Behavioural and Objective Assessment of Binaural Hearing in Adult Listeners with Acquired Unilateral Conductive Hearing Loss Before and After Middle Ear Surgery

In normally hearing listeners, binaural hearing relies on symmetrical input from the two ears. Previous studies on human listeners have assessed the effect of induced unilateral conductive hearing loss (UCHL) during adulthood via earplugging. These experiments indicated initial difficulty in sound localization followed by gradual improvement due to adaptation to the perturbed binaural cues. The limited duration of earplug use does not represent the consequences of chronic UCHL secondary to disease. Furthermore, there is insufficient information regarding the adaptation of binaural hearing abilities after treatment of late-onset UCHL. The current study assessed the binaural hearing abilities of adult listeners with UCHL via behavioral and electrophysiological measurements. The dominant etiology of the hearing loss was otosclerosis. Furthermore, improving binaural hearing abilities following surgical treatment of UCHL caused by otosclerosis was monitored throughout one year post-surgery. Before including the binaural interaction component (BIC) of the auditory brainstem responses as the electrophysiological measurement, its test-retest reliability was confirmed on normal-hearing listeners. The largest evoked potentials were collected using a midline electrode configuration, and the effect of inter-session interval was investigated. Participants with UCHL showed elevated interaural time difference discrimination thresholds, but their near-normal sound localization ability suggested possible adaptation to the altered binaural cues. Spatial release from masking was lower than for a control group. Binaural loudness summation was inflated, and this abnormality was salient for those with moderate and moderately-severe UCHL. The brainstem BIC could not be detected in ten of eleven participants. Measurements were repeated up to three times throughout one year after stapedotomy in patients who registered for corrective surgery. A gradual improvement in binaural hearing tasks after the surgery continued for 6 to 14 months. The objective measurements (BIC) did not show improvement throughout the study for the majority of the participants. Overall, the results of this study suggest that UCHL-driven deficits in binaural hearing improved throughout a year after the corrective surgery. Some of these changes may last for a long time or remain unresolved, however. Counselling the patients regarding the consequences of UCHL and available intervention options, and creating reasonable expectations about the treatment will be promising

Improvement of Binaural Hearing in Long Sequential Bilateral Cochlear Implantation

Providing children with bilateral cochlear implants after many years of unilateral hearing leads to asymmetric hearing and a persistent mismatch in auditory development in the central auditory pathways. These abnormalities were evident when we compared auditory evoked responses from each of the two ears at the level of brainstem, cortex, loudness perception, and identifying binaural cues. We asked whether the asymmetry in auditory development could be resolved by asking the children to wear the second device alone for periods of time during the day (aural patching). Even though children did adhere to aural patching, they did not do it for the requested amount of time. Furthermore, changes occurred at the level of the brainstem and cortex which were not related to the aural patching regimen, suggesting that the aural patching cannot reverse the abnormal plasticity produced by several years of unilateral hearing with the first cochlear implant.MAS

An evaluation of the CARL manikin for use in patient-free real ear measurement: consistency and comparison to normative data.

OBJECTIVE: Simulation-based learning experiences provide low-risk opportunities for procedural training and practice in audiology. A series of real ear measurements (REM) were completed using Clinical Assistant for Research and Learning (CARL) manikins to determine expected responses and to compare to normative data. DESIGN: (1) Real-ear Unaided Response (REUR) curves were measured with one CARL and each of three ear styles. (2) Test/retest reliability was evaluated by repeating each REUR. (3) Real ear to coupler difference (RECD) values for foam-tip and custom earmolds were calculated. (4) The reliability across copies of the CARL heads was evaluated by comparing REUR measurement from one set of ears on 4 heads. STUDY SAMPLE: Four adult CARL manikins and thirty ears (5 sets of large, small, and bent). RESULTS: Within each ear category, the average difference across frequencies from one ear to the next was less than 2.5 dB with no significant individual difference more than 5.8 dB. Test/retest reliability was excellent. Typical REUR and RECD curves were created for each ear style and compared to published data on human ears. CONCLUSIONS: REM using the adult CARL head are predictable and repeatable making this simulator a good tool for audiological training

Perception of binaural cues develops in children who are deaf through bilateral cochlear implantation.

There are significant challenges to restoring binaural hearing to children who have been deaf from an early age. The uncoordinated and poor temporal information available from cochlear implants distorts perception of interaural timing differences normally important for sound localization and listening in noise. Moreover, binaural development can be compromised by bilateral and unilateral auditory deprivation. Here, we studied perception of both interaural level and timing differences in 79 children/adolescents using bilateral cochlear implants and 16 peers with normal hearing. They were asked on which side of their head they heard unilaterally or bilaterally presented click- or electrical pulse- trains. Interaural level cues were identified by most participants including adolescents with long periods of unilateral cochlear implant use and little bilateral implant experience. Interaural timing cues were not detected by new bilateral adolescent users, consistent with previous evidence. Evidence of binaural timing detection was, for the first time, found in children who had much longer implant experience but it was marked by poorer than normal sensitivity and abnormally strong dependence on current level differences between implants. In addition, children with prior unilateral implant use showed a higher proportion of responses to their first implanted sides than children implanted simultaneously. These data indicate that there are functional repercussions of developing binaural hearing through bilateral cochlear implants, particularly when provided sequentially; nonetheless, children have an opportunity to use these devices to hear better in noise and gain spatial hearing

Amplitude Changes of the Electrically Evoked Compound Action Potential in Children with Cochlear Implants: Preliminary Results

Objective: Use of electrical instead of acoustical stimulation has made much objective electrophysiological evaluation possible. This is useful for management process of young children before and after the cochlear implant. These evaluations have been used for assessment of neuronal survival before cochlear implant and for monitoring of prosthesis function during and after the surgery. Electrically evoked compound action potential is one of these tests which makes a valid and reliable objective evaluation possible. The aim of this study was to evaluate the potential's amplitude changes three months after receiving the device in pediatric cochlear implant recipients. Methods: In this longitudinal study, changes of the potential's amplitude in four given electrodes in four sessions after receiving the device are evaluated by approximately one month intervals in children implanted in Amir Alam and Hazrat-e-Rasoul hospitals, Tehran in July to December 2007. Findings: The mean amplitude of the electrodes did not significantly change in different sessions, while there was significant difference between the first and the other electrodes' responses in every session (P<0.05). Conclusion: Due to high reliability of the responses, the clinician can fit the speech processor for a long time. Better responses in apical electrodes may lead to develop an effective coding strategy

Experienced bilateral CI users and normal hearing peers perceived changes in ILDs as these cues moved from left to right weighted.

<p>Interaural level differences (ILDs) in CI users represent differences in CU and dB re: 20 Pa in the normal hearing group (∼0.08 dB re: 100 µA per acoustic dB change in ILD, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114841#pone-0114841-t003" target="_blank">Table 3</a> for additional details). Significant effects of ILD were found across groups (p<0.0001). Rate of change in ILDs delivered by CIs (CU) was reduced relative to acoustic ILD (dB) (p<0.05) with no significant difference between the 2 implanted groups (p>0.05).</p

Participant demographics.

<p>Participant demographics.</p

Mean (±1 SE) proportion of right responses from children with significant changes in interaural timing differences (ITDs) from the Normal Hearing Group (n = 16), the Sequential CI Group (10 with CI1 in the right ear), and the Simultaneous CI Group (n = 20).

<p>Responses changed significantly with ITD (p<0.0001) with no group effect (p>0.05) but with a group*ITD interaction (p<0.0001). The proportion of right responses for stimuli left leading by 400 µs was significantly greater in the Sequential CI group (p<0.005). The rate of change was significantly reduced in the CI groups relative to normal (p<0.0001) and there was a trend toward reduced rates of change in the Sequential CI group relative to the Simultaneous CI group (p = 0.05).</p

Auditory brainstem recording parameters.

<p>*monopolar 1+2 =  reference to CI plate and ball electrodes</p><p>Auditory brainstem recording parameters.</p

Detection, Speech Recognition, Loudness, and Preference Outcomes With a Direct Drive Hearing Aid: Effects of Bandwidth

Direct drive hearing devices, which deliver a signal directly to the middle ear by vibrating the tympanic membrane via a lens placed in contact with the umbo, are designed to provide an extension of audible bandwidth, but there are few studies of the effects of these devices on preference, speech intelligibility, and loudness. The current study is the first to compare aided speech understanding between narrow and extended bandwidth conditions for listeners with hearing loss while fitted with a direct drive hearing aid system. The study also explored the effect of bandwidth on loudness perception and investigated subjective preference for bandwidth. Fifteen adult hearing aid users with symmetrical sensorineural hearing loss participated in a prospective, within-subjects, randomized single-blind repeated-measures study. Participants wore the direct drive hearing aids for 4 to 15 weeks (average 6 weeks) prior to outcome measurement. Outcome measures were completed in various bandwidth conditions achieved by reducing the gain of the device above 5000 Hz or by filtering the stimuli. Aided detection thresholds provided evidence of amplification to 10000 Hz. A significant improvement was found in high-frequency consonant detection and recognition, as well as for speech in noise performance in the full versus narrow bandwidth conditions. Subjective loudness ratings increased with provision of the full bandwidth available; however, real-world trials showed most participants were able to wear the full bandwidth hearing aids with only small adjustments to the prescription method. The majority of participants had either no preference or a preference for the full bandwidth setting