The ear can be broken into three sections.
The first is the outer ear which is the part you see called the pinna as well as the ear
canal.
Next is the middle ear, which is a tiny chamber that houses the tiny ear bones—the malleus,
incus, and stapes.
And finally there’s the inner ear, which contains very special tissue structures called
the cochlea which converts sound waves into electrical impulses for the brain and the
semicircular canals which help with balance.
Between the outer and middle ear is an eardrum, also called the tympanic membrane, so no air
passes between the two areas.
But the middle ear does have another possible outlet, called the eustachian tube which acts
like a valve connecting the middle ear to the nasopharynx.
This tube has three main functions—equalizing pressure across the tympanic membrane, protecting
the middle ear from reflux of fluids going up from the nasopharynx, and clearing out
middle ear secretions.
Eustachian tube dysfunction describes situations when one or all of these functions aren’t
happening normally.
In an adult, the eustachian tube is a roughly 4 centimeter long part-bone, part-cartilage
canal that’s surrounded by four key muscles: the tensor veli palatini, the levator veli
palatini, the salpingopharyngeus, and the tensor tympani, and it’s those first two
that help a lot with opening up the tube.
Actions like chewing, swallowing, and yawning all pull on those muscles to help open up
the eustachian tube.
The first and most common type of eustachian tube dysfunction relates to a problem equalizing
pressure across the tympanic membrane, and a classic example is on an airplane.
As the plane rises, the air pressure decreases.
Since the middle ear chamber is a closed environment, it’s pressure stays relatively high and
the tympanic membrane can begin to bulge a bit into the outer ear.
That increased middle ear pressure pushes a tiny bubble of air down the eustachian tube
and into the nasopharynx where it gets breathed out.
This is sort of like what happens with a burp, where a bubble of air slips through the esophagus
to relieve pressure, in fact, sometimes there’s a popping sound that can be heard, like an
ear burp.
Through this process, the middle ear and the outer ear balance out their pressures.
The reverse process happens when a plane lands, since the air pressure on the ground is relatively
high and the middle ear pressure is relatively low because a tiny bit of air was “burped”
out.
The volume of air in the middle ear shrinks a bit creating a slight vacuum, and it can
cause the tympanic membrane to bulge a bit into the middle ear.
Again, a small bubble of air can slip into the middle ear to help bring up the pressure
and balance things out.
Now in eustachian tube dysfunction, the tube might not be open because of a functional
reason, the most common one being that a cold or allergies are cause the tube to be swollen
and full of secretions which block up the passageway.
Rarely, there might be an anatomic reason as well, like a large tumor or scarring in
the eustachian tube from long-standing inflammation.
Regardless of the cause, difficulty balancing out pressures can cause pain from stretching
of the tympanic membrane, as well as making the ears feel plugged and muffled; and if
the inner ear gets affected, it can also cause problems with balance.
The next sort of dysfunction is when the eustachian tube allows chemicals and bacteria to get
into the middle ear.
This sometimes happens when individuals are born with eustachian tubes that stay open
most or all of the time rather than being structurally built as valves.
Other times it can happen in infants and children who naturally have short, floppy eustachian
tubes that also don’t do a good job of preventing substances from refluxing back into the middle
ear.
This can be a real problem when there is a lot of positive pressure on the nasopharyngeal
end of the tube, which happens with crying and blowing your nose.
Finally, the third sort of dysfunction happens when the eustachian tube and the tiny cilia
within it are unable to clear out middle ear mucus secretions.
Sometimes this can result from toxins like cigarette smoke which damage the cilia, so
that they can’t flick back and forth normally to move the mucus.
The dysfunction can also be associated with systemic conditions like cystic fibrosis,
which cause the secretions to get very thick.
Regardless of the cause, stagnant secretions can get infected, leading to more complications
like otitis media—an infection of the middle ear.
Treating eustachian tube dysfunction is done by relieving the underlying issue, the most
common being a simple upper respiratory viral infection or allergies which can improve with
decongestants and sometimes a short courses of steroids.
In some cases, tympanostomy tubes are surgically placed between the middle and outer ear creating
a direct opening between them to allow pressures to equilibrate more easily.
Alright, as a quick recap, the eustachian tube connects the middle ear to the nasopharynx,
and is useful for equalizing pressure across the tympanic membrane, protecting the middle
ear from reflux, and clearing out middle ear secretions.
Eustachian tube dysfunction affects all of these functions and can cause pain, muffled
sound, balance problems, and can also lead to infections like otitis media.