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OCR for page 1
Introctuction
Hearing sounds that do not originate in the world outside
the body is an experience that probably every human has
at one time or another in life. The sounds heard range
from popping and clicking to intermittent roaring and
buzzing to continuous pure tones. In their diversity,
these experiences have two things in common: they all
originate, in one way or another, from inside the head,
and they are all known as tinnitus.
Tinnitus can accompany a wide array of serious and
minor disorders of the ear and of the body in general.
As shall be seen, some causes are reasonably well under-
stood, but most are not. Effective palliative treatment
has been established for some forms of tinnitus, but for
most, effectiveness of treatment continues to be unpre-
dictable.
The following section provides an overview of the tin-
nitus problem and of the various topics that are discussed
in detail in subsequent sections.
OVERVIEW OF THE REPORT
Tinnitus can be defined as the conscious experience of a
sound that originates in the head of its owner. In some
cases tinnitus exists because there is actually a source
of acoustic energy located somewhere in the head and neck
area--a contracting muscle, a clicking jaw, a defective
vein or artery, etc.--that can also be heard by a second
party, with or without the aid of special devices. How-
ever, the majority of tinnitus cases have no detectable
acoustic basis, but instead arise from anomalies in one
or more of the elements of the neural chain that consti-
tutes the auditory nervous system. It is important to
1
OCR for page 2
2
emphasize at the outset that tinnitus is itself not a dis-
ease, but a symptom that is common to many maladies that
afflict many different structures within and without the
auditory system. A frequently drawn analogy is to fever
and headache--symptoms that accompany many different dis-
orders. Like those two symptoms, tinnitus can range in
severity from mild and easily overlooked to severe and
debilitating.
Existing estimates of the prevalence of tinnitus are
all flawed in one way or another, but all are in accord
over its ubiquity. A recent British survey indicates that
about 1 percent of the general population has severe,
occasionally debilitating tinnitus; were this percentage
an accurate estimate of prevalence in the United States,
there would be about 2.5 million Americans afflicted with
severe tinnitus. At the other extreme, it may be that
nearly everyone experiences a mild form of tinnitus at
one time or another in life and thus that mild episodes
of tinnitus are "normal" in the sense that an occasional
backache or pimple is normal.
The majority of tinnitus cases are probably never re-
ported as medical or auditory problems, but are simply
accepted as normal phenomena or as occasional minor irri-
tants. For some people, however, tinnitus can become as
totally debilitating as any serious systemic disorder.
It can be severe enough to turn an otherwise healthy,
well-adjusted person into someone unable to work or so-
cialize. Anecdotes persist about people committing, or
threatening to commit, suicide because of severe tinnitus
and of others begging to have their offending ear surgi-
cally destroyed in the hope of escaping a relentless tin-
nitus. Every experienced hearing specialist has seen
less severe, but nevertheless serious, cases.
Given the multiple origins of tinnitus, it should be
expected that no single treatment for tinnitus is likely
to be found. Also, it should be no surprise that many
forms of treatment have been attempted over the years.
Unfortunately, few of these have had much success until
recently. Indeed, until lately, hearing specialists have
had little to offer tinnitus sufferers in the way of re-
lief, and far and away the most common "treatment" even
for severe tinnitus has been the statement that lots of
other people have the problem, that there is nothing much
that can be done about it, and that the patient will
simply have to learn to live with it. This grim situ-
ation has brightened considerably, however, and the
prospects now appear good that the symptom of severe
OCR for page 3
tinnitus will eventually be alleviated for a substantial
fraction of its sufferers. The two most promising areas
of advancement in the treatment of tinnitus involve drugs
and masking.
In the past few years, several drugs have been iden-
tified as potent agents against several of the common
forms of tinnitus. These include lidocaine, carbamaze-
pine, and sodium amylobarbitone. So far each has draw-
backs of one sort or another that prevent its immediate
widespread use, but related drugs are being developed and
studied.
Many tinnitus sufferers independently discover that
sounds from the external world can cover up or mask their
tinnitus. Such people realize relief in relatively noisy
environments or from background sounds such as the inter-
station noise on a radio. Hearing specialists have known
about the effectiveness of masking against tinnitus for
decades, but not until recently was it offered in a
systematic way as a palliative for tinnitus.
In the mid-1970s a group of hearing specialists at the
University of Oregon Medical School developed a device
for generating a masking sound that could be mounted in a
standard hearing aid chassis. This tinnitus masker was
later combined with a hearing aid in the same chassis,
and this combination was called a tinnitus instrument.
For about 5 years, tinnitus maskers and instruments have
been prescribed and distributed to tinnitus patients com-
ing to the Oregon tinnitus clinic. The primary question
posed to CHABA Working Group 89 was to evaluate the
efficacy and safety of tinnitus maskers/instruments.
Nearly all the available information on efficacy comes
from follow-up questionnaire data collected, collated,
and published by the Oregon group. Their series of re-
ports contains some inconsistencies and some (perhaps
understandable) exaggerations, but overall the outcomes
are encouraging. It is important to remember in what
follows that the Oregon group surely does not see a ran-
dom selection of tinnitus sufferers, but rather, those
severely enough afflicted to be motivated to travel to
the clinic (and affluent enough to be able to). That is,
the patients in the Oregon sample probably include some
of the most severely afflicted tinnitus sufferers in the
country, and the various success rates should be
interpreted accordingly.
There are a number of reasonable ways to calculate
estimates of success from the Oregon data; the basic
issue is what number is most appropriate for use as the
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4
denominator of the success ratio. About 25 percent of
the people who appear at the Oregon clinic are sent away
without a recommendation to try a masker, hearing aid, or
instrument, and this number has been essentially constant
over the years. If these people are included in the de-
nominator when calculating a success ratio, the estimates
obtained are very conservative ones. Less conservative
estimates are obtained by excluding this 25 percent of
the people from the denominator on the grounds that they
were not regarded to be good candidates for masking and
thus should not be "counted against" the success of the
treatment. Still less conservative estimates involve
excluding both this 25 percent and those people who were
given a recommendation for one of the three devices-
-
masker, aid, or instrument--but who did not purchase one
after the trial period. Depending upon which of these
increasingly less conservative denominators is used, be-
tween about 42 percent and 83 percent of the respondents
to the Oregon clinic's questionnaire report either total
or partial relief from their tinnitus through use of the
recommended devices. Considering the presumed degree of
tinnitus severity in this sample, such success rates are
certainly encouraging. Masking of tinnitus is not a
panacea, but from these statistics, and from the absence
of other, equally effective treatments, masking must now
be regarded as the treatment of first choice. m e
primary reason for caution regarding this conclusion is
that at present essentially all of the data on efficacy
originate from a single source.
The safety of tinnitus maskers/instruments is more
difficult to evaluate at this time than is their efficacy
There are several reasons for this. First of all, there
is essentially no information available about the sound-
pressure levels (SPL) experienced by typical wearers of
tinnitus maskers/instruments, nor about the temporal pat-
terns of these exposures. Such information is crucial,
of course, if safety is to be evaluated by consulting
standard damage/risk criteria or exposure guidelines.
Most tinnitus maskers/instruments have maximum outputs of
85-95 dBA, and some are rated as high as 105-110 dBA.
The most widely used U.S. exposure guideline permits ex-
posure to 90 dBA for only 8 hours per day when the exPo-
sures occur 5 days per week. Emus, nearly all currently
available maskers/instruments are capable of exceeding
common damage/risk criteria and therefore have the poten-
tial to produce hearing loss.
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5
mere exists a serious question, however, of whether
tinnitus maskers/instruments should be regulated on the
basis of their presumed, or even demonstrated, risk to
hearing. The issue is that for many thousands of people
tinnitus is a severe, debilitating condition, and it can
be argued that the risk, or even the inevitability, of
some additional hearing loss caused by a masker/instrument
is a price worth paying for the relief from the tinnitus.
An obvious parallel exists with hearing aids. Evidence
is accumulating that the levels and durations experienced
by many wearers of hearing aids may eventually cause addi-
tional hearing loss, yet few hearing professionals regard
that risk (or inevitability) to be serious enough to war-
rant restricting the availability or use of hearing aids,
nor presumably would hearing-impaired people be willing
to forfeit their aids on these grounds. Similarly, cer-
tain drugs carry long-term risks (or inevitabilities)
that do not rule out their use when they are all~that is
available for treatment of a serious malady.
It appears that for the moment the best policy to
follow in regard to the safety of tinnitus maskers/
instruments is to make users explicitly aware of the
virtues for hearing conservation of low masker levels and
of intermittent patterns of exposure. Until more is known
about the levels and durations of exposure experienced by
typical users of tinnitus maskers/instruments, more re-
strictive policies are premature, and even when more is
known, such policies may be judged inappropriate.
In summary, after years of neglect, tinnitus is rapidly
coming to be a topic of active interest to clinicians,
physiologists, psychoacousticians, and other hearing spe-
cialists. Much is left to be learned, but it is clear
that tinnitus is now an established, legitimate research
area; it is not dust another buzz word.
In the rest of this report, the issues briefly men-
tioned here are examined in more detail, and the evidence
on which current beliefs about tinnitus are based is
presented and evaluated.
A DEFINITION OF TINNITUS
As is true for so many phenomena, a concise yet precise
definition of tinnitus is difficult to achieve. As noted,
one distinguishing feature of tinnitus is that the origin
of the perceived sound is inside the head. In some cases
there is an actual sound source--a vibrating body--under
OCR for page 6
6
lying the perception. Some examples are vascular anoma-
lies, muscular contractions, clicking jaws, and even
trapped insects. Obviously, the existence of such sound
sources raises the potential for their being detected by
others, with or without the aid of amplifying devices.
Indeed, some truly remarkable cases have been reported.
Glanville et al. (1971) discussed a case of a young child
having a high-pitched tinnitus that could be heard at a
distance of 4 feet.
The child's father and one of its
two siblings had similar, but less dramatic, emissions,
and, interestingly, the father was unable to hear his own
emission. Huizing and Spoor (1973) also reported on a
patient whose ear emitted a high-pitched tone that was
audible to a 1 but herself. She, and the father mentioned
previously, had circumscribed hearing losses in the ~-
tral region of their emissions.
Thus, technically speak
~ no , newer naa c~nnzcus, since they could not hear their
own sounds. Other examples of intense emissions have been
noted (see Zurek, 1981), one in a dog (Decker and Fritsch,
1982) and one in a cat (CIBA Foundation, 1981:133).
A long-standing distinction in the tinnitus literature
is between those instances of tinnitus that have a vibra-
tory origin and can be heard by others, as well as by the
patient, and those instances in which the tinnitus is
audible only to the patient, presumably because the site
of origin is inside the nervous system and there is no
vibratory concomitant. Various dichotomies have been
proposed for these two forms of tinnitus: for example,
vibratory/nonvibratory (Fowler, 1939, 1941), objective/
subjective, extrinsic/intrinsic (Atkinson, 1947), pseudo/
true (Jones and Knudsen, 1928). me intent behind the
distinction, of course, is to partition instances of tin-
nitus into two broad categories as an initial aid to
diagnosis and treatment.
Problems with all of these dichotomies have recently
been spotlighted by the development of new procedures for
monitoring acoustic activity in the outer ear canal (Kemp,
1978). The facts are discussed at length in the section
" m e Objective/Subjective Issues in Chapter 2; all that
need be noted here is that with these new techniques,
weak acoustic activity has been found to underlie some
instances of tinnitus that previously had been categorized
as subjective or nonvibratory. The point is that there
are a number of factors that can affect the ability of a
person to detect a sound, and failure by a clinician to
do so cannot reasonably be taken as evidence for the
nonexistence of the sound. So, while these various di
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7
chotomies are well intentioned, application of the cri-
teria has been, and surely will continue to be, much more
difficult than was initially apparent. Even more refined
procedures may eventually reveal acoustic concomitants of
other forms of tinnitus, thereby moving them from the sub-
jective to the objective category, and conceivably, non-
acoustic but nevertheless objective measures of some forms
of tinnitus may be developed that will further muddy the
distinction between objective and subjective forms of the
malady. To the extent that treatment and scientific in-
sight are dependent upon such categorizations, there is a
need for a new appreciation of the shortcomings of the
objective/subjective, vibratory/nonvibratory, and other
dichotomies. While these distinctions are sometimes used
in this report, our commitment throughout has been to the
view that objective measures may eventually be developed
for many, if not all, forms of tinnitus.
It should be noted that a recent major publication on
tinnitus (CIBA Foundation, 1981:Appendix I) explicitly
proposes to exclude from the definition of tinnitus those
cases previously classified as objective. While the
objective/subjective distinction may have become muddy in
recent times and may deserve to be dropped (see " m e
Objective/Subjective Issue" in Chapter 2), there is no
apparent justification for disregarding history and tradi
Lion by excluding from the definition of tinnitus those
ahead noises" that happen to have an acoustic concomitant
In this report, then, the term tinnitus is used to
describe the conscious experience of a sound that origi-
nates in the head, either acoustically or physiologically.
For inclusion in the definition, no criterion of severity,
loudness, annoyance, or other characteristic of the tin-
nitus need be met. A distinction not made by this defini-
tion, but which will eventually have to be drawn, is be-
tween the elementary sensory experiences of the tinnitus
sufferer and the organized perceptual experiences of the
hallucinating mental patient.
PREVALENCE OF TINNITUS
-
It is apparently widely believed that mild, occasional
tinnitus is experienced by nearly everyone at some time
or another and that these brief episodes are not neces-
sarily associated with, or precursors to, auditory path-
ology. Given this belief, it is peculiar that most formal
OCR for page 8
8
attempts to estimate tinnitus prevalence do not effec-
tively discriminate such instances of tinnitus from its
severe, annoying, and protracted forms, nor do they dis-
criminate between the tinnitus of normal-hearing and
hearing-impaired subjects. The ambiguity of past ques-
tionnaires and interview questions surely is a signifi
. . . . . .
cant source ot variability in prevalence statistics.
Nevertheless, over the years, the following prevalence
statistics have been reported:
1. About 32 percent of all U.S. adults report having
had tinnitus at one time or another, and about 6.4 per-
cent of that same population characterizes the tinnitus
as severe or debilitating (National Center for Health
Statistics, 1968).
2. About 85 percent of 2,000 consecutive patients
seen by an otologist complained of tinnitus (Fowler,
1944).
3. About 83 percent of 500 consecutive patients with
acoustic neuromas had tinnitus (House and Brackmann,
1981).
4. About 79 percent of 190 patients with otosclerosis
had tinnitus (Glasgold and Altmann, 1966).
5. About 75 percent of all cases of deafness report
tinnitus (Heller, 1955).
6. About 13 percent of school children with audio-
metrically normal hearing report having tinnitus, at
least on occasion (Nodar, 1972).
7. About one-half of a sample of deaf children had
tinnitus (Graham, 1980).
8. Tinnitus prevalence increases with age up to about
age 70 and declines thereafter (Reed, 1960).
A recent British survey (Institute of Hearing Research,
1981) has attempted to use less ambiguous questions than
those used in the past in order to better discriminate be-
tween chronic, problem tinnitus and occasional, ~normal"
tinnitus. Of course, the information obtained may not
generalize perfectly to the U.S. population. Neverthe-
~ess, preliminary analyses indicate that about 17 percent
~ ~ . . . .
of the British population sampled had problem tinnitus,
that about 1 percent had tinnitus that produced severe
annoyance, and that about 0.5 percent had tinnitus that
resulted in an inability to lead a normal life. About
equal percentages (9-10 percent) reported tinnitus with
and without apparent hearing impairment, fewer reported
unilateral tinnitus than tinnitus in both ears or "in the
OCR for page 9
9
head," prevalence increased with age, and there was little
sex difference in prevalence rate. (Note that if the
0.5-1 percent value does apply to the present U.S. popu-
lation, it would mean that approximately 1.2-2.3 million
people have severe or debilitating tinnitus.)
Some authors have attempted to estimate tinnitus Preva
lence In various subgroups or nearing-impaired people.
These attempts are typically plagued by small sample size
and other sampling problems. Nevertheless, Heller and
Bergman (1953) studied 100 consecutive patients at a Vet-
erans Administration audiology clinic and found that 73
percent had tinnitus. m e preponderance of these (39/100)
were diagnosed as perceptive deafness, with conductive
deafness (13/100) and otosclerosis (8/100) being the two
next most common categories.
Reed (1960) reported that
in a sample of 200 patients referred for severe tinnitus,
38 percent were diagnosed as suffering Primarily from
presbyousis, 16 percent primarily trom acoustic trauma,
12 percent primarily from Meniere's Disease, 10 percent
from idiopathic symptoms, and the remaining 24 percent
from a variety of other maladies. J. T. Graham (1965)
distilled some data from Heller showing that tinnitus is
reported by 71 Percent of those whose hearing impairment
. . _ . . , ~
was diagnosed as perceptive, by en percent or those alag-
nosed as conductive, by 88 percent of those diagnosed as
combined, and by 85 percent of those diagnosed as oto-
sclerotic.
One unexpected fact has been found in some surveys of
tinnitus. It appears that monaural tinnitus is about 1.5
times more likely to occur in the left ear than in the
right (Hazel!, 1981b; Institute of Hearing Research,
1981).
Verification should precede attempts at explana-
tion (see CIBA Foundation, 1981:31).
While the various official attempts to estimate tin-
nitus prevalence are subject to various procedural criti-
cisms, the resulting estimates do imply two things: that
the magnitude of the tinnitus problem has not been appre-
ciated and that effective treatment of tinnitus has not
been available. Whenever there is an ignored, afflicted
population of this size, the potential for abuse by char-
latans and misguided healers is great, as is the risk of
exaggerating the effectiveness of any new treatment.
Caution and critical restraint must be exercised when
evaluating new or modified treatments, and that has been
the attempt throughout the preparation of this report.
Representative terms from entire chapter:
hearing specialists
