New Data-Driven Analysis Procedure for Diagnostic Hearing Test

By Carol Stoll

Credit: Susan Prater, Flickr

Stimulus frequency otoacoustic emissions (SFOAEs) are sounds generated by the inner ear in response to a pure-tone stimulus. Hearing tests that measure SFOAEs are noninvasive and effective for those who are unable to participate, such as infants and young children. They also give valuable insight into cochlear function and can be used to diagnose specific types and causes of hearing loss. Though interpreting SFOAEs is simpler than other types of emissions, it is difficult to extract the SFOAEs from the same-frequency stimulus and from background noise caused by patient movement and microphone slippage in the ear canal.

2014 Emerging Research Grants (ERG) recipient Srikanta Mishra, Ph.D., and colleagues have addressed SFOAE analysis issues by developing an efficient data-driven analysis procedure. Their new method considers and rejects irrelevant background noise such as breathing, yawning, and subtle movements of the subject and/or microphone cable. The researchers used their new analysis procedure to characterize the standard features of SFOAEs in typical-hearing young adults and published their results in Hearing Research.

Mishra and team chose 50 typical-hearing young adults to participate in their study. Instead of using a discrete-tone procedure that measures SFOAEs one frequency at a time, they used a more efficient method: a single sweep-tone stimulus that seamlessly changes frequencies from 500 to 4,000 Hz, and vice versa, over 16 and 24 seconds. The sweep tones were interspersed with suppressor tones that reduce the response to the previous tone. The tester manually paused and restarted the sweep recording when they detected background noises from the subject’s movements.

The SFOAEs generated were analyzed using a mathematical model called a least square fit (LSF) and a series of algorithms based on statistical analysis of the data. This model objectively minimized the potential error from extraneous noises. Conventional SFOAE features such as level, noise floor, and signal-to-noise ratio (SNR) were described for the typical-hearing subjects.

Overall, the results of this study demonstrate the effectiveness of the automated noise rejection procedure of sweep-tone–evoked SFOAEs in adults. The features of SFOAEs characterized in this study from a large group of typical-hearing young adults should be useful for developing tests for cochlear function that can be useful in the clinic and laboratory.

Srikanta Mishra, Ph.D, was a 2014 Emerging Research Grants scientist and a General Grand Chapter Royal Arch Masons International award recipient. For more, see “Sweep-tone evoked stimulus frequency otoacoustic emissions in humans: Development of a noise-rejection algorithm and normative features” in Hearing Research.

We need your help supporting innovative hearing and balance science through our Emerging Research Grants program. Please make a contribution today.

Moving Toward a Future Free of Drug-Induced Hearing Loss

By Erik Robinson

A new special publication orchestrated by five of the nation’s leading hearing experts compiles the latest research into hearing loss caused by drugs and solvents—how it occurs, how to treat it, and how to prevent it.

HHF Council of Scientific Trustees member Peter Steyger, Ph.D., and colleagues produced a special Frontiers in Cellular Neuroscience publication on the topic of ototoxicity.

The compilation was published online as a special research topic by the journal Frontiers in Cellular Neuroscience on March 5, 2018. It includes both original research and focused reviews. The Pharmaceutical Interventions for Hearing Loss Working Group organized the effort at the behest of the Department of Defense (DoD) Hearing Center of Excellence.

“We’re trying to elevate ways for the human population to avoid losing this important sensation for experiencing and communicating with the world around us,” says coauthor Peter Steyger, Ph.D., a professor of otolaryngology/head and neck surgery in the Oregon Health & Science University (OHSU) School of Medicine, and a member of Hearing Health Foundation’s Council of Scientific Trustees.

“Ototoxicity is a threat to hearing at any age and hearing loss remains a significant side effect of chemotherapy. This review highlights how far we’ve come in understanding that threat and provides us with a roadmap for developing more effective ways to recognize and address the problem,” adds coauthor Jian Zuo, Ph.D., of the department of developmental neurobiology at St. Jude Children’s Research Hospital in Memphis, Tennessee.

In people, hearing cells don’t regenerate so the loss is irreversible. That’s why it is crucial to understand the mechanisms that affect hearing and how to prevent loss of hearing, Steyger says. The introductory editorial, “Moving Toward a Future Free of Ototoxicity,” highlights the latest scientific research exploring how certain pharmaceuticals damage the inner ear while others can protect it. It also highlights the need for better monitoring and detection of hearing loss over time, especially among patients being treated with antibiotics.

Steyger, who lost hearing as a child after being treated with antibiotics for meningitis when 14 months old, noted that hearing loss affects a surprisingly large proportion of the population—rising from an estimated 1 in 500 newborns to as many as half of all people age 75 or older. The research encapsulated in the new e-book includes 23 scientific articles from 93 authors and represents the state of the science in both prevention and treatment of ototoxicity hearing loss. (The e-book is available to all, free of charge.)

“This compilation will help to propel our knowledge forward and underscore the need to better understand the dangers of ototoxicity. The DoD Hearing Center of Excellence is honored to host and mobilize this important effort,” says coauthor Carlos Esquivel, M.D., a neurotologist and chief medical officer in the Clinical Care, Rehabilitation, and Restoration Branch of the DoD Hearing Center of Excellence at Joint Base San Antonio in Texas.

In addition to Steyger, Zuo, and Esquivel, the publication’s editors include Lisa Cunningham, Ph.D., of the National Institute on Deafness and Other Communication Disorders, and Kelly Watts, Au.D., of the DoD Hearing Center of Excellence.

This originally appeared in OHSU News and was republished with permission. 

Ménière's Disease Grantee Featured in Reader's Digest

Credit: Agnieszka Marcinska, Shutterstock

Ian Swinburne, Ph.D., a 2018 Ménière's Disease Grant (MDG) recipient, shared his expertise regarding vertigo with Reader's Digest in an article called "What Causes Vertigo? 15 Things Neurologists Wish You Knew" published in March 2018. 

"The spinning, dizzying loss of balance which earmarks vertigo can come without warning," the article opens. Various professionals provide information about its duration, how it feels, and different types.

HHF-funded Dr. Swinburne notes specifically that the inner ear and balance disorder Ménière's disease can cause vertigo. He explains that "[b]outs of vertigo likely arise in patients with Ménière's disease, because the inner ear's tissue tears from too much fluid pressure—causing the ear's internal environment to become abnormal.'" He is currently pursuing a research project to understand the inner ear stabilizes fluid composition, which he believes will help to identify ways to restore or elevate this function to mitigate or cure Ménière's disease.

View the full article from Reader's Digest, here.

Improving Diagnostic Test for Ménière’s Disease

By Wafaa Kaf, Ph.D., and Carol Stoll

Electrocochleography (ECochG) is a commonly used assessment of the auditory system, specifically the inner ear and the hearing nerve. ECochG is most often elicited by a brief acoustic stimulus, known as a “click,” at a relatively low repetition rate. It measures two key responses: summating potential (SP) and action potential (AP), which assist in the diagnosis of Ménière’s disease, an inner ear and balance disorder. Previous research has established that individuals with Ménière’s disease are likely to have abnormally large SPs and a large SP/AP ratio. Though click ECochG has great potential to detect Ménière’s disease, it lacks sensitivity, or the ability to correctly identify those with the disease. Only 69% of those with Ménière’s disease are correctly diagnosed, while 31% of those with the disease have normal ECochG results. This lack of accuracy prevents its use as a definitive diagnostic tool. Hearing Health Foundation 2015 Emerging Research Grants recipient, Wafaa Kaf, Ph.D., is researching the use of a novel analysis technique called Continuous Loop Averaging Deconvolution (CLAD) to best improve the sensitivity of ECochG to high click rate for diagnosing Ménière’s disease. Findings were recently published in Ear and Hearing 2017.

In a recently published paper in Frontiers in Neuroscience, Kaf’s research team shares its findings on the effects of altering the parameters of the acoustic stimulus on ECochG responses to quantify the effect of stimulus rate and duration of the elicited stimuli. Kaf and her research team obtained SP measurements to 500Hz and 2000Hz tone bursts that varied in duration and repetition rate from 20 adult females with normal hearing. CCLAD was used to interpret the tracings elicited by the differing stimuli of tone bursts.

They found that SP amplitude was significantly larger when using the highest stimulus repetition rate. It is believed that the high stimulus repetition rates minimize the neural contributions and mostly reflect hair cell responses, the target of ECochG. In addition, longer duration stimuli is believed to better reflect hair cell involvement while shorter stimuli may be useful in eliciting responses reflective of neural contributions. Lastly, 2000Hz tone bursts produced larger SP amplitude as compared to 500Hz tone bursts. Therefore, 2000Hz tone bursts with a high repetition rate and long duration can be used as parameters to minimize neural contributions to SP measures whereas short duration stimuli can be used if one wishes to asses neural activity.  

The data that Kaf’s team published is a critical initial advancement towards ultimately understanding the SP measurement in diseased ears. Their findings not only provide normative data for tone burst ECochG across stimulus frequencies, stimulus rates, and stimulus durations, but also help others better understand how to improve sensitivity of ECochG for early diagnosis of Ménière’s disease.  

Wafaa Kaf, Ph.D., is a 2015 Emerging Research Grants recipient. Her grant was generously funded by The Estate of Howard F. Schum.

WE NEED YOUR HELP IN FUNDING THE EXCITING WORK OF HEARING AND BALANCE SCIENTISTS. DONATE TODAY TO HEARING HEALTH FOUNDATION AND SUPPORT GROUNDBREAKING RESEARCH: HHF.ORG/DONATE.

Mapping Better Hearing

By Vicky Chan

Hearing Health Foundation (HHF) is grateful to the many individuals and organizations who have empowered groundbreaking hearing loss research in the last 60 years. A new interactive map displays every institution in the U.S. where HHF has been fortunate to fund groundbreaking research, yielding outstanding advancements in hearing and balance science. The map also indicates the rates of hearing loss in each state, signaling that additional work is urgently needed.

The colors—light yellow, yellow, green, teal, blue, and purple—represent the rates of hearing loss in each state. The calculations are based off 2015 U.S. Census Data, using estimates from the well-known prevalence of hearing loss among specific demographics. At the lowest end of the range in light yellow, hearing loss affects 13.71% of Colorado’s population. The highest rate was found in Missouri, purple, where the prevalence measured 20.15%. The mean for all states was 18.16%. The numbers signal the significance of hearing loss research.

Nearly all of the institutions on the map represent recipients of the Emerging Research Grants (ERG) who have carried out investigations related to tinnitus, hyperacusis, Ménière's disease, Usher syndrome, hearing loss in children, Central Auditory Processing Disorder, and strial atrophy.

A few institutions are home to the work of the Hearing Restoration Project’s (HRP) domestic consortium members, who focus on investigating hair cell regeneration as a cure for hearing loss and tinnitus. They conduct research at Baylor College of Medicine, Harvard Medical School, Oregon Health & Science University, Stanford University, Stowers Institute, University of Maryland, University of Michigan, University of Southern California, University of Washington, and Washington University.

By mid-year, the institutions corresponding to HHF’s newly formed Ménière's Disease Grants (MDG) program will be added to the map.

HHF envisions a world in which no one lives with hearing loss and tinnitus—until this is realized, we’ll do everything we can to put more innovative hearing loss research on the map.

Research Aims to Improve Fit and Increase Use of Hearing Aids in U.S.

By University of Maryland Department of Hearing and Speech Sciences

Photo Credit: Shutterstock

Although about 28.8 million Americans could benefit from wearing hearing aids, less than a third of that population actually uses them, according to the National Institutes of Health. While cost is a contributing factor, experts say many people with hearing loss choose not to wear hearing aids simply because they have difficulty adjusting to them. Researchers with the University of Maryland Department of Hearing and Speech Sciences (HESP) are hoping to improve those figures by developing better procedures for fitting people with hearing aids for the first time.

“Right now when someone is fitted with hearing aids, the focus is on increasing audibility of sounds reaching the ear,” says HESP Assistant Professor Samira Anderson, Au.D., Ph.D. “However, in order to actually understand what someone is saying, sound has to travel from the ear up to the brain. We’re interested in understanding how wearing a hearing aid affects that process.”

Dr. Anderson, University of Maryland Department of Hearing and Speech Sciences

In a study published recently in Ear & Hearing, Anderson and colleagues outfitted 37 older adults with mild to severe hearing loss with new, in-the-ear hearing aids donated by Widex USA. The researchers placed electrodes on the surface of the patients’ skin to measure electrical activity produced in response to sound in the auditory cortex and midbrain. They found that the brain’s processing of sounds improved while wearing hearing aids.

“There’s a growing body of research showing that hearing loss can lead to accelerated cognitive decline and isolation as people age,” Anderson says. “My hope is that we can develop enhanced testing procedures that will allow more people to benefit from hearing aids and enjoy a better quality of life.”

The UMD research team plans to continue evaluating the patients in their study during the first six months of hearing aid use. In future studies, researchers hope to investigate the effects of manipulating hearing aid parameters on neural processing. The study was funded by the UMD Department of Hearing and Speech Sciences, Hearing Health Foundation, and the National Institutes of Health (NIDCD Grant T32DC000046).

Samira Anderson, Au.D., Ph.D., is a 2014 Emerging Research Grants researcher generously funded by the General Grand Chapter Royal Arch Masons International. We thank the Royal Arch Masons for their ongoing support of research in the area of central auditory processing disorder. Read more about Anderson and her research in “A Closer Look,” in the Winter 2014 issue of Hearing Health.

We need your help supporting innovative hearing and balance science through our Emerging Research Grants program. Please make a contribution today.

New Method Enables Systematic Study of Hair Cell Loss and Regeneration in Chickens

By Carol Stoll

Most forms of hearing loss are permanent because damage to inner ear sensory hair cells is irreversible in mammals, including humans. Mammalian vestibular hair cells have the potential to regenerate albeit at a low rate, but the hair cells of the adult mammalian cochlea are not regenerated. Birds, however, have a robust regenerative response to hair cell damage and are able to restore structure and function in inner ear organs. Consequently, the study of the molecular mechanisms that trigger the onset of avian hair cell regeneration in the balance organs as well as in the cochlea is important and may lead to therapies for hearing loss in humans.

This image shows the undamaged and damaged utricle, an inner ear balance organ, in a chicken. HRP researchers have devised a new method to study the precise timing of hair cell regeneration in chickens using a single surgical application of an ototoxic drug. Photo by Amanda Janesick, Ph.D.

Past experiments that investigate these regeneration mechanisms in living chickens required multiple injections of a drug to induce hair cell loss, making it difficult to determine the exact timing of the regeneration response. A collaboration of two Hearing Restoration Project researchers, Stefan Heller, Ph.D. and Jennifer Stone, Ph.D., and two talented postdoctoral fellows from their laboratories was recently published in Journal of the Association for Research in Otolaryngology identifying a potential solution to this problem. They developed an experimental framework that uses a single ototoxic drug application, enabling them to study the precise onset and timing of hair cell regeneration in vivo.

Heller, Stone, and colleagues performed their experiments on a total of 75 chickens. At seven days of age, the chickens were anesthetized and underwent surgery to eliminate hair cells in the inner ear organs. During the surgery, streptomycin (an ototoxic antibiotic) was delivered to the chicken’s inner ear. At various time points after the surgery, two sensory organs—the utricle, a vestibular organ; and the basilar papilla, the hearing organ—were dissected, labeled for various cellular markers, and analyzed under a microscope. Hair cells and their surrounding supporting cells were counted and observed for damage. EdU, a marker of cell division, was administered to the chickens to determine whether or not new hair cells were generated by cell division. These techniques enabled the researchers to quantitatively characterize the regenerative response of the utricle after damage.

The results of the study demonstrate that surgical application of a single streptomycin dose is a feasible approach to elicit hair cell loss and regeneration in the chicken utricle and basilar papilla. Just hours after streptomycin delivery, hair cell numbers significantly declined and DNA replication was activated. The team was then able to record specific events of the regeneration process, which get initiated around 12 hours after streptomycin-induced hair cell loss, and continue over the course of several days.

Supporting cells produce new hair cells either by converting into a hair cell (direct transdifferentiation), or by dividing, usually asymmetrically, into a supporting cell and a hair cell.  Throughout this regenerative response, supporting cell numbers and density in the utricle remain relatively constant, suggesting that there is a mechanism that responds to specific levels of damage and coordinates the individual events of the regeneration process.

The study establishes a framework for the refined study of the two modes of hair cell regeneration in the chicken utricle. The next steps of the work will focus on understanding the exact timing and mechanism of coordination of the regeneration response. With only a single application of streptomycin necessary to induce near-complete hair cell loss in hearing and balance organs, the new animal model allows for study of the entire process including initiation, realization, and termination. The fundamental understanding of the avian regenerative mechanisms may lead to future development of therapies for loss of hearing and balance in humans.

Empower the Hearing Restoration Project's life-changing research. If you are able, please make a contribution today.

2018: Hear's to You

By Nadine Dehgan

From every one of us at Hearing Health Foundation (HHF)—scientists, staff, and volunteers—thank you for your support in 2017 and best wishes for 2018.

Because of folks like you, 2017 was an incredible year in which HHF:

• Increased funding for Hearing Restoration Project & Emerging Research Grants by 35%

• Launched Ménière's Disease Grants program to better understand & treat this condition

• Began to fund critical Ototoxic Drug Research so cancer survivors won't have to live with hearing loss as a result of their life-saving treatments

• Advocated for universal newborn hearing screenings, resulting in the passage of the Early Hearing Detection and Intervention Act

• Endorsed the Over-the-Counter Hearing Aid Act, which will provide a more affordable and accessible treatment option for adults with mild to moderate hearing loss

• Created Faces of Hearing Loss to show that hearing and balance disorders affect all of us

• Received Top Ratings from all Charity Watchdogs including Consumer Reports and BBB

With hearts full of gratitude, we look forward to the work to be done in 2018—HHF’s 60th anniversary year.

With your help, HHF will continue to fund groundbreaking discoveries for the tens of millions of Americans with hearing loss and tinnitus—among whom is Ethan, 6, born with bilateral (in both ears) hearing loss and fortunate to receive early intervention.

Ethan is a first-grader who loves his sisters, soccer, reading, math, and martial arts. Until a cure for hearing loss is realized, he will be dependent on hearing aids or other treatments.

New scientific findings in 2018—empowered by you—can change the future of hearing loss for Ethan and so many others. I look forward to updating you on progress made.