A cholesteatoma can form in the middle ear
in three ways. A perforation of the eardrum
occuring because of a chronic infection or
direct trauma can lead to a cholesteatoma. The
skin over the outer surface of the eardrum can
start to grow through the perforation and into
the middle ear. Some patients are born with
small remnants of skin which become entrapped
within the middle ear (congenital
cholesteatoma) or petrous apex (petrous apex
epidermoid). The third mechanism which his
most common involves an improperly functioning
eustachian tube. The eustachian tube is a
canal which connects the middle ear to the
back of the nose. It is responsible for
equilibrating middle ear pressure to the
pressure in the external environment. This
tube is normally collapsed in its resting
state and when we swallow or yawn, the muscles
around the tube contract and cause the tube to
open allowing the influx of air into the
middle ear space. When this tube does not work
appropriately, a relative negative middle ear
pressure is generated and maintained. Over
time the intact eardrum begins to retract back
toward the inner ear. Eventually a skin-lined
sac forms which continues to grow and cause
infection and bony destruction.
The problem occurs when the dead cells
accumulate in the middle ear and can not be
expelled. Typically an infection occurs with
intermittent drainage from the ear. As this
ball of dead cells acumulates it produces
enzymes which cause the destruction of bone.
Complications from untreated
cholesteatoma
Erosion of the ossicles or bones behind the
eardrum can lead to a conductive hearing loss.
The bone over the facial nerve can also be
destroyed and a facial paralysis can result.
The inner ear is composed of a bony labyrinth
which can also be partially destroyed. This
can lead to a sensorineural hearing loss and
dizziness. The infection can also spread into
the veins carrying blood from the brain to the
heart. This large vein called the lateral
venous sinus can obstruct and cause excessive
fluid to accumulate within and around the
brain leading to a condition called
hydrocephalus. The infection can also spread
to the covering of the brain and cause
meningitis. In rare circumstances, a brain
abscess can result.
Diagnostic Tests:
Tests which are oftentimes helpful include
an audiogram and a CT scan of the temporal
bone. An audiogram is a hearing test conducted
in a sound proof room by an experienced
audiologist. There the ability to hear various
frequencies can be checked. How loud the
various frequencies have to be before you hear
them is determined. The audiologist will
typically check the hearing through the air,
using the eardrum, bones behind the eardrum or
ossicles, inner ear and hearing, cochlear
nerve and central auditory pathways. This is
usually compared to the hearing obtained
through the mastoid bone or bony prominence
behind the ear. The latter checks the hearing
attained by directly stimulating the inner ear
thereby bypassing the ear canal, eardrum and
ossicles. This is also referred to as
sensorineural hearing. The difference between
the hearing through the air and bone is called
conductive hearing.
A CT scan is a special X-ray which is taken
with the patient lying down and wheeled into a
large doughnut-shaped machine. Images are
obtained of the temporal bone which is the
bone which houses the hearing and balance
mechanism. A regular CT scan of the head is
not sufficient to clearly see the minute
structures within the temporal bone. A
detailed study with thin sections through the
temporal bone is required. CT scans and all
other imaging techniques allow us to get a
gross idea of what might be going on in the
middle ear and mastoid. These scans are the
equivalent of shining light onto an object and
trying to make out what the object is by
studying the shadows made by it. Consequently
these scans are not absolute in telling us all
we want to know. Normally the middle ear and
mastoid should appear black on a CT scan.
Gray-colored areas may represent fluid,
infection, cholesteatoma or scar from previous
surgery.
Management Options
If the the sac is relatively small and the
ear can be kept without infection, and the
hearing remains at an acceptable level, the
keratin may be cleaned out in the office under
microscopic examination at periodic intervals.
In all other circumstances, surgery is
required to help prevent the progression of
infection.
The primary goal of surgery for
cholesteatoma is treating the infection. The
secondary goal is to restore hearing. As
previously stated, an uncontrolled infection
in this area can lead to complications.
In all circumstances, surgery involves
general anesthesia and the procedure can last
anywhere from one hour to three hours
depending on the size of the cholesteatoma and
extent of infection. The delicate procedure is
performed using a high powered microscope.
Patients typically go home either the same day
after surgery or the next day depending on how
they respond to general anesthesia. There are
temporary restrictions following surgery which
include restraining from heavy lifting,
straining, nose blowing and sneezing with the
mouth open only. Patients are typically seen
weekly until all ear canal packing is removed.
Surgical Outcomes
Whenever surgery is performed for
cholesteatoma, there are three possible
results of surgery depending on what is found
during the operation. If the cholesteatoma is
small and can be removed entirely in one
piece, the eardrum and the ossicles are
reconstructed all in one operation.
If the cholesteatoma can be removed only in
pieces, there is always a chance cholesteatoma
fragments left behind may regrow at a later
time. In this case it is our preference to
come back several months later to remove any
fragments which may have grown when they may
be a favorable size for total excision. We
would also delay ossicular reconstruction
until the second operation.
If the cholesteatoma is rather extensive
and adherent to the inner ear or facial nerve,
it may not be possible to remove the entire
cholesteatoma and a radical mastoidectomy is
performed. The portion of the cholesteatoma
that is adherent to the inner ear and/or
facial nerve is left. In this case a situation
is created where the keratin accumulation can
be safely removed in the office. The bony
partition between the back part of the ear
canal and the mastoid bone is removed. The
eardrum, malleus and incus are removed in
order to allow exposure of the inner ear and
facial nerve for cleaning in the office. The
opening to the ear canal is also enlarged. In
this case periodic cleaning of this mastoid
cavity every 3-6 months is essential.
Surgical Procedures:
Surgery can be performed either through the
ear canal or in combination with an incision
behind the ear.
Tympanoplasty
With a cholesteatoma limited to the
tympanic membrane or with a small congenital
cholesteatoma or with a limited cholesteatoma
forming through an eardrum perforation, the
procedure can be done through the ear canal.
Incisions are made within the ear canal and
the ear canal skin along with the eardrum are
lifted to inspect the middle ear.
Frequently the chorda tympani nerve (taste
nerve) may need to be moved aside to allow
adequate inspection. This may cause a
temporary taste disturbance from the front
part of the tongue on that side. If the nerve
becomes overly stretched, the patient can have
a permanent metallic taste. In order to avoid
this the nerve is divided. Eventually the
taste buds on that side usually become
reinnervated from taste fibers from the
opposite side of the tongue. Occasionally the
cholesteatoma may invade this nerve and it may
be necessary to resect the nerve anyway.
In order to allow clear visualization of
the cholesteatoma, frequently it is necessary
to remove the incus bone. Inner ear trauma
leading to temporary dysquilibrium from
overmanipulation of the stapes bone while
dissecting the cholesteatoma from the
surrounding structures can occur. Removal of
the incus bone helps prevent inner ear trauma.
The cholesteatoma and/or retracted porrtion
of the eardrum is then dissected and removed.
The eardrum is repaired using the covering
(fascia) of the chewing muscle (temporalis) as
a template for tympanic membrane growth. The
continuity of the ossicles is then restored
using either the patient’s own incus or an
artificial prosthesis.