Different contra-sound effects between noise and music stimuli seen in N1m and psychophysical responses

Auditory-evoked responses can be affected by the sound presented to the contralateral ear. The different contra-sound effects between noise and music stimuli on N1m responses of auditory-evoked fields and those on psychophysical response were examined in 12 and 15 subjects, respectively. In the magnetoencephalographic study, the stimulus to elicit the N1m response was a tone burst of 500 ms duration at a frequency of 250 Hz, presented at a level of 70 dB, and white noise filtered with high-pass filter at 2000 Hz and music stimuli filtered with high-pass filter at 2000 Hz were used as contralateral noise. The contralateral stimuli (noise or music) were presented in 10 dB steps from 80 dB to 30 dB. Subjects were instructed to focus their attention to the left ear and to press the response button each time they heard burst stimuli presented to the left ear. In the psychophysical study, the effects of contralateral sound presentation on the response time for detection of the probe sound of a 250 Hz tone burst presented at a level of 70 dB were examined for the same contra-noise and contra-music used in the magnetoencephalographic study. The amplitude reduction and latency delay of N1m caused by contra-music stimuli were significantly larger than those by contra-noise stimuli in bilateral hemisphere, even for low level of contra-music near the psychophysical threshold. Moreover, this larger suppressive effect induced by contra-music effects was also observed psychophysically; i.e., the change in response time for detection of the probe sound was significantly longer by adding contralateral music stimuli than by adding contra-noise stimuli. Regarding differences in effect between contra-music and contra-noise, differences in the degree of saliency may be responsible for their different abilities to disturb auditory attention to the probe sound, but further investigation is required to confirm this hypothesis.

On the Effect of Bimodal Rehabilitation in Asymmetric Hearing Loss

Background: Bone conductive implants (BCI) have been reported to provide greater beneficial effects for the auditory and perceptual functions of the contralateral ear in patients presenting with asymmetric hearing loss (AHL) compared to those with single-sided deafness (SSD). The aim of the study was to assess the effects of wearing a conventional hearing aid in the contralateral ear on BCI in terms of an improved overall auditory performance. Methods: eleven AHL subjects wearing a BCI in their worse hearing ear underwent an auditory evaluation by pure tone and speech audiometry in free field. This study group was obtained by adding to the AHL patients those SSD subjects that, during the follow-up, showed deterioration of the hearing threshold of the contralateral ear, thus presenting with the features of AHL. Four different conditions were tested and compared: unaided, with BCI only, with contralateral hearing aid (CHA) only and with BCI combined with CHA. Results: all of the prosthetic conditions caused a significant improvement with respect to the unaided condition. When a CHA was adopted, its combination with the BCI showed significantly better auditory performances than those achieved with the BCI only. Conclusions: the present study suggests the beneficial role of a CHA in BCI-implanted AHL subjects in terms of overall auditory performance.

A STUDY OF DRILL INDUCED HEARING LOSS IN THE CONTRALATERAL EAR FOLLOWING MASTOID SURGERY.

Background: Mastoidectomy is the mainstay of COM treatment . Usage of the micro motor drill has an effect on the contralateral ear due to the noise induced by the drill and the sound-conducting characteristic of the intact skull. Aims And Objectives: 1. To identify the drill induced hearing loss in the contralateral ear, by transient evoked otoacoustic emissions following mastoidectomy. 2. To identify the relation between the type of burr tip used and the amount of hearing loss. Methodology: This study consisted of 63 patients that underwent mastoidectomy. A pre-operative PTA and TEOAE was done. PTA was repeated on POD-1 and POD-7. TEOAE was done on POD-1,3 and 7. Intraoperatively, the type of burr tip used and the individual drilling time for each type of drill bit was recorded. Results: 37 patients developed transient SNHL by POD-3. All patients recovered by POD-30. Higher frequencies of 3000 Hz and 4000 Hz were commonly affected. No change was detected on PTA. Conclusion: The drill is not only a source of noise but is also a strong vibration generator. These strong oscillations are transmitted into the cochlea. Thus surgeons should select appropriate burrs and drills to minimize the temporal bone vibrations.

Retrospective Investigation of Contralateral Hearing Thresholds of Patients With Sporadic Vestibular Schwannoma

Objective The aim of this study was to investigate the contralateral hearing of patients with sporadic vestibular schwannoma (VS). Study Design Retrospective cohort study. Setting Pure-tone audiograms of the contralateral ear from patients with a wait-and-scan strategy were compared to the ones who received therapy. Due to a possible bias caused by the therapy, hearing thresholds before and after radiotherapy or surgery were compared separately with the wait-and-scan group. Methods From 1979 to 2017, 508 patients with sporadic VS could be included in the study. Of these, 240 received regular controls in the sense of wait-and-scan, 72 underwent radiotherapy (63 audiograms before and 43 after radiotherapy), and 196 had a surgery (186 audiograms before and 146 after surgery). Age-normalized hearing thresholds of the contralateral ear from patients with a wait-and-scan strategy were compared to ones who received therapy. In addition, hearing thresholds were compared to norm values. Results There was no evidence for a difference in the contralateral hearing of patients with sporadic VS between the wait-and-scan and therapy groups. The mean difference of hearing thresholds in our sample to norm values was found to be larger for the high frequencies and more pronounced in male patients. Conclusion There was no evidence for a difference in the contralateral hearing loss of patients with sporadic VS between the wait-and-scan and therapy groups. However, there was some indirect indication of poorer contralateral hearing in all patients with sporadic VS compared to normative values.

Speech Recognition With Informational and Energetic Maskers in Patients With Single-Sided Deafness After Cochlear Implantation

Purpose The aim of the study was to assess the susceptibility to energetic and informational masking in patients with single-sided deafness (SSD) with one normal-hearing (NH) ear and a cochlear implant (CI) in the contralateral ear, understand the effect on speech recognition when spatially separating noise and speech maskers, and investigate the influence of the CI in situations with energetic and informational masking. Method Speech recognition was measured in the presence of either a modulated speech-shaped noise or one of two competing speech maskers in 11 SSD-CI listeners. The speech maskers were manipulated with respect to fundamental frequency to consider the effect of different voices. Measurements were conducted in the unaided (NH) and aided (NHCI) conditions. Spatial release from masking (SRM) was calculated for each masker type and both listening conditions (NH and NHCI) by subtracting scores of the colocated target and masker condition (S 0 N 0 ) from the spatially separated target and masker conditions (S 0 N ≠0 ). Results Speech recognition was highly variable depending on the type of masker. SRM occurred in the unaided (NH) and aided (NHCI) conditions when the speech masker had the same gender as the target talker. Adding the CI improved speech recognition when this speech masker was ipsilateral to the NH ear. Conclusions The amount of informational masking is substantial in SSD-CI listeners with both colocated and spatially separated target and masker signals. The contribution of SRM to better speech recognition largely depends on the masker and is considerable when no differences in voices between the target and the competing talker occur. There is only a slight improvement in speech recognition by adding the CI.

Residual Hearing Affects Contralateral Routing of Signals in Cochlear Implant Users

<b><i>Introduction:</i></b> Contralateral routing of signals (CROS) can be used to eliminate the head shadow effect. In unilateral cochlear implant (CI) users, CROS can be achieved with placement of a microphone on the contralateral ear, with the signal streamed to the CI ear. CROS was originally developed for unilateral CI users without any residual hearing in the nonimplanted ear. However, the criteria for implantation are becoming progressively looser, and the nonimplanted ear can have substantial residual hearing. In this study, we assessed how residual hearing in the contralateral ear influences CROS effectiveness in unilateral CI users. <b><i>Methods:</i></b> In a group of unilateral CI users (<i>N</i> = 17) with varying amounts of residual hearing, we deployed free-field speech tests to determine the effects of CROS on the speech reception threshold (SRT) in amplitude-modulated noise. We compared 2 spatial configurations: (1) speech presented to the CROS ear and noise to the CI ear (S_CROSN_CI) and (2) the reverse (S_CIN_CROS). <b><i>Results:</i></b> Compared with the use of CI only, CROS improved the SRT by 6.4 dB on average in the S_CROSN_CI configuration. In the S_CIN_CROS configuration, however, CROS deteriorated the SRT by 8.4 dB. The benefit and disadvantage of CROS both decreased significantly with the amount of residual hearing. <b><i>Conclusion:</i></b> CROS users need careful instructions about the potential disadvantage when listening in conditions where the CROS ear mainly receives noise, especially if they have residual hearing in the contralateral ear. The CROS device should be turned off when it is on the noise side (S_CIN_CROS). CI users with residual hearing in the CROS ear also should understand that contralateral amplification (i.e., a bimodal hearing solution) will yield better results than a CROS device. Unilateral CI users with no functional contralateral hearing should be considered the primary target population for a CROS device.

Factors influencing cartilage tympanic perforation repair in children.

Objectives: The aim of the study was to identify factors that could influence the repair of eardrum perforation using cartilage graft (or cartilage tympanoplasty) in children. Methods: A cohort of children operated on between January 1998 and December 2012 was reviewed. We have studied the repair rate of the eardrum (anatomical result) and the hearing level with audiometric tests (functional result) at 1 year and 3 years after surgery. These results were correlated with size or location of the perforation, status of the contralateral ear, gender, allergies, cleft palate, craniofacial anomalies, expertise of the surgeon (junior, senior) and perioperative observations (mucosa, glue, etc.). Results: 1240 tympanoplasties were selected from the database, of which 139 ears (127 patients) could be analysed (perforation without concurrent disease, authorisation from patients obtained and sufficient information reported). Mean age at surgery was 9.6 years ± 2.6 (range 4-16). At one year, 129/139 (93%) tympanic membranes were closed and 112/139 (81%) were satisfactory (no residual perforation, nor retraction, cholesteatoma, myringitis or OME). Air-bone gap was < 20 dB in 102/127 ears (80%). At 3 years, the eardrum was closed in 64/66 (97%) ears (reperforation in one case) and 82% were satisfactory. Myringitis occurred in 5% and 9% of cases at one- and three-year follow-up. Surgery before the age of 8 years was the only risk factor of a non-satisfactory result at one-year follow-up (p = 0.024). Conclusions: Long-term results were satisfactory; the only risk factor was surgery before eight years of age. In the child, long-term yearly follow-up is necessary after tympanic perforation.

Sound Localization Bias and Error in Bimodal Listeners Improve Instantaneously When the Device Delay Mismatch Is Reduced

Users of a cochlear implant (CI) in one ear, who are provided with a hearing aid (HA) in the contralateral ear, so-called bimodal listeners, are typically affected by a constant and relatively large interaural time delay offset due to differences in signal processing and differences in stimulation. For HA stimulation, the cochlear travelling wave delay is added to the processing delay, while for CI stimulation, the auditory nerve fibers are stimulated directly. In case of MED-EL CI systems in combination with different HA types, the CI stimulation precedes the acoustic HA stimulation by 3 to 10 ms. A self-designed, battery-powered, portable, and programmable delay line was applied to the CI to reduce the device delay mismatch in nine bimodal listeners. We used an A-B-B-A test design and determined if sound source localization improves when the device delay mismatch is reduced by delaying the CI stimulation by the HA processing delay (τHA). Results revealed that every subject in our group of nine bimodal listeners benefited from the approach. The root-mean-square error of sound localization improved significantly from 52.6° to 37.9°. The signed bias also improved significantly from 25.2° to 10.5°, with positive values indicating a bias toward the CI. Furthermore, two other delay values (τHA –1 ms and τHA +1 ms) were applied, and with the latter value, the signed bias was further reduced in some test subjects. We conclude that sound source localization accuracy in bimodal listeners improves instantaneously and sustainably when the device delay mismatch is reduced.