Introduction
The Eustachian tube (ET) is an anatomical structure that extends from
the nasopharynx up to the middle ear and is composed of a bony and a
cartilaginous part. Its normal function is vital for healthy hearing
(1). This epithelial-lined tube has three main functions: (i)
equalization of the pressure in the middle ear to the atmospheric
pressure. This is important to curb the untoward effects of external
pressure fluctuations on the tympanic membrane. (i) clearance of middle
ear secretions, (iii) prevention of middle ear from nasopharyngeal
secretions containing microorganisms and precluding transmission of
one’s own speech sounds back to their ear (2).
Eustachian tube dysfunction might be due to either obstruction of the
tube or persistent opening of it (3). ET, under physiologic conditions,
remains passively closed and only briefly opens in case of swallowing or
Valsalva maneuver. When the ET remains permanently open, this condition
is called patulous Eustachian tube (PET). Although its prevalence is
much less compared with the obstructive pathologies of the ET, PET is
associated with annoying symptoms that lower the quality of life of the
affected patients. Patients with PET mainly complaint about hearing
their own voice (autophony), their breathing (aerophony) or sound of
eating or drinking in a disturbing way. Inflicted patients can also
report other more nonspecific symptoms such as aural fullness, vertigo,
and tinnitus (4).
Due in part to its inaccessible nature, there is not a single reliable
test correctly diagnose ET dysfunction. Constellation of the
aforementioned symptoms in a patient suggests the presence of PET;
however, these symptoms can also be reported by patients with several
other disorders. Thus, more objective and reliable tests are needed.
Tympanometry is the commonly used office-based test to evaluate the ET
function indirectly. This test measures the one-time middle ear
pressure. Normal pressures measured with tympanometry does not exclude
obstructive ET dysfunction or PET. Breathing-synchronous tympanic
membrane movement is accepted as a specific finding of PET but, to
diagnose PET, various objective and subjective findings, such as medical
history, physical examination and ET function tests, are combined,
because there is no single test available to evaluate ET function
accurately. Clinical tympanic membrane movement can be carried out by
visual observation, continuous impedance recording, or sonotubometry (5,
6). However, these tests are not well standardized and limited in cases
of intermittent PET or patients who had low acoustic impedance.
Radiologic imaging of the ET is also without its own problems.
Currently, there is no single radiologic imaging modality that can
provide details of all related structures of the ET per se. The
collapsed nature of the ET at rest makes it more difficult to image the
entire tube. One can think that this cannot be a problem for a PET
patient. However, the ET temporarily closes when the patient lies
supine, which is the usual position in sectional imaging modalities (7).
Thus, several investigators tried to find some ways to overcome these
difficulties, such as CT imaging in a seated patient or positioning the
patient in 45 degrees in a standard CT scanner (8-10). However, these
modifications are not always technically feasible. One other solution to
the imaging problem of PET is performing a Valsalva maneuver during CT
scanning. Self-administered pressure increases force the ET to open even
in a patient who is lying supine.