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Vestibular tests are
tests of function. Their purpose is to determine if there is something
wrong with the vestibular portion of the inner ear. If dizziness is not
caused by the inner ear, it might be caused by the brain, by medical
disorders such as low blood pressure or by psychological problems such as
anxiety. Studies have documented that vestibular tests are more accurate
than clinical examination in identifying inner ear disorders. Hearing
pathway tests (audiometry, Auditory Brainstem Response (ABR),
Electrocochleography (ECoG)) can also be used for the same purpose and are
frequently combined with vestibular tests.
Diagnostic otologic evaluation services are performed to detect presence or
absence of a hearing deficit and to identify the factors responsible for
the deficit. The assessment of a deficit involves both physical and
physiological measurements for appropriate diagnosis and referral.
Accurate assessment of hearing (audiometry) is vital to the diagnostic
evaluation of patients with suspected otologic disorders for the
determination of the underlying process, as well as in the planning of
rehabilitation of hearing loss. Originally, audiometry was limited to the
psychophysical measurement of the sensation of hearing; thus, patient
cooperation was essential. However, other tests have been developed over
the years that permit more objective assessment of hearing even in infants,
small children, malingerers and hysterics.
Most humans hear sounds in the range of 20 to 20,000 Hz. Sensitivity varies
as a function of frequency, with sounds in the middle frequencies being
heard best. The ability to hear higher frequencies declines with age.
Basic Audiometry: Adequate testing requires an audiometer (device
for presenting sounds to the patient at precisely controlled intensity), a
sound proof environment, a competent audiologist and a cooperative patient.
The standard testing battery may vary depending on purpose.
- Pure Tone Audiometry, Speech Audiometry, and Immittance Audiometry
A. Pure Tone Audiogram: This is a graphic plot of the patient’s
thresholds of audiometry sensitivity for pure tone (sine wave) stimuli.
Threshold hearing levels are indicated for each frequency tested. By
convention, normal hearing levels are shown at the top of a graph; a
decrease in hearing sensitivity is indicated by larger values of hearing
level. Hearing level is plotted on a logarithmic decibel scale. Sounds are
tested with presentation by air conduction (earphones) as well as bone
conduction (skull vibrator). An air bone gap indicates a conductive
component of hearing loss. A decrease in threshold sensitivity by bone
conduction reflects a sensory or neural loss.
B. Speech Audiometry: These tests utilize spoken words and sentences
rather than pure tones. Tests are designed to assess sensitivity
(threshold) or understanding (intelligibility).
- Threshold - The level at which the patient can correctly repeat 50
percent of test materials: Phoneme-Balanced words (PB), synthetic
sentences, etc.
- Intelligibility - By convention, the percentage of words or sentences a
patient can correctly repeat when presented at supra-threshold levels.
- Provides information about hearing handicap. Problem may be worse than
indicated by pure tone average (PTA) for the speech frequencies. Useful to
determine candidacy for hearing aid.
- Very poor results, out of proportion to PTA, suggest probable
retrocochlear cause of hearing loss.
C. Immittance Audiometry: These hearing tests utilize an
electroacoustic immittance bridge. This device is designed to quantify the impedance
(resistance to movement) of the conductive mechanism of the ear by bouncing
a probe tone off the tympanic membrane and measuring the proportion of
reflected sound. Impedance testing can measure either the impedance or
admittance (the American Speech-Language-Hearing Association term that
encompasses both is "immittance"). Typically, today’s equipment
measures admittance. The purpose of the test is to assess middle ear
integrity. Maximal reflection of sound occurs when the mechanism is very
stiff, while a compliant system transmits more sound and reflects less.
There are two principal applications of this device:
- Tympanometry: A tympanogram is a graphic representation of the
relationship of external auditory canal air pressure to impedance; the
latter is usually reported in terms of tone of its derivatives, compliance
in arbitrary units. Pressure in the external auditory canal is varied from
-200 daPa through +200 daPa while monitoring impedance. Impedance is the
lowest (maximal compliance) when pressure in the canal equals pressure in
the middle ear. Ears can be classified into three basic groups (Type A,
Type B and Type C) on the basis of the configuration of the tympanogram.
- Acoustic Reflex (AR): Contraction of the stapedius muscle occurs
with loud sounds, producing a measurable change in compliance.
Diagnostic Audiometry: Consists of a battery of tests intended to
determine the site of lesion in patients with otologic or neurologic
disorders. The constellation of tests varies according to the available
test battery and provisional diagnosis.
A. Immittance audiometry (see above)
B. PI-PB functions - Speech discrimination is plotted as a function
of sound intensity. Normally, discrimination improves with intensity up to
a maximal level, then plateaus. In eighth nerve disorders, discrimination
often declines dramatically as intensity increases above the level yielding
maximum performances.
C. Bekesy Audiometry - This test has a significant historical
interest in the development of assessment of hearing. However, today it is
used predominantly only in industrial and military hearing screening
situations. Patient traces his own auditory threshold by means of a
self-recording audiometer. Tracings are obtained for pulsed as well as
continuous tones. The relationship between the two categories can be
categorized into diagnostic patterns.
D. Tone Decay Tests - Abnormal adaptation to a continuous tone is
seen in retro-cochlear lesions.
E. Stenger Test - Performed to detect malingering of unilateral
loss. If sound is presented to both ears, patient will deny hearing in the
ear with the feigned loss. If sound is presented to the good ear at a
suprathreshold level, simultaneous to a louder sound in the questionable
ear, a malingerer will localize the sound to his ‘bad’ ear, and therefore
deny hearing anything at all.
F. ABR - Evoked Auditory Brainstem Responses - Scalp electrodes
measure electrical activity in response to sound clicks. The response is
quite small in relation to other ongoing brain activity, but by presenting
a large number of clicks and averaging the responses by computer, unrelated
events can be canceled out. This is useful for documenting hearing in
uncooperative or unresponsive patients. The disadvantage is that it tests
mainly the 1,000-4,000 Hertz frequency range of hearing and is a poor
indicator of the overall auditory function. An abnormal ABR is seen in
eighth nerve or brainstem lesions.
G. ECOG (Electrocochleography) - Electrical activity is measured
from the promontory, and responses to a large number of clicks are
averaged. These will be abnormal in eighth cranial nerve lesions and
certain cochlear disorders.
Audiologist’s Services
Diagnostic testing, including hearing and balance assessment services,
performed by a qualified audiologist is covered as "other diagnostic
tests" under Section 1861(s)(3) of the Social Security Act. This type
of testing can be allowed when a physician orders the tests to obtain
information as part of his/her diagnostic evaluation or to determine the
appropriate medical or surgical treatment of a hearing deficit or related
medical problem. Payment for diagnostic services performed by a qualified
audiologist is determined by the reason the tests were performed, rather
than the final diagnosis or the patient’s condition.
The practice of the profession of audiology means the application of
principles, methods and procedures of measurement, testing, evaluation,
consultation, counseling, instruction and rehabilitation related to
hearing, its disorders and related communication and impairments for the
purpose of non-medical diagnosis, prevention, identification, amelioration
or modification of such disorders and conditions in individuals and/or
groups of individuals.
As provided in Section 1861(II)(3) of the Social Security Act, a qualified
audiologist is an individual with a master’s degree or doctoral degree in
audiology and who has a valid license issued by the state in which the
services are rendered.
In addition to the above qualification criteria, the following requirements
must also be met:
- The testing is ordered by a physician to obtain additional information to
evaluate the need for or appropriate type of medical or surgical treatment
for a hearing deficit or related medical problem even if the only outcome
is the prescription of a hearing aid.
- The name of the physician ordering the testing is reported on the
audiologist’s claim. For example, if a beneficiary undergoes diagnostic
testing performed by an audiologist without a physician’s referral, these
tests are not covered even if the audiologist discovers a pathologic
condition.
Indications
- Vestibular function tests and/or diagnostic audiometric tests are covered
when testing is for the purpose of determining the appropriate medical
or surgical treatment for disorders of auditory, balance and other
neural systems.
- For conductive hearing loss, hearing should be retested after medical or
surgical treatment. For sensorineural hearing loss, the audiologist or
physician will recommend when repeat testing should be done. Since hearing
may change or fluctuate, it is important to detect this as early as
possible to prevent further loss and to obtain medical treatment if needed.
- Audiologic testing (CPT codes 92553, 92557, 92568, 92569) may be
performed for patients on continuing (current) long-term (more than 14
days) use of antibiotics known to be ototoxic, such as streptomycin and
aminoglycosides.
- If a physician refers a beneficiary to an audiologist for evaluation of
signs and symptoms associated with hearing loss or ear injury, the
audiologist’s diagnostic services are covered, even if the only outcome is
the prescription of a hearing aid. It is the intent of the evaluation
(identification or exclusion of pathology) not the outcome that determines
medical necessity.
Limitations
- Screening evaluation or testing for hearing aid evaluation is
specifically excluded by statute.
- Services are excluded under Section 1862(a)(7) of the Social Security Act
when the diagnostic information required to determine the appropriate
medical or surgical treatment is already known to the physician or are not
under consideration and the diagnostic services are performed only to
determine the need for the appropriate type of hearing aid. These services
are excluded from Medicare coverage whether performed by a physician or
non-physician; they are both statutorily excluded and not medically
necessary.
- If a beneficiary undergoes diagnostic testing performed by an audiologist
without a physician’s referral, these tests will not be covered even if the
audiologist discovers a pathologic condition. These services are both
statutorily excluded and not medically necessary.
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