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Researchers develop word-scoring model to estimate hidden hearing loss

Overview: A newly developed word scoring model is able to estimate hidden hearing loss and the effectiveness of hearing loss interventions.

Source: Mass eye and ear

Researchers at Mass Eye and Ear have developed a word-scoring model that can estimate the amount of hidden hearing loss in the human ear.

In a new study published June 23 in scientific reports, a team of researchers from Mass Eye and Ear’s Eaton-Peabody Laboratories determined mean speech scores as a function of age from data from nearly 96,000 ears examined at Mass Eye and Ear.

They then compared the data with a previous study at Mass Eye and Ear that tracked the average loss of cochlear nerve fibers as a function of age. By combining both data sets, researchers constructed an estimate of the relationship between speech scores and nerve survival in humans.

According to lead study author Stéphane F. Maison, Ph.D., CCC-A, principal investigator of the Eaton-Peabody Laboratories and associate professor of Otolaryngology-Head and Neck Surgery at Harvard Medical School, the new model leads to better evaluations of cochlear nerve damage in patients and the associated speech intelligibility deficits associated with the neural loss.

The model also provides ways to estimate the effectiveness of hearing loss interventions, including the use of personal sound reinforcement products and hearing aids.

“Prior to this study, we could either estimate neural loss in a living patient using a long battery of tests or measure damage to the cochlear nerves by removing their temporal bones when they died,” said Dr. house.

“Using common speech scores from hearing tests — the same ones collected in clinics around the world — we can now estimate the number of neural fibers missing from a person’s ear.”

Discover hidden hearing loss

Two important factors determine how well a person can hear: audibility and intelligibility. Hair cells, the sensory cells in the inner ear, contribute to the audibility of sounds — or how loud a sound has to be to be heard.

When receiving a sound, hair cells transmit electrical signals to the cochlear nerve, which then relays these signals to the brain. How well the cochlear nerve transmits these signals contributes to the clarity or intelligibility of sound processed in the central nervous system.

For years, scientists and clinicians believed that hair cell decline was the leading cause of hearing loss and that damage to the cochlear nerves was not widespread until after the hair cells were destroyed.

Audiograms, long considered the gold standard for hearing tests, provide information about hair cell health. Because nerve loss was believed to be secondary to hair cell loss or dysfunction, patients with a normal audiogram received a clean bill of health despite having trouble hearing in noisy environments.

Experts now understand why the audiogram is not informative about auditory nerve health.

“This explains why some patients who report having difficulty understanding conversation in a crowded bar or restaurant may undergo a ‘normal’ hearing test. Likewise, it explains why many hearing aid users who receive amplified sounds still have difficulty with speech intelligibility,” said Dr. house.

In 2009, M. Charles Liberman, Ph.D., and Sharon Kujawa, Ph.D., principal investigators at the Eaton-Peabody Laboratories, changed the way scientists think about hearing when they discovered hidden hearing loss.

Their findings revealed that cochlear nerve damage preceded hair cell loss due to aging or noise exposure and suggested that, by failing to provide information about the cochlear nerve, audiograms had not assessed the full extent of damage to the ear.

Building a model to predict cochlear nerve damage

In the study, Dr. Maison and his team used a speech intelligibility curve to predict what a person’s speech score should be based on their audiogram. They then measured the differences between the predicted word recognition scores and those obtained during the patient’s hearing evaluation.

Since the list of words was presented at a level well above the patient’s hearing threshold — where audibility is not an issue — any difference between the predicted and the measured score would have reflected a lack of intelligibility, explained Dr. House out.

After considering a number of factors, including the cognitive deficits that can come with aging, the researchers argued that the size of these discrepancies reflected the amount of cochlear nerve damage or hidden hearing loss a person had. They then applied measurements of neural loss from existing histopathological data from human temporal bones to devise a predictive model based on a standard hearing exam.

This shows a hearing aid\
The model also provides ways to estimate the effectiveness of hearing loss interventions, including the use of personal sound reinforcement products and hearing aids. Image is in the public domain

The findings confirmed a link between poorer speech scores and greater amounts of cochlear nerve damage. For example, the worst scores were found in patients with Ménière’s disease, consistent with studies of temporal bones showing dramatic loss of cochlear nerve fibers.

Meanwhile, patients with conductive hearing loss, drug-induced, and normal age-related hearing loss — etiologies with the least amount of cochlear nerve damage — showed only moderate to minor discrepancies.

Changing the landscape of hidden hearing loss research and beyond

According to the World Health Organization, more than 1.5 billion people live with some degree of hearing loss. Some of these individuals may not qualify as candidates for traditional hearing aids, especially if they have mild to moderate high-frequency hearing loss.

Knowing the extent of neural damage should inform clinicians about the best ways to meet a patient’s communication needs and offer appropriate interventions in addition to using effective communication strategies.

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This new research was part of a five-year $12.5 million P50 grant from the National Institutes of Health to better understand the prevalence of hidden hearing loss.

By identifying which patients are most likely to have cochlear nerve damage, Dr. Maison that this model can help clinicians assess the effectiveness of traditional and newer sound reinforcement products.

The researchers also hope to introduce new audiometric protocols to further refine their model and offer better interventions by evaluating word performance scores in noise, rather than in silence.

About this hearing loss news

Author: press office
Source: Mass eye and ear
Contact: Press Agency – Mass Eye and Ear
Image: The image is in the public domain

Original research: Open access.
Predicting neural impairment in sensorineural hearing loss from word recognition scoresby Kelsie J. Grant et al. Scientific Reports


Abstract

Predicting neural impairment in sensorineural hearing loss from word recognition scores

The current gold standard for clinical hearing assessment includes a pure-tone audiogram in combination with a word recognition task. This retrospective study tests the hypothesis that deficits in word recognition that cannot be explained by loss of audibility or cognition may reflect underlying cochlear nerve degeneration (CND).

We collected the audiological data from nearly 96,000 ears of patients with normal hearing, conductive hearing loss (CHL), and a variety of sensorineural etiologies, including (1) age-related hearing loss (ARHL); (2) neuropathy related to vestibular schwannoma or type 2 neurofibromatosis; (3) Meniere’s disease; (4) sudden sensorineural hearing loss (SSNHL), (5) exposure to ototoxic drugs (carboplatin and/or cisplatin, vancomycin, or gentamicin), or (6) noise impairment, including those with a 4-kHz “noise notch” or occupational or exposure to recreational noise.

Word recognition was scored using CID W-22 monosyllabic word lists. The articulation index was used to predict the speech intelligibility curve using a transfer function for CID W-22. The level at which maximum intelligibility was predicted was used as the presentation level (minimum 70 dB HL). Word scores decreased dramatically with age and thresholds in all groups with SNHL etiologies, but relatively little in the group with conductive hearing loss.

The discrepancies between measured and predicted word scores were greatest in patients with neuropathy, Ménière’s disease and SSNHL, intermediate in the noise-damaged and ototoxic drug groups, and smallest in the ARHL group. In the CHL group, the measured and predicted word scores were very similar. Since word score predictions assume that audiometric losses can be compensated by increasing the stimulus level, their accuracy in predicting word score for CHL patients is not surprising.

The lack of a strong age effect on word scores in CHL shows that cognitive decline is not an important factor in this test. Of the possible contributors to discrepancies in word scores, CND is a prime candidate: it should impair intelligibility without affecting thresholds and has been documented in human temporal bones with SNHL.

Comparing the audiological trends observed here with the existing histopathological literature supports the idea that discrepancies in word scores may be a useful CND metric.

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