Can Middle Ear Dysfunction Impact Cochlear Implant Function?
Jeffrey L. Simmons, M.A., CCC-A, Boys Town National Research Hospital, Omaha, NE
Because a cochlear implant (CI) bypasses the
conductive component of the normal auditory
process, logic might suggest that a middle ear
problem cannot impact the function of a CI.
Anecdotal and scientiﬁ c evidence suggest that this
may not be the case. Inﬂ ammatory processes in
the tissue of the inner ears of implant recipients
can result in increased electrode impedance values
1-3. This inﬂ ammation has been associated with
middle ear dysfunction in some cases 3. Impedance
indicates the amount of electrical resistance for a
stimulating electrode and the surrounding tissue.
When impedances increase between the active
and return electrodes, terminal voltage will increase
to maintain a constant charge. If the impedance
is too high, the terminal voltage could reach the
maximum supply voltage (compliance limit), and
it may become impossible to attain the desired
charge from the implant. The function of the CI
would consequently be affected (see Fig. 1). The
following is a retrospective case review of a pediatric
cochlear implant recipient for whom changes in
electrode impedances and auditory function were
closely associated with middle ear dysfunction.
Fig. 1 -- Cycle described by Neuberger et al. 3
in which a triggering event such as inﬂ ammation
might lead to a self-perpetuating problem with per-
formance of the CI. In this cycle, increased imped-
ances that cause some or all electrodes to reach
compliance limits result in asymmetries in the bi-
phasic stimulus pulses from the affected elec-
trodes. This can lead to electrolytic changes and
Platin dissolution that can increase impedances
Female, Age 3;8
• Right Advanced Bionics HR90K at age 1;1
• Home schooled
• Speech-language standard scores in the high
• Concern for “overnight” change in auditory per-
formance at 2;6 post-implant (inconsist ability to
identify Ling sounds, uncharacteristic “self-talk”
and humming, frequent requests of needing to
change the battery, and generally listless behav-
ior as if she did not feel well).
Figure 2: Baseline Performance (2 yrs., 1 mos. Post Implant)
B: electrode impedances
C: map levels
D: behavioral audiogram with implant in use 4 months prior to the
ﬁ rst parental report of changes in cochlear implant performance.
Figure 3: 1st Episode of Change in Auditory Behavior (2 yrs.,6 mos. Post Implant)
Figure 4: Resolution of Symptoms (One Month Later)
Figure 5: 2nd Episode of Changes in Auditory Behavior (Two Months Later)
Figure 6: Serial Impedances
Pattern of impedances across nearly four years.
Black boxes highlight occurrences of signiﬁ cantly
elevated impedances associated with possible
middle ear problems. Periodic impedance
measures since 2008 (not all shown) have all been
in the normal range with no signiﬁ cant increases.
There have been no further reported episodes of
ﬂ uctuations in auditory performance and no known
episodes of middle ear dysfunction or effusion.
• Two transient episodes of changes in CI electrode
impedances and auditory performance apparently
associated with the occurrence of middle ear
• Neuberger et al.3 refer to increases in impedances
in implant recipients that occur in connection with
common colds. For 7 individuals, spontaneous
increases in impedances closely correlated in
time with inﬂ ammatory events believed to have
resulted from labyrinthitis were reported.
• One possible explanation for the changing
impedances for the child in this case study might
be an inﬂ ammation in cochlear tissue triggered
by the presence of otitis media.
• A possible cause could be pressure changes in the
middle ear from effusion that increases pressure
in the cochlea via the round window, which may
alter the position of the electrode array. When
the ﬂ uid resolves, intracochlear pressure returns
to its normal state, and the electrode array moves
back to where it was formerly situated. However,
ﬁ brous tissue growth around the array may
preclude this as a possible explanation.
• Another possible explanation would be that ﬂ uid in
the middle ear changes the pathway of electrical
current generated by the implant.
Suggested protocol to address this issue:
• Regular monitoring of middle ear function and
electrode impedances, especially for young
children or poor self-reporters
• ENT referral for antibiotic or anti-inﬂ ammatory
• Adjustment of implant stimulus levels if auditory
responses are affected
• Manual widening of stimulus pulsewidth or use
of Automatic Pulsewitdth II (APW II) to maintain
adequate loudness and remain within voltage
• Creation of an “emergency” program for patients
with frequent or recurrent middle ear problems
and/or ﬂ uctuations in auditory performance
1. Clark, G.M, Fracs, S.A., Shute, M.B., Shepherd, R.K., Carter, T.D. (1995). Cochlear implantation:
Osteoneogenesis, electrode-tissue impedance, and residual hearing. Annals of Otology, Rhinology,
& Lanrygology, 104(Suppl. 166), 40-42
2. De Ceulaer, G., Johnson, Yperman, M., Daemers, K., Offeciers, F.E., O’Donoghue, G.M., Govaerts
(2003). Long-term evaluation of the effect of intracochlear sterioid deposition on electrode
impedance in cochlear implant patients. Otology & Neurology, 24, 769-774.
3. Neuburger, J., Lenarz, T., Lesinski-Schiedat, A., Büchner, A. (2009) Spontaneous increased in
impedance following cochlear implantation: Suspected causes and management. International
Journal of Audiology, 48, 233-239.
4. Tykocinski, M., Cohen, L.T., Cowan, R.S. (2005). Measurment and analaysis of access resistance
and polarization impedance in cochlear implant recipients. Otology & Neurotology, 26, 948-956.
A-B: Follow-up visit to the clinic one month after the middle ear
dysfunction was identiﬁ ed. Static admittance measured during
tympanometry and electrode impedances were more similar to the
C: Map levels similar baseline.
D: The threshold for 250 Hz narrowband noise on the behavioral
audiogram showed an improvement of 35 dB even though stimula-
tion levels (M levels) were lower than one month earlier.
Recurrence of concerns for auditory performance and implant
A: Static admittance on the typanogram was just within normal
limits but was reduced compared to the baseline obtained for the
child’s right ear.
B: Impedances for E 1-11 were elevated once more, and E 6 was
classiﬁ ed as an open circuit.
C-D: The behavioral audiogram for a newly created “emergency”
program intended for use immediately as well as in the event that
episodes of worsening auditory performance again. This program
featured increased M levels and deactivated E 6 due to the open
circuit for the electrode.
A: Compared to baseline, her tympanogram showed reduced
static admittance consistent with middle ear effusion, which was
medical diagnosis at the time.
B: Impedance values for E 1-11 were elevated relative to baseline
what is typically seen for the more recent generations of electrode
systems 4. Electrodes 5 and 6 were open circuits.
C: The modiﬁ ed map used for testing.
D: Even after increasing stimulation levels for the implant in
an attempt to restore an adequate perception of loudness, the
behavioral threshold for narrowband noise at 250 Hz was 25 dB
poorer than that measured 4 months previously, and the child
continued to have difﬁ culty discriminating between or identifying the
phonemes /i/ and /u/. Formants for the Ling sounds (conversational
level) are plotted in terms of frequency and amplitude. Note how the
low-frequency phonemes may have had their audibility impacted
by the poorer threshold observed for 250 Hz.
AUTHOR CONTACT INFORMATION
Jeffrey Simmons, M.A., CCC-A
425 N. 30th St., Omaha, NE 68131