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serious maladies as well as issues such as persistent otitis media
can result in delays. Inefficient programmatic designs requir-
ing multiple transitions of care between physicians, audiologists
who provide hearing aids, speech and auditory verbal therapists,
as well as audiologists who work with cochlear implants may
result in further delays.
This study aimed to better characterize the clinical course of
children with a bilateral NR result on diagnostic ABR (dABR)
as managed with the paradigm described above. We compared
the clinical time course and outcomes of children with NR
result on ABR testing who went on to obtain a CI and those
who did not. We also demonstrated the time course to CI in
this distinct group of patients, identifying any systematic and/
or incidental delays. We believe that if all children with a NR
ABR can be shown to consistently progress to a CI, then the NR
ABR could potentially be considered as one of the early indica-
tions for CI. With such knowledge at hand, we can anticipate
the needs of such a child who is expected to progress to a future
CI and therefore mitigate many of the aforementioned delays.
MATERIALS AND METHODS
The institutional review board at the study institution
approved the study. A retrospective review of all pediatric
patients (<18 years of age) who underwent ABR testing at the
study institution between July 1, 2006, and June 30, 2011, was
undertaken to identify those with a binaural NR result. All test-
ing was performed and analyzed by experienced pediatric audi-
ologists. Patients were tested either in natural sleep conditions
in the clinic or under sedation/general anesthesia in an operat-
ing room, imaging center, or a sedation suite. All ABRs were
included in the review, regardless of location (operating room
or clinic) or condition (sedation or natural sleep). ABR testing
was recorded with the Biologic Navigator Pro system (Natus
Medical Inc., San Carlos, CA). The ABR protocol includes at
a minimum of two main stimulus types: a 100
μ
sec click and
a “single-cycle” 250 Hz tone burst. Responses to tone bursts at
frequencies of 500, 1000, 2000, and 4000 Hz were tested when
possible. Because of time constraints, not all frequencies could
be completed for all patients. The single-cycle 250 Hz tone
burst is shaped by a Blackman window with 2-msec rise/fall
times and no plateau. A 2-channel recording is undertaken (Fz –
A1 or A2, referenced to Fpz) using a bandwidth of 100 to 3000
Hz (clicks) or 30 to 3000 Hz (250 Hz tone bursts) and a time
window of 20 msec. The physiologic ABR threshold is taken
as the lowest stimulus level at which a wave V response can
be visually detected in the response. A NR result was defined
as no definable response waveforms at the maximum outputs
of the equipment (90 dB nHL) for clicks and at least a 250
Hz tone burst. Those with response morphologies consistent
with Auditory Neuropathy Spectrum Disorder (ANSD) were
excluded from the study. Diagnosis of ANSD is made based
on an absent or grossly abnormal ABR and the presence of a
cochlear microphonic using single-polarity stimulation and/or
presence of otoacoustic emissions. The cochlear microphonic is
distinguished from neural responses if the response inverts with
polarity inversion and latency remains constant with changing
stimulus level. Stimulus artifact is also ruled out by disconnect-
ing the sound tube during recording.
Only children with bilateral NR results were included in
the study. For these children, demographic and medical data
were extracted from the electronic medical record to include
date of birth, newborn hearing screening (NBHS) results, age
of diagnosis, comorbidities, and radiographic imaging results.
Behavioral audiometric measures were also collected for those
children with testing performed at the study institution, by
experienced pediatric audiologists, using standard visual rein-
forcement audiometry techniques. This testing was attempted
on all patients starting between 6 and 8 months of age unless
severe medical comorbidities precluded testing. Children were
tested at regular intervals of 3–4 weeks until reliable data were
collected. Children without reliable test results, those with only
behavioral observation results, those unable to complete testing,
and those with only tests performed outside the study institution
were excluded.
All children were fit with hearing aids at the study institu-
tion using desired sensation level prescriptive targets. Probe
microphone measures were used to quantify the real-ear-to-
coupler-difference (RECD) for verification of speech audi-
bility and maximum output (Bagatto et al. 2005). When the
RECD could not be measured because of limited cooperation
or subject noise, an age-related average RECD estimated the
acoustic characteristics of the child’s occluded ear. Progress in
communication and audition skills during amplification trial
was assessed by a speech language pathologist and compared
with age-matched hearing peers. Referral to the CI program
was based on the amount of residual hearing and/or progress
with amplification while being enrolled in an active, diagnos-
tic auditory-based intervention program. This referral process
from the diagnostic/hearing aid audiologists to the CI program
is a highly integrated one that is enhanced by an electronic, real-
time management system as well as a weekly, multidisciplinary
meeting in an effort to expedite transitions. The time course of
clinical progression and final hearing assistive device strategy
was documented.
Data were entered in a Microsoft Excel Spreadsheet (Red-
mond, Washington, USA) and outcomes summarized. In an
effort to accurately understand the time course of clinical pro-
gression between ABR testing, behavioral audiometric testing,
and CI surgery, two distinct categories of patients emerged and
were analyzed separately. ABRs were considered as dABR
if the ABR was performed before any behavioral testing. In
TABLE 1. Factors that can delay cochlear implantation
Auditory
Delay in diagnosis
Significant residual hearing
Fluctuating hearing
Unreliable or conflicting test results
Under-fit amplification
Speech development
Good progress despite profound hearing loss
Medical
Anatomic uncertainty (cochlear nerve deficiency severe inner
ear malformations, etc.)
Multiple comorbidities (prematurity, CP, autism, etc.)
Auditory neuropathy spectrum disorder
Parental issues
Poor follow-up
Poor compliance with amplification trial
Socioeconomic barriers
Parental education/understanding
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