Binaural responses to a speech syllable are altered in children with hearing loss: Evidence from the frequency-following response.

BACKGROUND & RATIONALE: In prior work using non-speech stimuli, children with hearing loss show impaired perception of binaural cues and no significant change in cortical responses to bilateral versus unilateral stimulation. Aims of the present study were to: 1) identify bilateral responses to envelope and spectral components of a speech syllable using the frequency-following response (FFR), 2) determine if abnormalities in the bilateral FFR occur in children with hearing loss, and 3) assess functional consequences of abnormal bilateral FFR responses on perception of binaural timing cues. METHODS: A single-syllable speech stimulus (/dα/) was presented to each ear individually and bilaterally. Participants were 9 children with normal hearing (MAge = 12.1 ± 2.5 years) and 6 children with bilateral hearing loss who were experienced bilateral hearing aid users (MAge = 14.0 ± 2.6 years). FFR temporal and spectral peak amplitudes were compared between listening conditions and groups using linear mixed model regression analyses. Behavioral sensitivity to binaural cues were measured by lateralization responses as coming from the right or left side of the head. RESULTS: Both temporal and spectral peaks in FFR responses increased in amplitude in the bilateral compared to unilateral listening conditions in children with normal hearing. These measures of "bilateral advantage" were reduced in the group of children with bilateral hearing loss and associated with decreased sensitivity to interaural timing differences. CONCLUSION: This study is the first to show that bilateral responses in both temporal and spectral domains can be measured in children using the FFR and is altered in children with hearing loss with consequences to binaural hearing.

Toward a method of achieving balanced stimulation of bilateral auditory nerves: Evidence from children receiving matched and unmatched bilateral cochlear implants simultaneously.

OBJECTIVES: To identify whether mismatched bilateral cochlear implants compromise balanced stimulation of the two auditory nerves and establish asymmetric hearing in children. METHODS: Behavioural and electrophysiological measures were completed in 47 children receiving bilateral CIs in the same surgery (simultaneously): 27 children received a peri­modiolar N24RE array in one ear and a 422 anti-modiolar array in the other (experimental group) and 20 children received 2 peri­modiolar arrays (control group). Differences in current levels between the two devices were measured by electrically evoked compound action potentials (ECAPs) at the time of surgery. These data were compared with minimum and maximum comfortably loud levels programmed in each speech processor (T-levels, C-levels, respectively) after 12 months of bilateral CI use. Asymmetries in functional hearing between arrays were measured in open set speech perception testing between 3 to 5 years of CI use. RESULTS: Higher current levels were required from the anti-modiolar than peri­modiolar array to evoke balanced interaural ECAP amplitudes (mismatched group: mean ± SD difference: -9.9 ± 22.6; matched group: -0.8 ± 26.5). This difference was larger in the experimental group than control group (t = -2.51; p = 0.016) and remained constant with increases in current level from ECAP threshold to maximum amplitudes (dynamic range) in many but not all children in both groups. T and C-levels were poorly predictive of levels needed to evoke balanced ECAP amplitudes in children with mismatched devices (F(1, 312) = 1.3, p = 0.263). Speech perception scores were more asymmetric between ears in children using bilateral mismatched arrays (mean ± SD: 73.8 ± 16.4 at the peri­modiolar array; 57.7 ± 26.4 at the anti-modiolar array), compared to children with bilateral matched arrays (right ear: 78.0 ± 10.4; left ear: 74.9 ± 13.5). CONCLUSION: Higher current level requirements at the anti-modiolar array compared to the peri­modiolar array in children with bilateral mismatched CIs are not fully accounted for in device programming. Mismatched electrodes in children receiving bilateral cochlear implants increases the risk of asymmetric hearing.

Etiology and therapy indication for cochlear implantation in children with single-sided deafness : Retrospective analysis.

OBJECTIVE: The characteristics of children with single-sided deafness (SSD) who become candidates for unilateral cochlear implantation (uCI) were identified. STUDY DESIGN: In all, 118 children with SSD presenting from 2013-2019 to a tertiary pediatric children's hospital were retrospectively assessed regarding candidacy for uCI. RESULTS: Of the 118 children, 103 had completed uCI candidacy assessment, while 15 were undergoing this assessment at the time of review. More than half of children did not go on to implantation (63/103, 61%), with the 2 main reasons being (1) half (31/63) did not meet candidacy criteria for implantation, most commonly due to cochlear nerve aplasia/hypoplasia (31/82 who were assessed with MRI, 38%) and (2) families (30/103; 29%) declined participation in the surgical arm of the trial. The most common etiologies of SSD in the 37/103 (36%) children who both met candidacy and consented to implantation were congenital cytomegalovirus (cCMV; 16/37, 43%), unknown (6/37, 16%), cochleovestibular anomaly and trauma (each 5/37, 14%). CONCLUSIONS: Many children with SSD who present for implant candidacy assessment do not ultimately receive uCI. Major factors contributing to noncandidacy are cochlear nerve aplasia and parental acceptance of the intervention. While approximately half of children with SSD in our cohort were candidates for implantation, only 1/3 of the total cohort proceeded with implantation with the main predictors of acceptability of this intervention being an etiology (i.e., cCMV) that carries risk of progressive deterioration in the better hearing ear or SSD that was sudden in onset. These findings provide important insight into this new population of cochlear implant users and the emerging acceptance of intervention in children with SSD.

The combination of vestibular impairment and congenital sensorineural hearing loss predisposes patients to ocular anomalies, including Usher syndrome.

The co-occurrence of hearing impairment and visual dysfunction is devastating. Most deaf-blind etiologies are genetically determined, the commonest being Usher syndrome (USH). While studies of the congenitally deaf population reveal a variable degree of visual problems, there are no effective ophthalmic screening guidelines. We hypothesized that children with congenital sensorineural hearing loss (SNHL) and vestibular impairment were at an increased risk of having USH. A retrospective chart review of 33 cochlear implants recipients for severe to profound SNHL and measured vestibular dysfunction was performed to determine the ocular phenotype. All the cases had undergone ocular examination and electroretinogram (ERG). Patients with an abnormal ERG underwent genetic testing for USH. We found an underlying ocular abnormality in 81.81% (27/33) of cases; of which 75% had refractive errors, and 50% of those patients showed visual improvement with refractive correction. A total of 14 cases (42.42%; 14/33) had generalized rod-cone dysfunction on ERG suggestive of Usher syndrome type 1, confirmed by mutational analysis. This work shows that adding vestibular impairment as a criterion for requesting an eye exam and adding the ERG to detect USH increases the chances of detecting ocular anomalies, when compared with previous literature focusing only on congenital SNHL.

Stimulation parameters differ between current anti-modiolar and peri-modiolar electrode arrays implanted within the same child.

OBJECTIVE: To compare stimulation parameters of peri-modiolar and anti-modiolar electrode arrays using two surgical approaches. METHODS: Impedance, stimulation thresholds, comfortably loud current levels, electrically evoked compound action potential thresholds and electrically evoked stapedial reflex thresholds were compared between 2 arrays implanted in the same child at 5 time points: surgery, activation/day 1, week 1, and months 1 and 3. The peri-modiolar array was implanted via cochleostomy in all children (n = 64), while the anti-modiolar array was inserted via a cochleostomy in 43 children and via the round window in 21 children. RESULTS: The anti-modiolar array had significantly lower impedance, but required higher current levels to elicit thresholds, comfort, electrically evoked compound action potential thresholds and electrically evoked stapedial reflex thresholds than the peri-modiolar array across all time points, particularly in basal electrodes (p < 0.05). The prevalence of open electrodes was similar in anti-modiolar (n = 5) and peri-modiolar (n = 3) arrays. CONCLUSION: Significant but clinically acceptable differences in stimulation parameters between peri-modiolar and anti-modiolar arrays persisted four months after surgery in children using bilateral cochlear implants. The surgical approach used to insert the anti-modiolar array had no overall effect on outcomes.

Surgical efficiency in bilateral cochlear implantation: a cost analysis.

OBJECTIVE: (1) Compare the non-device-related costs of bilateral simultaneous cochlear implantation (BSiCI) vs. unilateral, and (2) establish a dollar amount for potential cost savings in direct costs for BSiCI vs. sequential cochlear implantation (CI). METHODS: Data from all CI cases performed during the fiscal year 2010-2011 were retrospectively reviewed without exception. Fifty-four patients received unilateral CI and 36 received BSiCI. Demographics and data regarding direct costs associated with the operation and immediate in hospital post-operative period were collected. RESULTS: The total operating room (OR) time for unilateral and BSiCI was 3 hours 00 minutes and 4 hours 37 minutes, respectively, with a mean difference of 1 hour and 36 minutes (SD = 0 hours:06 minutes). The cost of OR and post-anesthetic care unit supporting staff was $3102 and $4240 for unilateral and BSiCI, respectively, with a mean difference of $1138 (SD = 216). Unilateral CI supplies totaled $1348 compared to $1822 for BSiCI supplies with an average difference of $438 (SD = 123). CONCLUSION: The total direct costs for a unilateral CI (excluding implantable device and surgeon fees) were $4362 compared to $5823 dollars for BSiCI. Simultaneous implantation can lead to a potential saving of $2901 compared to sequential implantation.