Park JJ, Luedeke I, Luecke K, Emmerling O,
Westhofen M.
Department of
Otorhinolaryngology and Head and Neck
Surgery
Aachen Universit
Germany
The influence of Eustachian
tube (ET) dysfunction on the inner ear fluid
pressure and thus on the inner ear function in
Meniere's disease has been discussed
controversially. So far, most of the studies
examining ET function in inner ear disorders
indirectly analyzed ET function by tympanometric
methods.
The present study directly studied ET
function in inner ear disorders by
sonotubometry. Healthy subjects and patients
with Meniere's disease, sudden sensorineural
hearing loss, cholesteatoma and chronic
suppurative otitis media were examined by
sonotubometry.
Mean increase of sound pressure intensity
(dB) and mean duration of sound pressure
increase (s) were analyzed. Highest mean
increase of sound pressure intensity was seen in
healthy subjects when using >5 dB peaks (11.6
± 0.7 dB) and >0 dB peaks (9.6 ±
0.6 dB). Comparative analysis including
bilateral ears showed decreased ET function in
patients with cholesteatoma (p = 0.002) and in
patients with Meniere's disease (p = 0.003) when
using >0 dB peaks. Examination of each
specific ET opening maneuver showed impaired ET
function in pathological ears of patients with
cholesteatoma and with Meniere's disease, during
yawning (p = 0.001; p < 0.001), dry
swallowing (p = 0.010; p = 0.049), Toynbee
maneuver (p = 0.033; p = 0.032) and drinking (p
= 0.044; p = 0.027).
Mild ET dysfunction is detected in patients
with Meniere's disease by direct sonotubometric
assessment of ET function.
Introduction
Eustachian Tube (ET) function is
predominately known for ventilation, drainage
and protection against ascending infection of
the middle ear. An indirect effect of ET
function on inner ear function by changing
middle ear pressure has been discussed
controversially. The possible involvement of ET
function in cochleovestibular disorders has been
proposed by Tumarkin. Supporting observations
were made by other authors, placing a
transtympanic ventilation tube in patients with
Meniere's disease. Lall reported an improvement
of vertigo after tube insertion and Montandon et
al. noticed a prevention of vertigo attacks.
Contrarily, other studies showed no change of
symptoms after ventilation tube placement.
Different study results might be due to the
diagnostic methods used to assess ET function.
Most of the studies examining ET function in
patients with cochleovestibular disorders only
assessed indirectly ET function by different
tympanometric methods in combination with
pressure altering methods.
Sonotubometry is an acoustic method to
measure ventilatory function of ET. The
principle of sonotubometry was first described
by Politzer. He reported an increasing sound of
a tuning fork held in front of the nostril when
the subject swallowed. During sonotubometric
measurements, ET opening is measured by
recording changes of sound pressure level in the
external auditory canal; when a sound is applied
to the nostril by a microphone while the subject
actively performs ET opening maneuvers. Virtanen
described the standard procedure for
sonotubometry using frequencies between 6 and 8
kHz. Sonotubometry allows to evaluate ET
function by assessing actual ET openings.
Until now, there have been no investigations
examining directly ET function in patients with
inner ear disorders. The present study examined
ET function in patients with Meniere's disease
and with sudden sensorineural hearing loss by
using sonotubometry. ET function was compared to
healthy persons and to patients with known ET
dysfunction such as patients with cholesteatoma
and with chronic suppurative otitis media.
Discussion
During the first analysis, ET function of
bilateral ears in patients was compared to
bilateral ears in healthy persons. Bilateral
ears were involved to assess the overall ET
function of patients with cochleovestibular
disorders. The comparison showed a significant
reduction only in patients with cholesteatoma
compared to healthy persons, when peaks>5 dB
in sonotubometric recordings were regarded. When
considering peaks >0 dB, patients with
Meniere's disease also showed reduced
sonotubometric amplitudes compared to healthy
persons.
The separate examination of each ET opening
maneuver displayed impaired bilateral ET
function during yawning in patients with
cholesteatoma and also with Meniere's disease,
but not in patients with sudden hearing loss.
These observations indicate an overall ET
dysfunction of both ears in patients with
Meniere's disease. Since malfunction of ET could
only be found in analysis for sonotubometric
amplitudes>0 dB, ET dysfunction in patients
with Meniere's disease can be assumed to be
rather mild than severe. Most studies applying
sonotubometry defined amplitudes >5 dB as an
ET opening. Using sonotubometric peaks >0 dB
might not be able to distinguish between actual
ET openings from nearly ET openings. Amplitudes
>0 dB might also include artifacts caused by
pharyngeal muscle activities and nose
pollution.
In fact, not in every case a definite
discrimination between ET opening and artifacts
could be made. Still, including peaks >0 dB
might detect subtle ET dysfunctions which would
be missed when exclusively analyzing peaks >5
dB. Patients with Meniere's disease might have
an unknown underlying mild ET dysfunction which
is clinically not predominant, but which might
effect cochleovestibular function by influencing
middle ear and thus indirectly inner ear
pressure when present over years. Impaired ET
function in patients with Meniere's disease was
confirmed by comparing pathological ears only
with healthy persons. Maneuver specific analysis
showed limited ET opening function not only
during yawning, but also during dry
swallowing, Toynbee maneuver and drinking when
analyzing affected ears.
The fact that rather subtle than predominant
ET dysfunction was found might explain the
findings that only sonotubometric amplitude was
reduced but duration of opening was not
prolonged significantly in statistical analysis.
It should be mentioned that none of the patients
with inner ear disorders showed
micro-otoscopical signs of middle ear
dysventilation. The influence of ET function on
inner ear function has been discussed
controversially. Abnormal patulous ET was
observed in patients with sudden hearing loss
and with vestibular symptoms . Although
pathologically increased patency of ET could not
be confirmed in patients with cochlear
dysfunction by further studies, an influence of
ET on the inner ear function could not be
excluded. Indications of rather decreased
patency of ET in patients with sudden hearing
loss were found.
Patients with aural fullness, which is a
common symptom of patients with
cochleovestibular defects, showed ET
dysfunction. Whereas several authors found
pathological negative middle ear pressure in
patients with Meniere's disease, others observed
no abnormal findings in tympanometry in patients
with inner ear disturbances. In these studies,
normal tympanometric middle ear pressure was
referred as healthy ET function.
However, normal tympanometric results of the
middle ear does not necessarily reveal mild
hypo- or dysfunction of ET. Although
tympanometry showed no pathological findings, ET
dysfunction was recorded in
tubotympanoaero-dynamic graphy (TTAG). One
reason data of above-mentioned studies about ET
function in patients with Meniere's disease
contradict so far might be the predominant usage
of tympanometric methods. Almost all
investigations examining the role of ET in
patients with inner ear disease used indirect
methods by either applying tympanometry alone or
in combination with whole body pressure
chambers.
The present study reveals mild ET opening
dysfunction in patients with cochleovestibular
disorders by direct evaluation of ET function.
Mechanisms influencing inner ear pressure by
middle ear pressure changes have been described.
Adjacent to the cochlear aqueduct, a pouch-like
extension of the round window membrane can be
found. Depending on the position of the round
window membrane, which is modified by middle ear
pressure, the entrance of the cochlear aqueduct
is opened or closed. Since the cochlear aqueduct
plays a key role in inner ear pressure
regulation, inner ear pressure can be altered by
middle ear pressure changes via the described
way. Mild persistent malfunction of ET might
lead to intermittent pathologic middle ear
pressure not detected in a single tympanometric
examination, but influencing inner ear
hydrostatic pressure and therefore inner ear
function.
Subtle ET dysfunction might be more advanced
on the affected pathological ear side of
patients with inner ear disease. When comparing
overall ET function, which means comparing
bilateral ears, malfunction was only noticed in
patients with concurrent vestibular and cochlear
damages, i.e in Meniere's disease, but not in
patients with sudden hearing loss. However,
analysis of affected ears displayed limited ET
function also in patients with isolated cochlear
damages. Further investigations comparing ET
function of pathological and contralateral ear
side in patients with inner ear disorders are
needed to examine potential intraindividual
differences.
Such examinations would be interesting to
conduct due to the fact that about 30 % of
patients with Meniere's diesease show
involvement of bilateral ears. Still, it remains
speculative whether ET function influences the
pathogenesis of cochleovestibular diseases. But
it is conceivable that in addition to
intralabyrinthine functional and anatomical
abnormalities ET malfunction might contribute to
the development of inner ear disorders with the
clinical appearance of Meniere's syndrome.
Long-term middle ear pressure measurements and
if possible inner ear pressure measurements in
patients with inner ear disorders and with
sonotubometric proven ET dysfunction would be
helpful for enhanced understanding of this
matter. Additionally, further studies with more
advanced sonotubometric techniques need to be
performed in patients with Meniere's
disease.
The present study used a 8 kHz signal for
sonotubometry, which is known to have its limits
in sensitivity of detection of ET opening. It
has been shown that so-called perfect sequences
(PSEQ) enhance the sensitivity of sonotubometr.
For improved understanding of ET function in
Meniere's disease PSEQ should be applied in
future investigations.
