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| Tinnitus |
Tinnitus is
the perception of sound without external acoustic stimulation.
Some call it “ringing in the ears” although the sound perceived may not
sound like a bell or phone ringing. Frequently, the sound may be
a solid or intermittent pure tone, clicking, hissing, roaring, buzzing
or white noise static-like sound. Most people with tinnitus have
an intermittent tinnitus that comes for a short time and then goes
away. Although inconvenient, it is a condition that they can
adjust to and live with.
According to the American Tinnitus Association (ATA), 20% of the world
population suffers from tinnitus. In the U.S. more than 50 million
Americans experience tinnitus to some degree and for 12 million the
problem is so severe that it affects their daily lives.1
The
Hearing Industry Resource estimates that 10-15% of the U.S. population
experiences chronic or persistent tinnitus and about 1% report that
tinnitus substantially affects their lives.2 Tinnitus
is a worldwide
problem too. According to the Deutsche Tinnitus Liga (DTL), in
Germany alone, more than 1 million people experience severe to very
severe tinnitus.3 The British Tinnitus Association (BTA) recently
reported that 25% (15 million) of the UK population experiences
tinnitus at some stage of their lives and 6% of the total population
(3.6 million) suffer moderate to severe tinnitus. Eight percent
of the population visit their primary physicians and 2-4% visit
hospitals in search of treatment for their tinnitus.4
The number
of tinnitus sufferers is expected to increase based on war-related
cases of tinnitus and hearing loss alone (acoustic trauma and blast
injury). The number of veterans with war-related tinnitus
disabilities is expected to more than double from 390,900 veterans in
2006 to 818,811 veterans in 2011,5 at a cost to American
taxpayers of
more than $1.1 billion. Clearly tinnitus is a significant medical
problem.
For a smaller but significant population of 10-15% of the tinnitus
sufferers, tinnitus is loud, very bothersome, and can be quite
debilitating. In such cases the tinnitus is very annoying and
affects sleeping, concentration, hearing, working, relaxation and could
be associated with or lead to other diseases such as depression.
Tinnitus is primarily associated with hearing loss and, as such, is
found commonly in older people (both men and women). Even
hearing-impaired or profoundly deaf patients frequently suffer from
tinnitus, even when they are incapable of hearing external
sounds. Tinnitus may also be in one or both ears. In
addition, diseases such as Ménière's Disease,
hyperacussis, jaw or neck conditions, heart problems, allergies or
following acoustic trauma or therapeutic or exposure to ototoxic drugs
or chemicals. NIDCD estimates that there are more than 200
medicines that can cause tinnitus. The most famous tinnitus
causing chemical is aspirin. For these reasons, there is no
common cause of tinnitus and the different etiologies of tinnitus may
require different approaches for its treatment.
Currently, there is no approved drug treatment for tinnitus.
There are a number of therapies and devices that are being tested or
promoted for control or cure of tinnitus. The main treatments for
tinnitus are hearing aids, sound maskers, tinnitus retraining therapy,
counseling and relaxation and diversion from thinking about the
sound. To summarize, these approaches are either ineffective or
present safety or efficacy problems when utilized long-term. Some
of the more commonly used approaches treat the symptoms and not the
tinnitus itself.
The cause(s) of tinnitus is not well understood, but it is thought to
be primarily a disorder of the nervous system; that is, the “sound” is
perceived because of abnormal neuronal firing or a hyperactivity in
cells of the auditory system. The lack of innovative and
effective therapeutic treatments for tinnitus has led NeuroSystec to
develop the drug, NST-001. NST-001 is a non-competitive
N-methyl-D-aspartate (NMDA) receptor antagonist that has relatively
little effect on other receptors in the glutamatergic signaling
pathways, such as AMPA
(α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate) receptors required
for hearing. Antagonists of NMDA receptors suppress nerve firing
in the central nervous system and inner ear, thereby suppressing the
elevated activity of spiral ganglion in the cochlea. NST-001
should, therefore, result in suppression, reduction of annoyance or
elimination of tinnitus (depending upon the etiology and type of
tinnitus). If this hypothesis is confirmed, then the approach to
treating this disease would be to administer NST-001 directly to the
affected tissue to suppress the nerve’s hyperactivity.
NeuroSystec is presently focused on developing therapies for the
treatment of severe tinnitus and to specifically deliver directly to
the diseased tissue a drug that would inhibit this hyperactivity.
Our main project is to develop an implantable pump system that would
deliver NST-001 to the inner ear and directly treat the auditory nerve
(Spiral Ganglion) in the cochlea. This then would inhibit the
peripheral tinnitus for those conditions where the tinnitus is due to
the hyperactivity of the cochlear nerve.
NeuroSystec believes that there is a need in the medical marketplace
for implantable medical devices that enable targeted drug delivery with
potent therapeutics into difficult to reach anatomical locations.
This delivery device is to be used initially to treat cochlear
tinnitus. The device would also be useful in a broader range of
diseases for which parenteral drug delivery is not optimal.
Please contact us if you have any questions or want more detail about
this review of tinnitus.
References:
1. American Tinnitus Association Website, Frequently
Asked Questions, http://www.ata.org/about-tinnitus/patient-faq1,
accessed March 24, 2009.
2. Kochkin S, Tyler R (2008) Tinnitus treatment and
the effectiveness of hearing aids: hearing care professional
perceptions, Hearing Review 15(13):14-18.
3. Deutsche Tinnitus-Liga e.V. website, Tinnitus in
Germany, http://www.tinnitus-liga.de/index_e.htm,
Accessed March 24, 2009.
4. British Tinnitus Association website, Research, http://www.tinnitus.org.uk/index.php?q=node/75,
accessed March 13, 2009.
5. American Tinnitus Association Website, Support for
Vets, http://www.ata.org/action-alliance/support-for-veterans,
accessed March 24, 2009.
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