Unilateral Hearing Loss Patients Research Articles

The Efficacy of Wireless Auditory Training in Unilateral Hearing Loss Rehabilitation.

The purpose of this study was to evaluate the efficacy of auditory training (AT) in patients with unilateral hearing loss (UHL) using hearing aids (HAs), comparing traditional methods with a new approach involving a wireless remote microphone. The study included 96 participants, divided into two groups, with ages ranging from 42 to 64 years, comprising both male and female subjects. A clinical trial including consecutive moderate UHL patients was performed at our institution. For the study group, a Roger Pen was used during AT with patients inside a sound-attenuating cabin. Controls followed conventional sessions. Professional speech and language pathologists performed the rehabilitation. Audiological outcomes were measured, including word recognition at signal-to-noise ratios (SNRs) of 0 dB, +5 dB, and +10 dB, to determine the effectiveness of the training. Measurements also included the Speech, Spatial, and Qualities of Hearing Scale to assess perceived auditory abilities. A total of 46 and 50 UHL patients were randomly included in the study and control groups, respectively. No differences were found in terms of sex, age, presence of tinnitus, duration of hearing loss, pure tone average, and speech-in-noise perception without an HA. Following HA fitting and AT, a notable enhancement in the ability to identify speech in noisy environments was observed in the study group. This improvement was significant at SNRs of +5 and +10. When comparing the ability to identify speech in noise using HAs across both groups, it was observed that hearing capabilities post-wireless AT showed a significant improvement at an SNR of +5. Only the study group had a significant improvement in the total Speech, Spatial, and Qualities of Hearing Scale score after the training. In our group of UHL patients, we found significantly better speech-in-noise perception when HA fitting was followed by wireless AT. Wireless AT may facilitate usage of HAs, leading to binaural hearing in UHL patients. Our findings suggest that future interventions might benefit from incorporating wireless technology in AT programs.

Changes in Structure and Connectivity of Auditory Cortex in Patients with Unilateral Hearing Loss

The purpose of this study was to investigate cortical structural and connectivity changes in the auditory system due to the absence of unilateral input signals from the hearing-impaired ear in patients with unilateral hearing loss. Twenty-seven patients who have severe to profound unilateral hearing loss participated. T-1 images were acquired to calculate the normalized cortcial volume (nCV), and seed-based connectivity analysis was performed. It was shown that the nCV of Te 3.0 was decreased in the left unilateral hearing loss (LUHL). In LUHL group, a significant structural correlation was observed between region of interests (ROIs) within the auditory cortices of bilateral hemispheres, while right unilateral hearing loss (RUHL) group showed significant correlation between thalamus and auditory cortical regions. We proposed that cortical structural reorganization in unilateral hearing loss patients, that is different by deafness side. These results are expected to be related to individual binaural hearing performance in unilateral hearing loss.

Cochlear Implantation Outcomes in Pediatric Unilateral Hearing Loss: Impact of Device Use and Direct Input.

To investigate the impact of daily cochlear implant (CI) use on speech perception outcomes among children with unilateral hearing loss (UHL). Multi-institutional retrospective case series of pediatric patients with UHL who underwent CI between 2018 to 2022. Three tertiary children's hospitals. Demographics were obtained including duration of deafness and age at CI. Best consonant-nucleus-consonant (CNC) word scores and data logs describing hours of CI usage were assessed postimplantation. Use of direct audio input (DAI) during rehabilitation was recorded. Twenty-seven children were included, with a mean age at CI of 7.8 years. Mean datalogging time was 7.8 ± 3.0 hours/day. 40.7% of children utilized daily DAI. The mean CNC score using the best score during the study period was 34.9%. There was no significant correlation between hours of CI usage and CNC score. There was a significant improvement in CNC score associated with whether the child used DAI during rehabilitation (CNC 50.91% [yes] vs 23.81% [no]), which remained significant when adjusting for age at CI, duration of deafness, and data log hours. Unlike children with bilateral hearing loss and CI, children with UHL and CI demonstrate no significant correlation between hours of daily CI usage and CNC scores. However, children who used DAI during postoperative rehabilitation achieved significantly higher CNC scores than those who did not. This suggests that rehabilitation focused on isolated listening with the implanted ear maybe critical in optimizing outcomes with CI in UHL patients.

Audiovisual Training in Virtual Reality Improves Auditory Spatial Adaptation in Unilateral Hearing Loss Patients.

Unilateral hearing loss (UHL) leads to an alteration of binaural cues resulting in a significant increment of spatial errors in the horizontal plane. In this study, nineteen patients with UHL were recruited and randomized in a cross-over design into two groups; a first group (n = 9) that received spatial audiovisual training in the first session and a non-spatial audiovisual training in the second session (2 to 4 weeks after the first session). A second group (n = 10) received the same training in the opposite order (non-spatial and then spatial). A sound localization test using head-pointing (LOCATEST) was completed prior to and following each training session. The results showed a significant decrease in head-pointing localization errors after spatial training for group 1 (24.85° ± 15.8° vs. 16.17° ± 11.28°; p < 0.001). The number of head movements during the spatial training for the 19 participants did not change (p = 0.79); nonetheless, the hand-pointing errors and reaction times significantly decreased at the end of the spatial training (p < 0.001). This study suggests that audiovisual spatial training can improve and induce spatial adaptation to a monaural deficit through the optimization of effective head movements. Virtual reality systems are relevant tools that can be used in clinics to develop training programs for patients with hearing impairments.

Predictable Factors of People with Asymmetrical Hearing Loss Wearing a Hearing Aid in the Worse Ear Only.

In patients with bilateral asymmetrical hearing loss (AHL), where only one hearing aid is available, it is difficult to decide which ear to amplify. The aim of this study was to evaluate the outcomes of hearing aid use for AHL patients fitted with a hearing aid in their worse ear only. One-hundred-two adults with asymmetrical-mixed or sensorineural hearing loss were retrospectively included. AHL was classified into three subgroups: unilateral hearing loss (UHL) and AHL type 1 (AHL1) and type 2 (AHL2). The main outcome measures were (1) the time spent wearing a hearing aid, (2) the hearing in a noise test (HINT), (3) the sound localization test and (4) the Korean version of the International Outcome Inventory for Hearing Aids (IOI-HA). The 1 kHz-hearing threshold of the better ear was significantly better in the successful users than in the intermittent users for UHL. Younger age was associated with significantly better outcomes than older for AHL1 and AHL2. Among the etiologies of AHL, sudden hearing loss was associated with significantly better outcomes of hearing aid use for AHL, UHL and AHL1 patients. In this study, the success rate and usage rates were 43.1% and 67.6% in AHL patients wearing a hearing aid in the worse ear. This study identified the hearing threshold of 1 kHz from the better ear, age and etiology of sudden hearing loss as audiometric and non-audiometric factors that affected the outcomes of hearing aid use.

Sound localization in patients with a unilateral hearing aid: Discordance between the right and left ears.

ObjectivesPatients with unilateral hearing loss (UHL) have difficulty in recognizing the direction of a sound. Previous studies have shown that hearing aids (HAs) could improve the directional perception of sound. In this study, we analyzed the results of sound localization tests in patients using a unilateral HA.MethodsAll patients with UHL who had performed sound localization tests since 2018 were included in this study. Sound localization tests, functional gain tests, and the speech discrimination scores (SDSs) were analyzed. The tests were obtained at 1‐, 3‐, and 6‐month after fitting the HA.ResultsOf the 32 patients with UHL, 13 were right‐sided and 19 were left‐sided. After 6 months of using a HA, the results of the sound localization test were significantly better in patients with right than left UHL (percent correct [PCT], 61.9 ± 24.0% vs. 37.9 ± 24.6%, p = .011; mean absolute error (MAE), 41.4 ± 23.9° vs. 65.5 ± 28.6°, p = .018; root‐mean‐square error (RMS), 25.8 ± 17.6° vs. 48.8 ± 24.5°, p = .007]. The aided SDSs were not different between the two groups (78.7 ± 16.5% vs. 77.2 ± 18.5%, p = .825).ConclusionThe side of the hearing loss could have a substantial effect on sound localization in UHL patients using a HA. Sound localization test results should be interpreted with the consideration of this discordance.Level of Evidence4

Rehabilitation of sound localization ability in patients with unilateral hearing loss or single-sided deafness

The prevalence of unilateral hearing loss（UHL） is higher, and the clinical attention to the hearing rehabilitation of UHL is not enough, resulting in many UHL patients cannot get rehabilitation timely and effectively. Severe to profound UHL（also known as single-sided deafness） patients lack binaural hearing superiority, especially the inadequate ability of sound localization, which will seriously affect their daily life and academic performance. At present, the main rehabilitation methods of UHL include various kinds of bone conduction hearing aids, vibrant soundbridge and cochlear implantation, etc. However, the rehabilitation effect of UHL patients' ability to locate the sound source is affected by the occurrence age, the type, the degree and the duration of the hearing loss. The results of rehabilitation in different literature vary greatly. This paper reviews the effects of different rehabilitation strategies on the ability of sound location and analyzes its possible causes and mechanisms.

Audiological benefits and performance improvements of Baha® attract implantation in patients with unilateral hearing loss

Objectives To evaluate the overall functional and audiological benefits in unilateral hearing loss, as well as performance improvements with Cochlear™ Baha® Attract System with Baha® 5 sound processor. Methods We performed a prospective study. Fourteen consecutive adult patients with unilateral hearing loss who were audiologically eligible for Baha® Attract were included in this study. All patients were followed-up, and a series of tests were performed in the sound field before surgery, one, two, three, and 6 months after surgery. Results Patients were categorized based on their hearing impairment type and severity. Ten patients had conductive hearing loss (CHL), or mixed hearing loss (MHL), and four patients had sensorineural hearing loss (SNHL). The hearing threshold in the sound field aided with Baha® Attract was similar to the preoperative bone conduction hearing threshold of the better ear. The results of the speech audiometry improved post-operatively, but they did not match that of the better ear before surgery. The overall score of the hearing-in-noise test was gradually improved from one month to 6 months after surgery. The results of the sound localization test for SNHL patients were not as good as those for CHL or MHL. All the questionnaires demonstrated additional benefits that implied performance improvements. Conclusions The Baha® Attract provides enough auditory benefits and performance improvements for hearing impaired patients, though there are different benefits according to the type of hearing loss. Clinicians need to counsel the unilateral hearing loss patients for Baha® Attract System carefully, according to their type of hearing loss.

Evidence of a functional reorganization in the auditory dorsal stream following unilateral hearing loss

Unilateral hearing loss (UHL) generates a disruption of binaural hearing mechanisms, which impairs sound localization and speech understanding in noisy environments. We conducted an original study using fMRI and psychoacoustic assessments to investigate the relationships between the extent of cortical reorganization across the auditory areas for UHL patients, the severity of unilateral hearing loss, and the deficit in binaural abilities. Twenty-eight volunteers (14 UHL patients) were recruited (twenty-two females and six males). The brain imaging analysis demonstrated that UHL induces a shift in aural dominance favoring the better ear, with a cortical reorganization located in the non-primary auditory areas, ipsilateral (same side) to the better ear. This reorganization is correlated not only to the hearing loss severity but also to spatial localization abilities. A regression analysis between brain activity and patient’s performance clearly showed that the spatial hearing deficit was linked to a functional alteration of the posterior auditory areas known to process spatial hearing. Altogether, our study reveals that UHL alters the dorsal auditory stream, which is deleterious to spatial hearing.

Does maternal age at childbirth and parity have any effect on hearing loss? The 2008-2012 Korean National Health and Nutrition Examination Survey

Objective: This study aimed to assess hearing loss according to maternal age at childbirth and parity. Materials and Methods: The data used in this study were obtained from the 2008-2012 Korean National Health and Nutrition Examination Survey. This study included a total of 3,961 females that were subdivided into groups of unilateral and bilateral hearing loss. Pure tone threshold above 40 dB was defined as hearing loss. T-tests or Chi-squared tests were performed to identify differences in baseline clinical characteristics. A multivariate regression and multivariate logistic regression analysis were used to identify associations between childbearing age and hearing loss. Result: Bilateral hearing loss was significantly higher in women with younger age at first birth and older age at last birth. Bilateral hearing loss patients had higher parity than unilateral hearing loss patients, and unilateral hearing loss patients had higher parity than normal hearing group. Age at first childbirth showed a positive relationship with hearing loss after adjusting for lifestyle factors. Age at last childbirth also showed a positive relationship with hearing loss after adjusting for life style factors. Parity showed a positive relationship with hearing loss after adjusting for life style factors. Conclusion: This study suggests that hearing loss is increased in females who experienced their first childbirth at a younger age or their last childbirth at a later age. Bilateral and unilateral hearing loss also have positive correlation with higher parity. Some studies suggest that estrogen has a protective effect on hearing function. Because childbearing age and parity could be related to the women’s estrogen level, future studies will be access the relationship between childbearing age and hearing loss, or the relationship between parity and hearing loss due to an effect of estrogen.

Altered functional networks in long-term unilateral hearing loss: A connectome analysis.

IntroductionIn neuroimaging studies, long‐term unilateral hearing loss (UHL) is associated with functional changes in specific brain regions and connections; however, little is known regarding alterations in the topological organization of whole‐brain functional networks and whether these alterations are related to hearing behavior in UHL patients.MethodsWe acquired resting‐state fMRI data from 21 patients with UHL caused by acoustic neuromas and 21 matched healthy controls. Whole‐brain functional networks were constructed by measuring interregional temporal correlations of 278 brain regions. Alterations in interregional functional connectivity and topological properties (e.g., small‐world, efficiency, and nodal centrality) were identified using graph‐theory analysis. The subjects also completed a battery of hearing behavior measures.ResultsBoth UHL patients and controls exhibited efficient small‐world properties in their functional networks. Compared with controls, UHL patients showed increased and decreased nodal centrality in distributed brain regions. Furthermore, the brain regions with significantly increased and decreased functional connections associated with UHL were components of the following important networks: (1) visual network; (2) higher‐order functional networks, including the default‐mode and attention networks; and (3) subcortical network and cerebellum. Intriguingly, the changes in intranetwork connections in UHL were significantly correlated with disease duration and hearing level.ConclusionsThis study revealed connectome‐level alterations involved in multiple large‐scale networks related to sensory and higher‐level cognitive functions in long‐term UHL patients. These reorganizations of the brain in UHL patients may depend on the stage of deafness and hearing level. Together, our findings provided empirical evidence for understanding the neuroplastic mechanisms underlying hearing impairment, establishing potential biomarkers for monitoring the progression and further treatment effects for UHL patients.

Alterations in gray matter volume due to unilateral hearing loss.

Although extensive research on neural plasticity resulting from hearing deprivation has been conducted, the direct influence of compromised audition on the auditory cortex and the potential impact of long durations of incomplete sensory stimulation on the adult cortex are still not fully understood. In this study, using voxel-based morphometry, we evaluated gray matter (GM) volume changes that may be associated with reduced hearing ability and the duration of hearing impairment in 42 unilateral hearing loss (UHL) patients with acoustic neuromas compared to 24 normal controls. We found significant GM volume increases in the somatosensory and motor systems and GM volume decreases in the auditory (i.e., Heschl’s gyrus) and visual systems (i.e., the calcarine cortex) in UHL patients. The GM volume decreases in the primary auditory cortex (i.e., superior temporal gyrus and Heschl’s gyrus) correlated with reduced hearing ability. Meanwhile, the GM volume decreases in structures involving high-level cognitive control functions (i.e., dorsolateral prefrontal cortex and anterior cingulate cortex) correlated positively with hearing loss duration. Our findings demonstrated that the severity and duration of UHL may contribute to the dissociated morphology of auditory and high-level neural structures, providing insight into the brain’s plasticity related to chronic, persistent partial sensory loss.

Cochlear Implants as a Treatment Option for Unilateral Hearing Loss, Severe Tinnitus and Hyperacusis

Tinnitus is an incapacitating condition commonly affecting cochlear implant (CI) candidates. The aim of this clinical study is to assess the long-term effects of CI treatment in patients with severe-to-profound, sensorineural, unilateral hearing loss (UHL) and incapacitating tinnitus. We performed a prospective Cochlear™ company-sponsored multicentre study in five Spanish centres. Sixteen patients with UHL and incapacitating tinnitus, which was indicated by a Tinnitus Handicap Inventory (THI) score >58%, received a Nucleus® CI in their deaf ear. The study design includes repeated within-subject measures on hearing, tinnitus, hyperacusis and quality of life up to 12 months after initial CI fitting. In addition to hearing loss and tinnitus, all patients suffered from hyperacusis. Most patients had a sudden hearing loss and received a CI within 2 years after their hearing loss. Preliminary 6-month, post-CI activation data of 13 subjects showed that the majority of patients perceived a subjective benefit from CI treatment, which was assessed using the THI, a Visual Analogue Scale of tinnitus loudness/annoyance and the Speech, Spatial and Qualities of Hearing Scale. Preliminary 12-month data of 7 subjects showed that most patients also perceived a degree of relief from their hyperacusis. One patient showed no improvements in any of the applied scales, which could be explained by partial insertion of the electrode due to obstruction of the cochlea by otosclerosis. In conclusion, CI can successfully be used in the treatment of UHL patients with accompanying severe tinnitus and hyperacusis. Implantation resulted in hearing benefits and a durable relief from tinnitus and hyperacusis in the majority of patients. These findings support the hypothesis that pathophysiological mechanisms after peripheral sensorineural hearing loss are at least partly reversible when hearing is restored with a CI.

Brain structural and functional alterations in patients with unilateral hearing loss

Alterations of brain structure and functional connectivity have been described in patients with hearing impairments due to distinct pathogenesis; however, the influence of unilateral hearing loss (UHL) on brain morphology and regional brain activity is still not completely understood. In this study, we aim to investigate regional brain structural and functional alterations in patients with UHL. T1-weighted volumetric images and task-free fMRIs were acquired from 14 patients with right-sided UHL (pure tone average ≥ 40 dB HL) and 19 healthy controls. Hearing ability was assessed by pure tone audiometry. Voxel-based morphometry (VBM) was performed to detect brain regions with changed gray matter volume or white matter volume in UHL. The amplitude of low-frequency fluctuation (ALFF) was calculated to analyze brain activity at the baseline and was compared between two groups. Compared with controls, UHL patients showed decreased gray matter volume in bilateral posterior cingulate gyrus and precuneus, left superior/middle/inferior temporal gyrus, and right parahippocampal gyrus and lingual gyrus. Meanwhile, patients showed significantly decreased ALFF in bilateral precuneus, left inferior parietal lobule, and right inferior frontal gyrus and insula and increased ALFF in right inferior and middle temporal gyrus. These findings suggest that chronic UHL could induce brain morphological changes and is associated with aberrant baseline brain activity.

Central auditory plasticity indexed by mismatch negativity

Introduction Unilateral hearing loss (UHL) represents a particular model for investigating the functional auditory plasticity in humans. Normally, monaural stimulation produces a normal pattern of a contralateral dominance. With UHL, this pattern changes. Objective The aim of the study was to investigate the effects of UHL side and age at onset on auditory processing. Design Mismatch negativity (MMN) was recorded in response to speech and tone stimuli. Study sample This study included two groups: the control (50 bilateral normal hearing) and study (206 UHL patients) groups. This group was further classified according to UHL side and age at UHL onset. Results In controls, higher speech-evoked MMN amplitude was recorded in the right ear. The study group showed impaired speech-evoked MMN in either left or right UHL patients, especially in early onset UHL patients. Tone-evoked MMN was not affected in controls or UHL patients. Conclusion Cortical reorganization induced by UHL occurs mainly in patients with left-side affection. Speech processing is affected in UHL irrespective of the affected side, especially in early onset patients.

Functional magnetic resonance imaging in patients with long-term unilateral hearing loss

To evaluate the potential functional reorganization by functional magnetic resonance imaging (MRI) to measure the brain activation in responses to stimulation to healthy ears in patients with long-term unilateral hearing loss (UHL). From June 1998 to December 2009, 23 patients with serious UHL (15 left, 8 right) were recruited along with 15 matched normal hearing subjects. Laterality index (LI) for activated voxel in primary auditory cortex (PAC) was calculated. And the activations outside auditory cortex were also evaluated. The data were discarded in 3 patients with left-ear UHL and 1 normal subject because of head motion. All control subjects showed contralateral dominant activation of PAC in group analysis. However, the group data of UHL patients showed that the activation was more symmetrical and the contralateral dominance diminished versus the control group. As compared with normal subjects outside PAC, heightened activation in left prefrontal cortex, bilateral inferior parietal lobule and left occipital/precuneus was found in UHL patients while reduced activation in left superior temporal gyrus was also found. The diminished contralateral dominance in PAC and heightened activation in non-auditory region suggest the reduction of interhemispheral inhibition and general increase in brain excitation in long-term UHL patients potentially occur as a result of functional reorganization adaptive to UHL. However, the reduced activation in superior temporal gyrus may be correlated with the deterioration of speech perception in these patients.

The Metz-Test (Comparison with the ABLB-Test, the SISI-Test, and Békésy Audiometry)

The Metz-test is based on elicitation of the bilateral stapedius reflex. The stapedial reflex is elicited by acoustic stimulation in the ear to be examined and measured by impedancce meter in the contralateral ear. In the normal ear, the reflex threshold is 50-90 dB above the hearing threshold. In the ear with loudness recruitment, however, the difference between the threshold for hearing and the threshold for induction of the stapedius reflex reduces.In the present study forty-seven patients suffering from neurolabyrinthopathy were subjected to examine recruitment by the following methods: the Metz-test, SISI-test, Bekesy audiometry, and with the unilateral hearing loss patients, ABLB-test. Sixteen ears showed the unilateral hearing loss and sixty-two ears bilateral hearing loss.As the result, there was the almost complete agreement among the Metz-test, ABLB-test, SISI-test and Bekesy audiometry in the patients showing recruitment. The Metz-test showed the highest degree of validity among all the the tests. Furthermore, the method is objective and does not require the subject's collaboration, and it can be used in the cases of bilateral hearing loss.