB HL
47
68
23
38
39
41
41
46
54
51
31
43
31
4
34
6
10
11
110
10
9
4
Sudden hearing loss
Sudden hearing loss
Temporal bone fracture
Sudden hearing loss
Sudden hearing loss
Labyrinthitis
Labyrinthitis
Ménière_s disease
Sudden hearing loss
Sudden hearing loss
After ear surgery
Left
Left
Left
Left
Right
Left
Right
Left
Left
Left
Right
13
18
8
8
9
9
8
7
16
30
16
80
91
110
86
115
99
83
117
99
99
103
Otology & Neurotology, Vol. 00, No. 00, 2010
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COCHLEAR IMPLANTATION IN UNILATERAL DEAF PATIENTS
and speech comprehension was scored as critical SNR. Before
testing, one training list was applied in each listening condition
and presentation configuration.
Localization was tested using OLSA sentences as stimuli.
These stimuli were chosen instead of artificial nonspeech stimuli
because sentences are acoustic stimuli used in human communication, and unilaterally deaf patients have problems detecting
the position of a person addressing the patient from the side or
behind. Furthermore, these stimuli were applied because unilaterally deaf patients showed no localization ability using a
BAHA or CROS device when artificial short narrow band noise
stimuli were applied (11). For the localization tests, 7 loudspeakers were located at intervals of 30 degrees from j90
degrees to 90 degrees in a frontal semicircle 2 m in diameter in a
horizontal plane at the subject_s head level. The subjects were
not allowed to search the presenting speaker by moving their
heads during the stimulus presentations; this was controlled by
the examiner. In each test, 10 sentences at 5 different intensity
levels between 59 and 71 dB SPL and a mean level of 65 dB
SPL were offered from each speaker in random sequence. For
each of the 70 stimulus presentations, the speaker indicated by
the subject as the sound-delivering speaker was recorded,
resulting in a total of 70 responses. Localization ability was
measured as the percentage of the 70 presenting speakers correctly indicated by the subject as the sound-delivering speakers.
The chance level of correct speaker localization is 100% divided
by the number of speakers, that is, 14.3%. For each subject and
test, the localization ability also was measured as the localization deviation or error le in degrees, calculated as the mean of
the magnitudes of the differences between the azimuth angle of
the sound presenting speaker 8 p and the azimuth angle of the
judged speaker 8 j across all N = 70 stimulus presentations:
le ¼
1 N
~ j8pk 8jk j
N k¼1
ð1Þ
3
The smaller the value of the localization error is, the better
the localization ability. The chance level of the localization
error clle is calculated as the mean of the magnitudes of the
differences between the azimuth of a judged speaker 8 p and
the azimuth of a presenting speaker 8 j across all S2 = 49 possible combinations of presenting and judged speakers yielding
68.6 degrees:
cl le ¼
1 S S
~ ~ j8pl 8jm j
S 2 l¼1 m¼1
ð2Þ
Questionnaires
For the subjective part of our study, we used the standardized
Speech, Spatial and Qualities of Hearing (SSQ) questionnaire
(12). This questionnaire has 3 sections and assesses speech
understanding, spatial hearing, and hearing quality with a
scoring system of 0 to 10 for each item, in which 0 represents
unable to hear and 10 means hears perfectly. Quality of life
(QoL) was evaluated by means of the Health Utilities Index 3
(HUI-3) (13). The HUI-3 is a generic, multiattribute, preferencebased classification system and is administered as a measure of
general health status. Responses from the HUI-3 survey were
computed to a health utility index score between 0 (dead) and
1 (perfect health). Single-attribute utility scores were reported
based on a scale from 0 (lack of function) to 1 (full function).
The SSQ and HUI-3 were completed by the patients before any
treatment, after CROS and BAHA test periods, and 6 months
after CI fitting. Tinnitus distress was measured with the visual
analogue scale (VAS) before and 6 months after CI activation.
The patients had to mark the tinnitus strength on a scale from
0 (no tinnitus) to 10 (maximum strength). The International
Outcome Inventory for Hearing Aids (IOI-HA) is a self-report
FIG. 1. Box-whisker plots of the HSM sentence in (background) noise test percent correct scores of the 11 subjects for the presentation
configurations S0N0, SnhNssd, and SssdNnh in the unaided as well as the aided conditions with CROS hearing aid, BAHA, and CI after
6 months. Significant improvement using the CI compared with each of the other conditions is shown on top of their box plots: *p G 0.05;
**p G 0.01 (Wilcoxon signed-rank test).
Otology & Neurotology, Vol. 00, No. 00, 2010
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97.64
93.87
100.00
100.00
100.00
99.53
98.58
99.06
74.06
96.70
93.87
98.58
74.06Y100.00
100.00
93.40
91.51
100.00
100.00
100.00
99.53
86.79
99.06
100.00
96.70
100.00
100.00
96.23
99.53
100.00
67.45
36.32
100.00
98.11
97.17
98.58
99.53
98.58
67.45Y100.00 36.32Y100.00
51.89
47.64
94.34
79.72
85.38
77.83
74.06
52.36
22.64
76.42
77.83
76.42
22.64Y94.34
60.85
40.09
85.85
76.42
74.06
88.68
76.42
71.70
16.98
62.74
76.89
74.06
16.98Y88.68
56.13
20.75
93.40
73.11
79.72
82.08
76.89
63.21
9.43
77.83
79.72
76.89
9.43Y93.40
43.40
66.98
19.81
43.40
89.62
92.45
60.85
78.30
19.34
83.96
42.45
90.57
37.26
93.40
52.36
74.06
22.64
10.38
31.60
61.79
50.00
68.87
42.45
74.06
19.34Y89.62 10.38Y93.40
0.00
0.00
50.94
41.51
10.38
31.13
8.49
0.94
0.00
25.94
31.13
10.38
0.00Y50.94
21.23
0.00
56.13
77.36
30.66
24.53
19.81
21.23
5.19
45.75
41.98
24.53
0.00Y77.63
Unaided
Unaided
Patient
1
14.62
2
6.13
3
39.15
4
16.98
5
9.43
6
16.98
7
18.40
8
8.49
9
0.00
10
8.02
11
21.23
Median
14.62
Range 0.00Y39.15
Unaided
SnhNssd
Cochlear
implant
S0N0
Contralateral
Bone-anchored
routing of signal
hearing aid
Cochlear
implant
SssdNnh
Group HSM sentence scores for the different treatment
options and presentation configurations are shown in
Figure 1 and the individual and median scores in Table 2.
Speech comprehension for the configuration SssdNnh
with the CI is significantly improved (CI versus unaided,
p = 0.001; CI versus CROS, p = 0.03; CI versus BAHA,
p = 0.001). There is no statistically significant difference
in speech comprehension for the presentation configuration S0N0 (CI versus unaided, p = 0.75; CI versus CROS,
p = 0.76; CI versus BAHA, p = 0.70). For the configuration SnhNssd, there is a significant improvement of speech
comprehension with the CI in comparison with CROS
and BAHA (CI versus CROS, p = 0.031; CI versus
BAHA, p = 0.023), but no improvement in comparison
with the unaided condition (CI versus unaided, p = 0.094).
Group OLSA critical SNRs for the different test configurations are illustrated in Figure 2. For the SssdNnh
configuration, a significant improvement of critical SNR
was found when comparing the unaided (median,
j0.6 dB) to the aided condition with CI (median,
j6.2 dB; p = 0.001). There is no difference in speech
comprehension between the unilateral and the bilateral
condition for the configurations S0N0 and SnhNssd. The
S0N0 configuration, in which each ear is presented with
the same SNR, allows for the computation of the summation effect, which is the difference in speech comprehension in the bilateral compared with the unilateral
condition. Our patients did not show a summation effect
on group median (0 dB). For the SnhNssd configuration, the median critical SNR is j14.1 dB in the unaided
condition and j14.6 dB in the binaural condition
( p = 0.15). The small difference of 0.5 dB representing
the binaural squelch effect is not statistically significant.
Figure 3 shows the group localization errors. Localization error is significantly reduced with the CI (median,
15.0 degrees) compared with the unaided condition
(median, 33.9 degrees; p = 0.003), to CROS (median,
39.9 degrees; p = 0.001) and to BAHA (median,
30.4 degrees; p = 0.002).
The SSQ scores of the 3 questionnaire sections are
illustrated in Figure 4. There was significant improvement with the CI in the speech section. The CI median
score was 5.76 versus the unaided median score of 2.55
( p = 0.014), the CROS median score of 3.13 ( p = 0.014),
and the BAHA median score of 2.93 ( p = 0.007). In the
TABLE 2.
RESULTS
Individual and group median Hochmair-Schulz-Moser sentence test scores (% correct) for the different presentation configurations
Data Analysis
Data were analyzed with SAS 9.2. Normality of preoperative
and postoperative differences could not be assumed for many of
the investigated items. Therefore, comparisons of CI with preoperative conditions were performed using Wilcoxon signedrank test for paired observations, and p values were calculated
based on the exact distribution of the test statistic.
Because this is a pilot study with 11 patients, we present
p values without adjustment for multiple testing.
Contralateral
Bone-anchored
routing of signal
hearing aid
Cochlear
implant
outcome measure in rehabilitation with hearing devices and
contains 7 questions (14).
100.00
100.00
100.00
99.06
100.00
100.00
99.06
99.53
92.45
100.00
99.53
100.00
92.45Y100.00
S. ARNDT ET AL.
Contralateral
Bone-anchored
routing of signal
hearing aid
4
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COCHLEAR IMPLANTATION IN UNILATERAL DEAF PATIENTS
5
FIG. 2. Box-whisker plots of the critical SNRs of the 11 subjects obtained with the OLSA sentence in noise test for the unaided condition
and the aided condition with CI after 6 months. Significant improvement using the CI compared with the unaided condition is shown:
**pG 0.01 (Wilcoxon signed-rank test).
spatial section, the scores also were significantly better
with the CI (median, 5.71) versus the unaided condition (median, 2.29; p = 0.001), the CROS (median, 2.59;
p = 0.027), and the BAHA (median, 2.36; p = 0.002). In
the section on hearing quality, the CI median score was
7.81 versus a median score of 5.86 for the unaided group
( p = 0.21), a median score of 5.50 for the CROS group
( p = 0.1934), and a median score of 5.34 points for the
BAHA group (p = 0.15). Thus, the subjective assessment
of the patients shows no significant differences in the
quality of hearing. The tinnitus VAS scores are shown in
Figure 5. The median tinnitus intensity before CI surgery
of the 11 patients was 5. One patient had no tinnitus either
before surgery or after CI implantation. Six months after
CI use, the median tinnitus intensity decreased significantly to 0 when the CI was switched on (p = 0.0078).
The tinnitus intensity increased after switch-off of the
speech processor to a median score of 5. Five of 10
patients showed complete suppression of tinnitus with
the activated speech processor, and 3 patients reported
a reduction from preoperative score of 9 to 10 to postoperative score of 2 to 3. Another patient had constant tinnitus strength of 5 before surgery and after
implantation, independent of speech processor use. In 1
FIG. 3. Box-whisker plots of localization deviations of the 11 subjects in the unaided as well as the aided conditions with CROS hearing
aid, BAHA Intenso, and CI after 6 months. Significant improvement using the CI compared with each of the other conditions is shown on top
of their box plots: **p G 0.01 (Wilcoxon signed-rank test).
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6
S. ARNDT ET AL.
FIG. 4. Box-whisker plots of the scores of the 11 subjects for each section of the SSQ in the unaided as well as the aided conditions with
CROS hearing aid, BAHA Intenso, and CI after 6 months. Significant improvement using the CI compared with each of the other conditions
is shown on top of their box plots: *p G 0.05; **p G 0.01 (Wilcoxon signed-rank test).
patient, the tinnitus did not change after implantation
when using the processor but increased from 5 to 8 when
the speech processor was deactivated. In the HUI-3, the
overall group score for the CI condition is significantly
increased compared with the CROS ( p = 0.004) and the
BAHA ( p = 0.008). There is a tendency of preponderance
with the CI compared with the unaided condition ( p =
0.051). Closer inspection of individual subdomains in the
HUI-3, especially hearing and speech, did not reveal any
significant change (Table 3). The 7 domain scores of the
IOI-HA are presented in Figure 6. The highest scores
are obtained with the CI in all subdomains. The patients
used the CI significantly longer per day than the other
devices (CI versus BAHA, p = 0.002; CI versus CROS,
p = 0.016). Especially the most important subdomains
benefit (CI versus BAHA, p = 0.002; CI versus CROS,
p = 0.004), satisfaction (CI versus BAHA, p = 0.016;
CI versus CROS, p = 0.008), and QoL (CI versus BAHA,
p = 0.016; CI versus CROS, p = 0.016) show significant
improvement with the CI. The responses in the subdomains residual activity limitation (RAL) and residual
participation restrictions (RPR) demonstrated a significant advantage of the CI over the BAHA (RAL, p =
0.0137; RPR, p = 0.0078) but not in comparison with
the CROS (RAL, p = 0.0625; RPR, p = 0.1094). There
was no difference between the devices in the belief that
FIG. 5. VAS tinnitus loudness of the 11 subjects before CI implantation (unaided), 6 months after CI activation, with CI switched on and off.
Significant improvement using the CI compared with unaided condition is shown: **p G 0.001 (Wilcoxon signed-rank test).
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COCHLEAR IMPLANTATION IN UNILATERAL DEAF PATIENTS
TABLE 3.
Health utilities index 3
Vision
Hearing
Speech
Emotion
Pain
Ambulation
Dexterity
Cognition
Health utility index score
7
Group median and range (in parentheses) on the domains of the Health Utilities Index 3
Unaided
Contralateral routing of signal
Bone-anchored hearing aid
Cochlear implant (6 mo)
1.00 (0.98Y1.00)
0.80 (0.61Y1.00)
1.00 (1.00Y1.00)
0.95 (0.38Y1.00)
0.96 (0.77Y1.00)
1.00 (0.93Y1.00)
1.00 (0.95Y1.00)
1.00 (0.83Y1.00)
0.56 (j0.07 to 1.00)
Cochlear implant
versus unaided
p = 0.0508
0.99 (0.98Y1.00)
0.80 (0.61Y1.00)
1.00 (1.00Y1.00)
0.95 (0.85Y1.00)
0.98 (0.90Y1.00)
1.00 (0.93Y1.00)
1.00 (1.00Y1.00)
1.00 (0.83Y1.00)
0.65 (0.22Y0.93)
Cochlear versus contralateral
routing of signal
p = 0.0039
1.00 (0.98Y1.00)
0.89 (0.61Y1.00)
1.00 (1.00Y1.00)
0.95 (0.85Y1.00)
0.96 (0.77Y1.00)
1.00 (1.00Y1.00)
1.00 (1.00Y1.00)
1.00 (0.95Y1.00)
0.67 (0.41Y1.00)
Cochlear implant versus
Bone-Anchored Hearing Aid
p = 0.002
1.00 (0.98Y1.00)
0.89 (0.74Y1.00)
1.00 (1.00Y1.00)
1.00 (0.95Y1.00)
1.00 (0.90Y1.00)
1.00 (1.00Y1.00)
1.00 (0.95Y1.00)
1.00 (0.92Y1.00)
0.80 (0.54Y1.00)
Significant changes (Wilcoxon signed-rank test) after 6 months of cochlear implant use in comparison with the unaided situation, the contralateral
routing of signal, and the Bone-Anchored Hearing Aid test trials are indicated.
others are bothered by the patient_s hearing limitations
(impact on others).
DISCUSSION
Our investigation shows that the rehabilitation of
patients with unilateral deafness with a CI yields better
results in speech comprehension and localization than
conventional pseudobinaural hearing rehabilitation with
CROS or BAHA or than in the unaided condition. The
subjective self-assessments of the patients with questionnaires correlate with the objective speech comprehension and localization results.
For HSM testing, speech comprehension in noise in the
most difficult configuration for patients with unilateral
deafness (SssdNnh) was significantly superior with the
CI. These results were confirmed by the critical SNR
obtained by the OLSA test. Although Dillon (15) writes
that there is no point in verifying binaural gain from the
head shadow effect in the objective evaluation of hearing
aids because Bthis advantage will occur, in some real life
situations, for everyone who has a head![, unilaterally deaf
patients will profit from this purely physical effect only
when using a CI. In patients with unilateral hearing loss,
the head shadow effect still occurs but may be a detriment
if speech originates on the opposite side of the head from
their only hearing ear (16). It is important to offer this
group of patients the opportunity of using both ears, with
the CI ear receiving the sound with a better SNR, which is
impossible in the pseudobinaural situation. Like Vermeire
and Van de Heyning (17), we could not directly measure
the acoustic head shadow effect in the free-field condition
because of the difficulties in masking the normal hearing
ear. Following their recommendation to use the spatial
FIG. 6. Box-whisker plots of the scores of the 11 subjects for each outcome domain (USE, daily use; BEN, benefit; RAL, residual activity
limitation; SAT, satisfaction; RPR, residual participation restrictions; Ioth, impact on others; QoL, quality of life) and the overall score in the
IOI-HA for CROS, BAHA, and CI after 6 months. Significant improvement using the CI compared with each of the other conditions is shown
on top of their box plots: *p G 0.05; **p G 0.01 (Wilcoxon signed-rank test).
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8
S. ARNDT ET AL.
configuration SciN0 where a combination of head shadow
and squelch effect can be evaluated, we calculated the
combined effect as the difference between the aided condition with CI and the unaided condition for the spatial
configuration SssdNnh. The contribution of the head shadow effect to this combined effect remains unclear. The
combined effect is 4.9 dB and represents a significant
improvement with the CI. The size of this effect in the
unilateral group reported by Vermeire and Van de Heyning
(17) was 1.7 dB, which cannot be compared with our
results because of the different presentation setups used.
Although we could not prove a significant squelch effect,
like Vermeire and Van de Heyning (17) in their unilaterally
deaf group with a more difficult presentation configuration, it seems that binaural performance is better than the
performance with pseudobinaural treatment or unaided.
The only test configuration in which we could not find any
advantage with the CI was the S0N0 configuration. Consequently, the summation effect obtained from this presentation configuration was not significant. Vermeire and
Van de Heyning (17) even described a small deterioration
of the critical SNR in this configuration with the CI
12 months after activation compared with the unaided
situation. Dillon (15) voiced concern that binaural summation, similar to binaural squelch, will be affected by
significant interaural asymmetries for the test measures.
Our unilateral subjects have a clear interaural asymmetry
in the unaided as well as in the aided condition with CI.
That could explain the difficulties in detecting these 2
binaural effects.
The localization results demonstrate a significant improvement in the binaural condition with CI compared
with all other conditions and thus a significant binaural
advantage for localization ability for the group. Even in
the unaided condition, the patients showed a localization
error of approximately 34 degrees on median which is
approximately 34 degrees better than the chance level of
68.6 degrees. Probably, these patients benefit from 2 cues
underlying monaural sound localization in the horizontal
plane, head shadow, and spectral pinna cues (18,19). As
in several published studies on sound localization in
hearing impaired patients, for example, Laszig et al. (20),
the intention of sound level roving in our study was to
reduce the head shadow cue as far as possible. However,
despite sound level roving, Laszig et al. (20) showed in
bilateral CI patients an average horizontal localization
root mean square error of 87 degrees for the left monaural
CI condition and 89 degrees for the right monaural CI
condition, which is better than the chance level of 105
degrees inherent to the full circle array of 12 speakers
used for localization tests. Van Wanrooij and Van Opstal
(19) reported that monaurally deaf listeners relied heavily
on the head shadow cue when localizing sound with
randomly interleaved sound levels in the horizontal plane.
Until now, there are no reports on localization ability in
patients with unilateral deafness after cochlear implantation. However, several studies consistently demonstrate a
statistically significant improvement of localization for
bilateral versus unilateral CI stimulation (20Y23).
The patients scored better in all sections of the SSQ
questionnaire with the CI. They scored significantly
higher in the sections spatial hearing and speech comprehension. These favorable results with the CI in unilaterally deaf patients are in agreement with Vermeire and
Van de Heyning (17). In contrast to them, we were able to
prove a significantly better score with the CI in the speech
understanding section than in the unaided situation. There
was no difference between the treatment options and the
unaided situation in the hearing quality section. Thus,
there is no decrement in perceived speech sound quality
when using the CI compared with the unaided condition,
which might be expected because of the use of 2 different
auditory stimulation modalities.
The initial intention of the cochlear implantation in
unilaterally deaf patients, published in 2008 (24), was not
binaural hearing and improvement of sound localization,
but the treatment of seriously bothersome tinnitus. Van de
Heyning et al. (24) report on complete tinnitus inhibition
in 3 of 22 subjects after 6 months of CI use. Our tinnitus
VAS results also demonstrate a significant reduction or
even complete suppression of tinnitus in 8 of 10 patients.
The findings of the first report and of our study represent
a very encouraging side effect for patients with unilateral
deafness after cochlear implantation. Although we could
demonstrate a higher overall QoL score with the CI using
the HUI-3 questionnaire, we did not see any significant
differences in the QoL subdomains. There was a tendency
to improvement with the CI in comparison with the
CROS device only in the subdomains hearing and emotion. One reason for the lack of improvements in comparison with other studies with bilaterally deaf patients
(25) may be that hearing impairment in unilateral deafness involves fewer complaints because of one normal
hearing ear. The IOI-HA outcome in this study showed a
substantial amount of benefit, satisfaction, and improvement in QoL with the CI. All but 1 patient used the CI for
more than 8 hours per day; it was significant in helping
them to improve their hearing, reduced the number of
situations in which hearing loss was significantly problematic, and had a significant positive impact on the
enjoyment of life for most of the patients.
One weakness of our study is that the BAHA was
mounted on the headband. We have to keep in mind that
the difference in bone conduction thresholds can vary up to
15 dB particularly in the higher frequencies compared with
the use of the BAHA processor mounted to the titanium
implant because of the damping of the skin and hairs (26).
That may imply better results in the SssdNnh configuration
after BAHA surgery. Linstrom et al. (27) demonstrated that
the implanted BAHA does indeed enhance communication
in unilaterally deaf patients when speech is presented on
the BAHA side. They also showed poorer speech comprehension when noise was presented on the BAHA side.
However, we assume that even after implantation of the
titanium screw, the advantages of binaural hearing restoration are predominant with the CI. To prove this assumption, it would be necessary to perform BAHA surgery
before CI surgery. Nevertheless, this procedure would not
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COCHLEAR IMPLANTATION IN UNILATERAL DEAF PATIENTS
conform to the Declaration of Helsinki. We are able to
compare these results from 1 patient who had 3 years of
experience with the BAHA Intenso (Subject 4 in Table 1).
The CI was provided to the patient after BAHA surgery
because she complained of persistent difficulties. Speech
comprehension of HSM sentences in the configuration
SssdNnh improved from 31.1% with the BAHA to 60.8%
with the CI. In the reverse configuration SnhNssd, the
patient attained 100% with both devices. In the S0N0
configuration, speech comprehension also increased from
76.4% to 79.7%, and localization ability improved from
22.7- to 13.7-degree deviation. The second weakness of
our study is associated with the bias related to the inclusion
criteria of our study. Only patients whose conventional
CROS or BAHA therapy was not successful were enrolled.
This could imply that we have a nonrepresentative selection of unilaterally deaf patients who showed no improvement with conventional treatment options. However,
we could demonstrate the superiority of the CI in patients
with unilateral hearing loss in comparison with the BAHA
and the CROS hearing aid using both objective and subjective measures. Our data prove that the integration of
acoustic stimulation of 1 ear and electrical stimulation of
the contralateral ear is possible. In our opinion, one important prerequisite for the success of cochlear implantation in unilateral deafness is the careful selection of
patients. In patients with profound bilateral hearing loss,
the duration of deafness is one important factor influencing
the outcome in speech comprehension (28). In conformity
with these findings, patients with postlingually acquired
unilateral deafness should be provided with a CI shortly
after confirming the persistence of deafness. However, for
patients deafened because of other reasons (complete
cochlear ossification, nonintact auditory nerve), the conventional treatments still represent an option for improvement of speech comprehension in noisy environments and
QoL. Of course, cochlear implantation in patients with
unilateral deafness is considerably more expensive than the
other treatment options. However, restoration of binaural
hearing seems possible with the CI. In our opinion, the
additional expense can be justified by greater benefit in
both professional and private life, thus improving the
overall QoL.
CONCLUSION
The different treatment options including cochlear
implantation for patients with unilateral deafness were
compared for the first time. The cochlear implantation
turned out to be the best option for improvement of
speech comprehension in noise and localization abilities.
Although we could not demonstrate a significant true
binaural effect with the CI, there was a clear tendency for
the existence of these effects.
REFERENCES
1. Fowler EP. Bilateral hearing aids for monaural total deafness. A
suggestion for better hearing. Arch Otolaryngol 1960;72:41Y2.
9
2. Tonning FM. Directional audiometry. IV. The influence of azimuth
on the perception of speech in aided and unaided patients with
monaural hearing loss. Acta Otolaryngol 1972;73:44Y52.
3. Giolas TG, Wark DJ. Communication problems associated with
unilateral hearing loss. J Speech Hear Disord 1967;32:336Y43.
4. Tillman TW, Bucy PC, Carhart R. Monaural versus binaural discrimination for filtered CNC materials. The impaired auditory
mechanism. SAM-TR-66-64. Tech Rep SAM -TR 1966;1Y9.
5. MacKeith NW, Coles RR. Binaural advantages in hearing of
speech. J Laryngol Otol 1971;85:213Y32.
6. Cox RM, DeChicchis AR, Wark DJ. Demonstration of binaural
advantage in audiometric test rooms. Ear Hear 1981;2:194Y201.
7. Bronkhorst AW, Plomp R. Binaural speech intelligibility in noise
for hearing-impaired listeners. J Acoust Soc Am 1989;86:1374Y83.
8. Hochmair Desoyer I, Schulz E, Moser L, et al. The HSM sentence
test as a tool for evaluating the speech understanding in noise of
cochlear implant users. Am J Otol 1997;18:83.
9. Wagener K, Kuhnel K, Kollmeier B. Development and evaluation
of a German sentence test: I. Design of the Oldenburger sentence
test. Z Audiol 1999;38:4Y15.
10. Wagener K, Brand T, Kollmeier B. Development and evaluation of
a German sentence test: Part III. Evaluation of the Oldenburg sentence test. Z Audiol 1999;38:86Y95.
11. Wazen JJ, Ghossaini SN, Spitzer JB, et al. Localization by unilateral
BAHA users. Otolaryngol Head Neck Surg 2005;132:928Y32.
12. Gatehouse S, Noble W. The Speech, Spatial and Qualities of
Hearing Scale (SSQ). Int J Audiol 2004;43:85Y99.
13. Furlong WJ, Feeny DH, Torrance GW, et al. The Health Utilities
Index (HUI) system for assessing health-related quality of life in
clinical studies. Ann Med 2001;33:375Y84.
14. Cox RM, Alexander GC. Expectations about hearing aids and their
relationship to fitting outcome. J Am Acad Audiol 2000;11:368Y82.
15. Dillon H. Hearing Aids. New York, NY: Thieme, 2001:370Y440.
16. Markides A. Binaural Hearing Aids. London, U.K.: Academic
Press, 1977. Advantages of Binaural Hearing over Monaural
Hearing.
17. Vermeire K, Van de Heyning P. Binaural hearing after cochlear
implantation in subjects with unilateral sensorineural deafness and
tinnitus. Audiol Neurootol 2009;14:163Y71.
18. Slattery WH III, Middlebrooks JC. Monaural sound localization:
acute versus chronic unilateral impairment. Hear Res 1994;75:
38Y46.
19. Van Wanrooij MM, Van Opstal AJ. Contribution of head shadow
and pinna cues to chronic monaural sound localization. J Neurosci
2004;24:4163Y71.
20. Laszig R, Aschendorff A, Stecker M, et al. Benefits of bilateral
electrical stimulation with the nucleus cochlear implant in adults:
6-month postoperative results. Otol Neurotol 2004;25:958Y68.
21. van Hoesel RJ, Tyler RS. Speech perception, localization, and
lateralization with bilateral cochlear implants. J Acoust Soc Am
2003;113:1617Y30.
22. Nopp P, Schleich P, D’haese P. Sound localization in bilateral users
of MED-EL COMBI 40/40+ cochlear implants. Ear Hear
2004;25:205Y14.
23. Laske RD, Veraguth D, Dillier N, et al. Subjective and objective
results after bilateral cochlear implantation in adults. Otol Neurotol
2009;30:313Y8.
24. Van de Heyning P, Vermeire K, Diebl M, et al. Incapacitating
unilateral tinnitus in single-sided deafness treated by cochlear
implantation. Ann Otol Rhinol Laryngol 2008;117:645Y52.
25. Damen GW, Beynon AJ, Krabbe PF, et al. Cochlear implantation
and quality of life in postlingually deaf adults: long-term follow-up
2. Otolaryngol Head Neck Surg 2007;136:597Y604.
26. Grunder I, Seidl RO, Ernst A, et al. [Relative value of BAHA
testing for the postoperative audiological outcome]. HNO 2008;56:
1020Y4.
27. Linstrom CJ, Silverman CA, Yu GP. Efficacy of the bone-anchored
hearing aid for single-sided deafness. Laryngoscope 2009;119:
713Y20.
28. van den BE, Dunnebier EA. Cochlear implantation in postlingually
hearing-impaired adults: choosing the most appropriate ear. Int J
Audiol 2009;48:618Y24.
Otology & Neurotology, Vol. 00, No. 00, 2010
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