What if hearing healthcare professionals could do more than fit hearing aids or warn patients about damaging noise levels? What if there were other, even better, ways to protect and restore a person's hearing, such as pills, injections, lasers, or a little “hair of the dog”? That day is coming.
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Scientists in the United States and abroad are exploring approaches to help more than 275 million people globally who have hearing loss, from members of the military who sustain auditory injury in combat to ordinary citizens who lose their hearing as a consequence of aging, noise, disease, or ototoxic drug exposure. Treatments are in the works for decreasing the relentless clamor of tinnitus, rescuing hearing after noise exposure, reversing congenital deafness, and staving off age-related hearing loss. Some alternative therapies have already found a place in clinical care and may one day become the standard of care.
A tinnitus sufferer's posting on an online message board referred to sound therapy as “hair of the dog.” It is a reasonable description because this treatment is designed to lessen the effects of ringing in the ears by listening to more sound. The newest technologies are not intended to mask tinnitus but to instigate brain changes that reduce the annoyance. Sound therapy, while still under investigation, is becoming the go-to treatment among a number of hearing healthcare practitioners. “Pretty much most of us who know tinnitus are getting somewhere between 85 and 90 percent success working with patients,” said Melanie Herzfeld, AuD, of the Hearing and Tinnitus Center in Woodbury, NY. “It doesn't mean the tinnitus goes away. It just means it becomes less disturbing.”
Figure. Melanie Herz...Image Tools
Success is typically measured by a 40 percent reduction or more in one of two indices: the Tinnitus Handicap Inventory or the Tinnitus Reaction Questionnaire, Dr. Herzfeld added. (See FastLinks.) Neuromonics, Inc., of Bethlehem, PA, introduced its sound therapy system in Australia in 2004 and in the United States the following year. Tinnitus patients listen to “spectrally modified, precisely designed music embedded with an acoustic neural stimulus” through its Oasis device, according to Neuromonics. These sounds “stimulate the auditory pathway to promote neural plastic changes” that relieve tinnitus symptoms over time. Clinical trial data show that users experience improvement lasting up to 12 months.
Earlier this year, SoundCure, Inc., in San Jose, CA, launched its Serenade sound therapy system based on S-Tone technology developed at the University of California, Irvine. S-Tones, used through a handheld device and earphones, are aimed at “generating neural activity to reduce a patient's perception of his tinnitus, with passive listening… as part of a long-term habilitation program,” SoundCure CEO Bill Perry explained in response to an e-mail inquiry. The company recently announced a four-year contract with the Veterans Administration allowing VA hospitals and clinics to provide the Serenade to patients as needed.
Dr. Herzfeld uses both companies’ technologies and “combination devices” — hearing aids that combine amplification and sound generation technology. These units have an advantage for patients who also have hearing loss, she said, but ultimately it is up to patients to choose based on “their lifestyle and their pocketbooks.” The new sound therapy technologies and many of the combination devices can run from a couple thousand dollars to between $5,000 and $7,000, she said.
This ancient Chinese practice involves inserting thin needles strategically into body points to restore qi — the flow of energy. It has gained popularity in the United States over the past two decades, mostly for pain management. (See FastLinks.) The body of evidence, however, demonstrating its efficacy for various medical conditions is still developing. The findings are mixed for hearing loss.
A paper published in July from researchers at the College of Oriental Medicine in Seoul, Korea, reviewed nine randomized controlled trials on acupuncture's effectiveness in treating tinnitus. (BMC Complement Altern Med 2012;12:97.) Five of the studies, comparing acupuncture or electroacupuncture (use of electric pulses) with sham acupuncture (needling at nonacupuncture points), failed to show any statistically significant improvement. Only two of the other studies, one comparing a one-time scalp acupuncture to sham treatment and another comparing acupuncture with drug therapies, had positive results. Overall, researchers found no convincing evidence that acupuncture is beneficial for treating tinnitus, but given the number, size, and quality of the studies reviewed, they concluded that further rigorous trials are needed.
The story is much the same for other hearing impairments. A review published in 2005 from Tianjin University in China examined evidence from 60 papers published from 1994 to 2004 on the use of auricular and body acupuncture, mostly for treating sudden deafness. They concluded that higher quality studies are needed because of problems with the way the studies were designed. (Zhongguo Zhen Jiu 2005;25:893.)
The Cochrane Collaboration, which publishes reviews of clinical trials and observational studies on various health issues, intends to weigh in on the topic. Future reviews will examine whether acupuncture reduces the severity of tinnitus and relieves sudden sensorineural hearing loss (SNHL). Some clinicians are willing to give it a try, despite a dearth of large, well designed studies confirming acupuncture's value.
“We offer acupuncture because tinnitus is so difficult to treat and we want to provide our patients with a full spectrum of options,” explained Timothy Hain, MD, the lead physician at Chicago Dizziness and Hearing and a professor of neurology, otolaryngology, and physical therapy at Northwestern University in Evanston, IL. “We would be particularly likely to recommend acupuncture in patients who are unable to tolerate medications or who have had success in the past with acupuncture for other problems,” he said in response to an email inquiry.
Treating SNHL with a zap of laser light may sound like science fiction, and Dwayne Paschall, PhD, an associate professor of speech, language, and hearing sciences at Texas Tech University Health Sciences Center in Lubbock, was skeptical when he first heard about laser light as a hearing loss treatment. “It didn't pass through my malarkey filter for a long time,” he said.
Figure. Dwayne Pasch...Image Tools
It began to make sense the more Dr. Paschall thought about it. All cells have a photoreceptor that is able to use light as an energy source if it is available, and laser light is able to penetrate skin and bone enough to reach the structures of the inner ear, he said. Scientists do not know exactly how laser light improves hearing, but research by Erchonia Medical, Inc., a maker of medical lasers in McKinney, TX, suggested that light energy triggers biochemical reactions in the body that aid cell repair and regeneration.
Most research on low-level laser therapy takes place in other countries. A Korean study posted online last December used rats exposed to the ototoxic drug gentamicin to show that low-level laser therapy may help restore hair cell growth. (Lasers Med Sci 2012;27:987.) Iranian researchers in another study treated 61 tinnitus patients for 20 minutes per day over 20 days. (J Res Med Sci 2011;16:33.) Thirty patients experienced a reduction in tinnitus and 11 no longer had tinnitus after two weeks of treatment.
Dr. Paschall is involved in early, unpublished research using Erchonia's lasers with small numbers of hearing-impaired individuals. “What we found is that at some frequencies, their hearing actually improved quite a bit; other frequencies, their hearing really didn't improve much at all,” he said. The challenge now is to figure out the type of laser that works best.
“One of the other things we don't know is that if you stimulate just the inner ear, is that all you need? Or do you also need to stimulate the neural structures to receive the information?” he added.
Antioxidants are touted for their heart disease-fighting properties. Many people may not appreciate that these free-radical scavengers may also mitigate cellular and molecular damage that leads to hearing loss. A number of antioxidants are being studied for their ability to protect people's hearing against the ravages of noise, chemotherapy drugs, and aging.
D-methionine, for one, has been shown in animal models to prevent noise-induced hearing loss. Southern Illinois University School of Medicine's Kathleen C.M. Campbell, PhD, recently received a $1.2 million grant from the US Department of Defense to study optimal “D-meth” dosing and timing in humans. (See FastLinks.) A phase III clinical trial will examine whether oral D-methionine given to drill sergeant trainees during and after weapons training is effective in reducing noise-induced hearing loss and tinnitus.
N-acetylcysteine, another antioxidant shown to be helpful in preventing acoustic trauma, is even more effective in combination with the chemical compound 4-hydroxy PBN (a product of a family of free radical scavengers). The combination, tested in chinchillas, may soon be headed to clinical trials. Otologic Pharmaceutics, Inc., a company formed by Oklahoma Medical Research Foundation scientist Robert Floyd, PhD, and Hough Ear Institute CEO Richard D. Kopke, MD, announced in March a $2.4 million Defense Department grant to test the experimental treatment. (See FastLinks.)
Do antioxidants stave off age-related hearing loss? Michael Seidman, MD, the director of otologic/neurotologic surgery and the medical director of the Center for Integrative Medicine for the Henry Ford Health System in West Bloomfield, MI, has conducted animal research demonstrating the protective effects of various antioxidants, such as acetyl-l-carnitine, against age-related hearing loss. Dr. Seidman noted that clinical trials would take decades and be prohibitively expensive, so most of the research in this area is based on animal studies.
Figure. Michael Seid...Image Tools
Dr. Seidman, who is also a founder and the CEO of Body Language Vitamin, Co., in West Bloomfield, MI, holds a patent on an antioxidant-rich, anti-aging formula shown to reverse age-related hearing loss by seven to 12 decibels. “One could argue that 7 to 12 decibels ain't much, and I would agree, but it might be the difference between the big hearing aid and a smaller hearing aid or a small hearing aid and no hearing aid,” he said.
Genetic factors are believed to cause roughly half of all cases of congenital deafness, so it is no surprise that scientists are exploring gene-based therapies. Lawrence R. Lustig, MD, of the University of California, San Francisco, and colleagues at the University of Pittsburgh and Ohio State University, offered the first evidence that an inherited, genetic hearing loss can be successfully treated in mice. (Neuron 2012;75:283.) The study used mice with hereditary deafness caused by a mutation in gene coding for a protein considered crucial for inner hair cells to send the electronic signals to the brain that enable hearing. Hearing was fully restored in the mice for an average of seven weeks just two weeks after injecting their inner ears with the VGLUT3 gene. Two mice maintained their hearing for one and a half years.
Yehoash Raphael, PhD, of the University of Michigan's Kresge Hearing Research Institute in Ann Arbor, and Donna M. Martin, PhD, of Michigan's department of human genetics, said in an accompanying editorial that the study supported the promise of gene therapy. “Results presented in their paper are a true breakthrough because they show that gene therapy can lead to functional recovery from sensorineural deafness. Even more exciting is the direct relevance of this work to a large population of humans who have mutations in the VGLUT3 gene,” they wrote.
Scientists are exploring a variety of ways to protect, repair, and regrow hair cells. Drug therapy is one option. The May issue of Nature Medicine describes a number of experimental drugs in clinical trials for treating hearing loss. (Nature Medicine 2012;18:642.) One is AM-111, a compound of amino acids that blocks apoptosis, or programmed cell death, of hair cells and cochlear neurons. Auris Medical, Inc., the Chicago-based unit of Swiss drugmaker Auris Medical AG, is conducting a phase IIb trial of the injectable drug at two different dosing levels. A total of 210 people with acute SNHL will receive either AM-111 or a placebo. Trial results are due out this fall. (See FastLinks.)
Separately, a Seattle-based research team is involved in the Blueprint Neurotherapeutics Network, a unique partnership between academia and the National Institutes of Health to develop new drugs for nervous system disorders. Lead investigator Edwin Rubel, PhD, a professor of otolaryngology/head and neck surgery at the University of Washington, along with David Raible, PhD, a UW professor of biological structure, and Julian Simon, PhD, a principal investigator at Fred Hutchinson Cancer Research Center, said they hope to identify drugs that protect against hair cell death and hearing loss in people taking antibiotics for bacterial infections. Unpublished data show that the team's lead compound, PROTO-1, protects hair cells in rats after antibiotic-induced hearing loss.
Figure. Edwin Rubel...Image Tools
Members of the Hearing Restoration Project, which is funded by the Hearing Health Foundation in New York, is a consortium of US scientists focused on hair cell regeneration that is working toward a biologic cure for severe SNHL in the next decade. (See FastLinks.) “The future is incredibly bright. We are really on the cusp in the next two decades of being able to prevent hearing loss,” Dr. Rubel said of the scientific community's progress, adding that delaying age-related hearing loss and regenerating most of the cells responsible for hearing loss is also in the future.
* Check out questionnaires about tinnitus at http://bit.ly/TinnitusHandInv and http://bit.ly/TinnitusReaction.
* Learn more about acupuncture at http://bit.ly/NCCAMacupuncture.
* Read more about the grant to study D-meth at http://bit.ly/SIUpressrelease.
* See the details about D-meth's clinical trial at http://bit.ly/D-methClinTrials.
* Learn more about the grant to study N-acetylcysteine at http://bit.ly/Nacetylcysteine.
* Read more about recent gene therapy study at http://bit.ly/GeneTherapyStudy.
* Visit the Hearing Restoration Project at http://bit.ly/HearRestFound.
* Check out the clinical trials for AM-111 at http://bit.ly/AM111-trials.
* Visit HJ ’s Student Blog at http://bit.ly/HJStudentBlog.
* Check out HJ ’s R&D Blog at http://bit.ly/RDBlog.
* Click and Connect! Access the links in The Hearing Journal by reading this issue on our website or in our new iPad app, both available at thehearingjournal.com.
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© 2012 Lippincott Williams & Wilkins, Inc.