Key points:
- Meniere’s disease (MD) involves a low-to-mid-tone hearing impairment,
and it is not possible to predict hearing improvement after an attack.
- It is not possible to estimate hearing improvement in MD patients
using inner ear contrast magnetic resonance imaging.
- Pure tone audiometry could be used to estimate hearing improvement in
MD patients.
- Endolymphatic hydrops is not correlated with hearing improvement.
- According to pure tone audiometry results, patients with low-tone
hearing loss have a better prognosis than those with low-to-mid-tone
hearing loss.
Introduction
Meniere’s disease (MD) was first reported by Prosper Meniere in 1861,
and the name MD was proposed in 1867 [1, 9]. It has been proposed
that MD combines cochlear symptoms and vestibular symptoms, and this
differentiates it from Meniere’s syndrome. The Bárány Society emphasizes
that hearing impairment in the low-to-mid-tones is observed in patients
with a confirmed diagnosis of MD [5], offering the following
definition of definite MD (DMD) [4]:
- Two or more spontaneous episodes of vertigo, each lasting 20 minutes
to 12 h
- Audiometrically documented low- to medium-frequency sensorineural
hearing loss in one ear, defining the affected ear on at least one
occasion before, during, or after one of the episodes of vertigo
- Fluctuating aural symptoms (hearing, tinnitus, or fullness) in the
affected ear
- Not better accounted for by another vestibular diagnosis
In this study, we focused on item B above, involving hearing impairment
in the low-to-mid-tones. We examined whether hearing prognosis could be
predicted depending on whether a hearing impairment is predominant in
the low-tones and examined whether the prognosis can be estimated using
inner ear contrast magnetic resonance imaging (IEC-MRI).
Materials and methods
The Strengthening the Reporting of Observational studies in Epidemiology
(STROBE) guideline was followed in this study. This study was conducted
with the approval of the(Blinded for review).
During the 2 years from April 2020 to March 2022, DMD patients who
visited our general outpatient department of otolaryngology were
enrolled. Patients with a normal healthy side were compared using a
left-right difference, and those with an abnormal hearing on the healthy
side were diagnosed with MD by comparison with the average hearing level
for the relevant age group.
The diagnostic criteria of the Bárány Society do not clearly describe Hz
in the low-to-mid-tone range. Therefore, in this study, the low-tone
range was defined as 125 Hz, 250 Hz, and 500 Hz; the mid-tone range was
defined as 1000 Hz and 2000 Hz, and the high-tone range was defined as
4000 Hz and 8000 Hz. Pure tone audiometry (PTA) was performed by
clinical laboratory technicians with an experience of more than 10 years
and who were fully proficient in the test technique. There was a total
of seven DMD patients.
To examine the hearing improvement rate of DMD patients, we compared the
low-to-mid-tone range on PTA and examined whether the hearing disorder
was predominantly low. Patients ≧5 dB between the low threshold average
and the mid-tone threshold average were defined as low-tone loss DMD
(LTL). Patients <5 dB were defined as low-to-mid-tone loss DMD
(LMTL) (Figure 1).
A hearing improvement was defined as an improvement of 5 dB or more in
all three consecutive sound regions. At the same time, all cases
underwent IEC-MRI and were evaluated by our radiologist. Hearing test
results were not reported to the radiologist in all cases. The image
conditions and shooting method used were as reported by Naganawa et al.
[8]. The evaluation method was based on the evaluation criteria
[8] by Naganawa et al. The evaluation was performed on the entire
inner ear, regardless of the cochlea or vestibule, and the judgment was
made based only on whether endolymphatic hydrops was observed in the
affected inner ear.
We used Fisher’s exact test for the statistical analysis method. A
p-value of <0.05 was considered significant.
Results
All DMD patients were women. The duration of the illness ranged from
months to years. Endolymphatic hydrops was found in three of seven
cases. Treatment involved diuretic administration [3] in the acute
phase, pulse steroid therapy [6] according to the results of
individual pure-tone hearing tests, and endolymphatic sac shunt surgery
[10] at a later date if both are ineffective. During the
asymptomatic periods, the patients did not receive medications as is the
standard of care.
Of the four cases of LTL, endolymphatic hydrops was found in two cases
based on imaging. One of the three cases of LMTL had prominent
endolymphatic hydrops. Therefore, there was no significant difference in
endolymphatic hydrops images in LTL and LMTL patients (p=0.62).
Moreover, endolymphatic hydrops detected on imaging did not correlate
with hearing prognosis (p=0.71).
Hearing improvement was observed in all cases of LTL. Only one LMTL
patient showed improvement in hearing. Neither the duration of illness
nor the treatment content correlated with the hearing improvement rate
or HYDROPS imaging (Table 1). A comparison between the hearing-improved
and non-improved groups showed that the presence or absence of
endolymphatic hydrops did not correlate with hearing improvement. The
method of differentiation used in this study was novel.
Discussion
In terms of treatment, five outpatient doctors consulted with patients
to decide each treatment policy, and no treatment intervention was
performed. In fact, LMTL patients showed a wide range of hearing
threshold increases from the low-to-mid-tone range, and there were no
patients with only mid-tone range hearing losses in this study. In LTL,
hearing was improved in all four cases, and in two cases, hearing was
improved at all frequencies. Based on this, it was shown that LTL has a
good hearing prognosis.
On the other hand, LMTL showed improvement in hearing in one case, but
in other cases, hearing did not improve across the whole sound region
but rather deteriorated in some frequencies. From this, it was shown
that it is difficult to recognize the improvement in hearing.
It is known that the cochlear top rotation dominates the low Hz and the
high Hz dominates the basal rotation [2]. In terms of PTA, the more
widespread the disorder is across the frequency range (low-to-mid-tone
range), the wider the range of damage (from the top rotation to the
basal rotation), and this indicates that the damage is more difficult to
heal.
From the above, it was concluded that MD patients with predominantly
low-tone disorders had a good hearing prognosis, suggesting that PTA can
predict the hearing prognosis in DMD patients.
No significant difference was found between IEC-MRI and the hearing
improvement rate. Since IEC-MRI screened not only for irritant internal
lymphedema but also for degenerative internal lymphedema and retentive
internal lymphedema [11,12], we considered that there was no
significant difference. Since IEC-MRI forms part of the complete
assessment at the patient’s first visit to our facility, we do not
perform MRIs during an acute attack. In terms of hearing improvement, it
is unlikely that IEC-MRI selectively captures irritant endolymphatic
hydrops. Therefore, it can be inferred that it does not correlate with
the improvement of auditory symptoms.
In the future, it will be necessary to improve the imaging time after
administration of the contrast medium [7] and to establish a medical
care protocol that enables IEC-MRI imaging at the time of an attack.
Conclusions
Using IEC-MRI, which is the current imaging method, it cannot be
concluded that hearing improvement estimation is possible. However, we
suggest that it is possible to estimate hearing improvement using PTA.
At this time, there were few populations, and a clear significant
difference could not be detected. We expect that multi-center
prospective studies for DMD using PTA and IEC-MRI will be conducted in
the future.