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Protecting Preemies: Audiology's Role in Early Intervention

Glantz, Gordon

doi: 10.1097/01.HJ.0000549520.86754.4e
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*Gordon Glantz is a freelance medical writer.

Thunderstorms in the summer. Blizzards in the winter. Leaves to rake come autumn.

All are examples of natural facts that no mortal need alters with science, other than to maybe assure the ecosystem remain in balance. When it comes to health and healing, though, there remains a need for raising the bar on accepted facts.

To this end, the medical community has made strides once seemed unimaginable generations ago in the success rate of positive outcomes for premature babies (born before 37 weeks). According to the World Health Organization, the survival rate now sits at an all-time best 90 percent (10 percent in developing nations, though). A study attributed this improvement in the “last generation” to enhanced neonatal units and specific advancements in anesthesiology (Anesth Analg. 2015 Jun; 120(6): 1337).

But with that comes a second layer of issues, up to and including the hard fact that hearing loss is among the many common net results that premature babies and their families face after the initial gargantuan sigh of relief of survival.

As recently as last year, the American Academy of Audiology reported that 15 out of every 100 premature babies are at risk for hearing loss, including loss that could be deemed “significant” (as opposed to one to three in every 1,000 full-term newborns).

“This is a challenging situation for parents, so they need to be given accurate, appropriate information and support regarding the risks and how these can be addressed and minimized,” said William Newman, PhD, a professor of translational genomic medicine in the Manchester Centre for Genomic Medicine at the University of Manchester, an honorary consultant at the Manchester University NHS Foundation Trust, and the chair of the British Society of Genetic Medicine from 2015 to 2017.

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ANTIBIOTIC-INDUCED HEARING LOSS

The consensus among experts in the field is that antibiotics used to help premature infants battle all the infections for which they are at risk have left them more prone to side effects such as hearing and vision loss.

“Our work is particularly focused on antibiotic-induced hearing loss and the use of point-of-care genetic tests in the neonatal unit to avoid these,” said Newman. “We have known for 25 years that a variant in a gene inherited from mothers that is present in one in 500 people worldwide increases the risk of severe irreversible hearing loss in babies exposed to the antibiotic gentamicin. Many strategies have been considered as to how to inform health professionals and parents in a timely way so that this risk can be avoided and an alternative antibiotic prescribed.”

Newman said his team is conducting “a proof of principle study to show that we can undertake genetic testing in the acute neonatal setting without any adverse effects on normal clinical processes.”

This effort has produced results that Newman is anxious to put into circulation, saying: “We have developed a point-of-care test that can be undertaken on a cheek swab generating a result in less than 30 minutes so that antibiotics can be administered within the recommended first hour after admission.”

Meanwhile, an article in Stanford Medicine shed light on encouraging research at Stanford by Tony Ricci, PhD, and Alan Cheng, MD, whose primary focus is children with hearing loss (Stanford Med, Spring 2018 https://stan.md/2nEALFO).

According to the article, Ricci's research made a believer out of a once-skeptical Cheng. Working together over a span of years, they have reportedly developed three versions of aminoglyocides—the antibiotic commonly used around the world to fight infections, including in low-birthweight babies, and attributable to hearing loss in 20 percent of patients—that have yielded successful results in mice.

They have done this, according to the article, by making drug molecules that are “too big” to enter into the ion channels on the inner ear, therefore making the chance of hearing loss significantly lower.

Xue Zhong Liu, MD, PhD, FACS, is a professor of otolaryngology, human genetics, biochemistry, and pediatrics at the University of Miami Miller School of Medicine Department of Otolaryngology. Tabbed to serve as the principal investigator of a $3 million grant from the National Institutes of Health (NIH) to fund research related to biological treatments and clinical diagnosis of patients with hearing loss, he weighed in on using a genetic approach to predict, prevent, or treat hearing loss in this high-risk population.

“With recent advances in precision medicine tools, such as genetic sequencing and data analysis and better elucidating the nature of a hearing disorder, it is worthwhile to use a genetic/genomic approach to diagnose and prevent hearing loss in this high-risk population,” he said. “As you know, majority of hearing loss cases with preterm infants have no known etiology. Diagnosis and intervention are typically delayed, predisposing this population to poorer outcomes. There is a growing concern that the genetic causes play an important role in this group of babies, such as mitochondrial DNA mutations and aminoglycoside-induced ototoxicity in preterm babies. Some studies have shown that family history of hearing loss and prematurity are two of the most prevalent risk factors in severe-to-profound childhood hearing loss in addition to admittance to the neonatal intensive care unit.”

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CHALLENGES IN HEARING CARE

While the vital work continues in the area of long-range prevention, there is the reality of helping families charter the uncertain waters of the immediate future. Enter the likes of Oklahoma City-based Hearts for Hearing, where Tamara Elder, MS, has been fighting the good fight since 2001.

“Hearts for Hearing has established working relationships with hospitals and screeners contracted by hospitals who perform newborn hearing screenings,” said Elder, now the director of clinical care.

“Hospital screeners can contact Hearts for Hearing at the caregiver's bedside and an appointment is scheduled as soon as it is convenient for the family. This takes a huge burden off the families who may have to wait weeks or even months to have their baby's hearing checked,” she added.

Elder explained that Hearts for Hearing enters the picture when screening is referred for diagnostic audiological testing. A premature baby is seen by an audiologist and a speech-language pathologist (SLP).

“The initial appointment is, at times, one of a number of follow-up medical appointments for our families who have premature babies,” she said, adding that additional specialists include—but are not limited to—vision, pulmonology, heart, gastrointestinal, renal, or feeding specialists.

She continued: “This initial appointment is scheduled for three hours to give the family time to take care of baby's needs so their baby will sleep as deeply as possible. If there is a hearing loss, we have time during this appointment to provide counseling, answer questions, and—if the family is ready—move forward with hearing technology.”

An SLP for over 20 years, Elder was a medical technologist specializing in microbiology for around 17 years at a local hospital, but she longed for more interactions with people.

She observed the SLP department in a local hospital, realized what her calling was, and went for it. She earned her master's degree and explored job opportunities when the health industry was undergoing unique changes in the mid-1990s, ultimately landing a position in early intervention working with parents and young children, an experience that “greatly impacted my philosophy of parent coaching and the value of partnering with parents to achieve incredible outcomes for their child.”

She recalled: “I had a kiddo on my caseload who had acquired profound hearing loss after a bout of meningitis. He had a cochlear implant by age 2 and was receiving additional auditory-verbal therapy (AVT) to promote his listening and talking. He was making incredible progress, so I began to attend his AVT sessions with Teresa Caraway at the Hearing Enrichment Language Program now known as Hearts for Hearing.”

She's also a devotee of renowned Canadian author Warren Estabrooks, MEd, whom she met in Toronto in 2003 when Estabrooks served as the director of the Auditory Learning Center of the Learning to Listen Foundation at North York General Hospital.

“His relationships with families was evident the week I observed him working with families,” said Elder, who was compelled by the eclectic mixture of families under Estabrooks’ supervision. “This brought home to me the importance of forming a bond that is mutually trusting and respectful of the expertise the family brings to this dance we do together. Warren has supported me from afar, and I have always felt a shared sense of love we have for our careers in teaching children with hearing loss to listen and talk.”

Under the tutelage of Estabrooks and many others, Elder finds herself a compassionate translator for families facing a long road ahead. Though often heartbreaking and difficult, there is nowhere else she would rather be.

“Our goal is to provide information in a manner that is understandable for the family and answer any burning questions as they come up during the initial appointment,” she said. “During the follow-up diagnostic testing, the providers who will be attending to the baby's audiological care and auditory-verbal therapy are available to meet the family and answer any further questions regarding their baby's hearing loss.

“We pay careful attention to the family's needs, including continued follow-up for appointments with other specialists. A premature baby's needs in the future are not always unveiled right from the start.”

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VIGILANCE IN SCREENING

When it comes to best practices in audiology screening, diagnostics, and risk monitoring, Newman deferred to colleagues Rachel Booth, PhD, the head of pediatric audiology at Manchester University, and Iain Bruce, MD, a professor of pediatric otolaryngology at the Manchester Academic Health Science Centre (MAHSC).

In a joint statement, they affirmed that the usual role of audiological services is to diagnose the presence and severity of established hearing loss and, when necessary, to arrange early intervention with amplification in the first few months of life.

When it comes to at-risk newborns, such as those born prematurely, the ante is upped considerably.

“Failure to identify hearing loss in neonates and infants with other co-morbid factors can compound the negative impact of the hearing loss upon the development of speech, language, and communication,” the statement continued, adding that “understanding exists that several risk factors for sensorineural hearing loss (SNHL) are commonly found in neonates requiring neonatal intensive care unit (NICU) admission, such as low birth weight, jaundice, birth hypoxia, and a syndromic diagnosis.”

While noting that screening programs differ in their protocols across the world, they stressed that “all programs recognize the increased risk of hearing loss in this population.”

This recognition has led to this population being targeted for what they termed as “enhanced” testing in newborn hearing screening programs, the primary aim of which is to avoid late diagnosis of hearing loss in infants and children with multiple health and development needs and to identify milder hearing loss.

They stressed that the timing of screening can be “challenging” in this population because “protocols typically suggest the screen is performed when the baby is well enough and close to discharge.”

Meanwhile, some screening protocols do not allow screening beyond a certain age, and therefore close collaboration among screeners, neonatologists, pediatricians, and pediatric audiology teams is important so those children most at risk receive some hearing assessment. The danger is that those babies with complex health problems can be missed from the screen, particularly when moving between hospitals or when in hospitals for long periods of time—yet these are the ones most at risk.

Booth and Bruce noted the benefit of conducting diagnostic audiological assessments of babies using evoked potentials, which are objective measures of hearing that do not require any response from the baby.

“These can be carried out relatively easily under natural sleep but sometimes with the additional use of sedation or general anaesthetic alongside other procedures as the baby gets older and above 3 months of age,” they concurred, while warning that the health problems and medical support required can still make this testing difficult to carry out or limit the chances of conducting the test.

They added: “Having experienced pediatric audiologists who can perform diagnostic evoked potentials testing on the same site as neonatal and pediatric hospital wards is an advantage for [infants from lower-income situations], as the testing can be done as inpatients in conjunction with the medical professionals.”

Booth and Bruce stressed that once this early opportunity has passed—where objective hearing assessments can easily be used—it can be difficult for many local pediatric audiology departments to have the skills and ability to carry out the required assessments in this population.

Later tests, they explained, are typically behavioral tests of hearing for infants aged 8 to 10 months upwards. Often this at-risk population may have delayed developments alongside multiple health problems, “meaning that pediatric audiology teams need to have the systems, techniques, and experience to provide reliable assessments of the hearing.”

As a consequence, they warned, older infants are not able to get the age-appropriate behavioral hearing assessments, and special arrangements, often requiring the use of sedation or a general anaesthetic alongside support from medical professionals to carry out evoked potentials testing.

Infants in this at-risk population who meet certain criteria but have passed the newborn hearing screen will continue to be monitored beyond the initial screen for late onset or progressive hearing loss linked to the earlier risks in the peri- and neonatal periods.

However, as they explained, this monitoring of hearing can be affected by delays in development in this population, as later testing will typically involve assessments of hearing where the tests are designed to elicit conditioned behavioral responses to sound. Techniques may have to be modified on a child-by-child basis depending on each child's abilities. Sometimes, where there are concerns about repeat testing, evoked potentials typically with some form of sedation will be needed.

Booth and Bruce also spoke of ototoxicity and how it represents a different scenario in that the hearing loss is “acquired” following admission to the NICU and “potentially preventable.” Currently, gentamicin ototoxicity is diagnosed after the event, they warned, with prevention reliant upon the family's awareness of a predisposition to the problem.

They added: “Awareness of this complication of a routinely-used antibiotic by parents and clinicians will remain an important part of prevention strategies. Rapid point-of-care testing will enable clinicians to identify those neonates and infants at greatest risk. Ultimately, the incidence of severe-to-profound hearing loss in these infants and children will be reduced.”

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