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As printed in Hearing Health, volume 19:1,
Spring 2003
By Jack Vernon, Ph.D.
A pesky and sometimes debilitating phenomenon, tinnitus
is the perception of a sound in the absence of external
stimuli. People who experience it describe the sensation
as emanating from an internal source and that it is
usually “heard” by the ears. Although often
considered an auditory problem or disorder, tinnitus
is actually a symptom of one or more of a variety of
things. It can be related to hearing loss, particularly
sensorineural where there is hair cell, neurochemical
or neural damage or abnormalities. It can relate to
blood flow or muscle spasms in the middle ear. Or the
cause can be medication or a variety of health conditions,
including allergies, tumors, circulatory problems, jaw
and neck problems … the list is practically endless.
And in some cases, there is no known explanation.
With such a broad set of contributing factors, it
is not surprising that tinnitus is very common. The
numbers are a bit nebulous but according to a 1989 survey
performed in Sweden, 10 percent of people under 50 have
tinnitus that is bothersome in quiet. The percentage
increases to about 40 percent of those over 50 and jumps
to 75 percent for people seen in audiological clinics.
Today’s numbers are likely even higher as our
lifestyles are filled with exposure to loud noise that
contributes to hair cell damage, high stress levels,
poor nutrition and epidemic levels of allergies, diabetes
and other diseases.
Although tinnitus remains poorly understood and without
a “cure,” a cadre of researchers and clinicians
are dedicated to providing as much relief as possible
now and eventually finding a definitive treatment. When
over 200 of us from 26 countries attended the Seventh
International Tinnitus Seminar in 2002, we shared more
than our latest findings and theories. We expressed
the need for education of the general public on tinnitus,
starting at grade school level, as a preventative measure.
We called for standardized testing of treatment results
so we could draw the most meaningful conclusions when
comparing methods. And we discussed the importance of
providing thorough diagnostic testing in order to establish
baseline measures as an aid in evaluating the results
of proposed treatments.
We also emphasized the need to make available more
information on tinnitus to healthcare providers, particularly
in terms of diagnostic and therapeutic methods that
are currently available. General practitioners and nurses
are often the first and only professionals that hear
about their patients’ tinnitus and its effects
on the quality of their lives. If the message from those
clinicians is that there is nothing that can be done,
an all too common refrain, the opportunity is lost for
people to seek and receive tinnitus relief.
This article is an attempt to clarify for all clinicians
– providers of general as well as hearing healthcare
– one facet of the tinnitus diagnosis and treatment
continuum. Also, it may be a useful how-to guide for
audiologists who are not currently providing these tests.
And the information is valuable, I think, for individuals
with tinnitus who are seeking help; the descriptions
of tests to expect and request in getting the most informative
diagnosis can prepare them to be helpful and hopeful
participants in successful treatment.
It is certainly true that the more we know about the
topic of our concern, the better we can do in providing
care. It is for this reason that it is important to
test various aspects of the tinnitus in everyone who
seeks treatment. In addition to a physical exam by an
ear, nose and throat specialist and an audiometric work
up by an audiologist, it is essential for each potential
patient to undergo evaluation to determine:
• the frequency corresponding to the pitch of
the tinnitus
• the loudness of the tinnitus
• the maskability of the tinnitus
• the residual inhibition duration.
In addition, the suspected cause of the tinnitus should
be indicated for each patient.
To illustrate methods for testing and possible outcomes,
I am relying on detailed information collected through
a survey of 2,500 tinnitus patients attending the Tinnitus
Clinic at the Oregon Hearing Research Center over the
past 20 years. Self-descriptions by the respondents
report location of the tinnitus: both ears, 60 percent;
left ear only, 12 percent; right ear only, 10 percent;
in the head, 6 percent; variable location, 5 percent.
Sound type: tonal, 77 percent; noise, 8 percent; a combination
of both, 15 percent. The sound was constantly present
for 90 percent of these patients.
Pitch
First, a noise band centered at the frequency of 1 kHz
(kilohertz) and a tone at 1 kHz are presented in an
alternating fashion, both at the same loudness as the
tinnitus. The examiner asks patients to identify which
is most like their tinnitus. If the tone is chosen,
the examiner proceeds with a two alternative-forced-choice
(2AFC) procedure.
Since most tinnitus is relatively high pitched, it
is customary to start by comparing tones of 1 kHz vs.
2 kHz. Each is independently raised to match the loudness
of the tinnitus as closely as possible. For precision,
the loudness should be raised in small steps of one
to two decibels (dB). The two tones are then presented
alternately while the examiner asks the patient to select
the tone most like the tinnitus. If the selection is
2 kHz, the next comparison is 2 kHz vs. 3 kHz. The order
of presentation should be varied in order to prevent
response bias for always choosing either the first or
the second tone of the pair.
The 2AFC comparisons continue with successively higher-frequency
tone pairs until there is a frequency reversal. For
example, if the patient prefers 6 Hz to 5 kHz and also
prefers 6 kHz to 7 kHz, that suggests that the pitch
of the tinnitus is in the region of 6 kHz.
If in the initial comparison of 1 kHz vs. 2 kHz the
selection was 1 kHz, the 2AFC procedure would proceed
downward in frequency, using small frequency steps and
again setting all comparison tones at the same loudness
as the tinnitus.
Regardless of the final frequency selected, it must
be confirmed by a test for octave confusion. This is
done by comparing the selected tone with a tone one
octave higher. In the earlier example, the patient selected
6 kHz so that would be compared with 12 kHz which is
one octave above. About 60 percent of test subjects
select a final pitch match that is one octave higher
than their first pitch identification, suggesting that
octave confusion tests are an important check for properly
identifying the correct frequency for tinnitus masking.
For people who describe their tinnitus as being more
like a noise, testing is done by comparing different
bands of noise. One approach is to present a series
of relatively narrow noise bands (e.g., 1/3 octave)
starting at a center frequency of 2 kHz. The center
frequency of the noise band judged most similar to the
tinnitus is taken as the pitch match.
For participants in the survey, the average pitch
was around 6 kHz.
Loudness
During the 2AFC procedure used in determining pitch,
the loudness of each of the comparison tones has also
been determined. Now it is only necessary to insure
that the loudness measures are correct by repeating
the test at the tinnitus frequency, making sure that
the patient agrees that it is still a good match after
all tests for octave confusion and other pitch adjustments
are completed.
In some situations, however, more precise verification
is required (e.g., for presentation in a legal case
to recover damages or compensation for treatment). In
these scenarios, the examiner introduces a procedure
that can help identify “real” vs. feigned
tinnitus. This involves measuring the loudness match
at the tinnitus pitch six or seven times, separated
by five to 10 minutes with distracting activities in
between. If the various loudness matches do not differ
by more than 3 dB, their average is accepted as court’s
evidence that the tinnitus is really present.
When properly measured, tinnitus is not a loud affair.
The median loudness match for our 2,500 participants
was approximately 4 dB and 80 percent measured at 7
dB or less.
Maskability
This measure uses broadband noise, 2-12 kHz for example,
that is presented to the ear with the predominant tinnitus.
First, the threshold for the masking band of noise is
determined (i.e., the lowest intensity level at which
the masking sound is first heard). Loudness of the masking
noise is then raised in small steps. At each new level,
the patient is asked whether the tinnitus can be heard
in the stimulated ear. When it is no longer heard, the
dB level is recorded and referred to as the Minimum
Masking Level (MML). For bilateral tinnitus, the MML
for the second ear is determined separately. In our
clinic, median MMLs are on the order of 9-10 dB.
Residual Inhibition
To measure whether the sound of a patient’s tinnitus
returns immediately after stimulation ceases, the masking
band of noise is presented at 10 dB above the patient’s
MML for 60 seconds. The examiner then measures the length
of time until the tinnitus returns to its usual level.
If it is completely absent at the end of the masking
tone, that condition is Complete Residual Inhibition
(CRI) and its duration is recorded by asking when the
tinnitus first becomes audible again. If the tinnitus
is reduced but not totally absent, that condition is
Partial Residual Inhibition (PRI). Using a stopwatch,
duration is recorded by asking the patient to indicate
when the tinnitus is back to its usual level.
In most patients, a brief interval of CRI is followed
by a longer-lasting PRI. In our clinic the average total
recovery time, CRI plus PRI, was 67 seconds. Residual
inhibition is, however, highly variable and lasts for
several minutes or even longer for some patients. At
least one type was displayed in 88 percent of our survey
participants.
My colleagues and I encourage all hearing healthcare
professionals who work with people with tinnitus to
perform the test protocol as described above. In the
long run, information gleaned from the process may have
great import. It can provide more detailed understanding
of tinnitus that helps both clinicians and researchers.
Further, these four measures can highlight differences
and similarities between patients that are likely to
be important for understanding variations in response
to treatment.
Allow me to repeat: the more information we gather
about a given health problem, the more likely it is
that a solution to that problem will occur. If dedicated
to careful data collection throughout the diagnosis
and treatment process and in measuring effectiveness,
we will be ahead of the game in the ability to offer
increasingly improved tinnitus relief procedures.
Jack A. Vernon, Ph.D., is professor emeritus of otolaryngology
at Oregon Hearing Research Center, Oregon Health Sciences
University, Portland, and continues to write, lecture
and provide tinnitus counseling. Detailed information
about characteristics of participants in the survey
referenced above is available from The Oregon Tinnitus
Data Archive. Visit www.ohsu.edu/ohrc-otda.
Related Article:
Q & A: Screening
for Tinnitus
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