Differing Bilateral Benefits for Spatial Release From Masking and Sound Localization Accuracy Using Bone Conduction Devices.

OBJECTIVES: Normal binaural hearing facilitates spatial hearing and therefore many everyday listening tasks, such as understanding speech against a backdrop of competing sounds originating from various locations, and localization of sounds. For stimulation with bone conduction hearing devices (BCD), used to alleviate conductive hearing losses, limited transcranial attenuation results in cross-stimulation so that both cochleae are stimulated from the position of the bone conduction transducer. As such, interaural time and level differences, hallmarks of binaural hearing, are unpredictable at the level of the inner ears. The aim of this study was to compare spatial hearing by unilateral and bilateral BCD stimulation in normal-hearing listeners with simulated bilateral conductive hearing loss. DESIGN: Bilateral conductive hearing loss was reversibly induced in 25 subjects (mean age = 28.5 years) with air conduction and bone conduction (BC) pure-tone averages across 0.5, 1, 2, and 4 kHz (PTA 4 ) <5 dB HL. The mean (SD) PTA 4 for the simulated conductive hearing loss was 48.2 dB (3.8 dB). Subjects participated in a speech-in-speech task and a horizontal sound localization task in a within-subject repeated measures design (unilateral and bilateral bone conduction stimulation) using Baha 5 clinical sound processors on a softband. For the speech-in-speech task, the main outcome measure was the threshold for 40% correct speech recognition when masking speech and target speech were both colocated (0°) and spatially and symmetrically separated (target 0°, maskers ±30° and ±150°). Spatial release from masking was quantified as the difference between colocated and separated masking and target speech thresholds. For the localization task, the main outcome measure was the overall variance in localization accuracy quantified as an error index (0.0 = perfect performance; 1.0 = random performance). Four stimuli providing various spatial cues were used in the sound localization task. RESULTS: The bilateral BCD benefit for recognition thresholds of speech in competing speech was statistically significant but small regardless if the masking speech signals were colocated with, or spatially and symmetrically separated from, the target speech. Spatial release from masking was identical for unilateral and bilateral conditions, and significantly different from zero. A distinct bilateral BCD sound localization benefit existed but varied in magnitude across stimuli. The smallest benefit occurred for a low-frequency stimulus (octave-filtered noise, CF = 0.5 kHz), and the largest benefit occurred for unmodulated broadband and narrowband (octave-filtered noise, CF = 4.0 kHz) stimuli. Sound localization by unilateral BCD was poor across stimuli. CONCLUSIONS: Results suggest that the well-known transcranial transmission of BC sound affects bilateral BCD benefits for spatial processing of sound in differing ways. Results further suggest that patients with bilateral conductive hearing loss and BC thresholds within the normal range may benefit from a bilateral fitting of BCD, particularly for horizontal localization of sounds.

Cochlear implants before 9 months of age led to more natural spoken language development without increased surgical risks.

AIM: Evidence suggests that cochlear implants are beneficial for language development, but there is no consensus about the ideal age for surgery. We investigated how language development and surgical safety were affected by patients' ages. METHODS: This study comprised 103 children (52 boys) aged 4.3-16 years who received cochlear implants at 5-29 months at the Karolinska University Hospital, Stockholm, Sweden, between 2002 and 2013. All showed typical development and were from monolingual homes. Bilateral implants were common (95%). The children were regularly assessed on language understanding, vocabulary and speech recognition by a multi-disciplinary team for 10.0 ± 3.7 (4.7-16.0) years. RESULTS: There were no associations between complications after surgery and the age when children had their first implant. Children implanted at 5-11 months reached an age-equivalent level of language understanding and better vocabulary outcome sooner than subgroups implanted later. Children who had surgery at 12-29 months demonstrated more atypical and delayed language abilities over time. Early implantation, preferably before 9 months, may lead to a more typical trajectory of spoken language development. CONCLUSION: Our findings showed that cochlear implantation before 9 months was safe. Early implantation may reduce the negative effects of auditory deprivation and promotes more natural and synchronised language development.

Psychometric properties of the Swedish version of the Glasgow Benefit Inventory in otosclerosis subjects.

OBJECTIVE: To evaluate the psychometric properties of the Swedish version of the Glasgow Benefit Inventory (GBI). METHODS: A prospective multicenter cohort study was conducted. A total of 123 otosclerosis subjects were included in the study. The subjects were divided in three groups based on the following interventions: (a) stapedotomy without any prior hearing-aid rehabilitation (n = 60); (b) hearing-aid rehabilitation without any prior stapedotomy (n = 33); and (c) stapedotomy with prior hearing-aid rehabilitation (n = 30). Pre- and post-operative pure tone audiometry were measured. The Swedish version of the GBI was completed by the subjects 6 months after the intervention. Test-retest reliability and internal consistency, factor analysis, construct validity, and criterion validity, was assessed. RESULTS: The Swedish version of the GBI was well accepted by the subjects. It showed good psychometric properties with an overall high reliability. Factor analysis resulted in a 5-factor solution explaining 66.6% of the variance where factors 1 and 2 represented the general health domain. CONCLUSIONS: Overall, the Swedish version of the GBI showed good psychometric properties. Based on the factor analyses, there is the possibility that the general health domain should be divided in two separate domains: general health and psychosocial health. LEVEL OF EVIDENCE: 2c.

The choice of stimulation strategy affects the ability to detect pure tone inter-aural time differences in children with early bilateral cochlear implantation.

OBJECTIVES: To investigate if the interaural time difference (ITD) ability is dependent of stimulation strategy. To examine the correlation between ITD, interaural level differences (ILD) and the ability to localize different sounds. METHODS: Thirty subjects aged 8-13 who were implanted bilaterally before 3 years of age were tested. Twenty of the subjects used processors programmed with fine structure (FS) strategy on both sides. ITD and ILD just noticeable difference (JND) of a 250 Hz pure tone was measured using their clinical processors. Furthermore, their ability to localize sound in the horizontal plane was measured using eye tracking. RESULTS: Ten of the 20 subjects with FS obtained an ITD threshold compared to none in the group without FS (0/10). ILD JND was correlated to localization ability of the broadband (BB) sound. Mean absolute error of the localization of a low-frequency (LF) sound was larger than that of a BB sound. CONCLUSIONS: The ability to detect ITD was present only when the cochlear implant stimulation had FS. The LF sound was more difficult to localize than the BB sound and ITD ability of FS strategies did not affect the localization ability of either sound. A low ILD seems necessary to improve the localization ability.

High-frequency hearing, tinnitus, and patient satisfaction with stapedotomy: A randomized prospective study.

Otosclerosis is a common disorder that leads to conductive hearing loss. Most patients with otosclerosis also have tinnitus, and surgical treatment is known to improve hearing as well as tinnitus. Some patients however experience worsening of tinnitus after the operation, but there are no known factors that allow surgeons to predict who will be at risk. In this prospective observational study on 133 patients undergoing stapedotomy, we show that postoperative air conduction thresholds at very high stimulus frequencies predict improvement of tinnitus, as assessed with proportional odds logistic regression models. Young patients were significantly more likely to experience reduction of tinnitus and patients whose tinnitus became better were also more satisfied with the outcome of the operation. These findings have practical importance for patients and their surgeons. Young patients can be advised that surgery is likely to be beneficial for their tinnitus, but a less positive message should be conveyed to older patients.

A randomised, double blind trial of N-Acetylcysteine for hearing protection during stapes surgery.

BACKGROUND: Otosclerosis is a disorder that impairs middle ear function, leading to conductive hearing loss. Surgical treatment results in large improvement of hearing at low sound frequencies, but high-frequency hearing often suffers. A likely reason for this is that inner ear sensory cells are damaged by surgical trauma and loud sounds generated during the operation. Animal studies have shown that antioxidants such as N-Acetylcysteine can protect the inner ear from noise, surgical trauma, and some ototoxic substances, but it is not known if this works in humans. This trial was performed to determine whether antioxidants improve surgical results at high frequencies. METHODS: We performed a randomized, double-blind and placebo-controlled parallel group clinical trial at three Swedish university clinics. Using block-stratified randomization, 156 adult patients undergoing stapedotomy were assigned to intravenous N-Acetylcysteine (150 mg/kg body weight) or matching placebo (1:1 ratio), starting one hour before surgery. The primary outcome was the hearing threshold at 6 and 8 kHz; secondary outcomes included the severity of tinnitus and vertigo. FINDINGS: One year after surgery, high-frequency hearing had improved 2.7 ± 3.8 dB in the placebo group (67 patients analysed) and 2.4 ± 3.7 dB in the treated group (72 patients; means ± 95% confidence interval, p = 0.54; linear mixed model). Surgery improved tinnitus, but there was no significant intergroup difference. Post-operative balance disturbance was common but improved during the first year, without significant difference between groups. Four patients receiving N-Acetylcysteine experienced mild side effects such as nausea and vomiting. CONCLUSIONS: N-Acetylcysteine has no effect on hearing thresholds, tinnitus, or balance disturbance after stapedotomy. TRIAL REGISTRATION: ClinicalTrials.gov NCT00525551.

Panel 2: Eustachian tube, middle ear, and mastoid--anatomy, physiology, pathophysiology, and pathogenesis.

OBJECTIVE: This report reviews the literature to identify the advances in our understanding of the middle ear (ME)-Eustachian tube (ET) system during the past 4 years and, on that basis, to determine whether the short-term goals elaborated in the last report were achieved and propose updated goals to guide future otitis media (OM) research. DATA SOURCES: Databases searched included PubMed, Web of Science (1945-present), Medline (1950 to present), Biosis Previews (1969-present), and the Zoological Record (1978 to present). The initial literature search covered the time interval from January 2007 to June 2011, with a supplementary search completed in February 2012. REVIEW METHODS: The panel topic was subdivided; each contributor performed a literature search and provided a preliminary report. Those reports were consolidated and discussed when the panel met on June 9, 2011. At that meeting, the progress was evaluated and new short-term goals proposed. CONCLUSIONS: Progress was made on 16 of the 19 short-term goals proposed in 2007. Significant advances were made in the characterization of ME gas exchange pathways, modeling ET function, and preliminary testing of treatments for ET dysfunction. IMPLICATIONS FOR PRACTICE: In the future, imaging technologies should be developed to noninvasively assess ME/ET structure and physiology with respect to their role in OM pathogenesis. The new data derived from form/function experiments should be integrated into the finite element models and used to develop specific hypotheses concerning OM pathogenesis and persistence. Finally, rigorous studies of treatments, medical or surgical, of ET dysfunction should be undertaken.

Inadequate opening capacity of the eustachian tube in Meniere's disease.

CONCLUSION: In this physiological study subjects with Meniere's disease (MD) had high resistance to opening of the eustachian tube (ET) in three of four provocation tests. These subjects can be exposed to pressure deviations in the middle ear (ME) above their equalizing capacity. Transmission of the pressure deviations to the inner ear fluids and influence of the symptoms of MD are feasible. OBJECTIVE: The aim of the study was to reveal potential inadequacy in the ET equilibration capacity and deviations in ME pressure in patients with MD. METHODS: Direct ME pressure measurements were made during provocation tests of the ET, and continuously during the daytime and night-time in 21 patients with unilateral, definite and active MD. Twenty subjects with healthy ears (HEs) were used for comparison. RESULTS: In all, 15/21 subjects could not equilibrate an induced positive and/or negative pressure in the ME by deglutition; 9/21 subjects were not able to perform Valsalva's manoeuvre. All the controls could effectively perform these manoeuvres. However, the continuous measurements showed a similar pressure pattern in patients with MD and the controls, i.e. a slightly negative mean ME pressure during the daytime and positive pressure during sleep.

Middle ear pressure equilibration ability and spontaneous pressure changes in healthy ears with ventilation tubes.

CONCLUSION: The results of this study give support to the theory that opening the middle ear (ME) to the atmosphere leads to a deterioration in its pressure regulation capacity. However, this is probably not the reason why a perforation of the tympanic membrane becomes chronic. OBJECTIVE: Direct, continuous measurement is a method of studying ME pressure regulation. We found previously that subjects with chronic central perforation (CCP) had a negative ME pressure in the daytime, in contrast to subjects with healthy ears. In this study, in order to elucidate the cause of this negative pressure, measurements were performed in healthy ears with ventilation tubes (VTs). MATERIAL AND METHODS: A VT was inserted 1 week prior to the measurements in 18 subjects. A hearing protector was tightly fitted deep into the external ear canal and connected to a portable system consisting of a pressure transducer and a memory. RESULTS: The measurements revealed a mean ME pressure during the first 3 h of -27 daPa. Ten subjects showed an initial decrease in pressure leading to a considerable negative mean ME pressure and a poor ability to equilibrate pressure differences through the Eustachian tube, like the subjects with CCP.