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CE: S.S.; ON-17-300; Total nos of Pages: 6;
Otology & Neurotology
xx:xx–xx ß 2017, Otology & Neurotology, Inc.
Cochlear Implant Associated Labyrinthitis: A Previously
Unrecognized Phenomenon With a Distinct Clinical and
Electrophysiological Impedance Pattern
Deeyar A. Itayem, Douglas Sladen, Colin L. Driscoll, Brian A. Neff,
Charles W. Beatty, and Matthew L. Carlson
Department of Otolaryngology–Head and Neck Surgery, Mayo Clinic, Rochester, Minnesota
Objectives: To report a unique clinical entity ‘‘cochlear
implant associated labyrinthitis,’’ characterized by a distinct
constellation of clinical symptoms and pattern of electrode
impedance fluctuations.
Study Design: Retrospective chart review.
Methods: All patients that underwent cochlear implantation
between January 2014 and December 2016 were retrospectively reviewed. All subjects with acute onset dizziness,
device performance decline, and characteristic erratic pattern
of electrode impedances occurring after an asymptotic
postoperative interval were identified and reported.
Results: Five patients with the above criteria were identified,
representing 1.4% of all implant surgeries performed during this
time. The median age at time of implantation was 71 years, and
the median time interval between implantation and onset of
symptoms was 126 days. All patients exhibited acute onset
dizziness, subjective performance deterioration, erratic impedance pattern, and two experienced worsening tinnitus. Two of
five patients underwent subsequent CT imaging, where good
electrode placement was confirmed without cochlear ossification. Two of five patients received oral prednisone therapy. All
patients reported a subjective improvement in symptoms and
stabilization of electrode impedances. Three patients subsequently received vestibular testing, where significantly reduced
peripheral vestibular function was identified.
Conclusions: We describe a unique clinical entity, ‘‘cochlear
implant associated labyrinthitis,’’ characterized by a distinct
constellation of clinical symptoms and corresponding electrode
impedance anomalies. The exact cause for this event remains
unknown, but may be related to viral illness, delayed foreign body
reaction to the electrode, or a reaction to electrical stimulation.
Future studies characterizing this unique clinical entity are
needed to further elucidate cause and optimal management.
Key Words: Cochlear implant—Impedance—Labyrinthitis.
Cochlear implantation (CI) remains the gold standard
for aural rehabilitation of children and adults with bilateral
severe to profound sensorineural hearing loss. Despite
significant advances in device design and refinements in
surgical technique, a small subset of patients experience
unforeseen surgical and device-related events. Examples
of such events include scalp flap complications, meningitis, documented internal device failure, and unexplained
deterioration of performance (1). Such complications are
distressing to the patient and surgeon alike and result in
patient morbidity, unanticipated costs, and interruption in
device use. Perioperative complications and other events
that threaten device explantation have been well characterized by a number of clinical studies (2–5).
In recent years the authors have identified a distinct
pattern of transient device malfunction in a subset of
established implant users characterized by acute onset
dizziness, device performance decline, and distinctive
erratic pattern of electrode impedances. In sharing this
experience, providers at other centers have also observed
this unique constellation of findings in a small number of
patients. Raising awareness regarding this process and
further characterizing the clinical syndrome may help
facilitate timely recognition and management and potentially reduce risk of overtreatment.
Otol Neurotol 38:xxx–xxx, 2017.
Address correspondence and reprint requests to Matthew L. Carlson,
M.D., Department of Otolaryngology–Head and Neck Surgery,
Mayo Clinic, 200 First St SW, Rochester, MN 55905; E-mail: carlson.
Financial Material & Support: No financial support was used in this study.
The following manuscript was presented in oral form at the Combined Otolaryngology Spring Meeting (COSM), San Diego, CA 2017.
This material has not been previously published in part or whole, and is
not currently under consideration for publication elsewhere.
M.L.C. and C.L.D. are consultants for Advanced Bionics Corporation, Cochlear Corporation, and MED-EL GmbH.
The authors disclose no conflicts of interest.
DOI: 10.1097/MAO.0000000000001615
Following Institutional Review Board approval (IRB # 16–
006130) all patients that underwent cochlear implantation
between January 2014 and December 2016 at the authors’
Copyright © 2017 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
CE: S.S.; ON-17-300; Total nos of Pages: 6;
center were retrospectively reviewed. Nineteen patients with a
distinct erratic impedance pattern were identified. Of these, five
patients had acute onset dizziness and device performance
decline after an asymptomatic postoperative period. Patients
with neurological conditions such as hydrocephalus, stroke, or
vestibular migraines that could account for their symptoms
were excluded. Data regarding these five cases are presented
using descriptive statistics.
In each case, electrical impedances were tested on all intracochlear contacts at baseline, during disease presentation, and
following symptom cessation. A 25-microsecond biphasic pulse
was presented to each contact using a stimulation level of 80
clinical units. A normal value falls between 566 V and 30 kV. A
value below this range designates a short circuit, and a value
above this range is classified as an open circuit. Speech perception reported subjectively by the patients was used as a surrogate
for device performance as formal word and sentence recognition
testing was not routinely performed during episodes.
6 months before onset of symptoms. Two patients had
a history of previous otologic surgery in the implanted
ear—tympanoplasty (S2) and a left middle ear exploration (S5). The underlying cause of sensorineural loss was
hereditary (S1), iatrogenic (S2), noise-induced (S3),
idiopathic (S4), and Menière’s disease (S5). Further
baseline patient data are presented in Table 1.
All patients had lateral wall electrode designs: three were
implanted with the Cochlear Nucleus CI522 device and two
with the Nucleus CI422 device (Cochlear Americas, Englewood, CO). All patients had good initial device performance
before the development of symptoms as demonstrated by
speech perception scores (Table 2). In addition, all were
asymptomatic for at least 8 weeks following surgery, with
four of the five patients reporting onset of symptoms more
than 12 weeks later. The median time interval between
implantation and onset of symptoms was 126 days.
Patient Characteristics
Five patients met study criteria, representing 1.4% of
all cochlear implant surgeries performed during the time
period. The median age at the time of implantation was
71 years old (range, 55–81), four patients were men, and
four had left-sided implants. One patient (S5) had a
history of Ménière’s disease without any attacks for
Patient No.,
Sex, Age
Device Type
S1, M, 71
Nucleus 422
S2, F, 24
Nucleus 522
S3, M, 81
Nucleus 422
S4, M, 72
Nucleus 522
S5, M, 55
Nucleus 522
Disease Presentation and Management
Presenting symptoms are listed in Table 1. All patients
experienced acute onset dizziness exacerbated by head
movement and subjective performance deterioration.
Two patients experienced worsening tinnitus compared
with preimplantation including one with new onset tinnitus. None experienced other symptoms of non-auditory
stimulation such as facial spasm or pain.
Characteristics of five patients with ‘‘cochlear implant associated labyrinthitis’’
‘‘Motion Sickness’’;
exacerbated by head
movement; worsening
tinnitus; left aural
fullness; worsening
speech perception
Nausea; positional
dizziness; vertigo;
headache; worsening
speech perception
Dizziness; gait
instability; right
beating nystagmus;
worsening speech
Imbalance especially
with quick head
movement; mild
vertigo (began a
week after imbalance
onset); worsening
speech perception
Dizziness; oscillopsialike experience with
head movement;
static sounds;
(baseline stable
Menière’s disease);
worsening speech
Onset of
164 days
Imbalance remains at
visit 17 months
after symptom
40 mg taper
(10 days)
57 days
<1 week
Meclizine and
685 days
No symptoms at
visit 6 weeks after
symptom onset
126 days
16 weeks ¼ ‘‘70%
after 2nd course
of prednisone
60 mg
taper three
88 days
Symptoms improved
at 8 weeks
Estimated Time to
Recovery After
Symptom Onset
Otology & Neurotology, Vol. 38, No. xx, 2017
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CE: S.S.; ON-17-300; Total nos of Pages: 6;
Speech perception scores before cochlear implantation, and postoperatively before symptom onset
Pre-Cochlear Implantation
Post-Cochlear Implantation (And Before Symptoms)
Right (hearing aid): CNC word test list 2: 30% correct for words
and 58% correct for phonemes; AzBio sentence test in quiet list
4: 57% correct; AzBio sentence test at þ5SNR list 5: 13%
correct; BKB-SIN sentence test in noise: four list average
(paired lists 9 and 10) 9.75 Db SNR for 50% correct;
Left (hearing aid): CNC word test list 4: 22% correct for words
and 54% correct for phonemes; AzBio sentence test in quiet list
2: 48% correct; AzBio sentence test at þ5SNR list 7: 14%
correct; BKB-SIN sentence test in noise; four list average
(paired lists 5 and 6) 12 dB SNR for 50% correct
Left (hearing aid): CNC words (list 3): 25% words, 38%
phonemes; AzBio sentences (list 4): 32%; BKB-SIN (lists 7, 8
ab): 23.5 dB SNR for 50% correct; R-SPACE HINT (lists 1, 2):
2.1 dB SNR for 50% correct
Right (hearing aid): CNC words (list 10): 44% words, 70%
phonemes; AzBio sentences (list 10): 66%; Left (hearing aid):
CNC words (lists 10, 9): 62% words, 75% phonemes. AzBio
sentences (list 10, 9): 65%; Bilateral (hearing aid): CNC words
(list 10): 60% words, 83% phonemes; AzBio sentences (list 10):
62%; BKB-SIN (lists 7ab8ab): 12.5 dB SNR
Left (hearing aid): CNC word (list 2): 8% correct words, 32%
correct phonemes
Bilateral (hearing aid): CNC word (list 1): 0% correct for words
and 32% correct for phonemes; AzBio sentence, quiet list 9:
7% correct; BKB-SIN sentence: four list average (paired lists 9
and 10) 22.25 dB SNR for 50% correct
Left (cochlear implant): CNC words, quiet (list 1):
46% words; AzBio sentences, quiet (list 1): 71%
Left (cochlear implant): CNC words, quiet (list 2):
64% words, 80% correct phonemes; AzBio
sentences in quiet test (list 2): 85% correct
Right (cochlear implant): CNC words: 75% words
Left (cochlear implant): CNC words, quiet (list 3):
56% words, 73% phonemes; AzBio sentences, quiet
(list 3): 49%
Left (cochlear implant): CNC words, quiet (list 2):
40% words, 61% phonemes; AzBio sentences, quiet
(list 2): 58%
BKB-SIN indicates Bamford-Kowal-Bench speech in noise test; CNC, consonant-nucleus-consonant.
Imaging was obtained in cases S1 and S3; these scans
confirmed adequate device placement and revealed no
evidence of cochlear ossification. A head CT was obtained
for S1. Patient S3 had a head CT without contrast, head
magnetic resonance imaging with contrast, and MR angiography of the head and neck. Neurology was also consulted from the Emergency Department for patient S3 to
rule out stroke or other cerebral etiologies. Patients S2, S4,
and S5 did not have imaging after symptoms began. No lab
tests were performed on any patient.
Two patients received steroids (S1 and S4). The
duration between symptom onset and steroid treatment
was 52 and 85 days, respectively. Doses varied between
the two patients—40 mg taper for 10 days and three
courses of 60 mg taper for 14 days, respectively. Three
patients underwent vestibular rehabilitation. Patient S1
was not initially prescribed steroids when he presented
with symptoms. Instead, vestibular rehabilitation was
trialed first. Patient S2 was not prescribed steroids since
her symptoms largely resolved between the time she was
evaluated by audiology and seen in clinic. Steroids were
not initiated for patient S3 while other causes of his
symptoms were ruled out. Adjustments in CI programming seemed adequate to improve his speech perception
decrement. Patient S4 first underwent vestibular testing
and rehabilitation before beginning his steroid course.
However, once initiated, the first two courses of steroids
provided ‘‘30%’’ and ‘‘70%’’ subjective improvement in
symptoms, respectively. S5 was not prescribed steroids.
Instead, Meclizine and Ondansetron were chosen for
symptom management.
All patients reported subjective improvement in symptoms at last follow up. Tinnitus and vertigo has resolved
in patient S1, however, motion provoked unsteadiness
remains. All symptoms completely resolved in patients
S2 and S3. Residual imbalance and intermittent tinnitus
remains in patient S4, however, all other symptoms
resolved. Occasional imbalance remains in patient S5
with quick head movement, but he has otherwise resumed
normal daily activities without additional lasting
sequelae. All patients experienced stabilization of electrode impedance levels that correlated with improvement
in symptoms. Follow up with four of five patients continues while one patient now receives follow up care
closer to home. The estimated time to recovery for
individual subjects is reported in Table 1.
Impedance Pattern
All patients exhibited an erratic impedance pattern that
was particularly prominent in the basal electrodes as
shown in Figure 1. Device programming was performed
to minimize the out of range compliance values. Specifically, the pulse width of the stimulating electrodes was
increased, which resulted in lower stimulation levels
needed for adequate loudness growth. Achieving lower
stimulation levels allowed the contact to stay in compliance and remain active. However, some patients demonstrated compliance levels that were far out of range and
programming alterations were unable to minimize the
compliance conflicts. In those cases, select electrodes
were deactivated. The degree of electrode fluctuations
and stabilization correlated with symptom decline and
Otology & Neurotology, Vol. 38, No. xx, 2017
Copyright © 2017 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
CE: S.S.; ON-17-300; Total nos of Pages: 6;
FIG. 1. Fluctuating impedance values (in kV) in patients who reported dizziness and sudden onset device decline months after an
asymptomatic postoperative period. Baseline values, maximum divergent values, and the most recent impedance scores are shown for each
patient (S1–S5). Electrode number listed from basal (1) to apical (22).
improvement as subjectively reported by patients. For
example, patient S1 explained that his balance was
‘‘80% of normal’’ which is supported by the audiologist
report of incomplete stabilization of impedance levels.
Figure 1 depicts the baseline impedance levels, maximum divergence, and then return to baseline for each of
the five patients described (S1–S5). Contacts that had
been disabled were once again activated when electrical
impedance values returned to baseline.
The primary objective of this paper was to describe a
previously unrecognized, distinct symptom complex
with its corresponding objective impedance abnormality:
patients with initial successful cochlear implant use for
months to years developed acute decline in device
performance, dizziness, and an erratic impedance pattern.
These impedance values both fluctuated with onset of
symptoms and stabilized with improvement of symptoms,
providing an objective quantification of patients’ subjectively reported symptoms. Although it can occur in any of
the electrodes, the sawtooth impedance pattern specifically
appeared in the most basal electrodes in all five patients,
localizing the anomaly to that region. We hypothesize that
non-suppurative labyrinthitis may be responsible for this
clinical presentation and term the process ‘‘cochlear
implant associated labyrinthitis’’ as the development of
symptoms may be related to a delayed foreign body reaction, electrical stimulation, delayed perilymphatic leak or
perhaps some other unrecognized process. Since the clinical
picture involved a sudden onset of symptoms with gradual
improvement, labyrinthitis is suspected as opposed to the
recurrent symptomatology that would occur with
Otology & Neurotology, Vol. 38, No. xx, 2017
Copyright © 2017 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
CE: S.S.; ON-17-300; Total nos of Pages: 6;
endolymphatic hydrops, for example. While further
research is necessary to elucidate the exact mechanism,
improvement with steroid therapy in two patients additionally supports the possibility of an inflammatory hypothesis.
It is generally accepted that impedance levels increase
immediately following implantation as a result of inflammatory remodeling secondary to the trauma of surgery and
electrode insertion (6–8). Delivery of corticosteroids locally
during surgery may decrease electrode impedance values
further suggesting that an inflammatory process plays a key
role in altering impedance (9–12). Genes involved in tissue
remodeling such as MMP2 and MMP9 have been implicated
in loss of residual acoustic hearing following cochlear
implantation (13), and several studies are investigating
the pathways of inflammation specifically in the cochlea
(14–19). Zhang et al. (13) found a statistically significant
upregulation in inflammatory cytokines in guinea pigs with
cochlear implants. O’Malley et al. (14) also hypothesize
possible etiologies of delayed hearing loss after implantation
in their case report, including intracochlear scarring, dysfunction of hair cells, and synaptic transmission abnormalities. Quesnel et al. (15) further explain that activated
macrophages may contribute to ongoing inflammation.
Despite the number of publications evaluating immediate
post-implantation inflammatory changes and the wide
acceptance that impedance changes commonly occur in
the early postoperative period, impedance fluctuation
months or years after successful implantation is unusual
and the exact pathogenesis remains unknown.
A review of the literature unveiled one case report that
was consistent with the patients described in this study.
Wolfe et al. (20) report the clinical course of a patient
who experienced sudden performance decline after
months of successful implant use and exhibited the
impedance pattern we describe. Importantly, both the
symptoms and the impedance pattern matched our patient
profiles. In the current study, the range of symptom onset
after surgery was 2 to 22 months with a median of 126
days, which is similar to Wolfe et al.’s patient whose
symptoms surfaced 19 months after implantation. Like
our observations, the patient they described partially
recovered once steroid treatment was initiated. However,
this anti-inflammatory therapy was not administered for
10 months and not until reimplantation was attempted.
We agree with Wolfe et al. that ‘‘physical changes of the
surrounding tissues could be the cause of the fluctuation
of electrode impedances observed’’ and extend their
hypothesis to suggest that labyrinthine inflammation
may be involved. In discussing our observations, colleagues at other institutions have also anecdotally recognized this unique clinical picture in a small number of
patients despite its relative absence in the literature.
In closing, several limitations of this study are acknowledged: a small number of patients and their outcome are
described. Once this disease is recognized as a distinct
entity, a larger study compiling data from multiple implant
centers may help characterize the disease complex further.
Second, speech perception was reported subjectively
since objective speech perception testing was not performed
on all patients. Regardless of this limitation, speech perception and severity of symptoms correlated well with objective impedance values. As symptoms worsened, impedance
values fluctuated, and as symptoms improved, the impedance pattern stabilized towards baseline (Fig. 1). This
retrospective chart review design highlights the association
that steroid therapy may provide benefit in management of
this subset of patients, however, admittedly, several patients
experienced symptom resolution without treatment. Thus, it
might be reasonable to consider prompt intervention with
steroid therapy although this is only speculative. The duration between symptom onset and steroid treatment initiation
was 52 and 85 days (for patients S2 and S5, respectively)
making disease outcome predictions difficult. Follow up
studies are required to investigate both the pathophysiology
and the best course of therapy.
In this study, we describe the clinical manifestations
and impedance testing results in a subset of five cochlear
implant recipients with sudden onset implant performance decline, dizziness, and a characteristic erratic
impedance pattern. Further studies are needed to evaluate
the etiology as well as the optimal management of this
uncommon but distressing phenomenon.
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