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Procedure
Practice 07/15/99 - Coding
Recommendations
Feature
Article 07/15/99:
The
Ear - Part 2
Diagnostic
Tests - Surgical Procedures
Last month, we described structure
and function as well as diseases
and disorders of the ear. This month, our study focusses
on diagnostic tests and surgical procedures.
Conventional audiometry is the basic hearing
test that measures the ability to hear pure tones in each
ear. The patient sits in a soundproof room and earphones are
placed over the ears or in the ear canal. The patient signals
when tones or beeps are heard. These sounds are single frequency
sounds referred to as pure tones. Each ear is tested separately.
The results of the test are plotted on a graph called an audiogram.
The graph shows the amount of hearing loss expressed in decibels
at different sound frequencies (also called hertz). High frequencies
correspond to high tones, and low frequencies are low tones.
Most audiograms go from 200 hertz to 8000 hertz. Hearing losses
over 20 decibels are considered abnormal. A complete audiogram
tests both bone conduction and air conduction. A comparison
between these two types of conduction is useful in distinguishing
conductive hearing loss from sensorineural loss.
Electrophysiological measurements include
such testing methods as tympanometry, otoacoustic
emission testing, and auditory brainstem
response testing. These testing methods are designed
to evaluate the physiologic function of different parts of
the ear and do not require that the person being tested respond
overtly to any stimuli.
- Tympanometry
measures how easily the eardrum vibrates back and forth
and at what pressure the vibration is easiest. If the middle
ear is filled with fluid, the eardrum will not vibrate properly
and the tympanogram will be flat. If the middle ear is filled
with air but at a higher or lower pressure than the surrounding
atmosphere, the tympanogram will be shifted in its position.
To perform the tympanogram, a probe similar to an earplug
is placed up against the ear canal, and monitoring equipment
automatically makes the measurements.
- Otoacoustic emission testing
(OAE) measures the function of specific
hair cells that affect the ability to hear soft sounds.
Otoacoustic emissions are sounds that are produced by the
ear in response to sound stimulation of the ear. If these
sounds are present during OAE testing, hearing is most likely
normal. OAE can be measured in newborn infants and in elderly
patients to assess potential hearing loss.
- Auditory brain stem response
(ABR) testing tracks nerve signals from
the inner ear as they travel through the eighth cranial
nerve to the brain. The test is used to identify where along
that path hearing loss has occurred. ABR is often used for
individuals with a sensorineural loss in just one ear. This
loss can sometimes be caused by an acoustic neuroma. If
the ABR is normal along that region of the path, the chances
of having this tumor are quite small. ABR testing can be
done on small infants since it requires no conscious response
from the person being tested. A small speaker which produces
a clicking sound is placed near the ear. Electrodes automatically
record the nerve signal.
- Electronystagmogram (ENG)
tests measure balance function. The test is done in a darkened
room. Recording electrodes are placed near the eyes. Wires
from the electrodes are attached to a monitor. Alternating
warm and cool water (or sometimes air) is gently introduced
into each ear canal. Since the eyes and ears work in a coordinated
manner through the nervous system, measurement of eye movements
can be used to test the balance system.
- Electrocochleography (EcochG)
evaluates the cochlea and auditory nerve in patients with
Meniere’s disease or sensorineural hearing loss. Invasive
electrodes are placed either through the eardrum or the
round window onto the promontory, or noninvasive electrodes
may be placed on the eardrum or just in front of it. As
in ABR testing, a computer analyzes nerve responses to a
series of clicks.
Myringotomy and tubes/tympanostomy
and tubes is performed to drain fluid from
the middle ear. Many types of tubes exist, but all tubes serve
the same function. They keep the eardrum open, allow air to
enter the middle ear space, and permit fluid in the middle
ear to drain. Most tubes are gradually rejected by the ear
and work their way out of the eardrum. As they come out, the
eardrum seals behind the tube. Another set of tubes may be
needed if fluid accumulation recurs. T-tubes are silastic
tubes with flanged arms that open behind the eardrum and function
like a butterfly bolt. This type of tube rarely clogs with
blood or secretions and is held back within the eardrum by
its arms. When inserted, T-tubes can generally remain in the
ear for prolonged periods of time. T-tubes do not extrude
by themselves. They have to be physically removed. After removal,
over 90% of the defects in the eardrum heal within one month.
Endolymphatic sac decompression
(ESD) is the most common procedure performed
for Meniere's disease. The operation is performed by making
an incision behind the involved ear and exposing the mastoid
bone. The mastoid is opened and the semicircular canals are
visualized. Upon identification of the endolymphatic sac,
the surgeon uses a diamond bur and fine picks to remove bone
around the sac to decompress it. A silastic shunt may then
be inserted into the sac to allow for future drainage. Unfortunately,
studies have shown ESD often does not cure Meniere's sufferers.
Vertigo subsides after surgery in about 70 percent of cases,
but vertigo symptoms recur with the same severity as before
surgery in a significant number of individuals within three
years.
Labyrinthectomy
is performed on individuals with significant hearing loss
due to Meniere's disease. Using the same approach through
the mastoid bone as the endolymphatic sac operation, the inner
ear labyrinth is exposed. The semicircular canals are then
carefully drilled away, exposing the acoustic nerve, which
is then completely removed. Because the entire nerve is excised,
labyrinthectomy does not spare any residual hearing.
Chemical labyrinthectomy
involves the injection of either streptomycin or gentamicin
directly into the ear. These antibiotics are known toxins
to the vestibular nerve. The intent of this treatment is to
deliver sufficient medication to stabilize or partially destroy
the vestibular nerve endings without impairment of hearing.
In cases of Meniere's disease affecting both ears simultaneously,
the administration of streptomycin intramuscularly (injection
into the muscle of the arm or buttocks) can cure vertigo attacks
and hearing may also be spared. Treatment, of course, affects
both inner ears, and leaves the individual with complete absence
of balance nerve function. Most people adjust to this loss
of balance, although they may experience a sensation of bouncing
up and down when walking. This sensation is called ossiculopsia.
Vestibular neurectomy
is performed to improve cases of vertigo due to Meniere's
in individuals with minimal hearing loss. The procedure is
designed to preserve hearing. Vestibular neurectomy involves
the discrete sectioning of the vestibular nerve at its site
of exit from the brain, thus preserving the auditory branch
of the nerve. Ninety to 95 percent of vestibular neurectomies
result in cure of vertigo.
Reconstructive otoplasty
is performed in cases of atresia to create an adequate opening
over the auditory ossicles. The plug of solid bone between
the external canal and middle ear is drilled away with an
air drill to expose the ossicles. Once the ossicles are identified,
the surgeon gently frees them from the surrounding bone of
the ear canal with a diamond dust burr. Abnormal positioning
or other defects of the ossicles are corrected at this stage
of the procedure. Once the bones are fully freed and the middle
ear space exposed, the raw surfaces of the bony ear canal
are relined with a skin graft. A very thin .0010 inch skin
graft is generally harvested from the thigh or lower abdomen.
A fascial graft made of tissue from behind the eardrum is
also thinned and used to create a new eardrum. The fascial
graft is placed directly on the ossicles. The skin graft is
placed tightly against the raw bone of the external auditory
canal.
Simple tympanoplasty
is done to repair a perforated eardrum. The surgeon may anesthetize
the edges of the eardrum with Xylocaine or inject the ear
canal with Xylocaine. Once the eardrum is anesthetized, the
undersurface is scratched with a sharp right-angled hook.
This procedure stimulates the undersurface skin to heal and
if successful the drum will close. At the same time, the surgeon
places a patch made of very thin paper onto the outer surface
of the eardrum. The patch provides a matrix for the healing
process.
Microscopic tympanoplasty
is performed to repair eardrum perforations that are not amenable
to the above simple procedure. With the use of the operating
microscope for visualization, the physician makes an incision
into the ear canal and the remaining eardrum is elevated away
from the bony ear canal and lifted forward. If the perforation
is very large or the hole is far forward and away from the
surgeon’s view, it may be necessary to perform an incision
behind the ear. This incision elevates the entire outer ear
forward, gaining access to the perforation. Once the hole
is exposed fully, the perforated remnant is rotated forward,
and the auditory bones are inspected. Any scar tissue or fibrotic
bands around the auditory bones are removed with microhooks
or a laser. The ossicular chain is pressed to determine if
the chain is mobile and functional. If the chain is mobile,
then the remaining surgery concentrates on repairing the drum
defect. Tissue is taken either from the back of the ear or
from the tragus. The tissues are thinned and dried. An absorbable
gelatin sponge (Gelfoam) is placed under the drum to support
the graft. The graft is then inserted underneath the remaining
drum remnant and the drum remnant is folded back onto the
perforation to provide closure. Very thin silastic sheeting
is generally placed against the top of the graft to prevent
it from sliding out of the ear. A small amount of Gelfoam
is also placed on the outside of the silastic to hold it in
position in a sandwich type layer. If opened from behind,
the ear is then stitched together. Usually, the stitches are
buried in the skin and do not have to be removed later.
Ossicular reconstruction
is indicated if the bones of hearing are eroded. Reconstruction
may be done at the time of tympanoplasty, or the procedure
may be done separately. The most common bone erosion occurs
at the tip of the incus. This bone normally connects to the
stapes, and the connection is only 1.5 mm thick. With prior
infections, the circulation to the bone can become obstructed.
Infection can gradually wear away the connection to the point
where the incus is no longer in contact with the stapes. If
the gap is small, it can be bridged by inserting a small piece
of bone or cartilage. A larger gap requires removal and remodeling
of the incus into a tooth-like prosthesis. The reshaped incus
is then reinserted between the stapes and the malleus in order
to reestablish continuity of the ossicular chain. Other options
include the insertion of a strut made out of artificial graft
material. This artificial graft is porous and allows for the
ingrowth of blood vessels and the complete assimilation of
the graft into the individual's middle ear.
Depending upon the type and combination of ossicular defects
present, the ossicular chain is surgically recreated with
a partial ossicular replacement prosthesis (PORP) or a total
ossicular replacement prosthesis (TORP). Prosthetic materials
used for ossicular reconstruction may be autologous, homologous,
or artificial. Autologous grafts include a sculpted incus
as described above; an intact incus which is removed and replaced
in an inverted position; auricular and tragal cartilage. Homologous
grafts are obtained from banked rib or knee cartilage. The
most successful grafts use artificial materials, such as hydroxyapatite
and derivatives (flex H/A), polytetrafluorethylene and derivatives
(polytef), polyethylene and metal.
Stapedectomy
is a microsurgical procedure done to treat otosclerosis. An
incision is made in the ear canal near the tympanum. Under
microscopic guidance, the tympanum is carefully raised and
the surgeon opens the middle ear. The bones are evaluated
and otosclerosis confirmed, usually upon visualization of
a calcium deposit. The stapes bone is then tested, and if
it does not move when pressed, it is separated from the incus.
A laser or other micro instrument is then used to vaporize
the tendon and the arch of the stapes, and the stapes is removed
from the middle ear. The oval window is then opened, and with
a very low power setting, the laser is directed at the window
and a miniscule opening (.6 mm) is made. Once the opening
is made in the window, a prosthesis, usually made of Teflon
or platinum, is placed onto the incus bone and gently inserted.
The prosthesis is then clipped onto the incus and the new
assembly is pressed to confirm that its movement is correct.
A piece of fat or fascial tissue is taken from a small incision
behind the ear lobe and used to seal the hole in the window
and the space around the prosthesis. The tympanum is then
folded back into its normal position and held down with a
small Gelfoam sponge.
Mastoidectomy
is performed to clear the mastoid sinuses of disease. In the
transcanal approach, the surgeon enters the middle ear via
the external ear canal, elevates and retracts the tympanic
membrane, and progresses through the middle ear space in a
posterior and superior direction into the mastoid area. In
the postauricular approach, an incision is made behind the
ear and the mastoid area is entered in a more direct fashion.
Using suction and irrigation along with various cutting instruments,
the surgeon then removes all diseased tissue from the mastoid
cavity. A Penrose drain is inserted into the mastoid cavity
for external drainage, and a pressure equalization tube is
often inserted to ventilate the middle ear space.
Because mastoid disease generally results from extension
of disease in the middle ear and/or external canal, the surgeon
must be able to visualize, assess, and repair these areas
as well as the mastoid cavity during surgery. The surgeon
therefore drills away bone to fully expose the ear structures.
The most common methods used to excise bone and gain exposure
are:
- Antrotomy:
The superior portion of the external ear canal is drilled
away so that the attic space can be accessed. This approach
is used for limited disease such as a well-circumscribed
cholesteatoma.
- Intact wall technique:
For most cases of chronic ear diseases an intact wall operation
is the favored procedure. This operation preserves the wall
between the middle ear and mastoid. Via a postauricular
incision, the mastoid bone is first drilled and the surgeon
continues dissection to expose the middle ear attic. Diseased
tissue is removed from the mastoid and attic. The other
middle ear structures are accessed via the external ear
canal and appropriate surgery performed at the time of mastoidectomy.
- Wall down technique/radical
mastoidectomy: In this procedure the steps
of the intact wall mastoidectomy are performed and then
the thin wall between the middle ear and mastoid cavity
is drilled away. This approach offers the widest access
to the middle ear, attic, antrum and mastoid. The external
auditory canal is drilled down to the level of the facial
nerve, which is identified and left with a thin, protective
cover of bone. The result of this procedure is a wide-open
cavity between the mastoid and middle ear. This radical
procedure is used in cases of previously failed intact wall
surgery, or in cases of extensive cholesteatoma that is
inaccessible via a more conservative surgical approach.
Cochlear implants
are electronic prosthetic devices that restore limited hearing
to totally deaf individuals. Cochlear implants bypass nonfunctional
hair cells and provide direct stimulation to the auditory
nerve. Implants may be comprised of a single electrode or
multiple electrodes placed within the cochlea to stimulate
the auditory nerve. The physician makes a U-shaped incision
and creates a skin flap behind the mastoid area. Next a circular
depression is drilled in the squamous portion of the temporal
bone. The internal coil of the implant is secured to this
site. A ground wire leading from the internal coil is then
attached to the temporalis muscle. Next the surgeon threads
an array of electrodes into the cochlea. A microphone and
signal processor are worn outside the body, either behind
the ear or placed in the wearer’s pocket. The electrical
stimuli from the processor are sent inside the body to the
electrodes. The electrodes produce signals that stimulate
the auditory nerve fibers, and the signals are then sent to
the brain.
Practice Makes Perfect!
Are you ready for some hands-on practice?
Read the patient report(s) on our procedure
practice page. Assign the appropriate codes and
then compare your answers with our coding
recommendations. Good luck!
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- Diagnostic Tests - Surgical
Procedures
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or about any topic on our Coding Edge® pages, please e-mail
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