Tinnitus, or ringing in the ears, is a medical condition that significantly affects the
quality of life of patients and that can be disabling to many. It has become known that
acoustic and electrical stimulation of the inner ear can cause suppression and sometimes
elimination of tinnitus. The long term goal of this study is to devise new methods for
reduction/elimination of tinnitus. Multiple attempts at tinnitus suppression using
acoustic and electrical stimulation of the inner ear has been performed with variable
success. More commonly, acoustic stimulation is used to mask the tinnitus as opposed to
suppressing or inhibiting the tinnitus. More recently, however, cochlear implants have
been used for hearing as well as tinnitus suppression. The first hypothesis is that in
using acoustic stimulation at specific frequencies and levels of loudness, tinnitus can
be suppressed / eliminated. The second hypothesis is that using the same electrical
stimulation technology as used in the cochlear implant, tinnitus can be
suppressed/eliminated. These predictions will be tested in 3 specific aims. In Specific
Aim 1, an acoustic sound will be delivered through headphones to the subjects' ears at
various frequencies and loudness levels to evaluate suppression / elimination of
tinnitus. In Specific Aim 2, an electrical current will be delivered to the inner ear.
Pulse trains of various frequencies will be used to evaluate suppression/elimination of
the ringing in the ears. Specific Aim 3. The effect of electrical stimulation on the
subjects' quality of life will be measured using validated surveys.
In the past, attempts to suppress tinnitus using acoustic stimulation have succeeded in
only masking the tinnitus to a limited degree. Tinnitus masking devices only camouflage
the tinnitus. Patients frequently report an interference with hearing or complain that
the devices only substitute one unpleasant sound for another. Additionally, the masking
devices can only be used for a limited time and the patient's tinnitus often subjectively
becomes worse after the removal of the device. Patients also become habituated or
accustomed to the device thereby decreasing its effectiveness over time.
Attempts to suppress tinnitus using electrical stimulation have a long history. Starting
in 1801 and continuing throughout the 19th century, the effects of electrical stimulation
on the ear were described by several authors. Some of these early attempts showed that
direct current applied to the mastoid or zygoma could suppress and possibly eliminate
tinnitus in some patients. Aran et al have found that electrical stimulation of the inner
ear via an electrode inserted through the ear drum can cause suppression and sometimes
elimination of tinnitus.
The advent of the cochlear implant revolutionized the restoration of hearing to the deaf
by electrically stimulating the hearing nerve. As a side-benefit, the cochlear implant
was found to suppress tinnitus in 28% to 79% of patients. Electrical stimulation of the
inner ear may have a direct electrical influence on the tinnitus generated in the inner
ear, or it may have an indirect influence by creating activity centrally where tinnitus
reduction occurs. The success with cochlear implants has led to a number of studies to
evaluate electrical stimulation for suppression of tinnitus. These studies have used
electrodes externally and internally (behind the ear drum) and various stimulus
waveforms. They all suggest that in some patients, tinnitus can be suppressed and
occasionally eliminated using these techniques. It is important to note that none of
these studies was placebo-controlled.
Most recently in a preliminary study in 2003, Rubinstein et al, used a needle electrode
passed through the ear drum to suppress tinnitus. The authors used a high pulse rate of
4,800 pulse-per- second (pps) for their electrical stimulation. They found that 5 of 11
(45%) subjects with electrical stimulation of the inner ear through the ear drum using a
needle electrode showed substantial or complete tinnitus suppression with either no
perception or only a transient perception of the stimulus. Three (27%) showed tinnitus
suppression with the perception of the stimulus and three showed no suppression of the
tinnitus. In subjects with cochlear implants, the authors used the cochlear implant for
tinnitus suppression using the electrical signal sent through the implant to the inner
ear. The results of tinnitus suppression using the cochlear implant were similar to the
subjects without implants. Based on recent work performed on cochlear implant subjects,
it has been found that low pulse rate stimulation may be more beneficial in suppressing
tinnitus in cochlear implant patients. Electric stimulation will be delivered through an
optically-isolated constant-current source. The maximum output will be set at 1000
microamps and be periodically calibrated to ensure accuracy. This device has been used in
several previous studies on hearing perception and a similar device has been used to
treat tinnitus . The device is routinely used for cochlear implant patients, but is not
routinely used to stimulate people without cochlear implants (given their normal hearing
status). It has been used experimentally, however, used for people with hearing loss or
tinnitus.
The goal of this study is to expand on these studies and to evaluate the impact of
various modes of electrical stimulation for the suppression of tinnitus and to evaluate
the quality of life impact of tinnitus suppression on the patients. The predictor
variables include frequency, pulse width, and waveform of the electrical stimulation.
This study will determine which combination of amplitude, frequency, or waveform will
provide the best response. If successful, this method of treating tinnitus could form the
basis for development of hopefully the first effective treatment for tinnitus.
The outcome variables include tinnitus level (on a scale of 0-100, with 100 being the
loudest level of tinnitus they have experienced), tinnitus handicap inventory score, and
Short-form 36 results.
