J Am Acad Audiol 6: 264-270 (1995)
Intratympanic Gentamicin Treatment :
Preliminary Results in Two Patients
with Meniere's Disease
Mary Beth Trine*
Susan G. Lynn*
George W Facert
Jan L. Kasperbauert
Abstract
Meniere's disease is a vestibular disturbance characterized by episodic vertigo, tinnitus, and
fluctuant hearing loss . The long-term effectiveness of available medical and nonablative surgical treatments has been variable, with frequent symptom recurrence . Vestibular neurectomy
and labyrinthectomy, surgically ablative techniques, provide more permanent relief from vertiginous attacks. However, these procedures pose possible morbidity and cochlear risk . In
this paper, preliminary results are presented for two patients who underwent intratympanic
gentamicin application . Like surgical labyrinthectomy, intratympanic use of gentamicin is
intended as an ablative procedure, but with potentially less risk to hearing . More vestibulotoxic than cochleotoxic, gentamicin initially disrupts the endolymph-secreting vestibular dark
cells, thereby preventing endolymphatic hydrops development. Following gentamicin application, both patients demonstrated a significant change in peripheral vestibular function, as
characterized by a reduction of caloric response, impaired posturography performance, and
reduced low-frequency gain on rotary chair testing. Posturography performance subsequently
improved, confirming functional compensation . Both patients reported relief from vertiginous
attacks. However, word recognition ability was significantly worse in one of these two patients .
Changes in pure-tone thresholds were minimal.
Key Words: Aminoglycoside, cochlear hydrops, endolymphatic hydrops, gentamicin,
intratympanic gentamicin application, Meniere's disease
eniere's disease, or idiopathic endolymphatic hydrops, is characterized by
episodes of vertigo, tinnitus, aural
fullness, and fluctuant hearing loss . The hearing loss is typically low frequency and sensorineural, although a flat configuration may be
demonstrated . Documentation of hearing fluctuations helps to confirm the diagnosis. Caloric
testing may or may not demonstrate a unilateral
weakness .
There are many different types of medical
and surgical treatments for Meniere's disease.
An incomplete list includes labyrinthectomy,
M
'Section of Audiology, Vestibular Testing, Department
of Otorhinolaryngology, Mayo Clinic, Rochester, Minnesota ;
tDepartment of Otorhinolaryngology, Mayo Clinic, Rochester,
Minnesota
Reprint requests : Mary Beth Trine, Mayo Clinic,
Eisenberg 3-F, 200 First Street, SW, Rochester, MN 55905
264
vestibular neurectomy, sacculotomy, endolymphatic shunt, medications (Antivert, Meclizine,
Valium), low salt diet, vestibular rehabilitation,
and ototoxic agents . Unfortunately, the longterm effectiveness of most of these treatments
has been variable (Ruckenstein et al, 1991).
Nonablative surgeries and medical treatment are
frequently followed by the recurrence of symptoms . Documentation of treatment effectiveness is also complicated by the unpredictable remissions and exacerbations that characterize
Meniere's disease and by the strong placebo
effect that has been demonstrated in this population (Torok, 1977 ; Ruckenstein et al, 1991).
Only the ablative surgeries, such as labyrinthectomy and vestibular neurectomy, have been reliably effective, offering control of vertigo in over
90 percent of cases followed for a 5-year period
(Ruckenstein et al, 1991).
A recently popularized treatment involves
a reduction of vestibular functioning in the
Gentamicin 'Ireatment/1Yine et al
affected ear with the use of ototoxic medications. The use of transtympanic streptomycin
therapy was first described by Schuknecht in
1957 . A similar technique using gentamicin was
described in 1978 by Arslan and also by Beck .
Areview of recent literature indicates that relief
from vertiginous symptoms with intratympanic
gentamicin use is achieved in 66 percent to 90
percent of reported cases (Beck, 1986 ; Laitakari,
1990 ; Nedzelski et al, 1992, 1993). The preservation of residual hearing ranges from 56 percent to 85 percent, with some authors reporting
improvements in pure-tone averages and on
word recognition testing.
Research indicates that gentamicin is more
vestibulotoxic than cochleotoxic (Bagger-Sjoback
et al, 1990 ; Magnusson and Padoan, 1991). As
such, its intended role in the treatment of
Meniere's disease is to provide relief from vertigo while sparing residual hearing. Gentamicin
reduces vestibular function by initially affecting the secretory epithelia of the vestibular
labyrinth, the dark cells (Beck, 1986 ; BaggerSjoback et al, 1990 ; Laitakari, 1990 ; Nedzelski
et al, 1992, 1993). Located in the cristae ampullae of the semicircular canals, the vestibular
dark cells are responsible for the secretion of
endolymph. Intratympanic gentamicin application is, then, an ablative procedure that is
intended to selectively damage vestibular secretory dark cells, thereby preventing the development of endolymphatic hydrops. Compared to
surgical labyrinthectomy, there is less risk to the
overall well-being of the patient and to the
cochlea.
We have recently had experience with this
procedure in two patients with long-standing
diagnoses of Meniere's disease. Two cubic centimeters (80 mg) of IV gentamicin were injected
into the middle ear cavity of the symptomatic ear.
A single injection was provided, with the intent
of further injections should vertiginous symptoms persist. This procedure was completed on
an outpatient basis. In each case, use of intratympanic gentamicin was intended to reduce
vertiginous symptoms and to preserve residual
hearing.
METHOD
A
udiometric testing was performed pre- and
post-gentamicin treatment. This included
pure-tone air- and bone-conduction and word
recognition testing (CID W-22 word lists) .
Vestibular assessment, including electronystagmography (ENG) and computerized dynamic
posturography, was also completed prior to gentamicin use and twice after the intratympanic
injection. A caloric interear difference of >_ 20 percent constituted a peripheral vestibular deficit
for the ear with the weaker caloric response .
Directional preponderance was significant if
30 percent. Rotary chair testing was included
during the follow-up evaluations.
CASE REPORT
Patient A
Patient A was diagnosed with left ear endolymphatic hydrops possibly secondary to labyrinthine otosclerosis in 1980 at the age of 32 . Initial symptoms included left ear tinnitus, fluctuating left ear hearing loss, and vertigo with
nausea and vomiting. Typical episodes persisted
from 1 to 2 hours. Hearing testing revealed a
severe rising to mild sensorineural hearing loss
in the left ear. See Table 1 for documentation of
pure-tone threshold measurements and word
recognition testing. Patient A also reported
visual blurring and difficulties with gait and
hand-eye coordination . His gait was described
as ataxic . Antivert provided minimal control of
the vertigo. Sodium fluoride was prescribed to
treat the otosclerosis. Aneurologic examination
was negative .
The severity and duration of vertiginous
attacks increased in 1981, with episodes persisting from 4 hours to 3 days . Left ear tinnitus
and hearing fluctuations continued. Audiometric testing on May 5, 1981 revealed a relatively
flat, moderate sensorineural hearing loss in the
left ear. Aleft ear Cody tack sacculotomy was performed in July 1981(Cody, 1969, 1973 ; Cody and
McDonald, 1983).
Following surgery, patient A experienced
no vertigo until 1991, 10 years later. However,
onset of right ear aural fullness and tinnitus was
reported in 1987 . Table 1 documents minor fluctuations in right ear hearing. With recurrence
of the vertigo, patient A also experienced unsteadiness and loudness discomfort . A tentative diagnosis of early right ear hydrops was
made .
In 1992, he reported continued episodes of
vertigo with nausea and vomiting, right ear
hearing fluctuations, and increased right ear
tinnitus . Audiometric testing documented a
mild, low-frequency sensorineural hearing loss
in the right ear (see Table 1) . Bilateral endolymphatic hydrops was diagnosed, and a course of
prednisone was prescribed in an effort to improve
Journal of the American Academy of Audiology/ Volume 6, Number 3, May 1995
Table 1 Pure-tone Air-conduction Thresholds (dB HL) and Word Recognition Scores for Patient A
Frequency (Hz)
Date
250
500
1000
2000
3000
4000
6000
8000
Word Recognition % / dB SL
R
L
R
L
R
L
R
L
R
L
R
L
R
L
R
L
6/24/80
15
70
5
65
5
60
0
30
-
-
0
25
-
-
10
40
100/26
(a) 72 / 26
(b) 88 / 40
5/5/81
15
55
5
50
10
45
0
45
5
40
5
35
-
-
25
45
96/25
(a) 72 / 25
(b) 68 / 40
8/5/81
-
85
-
75
-
55
-
65
-
-
-
55
-
-
-
60
Not tested
16/20
5/19/87
25
80
15
70
15
75
10
70
5
70
5
65
25
65
30
70
100/40
8/25
10/16/91
25
85
10
75
15
70
5
65
5
60
10
65
30
60
25
70
88/25
12/25
5/8/92
R
L
40
80
25
75
20
70
15
75
10
65
10
65
35
65
30
70
92/40
32/25
* 12/30/93 50
80
50
75
40
70
20
65
25
65
20
60
40
65
45
70
96/40
28/25
13/10/94
70
45
70
25
70
15
65
20
65
20
65
45
70
60
75
96/40
24/25
50
Note: hearing losses are sensorineural.
*Rre-gentamicin hearing assessment, tpost-gentamicin hearing assessment .
R = right ; L = left.
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right ear hearing. Use of a transdermal scopolamine patch provided some relief, minimizing
the severity of the vertigo.
Patient Areturned in December 1993 reporting progression of right ear hearing loss, right ear
tinnitus, loudness discomfort, and continued
episodes of vertigo that persisted from 2 to 3
hours. Hearing testing revealed a moderate, lowfrequency sensorineural hearing loss with normal
thresholds at 2000 to 4000 Hz in the right ear;
word recognition was 96 percent. Vestibular
assessment documented a peripheral vestibular
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weakness on the left, normal posturography, and
abnormal phase at 0.01 Hz on rotary chair testing (Fig . 1) . Based on the frequency and severity
of his symptoms, patient A underwent an
intratympanic gentamicin injection under local
anesthesia on December 30, 1993 . With the use
of a spinal needle, 2 cc (80 mg) of IV gentamicin
were injected into the right middle ear space.
The patient remained supine with the head angle
to the left for 45 minutes.
Patient Areturned to the clinic on February
3, 1994, 5 weeks after the gentamicin injection,
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during the first post-treatment ENG improved significantly by the second post-treatment evaluation .
266
Gentamicin 'IYeatment/TYine et al
for follow-up assessment . At that time, he
described oscillopsia, imbalance, and one episode
of vertigo with nausea and vomiting . He stated
that the vertigo occurred on February 2, 1994
and persisted for approximately 1 hour. Patient
A described the vertigo as a "swinging pendulum," rather than a spinning, sensation. He
emphasized that this episode was less intense
and of less duration than previous episodes . He
declined audiometric testing, reporting no noticeable change in hearing. ENG assessment demonstrated a left-beating latent nystagmus, a significant left-beating directional preponderance,
and a borderline peripheral vestibular weakness bilaterally (see Fig. 1) . Posturography
revealed a vestibular deficit pattern ; falls
occurred on all trials of subtests 5 and 6. Rotary
chair testing produced borderline gain at 0.01
through 0.04 Hz . Abnormal low-frequency gain
measurements confirmed a bilateral peripheral
vestibular deficit with residual function at higher
frequencies of stimulation. A bilateral weakness was consistent with the patient's report of
oscillopsia . Based on post-gentamicin changes in
posturography performance (onset of a vestibular deficit pattern) and on the patient's complaints of imbalance, he was referred to physical therapy for vestibular rehabilitation .
Asecond post-gentamicin vestibular assessment was completed 1 month later, on March 10,
1994. Patient A reported continued fluctuations
in right ear hearing but noted that right ear tinnitus, although still present, was "less bothersome ." He stated that there had been no vertigo
since February 2, 1994 . Patient A reported
improved balance and resolution of the oscillopsia . He attributed these improvements to the
vestibular rehabilitation exercises. ENG testing
revealed a peripheral vestibular weakness on the
left, a left-beating directional preponderance,
and a left-beating latent nystagmus (see Fig. 1) .
Posturography was normal, suggesting that
functional compensation had occurred . Improved
posturography performance was consistent with
the patient's report of improved balance. Rotary
chair was similar to pre-gentamicin testing;
phase was abnormal at 0.01 Hz . Right ear audiometric testing revealed a moderate, low-frequency sensorineural hearing loss rising to normal thresholds at 1500 through 4000 Hz and a
word recognition score of 96 percent. A 15-dB
threshold improvement was demonstrated at
1000 Hz, while a 15-dB threshold decrement
was seen at 8000 Hz .
CASE REPORT
Patient B
Patient B was diagnosed with left ear
Meniere's disease in April 1979, at age 52 . At that
time, he reported a 2-year history of episodic
vertigo with nausea and vomiting, fluctuating left
ear hearing, left ear tinnitus, and loudness discomfort. Audiometric testing revealed moderate
low-frequency hearing impairment with normal
hearing thresholds at 2000 and 3000 Hz in the
left ear (Table 2) . Serologic tests and neurologic
Table 2 Pure-tone Air-conduction Thresholds (dB HL) and Word Recognition Scores for Patient B
Frequency (Hz)
Date
500
250
1000
2000
3000
4000
6000
8000
Word Recognition % / dB SL
R
L
R
L
R
L
R
L
R
L
R
L
R
L
R
L
R
4/26/79
10
50
5
45
5
40
5
25
20
25
40
45
-
-
55
50
92/26
(a) 60 / 26
(b) 64 / 40
1/3/83
15
60
5
50
5
35
0
25
10
25
35
55
70
55
60
50
92/25
(a) 76 / 25
(b) 84 / 40
6/11/92
55
65
45
60
35
60
35
30
55
15
60
65
70
50
70
65
88/40
(a) 24 / 25
(b) 56 / 40
6/22/92
30
70
30
65
45
60
50
30
55
15
60
65
65
45
65
55
88/40
(a) 20 / 25
(b) 44 / 40
7/14/92
40
65
20
60
35
60
40
30
60
15
55
65
65
50
70
55
92/40
(a) 32 / 25
(b) 68 / 40
4/5/93
50
65
35
60
45
55
45
25
60
20
55
60
65
50
60
50
80/25
(a) 32 / 25
(b) 52 / 40
'12/8/93
45
65
40
60
50
60
50
35
70
55
65
65
65
60
70
70
76/40
(a) 52 / 25
(b) 56 / 40
13/1/94
40
70
35
65
50
70
45
55
70
65
75
70
65
65
70
75
80/40
(a) 28 / 25
(b) 24 / 25
Note : hearing losses are sensorineural.
`Pre-gentamicin hearing assessment ; tpost-gentamicin hearing assessment .
R = right ; L = left .
L
(repeated)
Journal of the American Academy of Audiology/ Volume 6, Number 3, May 1995
assessment were negative . A low salt diet was
recommended, and Lipoflavinoid was prescribed.
In 1983, patient B described continued
episodes of intermittent vertigo. However, the
duration of these attacks had increased, with
one episode lasting 4 days . He noted progression of the left ear hearing loss and continued
left ear tinnitus and aural fullness . Hearing
testing demonstrated changes in left ear hearing, with poorer low-frequency thresholds (see
Table 2) .
He returned to the clinic on June 11, 1992
with roaring right ear tinnitus, sudden right
ear hearing loss, and imbalance. Pure-tone testing revealed an arched audiometric configuration in the right ear . Hearing sensitivity in this
ear had previously been normal through 3000
Hz. Right ear labyrinthitis (versus hydrops) was
diagnosed, with "old Meniere's left, inactive ." A
course of prednisone was prescribed in an effort
to restore right ear hearing thresholds . Two
weeks later, on June 22, 1992, audiometric testing demonstrated a mild sloping to moderately
severe sensorineural hearing loss in this ear.
Prednisone was discontinued in July 1992 subsequent to patient complaints of agitation. At
that time, the diagnosis was changed to right ear
hydropssuspected .
In April 1993, patient B reported recurrence
of tinnitus and occasional loss of balance. He
denied vertigo. Pure-tone testing documented
continued fluctuations in low-frequency right
ear hearing sensitivity (see Table 2) and a word
recognition score of 80 percent.
PATIENT
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268
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Patient B returned to the clinic on December 8, 1993, describing daily attacks of vertigo
with nausea and vomiting . Episodes persisted
from 20 to 60 minutes, with resolution of imbalance between attacks. Patient B had been vertigo-free since 1983 . He stated that previously
experienced tinnitus had ceased . ENT notes
documented no localizing ear symptoms . Audiometric testing revealed minimal changes in
hearing thresholds . The diagnosis was defined
as "hydrops suspect right, old Meniere's left ."
Patient B presented 2 weeks later on December 22, 1993 describing daily episodes of vertigo that were accompanied by increases in left
ear aural fullness and tinnitus . Vestibular
assessment on January 13, 1994 revealed a
mild, peripheral vestibular weakness on the left
(24% interear difference) and normal posturography (Fig . 2) . An MRI was negative . The
patient was diagnosed with left endolymphatic
hydrops. Based on the daily occurrence of vertigo, an intratympanic gentamicin procedure
was completed on January 18, 1994 . Two cubic
centimeters (80 mg) of IV gentamicin were
injected into the left middle ear.
Patient B returned to the clinic on February
1, 1994, 2 weeks after the intratympanic injection,
for follow-up. He complained of persistent imbalance, increased left ear tinnitus, and left ear deafness. He denied vertigo. Vestibular assessment
revealed a severe, peripheral vestibular weakness on the left (78% interear difference), a rightbeating directional preponderance, a borderline
vestibular deficit pattern on posturography, and
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Gentamicin Treatmentfrrine et al
abnormal gain at 0.01 through 0.16 Hz on rotary
chair testing (see Fig. 2) . Audiometric testing was
not completed, and as per ENT notes, referral to
vestibular rehabilitation was delayed for 1 month.
A second post-gentamicin assessment was
completed on March 1, 1994, 6 weeks posttreatment. Patient B reported that his equilibrium was gradually improving. Imbalance
remained noticeable but was less severe than
that experienced in the days immediately following the gentamicin injection. He denied vertigo. He described a reduction in the intensity
of left ear tinnitus ; however, he continued to
report left ear deafness . Hearing testing revealed
a relatively flat, moderately severe to severe
sensorineural hearing loss in the left ear and
word recognition scores of 28 percent and 24
percent for repeated testing at 25 dB SL (see
Table 2). A20-dB threshold decrement was noted
at 2000 Hz . Compared to testing in December
1993, word recognition ability was significantly
poorer ; previous scores were 52 percent and 56
percent at 25 and 40 dB SL, respectively. Vestibular assessment revealed a peripheral vestibular
weakness on the left (87% interear difference),
no significant latent nystagmus, abnormal gain
at 0.01 through 0.04 Hz on rotary chair testing,
and normal posturography performance (see
Fig. 2) . Due to the patient's complaints of continued imbalance, vestibular rehabilitation was
offered. Patient B declined rehabilitation at that
time, noting that he would soon undergo minor
orthopedic surgery.
DISCUSSION
B
oth of the patients presented in this paper
experienced severe and frequent episodes
of vertigo that interfered with professional and
social activities . Both presented with a diagnosis of Meniere's disease, or idiopathic endolymphatic hydrops, and with a history of symptoms
that had persisted for more than 12 years. Following a 2 cc (80 mg) intratympanic injection of
IV gentamicin, both patients demonstrated a
significant change in peripheral vestibular function, as measured by caloric testing. Changes in
the caloric response suggest that disruption of
the sensory epithelium, in addition to the
vestibular dark cells, was involved . Patient A
demonstrated a slightly stronger caloric response
in the gentamicin ear at the second follow-up
vestibular assessment . This finding may indicate
a recovery of sensory function ; possibly, cells
were impaired following ototoxic exposure, but
damage was not permanent.
Post-treatment performance on posturography produced a definite or borderline vestibular deficit pattern in both patients . This pattern
was consistent with patient complaints of imbalance following gentamicin application. However, repetition of posturography testing at the
second follow-up documented improved balance,
suggesting that functional compensation had
occurred, and concurred with patient reports of
gradually improving equilibrium. This finding
is consistent with research completed by Pyykko
and colleagues (1994) . These authors reported
increased postural sway or instability following gentamicin injection, with average postural
stability returning to pretreatment levels approximately 2 years after aminoglycoside use .
Vestibular rehabilitation may quicken this adaptation process. Recall that patient A demonstrated falls on posturography subtests 5 and 6
at the first post-gentamicin examination; posturography performance was normal 1 month
later. Patient A had been referred to physical
therapy for vestibular rehabilitation in February 1994 and had been actively participating in
a home therapy program since that time .
Rotary chair testing revealed abnormal or
borderline normal low-frequency gain following
gentamicin use. This finding implies bilateral
vestibular impairment with residual vestibular function only measurable at higher frequencies of stimulation. The demonstration of
a bilateral weakness was particularly consistent with patient As history. Recall that patient
A had a history of old Meniere's in the left ear;
the application of gentamicin was intended to
produce a change in the vestibular function of
the right ear. Bilateral impairment also concurred with his reports of imbalance and oscillopsia . Both patients demonstrated improved
function on rotary chair testing at the second
post-treatment evaluation . Low-frequency gain
was somewhat improved for patient B. Patient
A, however, demonstrated a recovery of gain; only
phase was abnormal at 0.01 Hz . Consistent with
this improvement, patient A reported recovery
of balance and resolution of oscillopsia . Again,
note that this patient was involved in a vestibular rehabilitation program.
At the second post-treatment examination,
both patients reported relief from vertigo. Since
the intratympanic application of gentamicin,
patient B had experienced no vertigo. Patient A
described only one episode, occurring approximately 4 weeks after gentamicin treatment. However, the duration and intensity of this episode
were significantly less than those experienced
269
Journal of the American Academy of Audiology/Volume 6, Number 3, May 1995
previously. Perception of the vertigo had also
changed from a true "spinning" to a "swinging pendulum" sensation. Changes in pure-tone threshold
measurements were minimal in the gentamicintreated ears . Patient Ademonstrated a 15-dB HL
threshold improvement at 1000 Hz and a 15-dB
threshold decrement at 8000 Hz in the right ear.
Patient B experienced a threshold decrement
of 20 dB at 2000 Hz in the left ear (see Figs. 1
and 2) . However, patient B also demonstrated a
significant change in word recognition ability.
Recall that patient B reported that he was deaf
in this ear subsequent to the aminoglycoside
injection. Without continued audiologic monitoring, it is difficult to determine if this decrement
in word recognition ability is a result of cochleotoxicity or a function of the hearing fluctuations
that characterize Meniere's disease.
CONCLUSION
ike labyrinthectomy and vestibular neurecL tomy, relief from vertigo following intratympanic gentamicin use has been achieved in
up to 90 percent of reported cases (Beck, 1986 ;
Bagger-Sjoback et al, 1990 ; Laitakari, 1990 ;
Nedzelski et al, 1992). Intratympanic gentamicin application may represent a less invasive
alternative to surgically ablative procedures but
with similar potential for relief from vertigo.
Issues that remain regarding the use of this
aminoglycoside in the treatment of Meniere's disease include:
1.
The long-term effectiveness of this treatment or the permanency of change to the
peripheral vestibular mechanism, as determined by caloric testing;
2.
The minimal effective dosage required to
ensure vertigo relief while preserving hearing and avoiding ataxia ;
3.
Administration of the aminoglycoside, that
is, one injection or a series of injections over
several days ; and
4.
The effect on hearing, as documented by
audiometric testing.
Resolution of these issues will require the
development of longitudinal studies that serially
monitor audiometric and vestibular testing over
an extended period. Indeed, revised AAOO guidelines recommend follow-up over a 24-month
period (Pearson and Brackmann, 1985). Such
studies are needed to evaluate the use of
intratympanic gentamicin as an alternative in
the battery of treatments for Meniere's disease.
270
Acknowledgment. We thank Terri Pratt, M.A. for
her assistance with the audiologic evaluations and our
colleagues at Mayo Clinic who reviewed earlier versions
of this manuscript .
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