Blake C. Papsin

An Evoked Potential Study of the Developmental Time Course of the Auditory Nerve and Brainstem in Children Using Cochlear Implants

Central auditory responses to electrical stimulation from a cochlear implant were studied in 75 pre-lingually deafened children and 11 adults. Electrically evoked auditory brainstem response (EABR) latencies significantly decreased with duration of cochlear implant use and were not significantly affected by the age at implant activation. Significant decreases in early latency waves and interwaves occurred within the first 1–2 months of implant use, whereas longer term changes (6–12 months) were found for eV and eIII-eV, which measure activity in the more rostral brainstem. Comparisons to acoustically evoked auditory brainstem response (ABR) in children with normal hearing suggested shorter interwave EABR latencies, reflecting either distinct neural generators or increased neural synchrony, but similar rates of change in the later latency eV and eIII-eV with time in sound. In sum, normal-like development of the rostral auditory brainstem is promoted by cochlear implant use in children of a wide range of ages.

What is the optimal timing for bilateral cochlear implantation in children

Abstract Bilateral cochlear implants (CIs) have been provided to children who are deaf in both ears with intent to promote binaural hearing. If it is possible to establish binaural hearing with two CIs, these children would be able to make use of interaural level and timing differences to localize sound and to distinguish between sounds separated in space. These skills are central to the ability to attend to one particular sound amidst a number of sound sources. This may be particularly important for children because they are typically learning and interacting in groups. However, the development of binaural processing could be disrupted by effects of bilateral deafness, effects of unilateral CI use, or issues related to the childs age at onset of deafness and age at the time of the first and second cochlear implantation. This research aims to determine whether binaural auditory processing is affected by these variables in an effort to determine the optimal timing for bilateral cochlear implantation in children. It is now clear that the duration of bilateral deafness should be limited in children to restrict reorganization in the auditory thalamo-cortical pathways. It has also been shown that unilateral CI use can halt such reorganization to some extent and promote auditory development. At the same time, however, unilateral input might compromise the development of binaural processing if CIs are provided sequentially. Mismatches in responses from the auditory brainstem and cortex evoked by the first and second CI after a long period of unilateral CI use suggest asymmetry in the bilateral auditory pathways which is significantly more pronounced than in children receiving bilateral implants simultaneously. Moreover, behavioural responses to level and timing differences between implants suggest that these important binaural cues are not being processed normally by children who received a second CI after a long period of unilateral CI use and at older ages. In sum, there may be multiple sensitive periods in the developing auditory system, which must be considered when determining the optimal timing for bilateral cochlear implantation.

Acoustic analysis of the voice in pediatric cochlear implant recipients: a longitudinal study.

Objective: To characterize inherent acoustic abnormalities of the deaf pediatric voice and the effect of artificially restoring auditory feedback with cochlear implantation.

The role of a graded profile analysis in determining candidacy and outcome for cochlear implantation in children

Assessment of candidacy for cochlear implantation in children continues to present a challenge to cochlear implant programs. The efficacy of implantation depends on a number of factors and as a result a multidisciplinary approach has been adopted. At the Cochlear Implant Program at The Hospital for Sick Children, Toronto, we use a graded profile analysis (GPA) which has been adapted from the Childrens Implant Profile (CHIP) developed by Hellman (S.A. Hellman, P.M. Chute, R.E. Kretschmer, M.E., Nevins, S.C. Parisier, L.C. Thurston, The development of a Childrens Implant Profile, Am. Ann. Deaf. 136 (1991) 77-81). This structured assessment allows each potential candidate to be scored in each category of assessment giving a potential range of -14 to +14. In this retrospective study of 109 candidates we examine the relationship between GPA scores and decision to implant. For those patients who were implanted, the relationship between GPA score and speech perception outcomes was also evaluated. Three distinct groups of children emerged from the analysis. The first group had scores less than 5 and were not considered to be suitable for implantation. Within the second group who scored between 5 and 8, there was no clear relationship between decision to implant and score. The last group, who scored 9-14, was considered to be generally suitable for implantation provided that there were no medical contraindications and the parents consented to implantation. There was a significant association between rate of improvement of speech perception and GPA score. Those patients with scores of 9 to +14 improved at a faster rate than group 5-8 (P < 0.05). The implications of these findings are discussed.

Characterizing responses from auditory cortex in young people with several years of cochlear implant experience

OBJECTIVEnTo determine if cortical responses evoked by a cochlear implant in children who are deaf differ from normal and to characterize these differences in children who achieve good versus fair speech perception outcomes post-implantation.nnnMETHODSnLate latency-evoked potential responses were recorded at 28 scalp locations in 16 children who were deaf from infancy and experienced cochlear implant users. Speech perception measures indicated that 8 had good scores and 8 had fair scores. In each child, responses were evoked by 36ms electrical pulse trains delivered from a single-implant electrode at the apical and basal ends of the array and by 36ms tone bursts (0.5, 2, and 6kHz). Responses to the tone bursts were also recorded in 14 age-matched children with normal hearing.nnnRESULTSnWe found (1) a dominant positive wave in all implant users and (2) a larger than normal negative amplitude peak in users with fair speech perception scores which had similar scalp topography to N1 but did not show the expected changes in amplitude with stimulus frequency.nnnCONCLUSIONSnLate latency-evoked potential responses in children using cochlear implants reflect abnormal and/or immature patterns of cortical activity.nnnSIGNIFICANCEnLimitations in auditory skills with a cochlear implant in children may be due to developmental processes in the cortex which are either slow to mature or which mature abnormally.

Bilateral simultaneous cochlear implantation in children: Our first 50 cases

To assess the safety and surgical technique of bilateral simultaneous cochlear implantation in children.

Factors contributing to limited open-set speech perception in children who use a cochlear implant

Cochlear implants have enabled many children with severe to profound sensorineural hearing loss to develop speech perception skills. However, some children experience few gains while others develop high levels of speech perception. We identified potential factors contributing to poor performance with an implant by studying implanted children who do not develop functional speech perception. Five children were identified as developing no open-set word recognition skills after at least 2 years of implant use. This study group was compared to a randomly selected control group (n=10) and an age-matched control group (n=5). Pre-implant factors were examined using a Graded Profile Analysis and post-implant factors were assessed in a retrospective chart review. A greater number of pre-implant concerns were raised in the study group than in randomized controls (P<0.01). Chronological age and duration of deafness were pre-implant concerns in all study group subjects. A greater number of post-implant concerns were found in the study group than in randomly selected controls (P<0.005). We conclude that while appropriate selection of candidates for cochlear implantation is important in predicting speech perception outcomes, post-implant follow-up is also essential and must include regular monitoring of equipment, monitoring of stimulation levels with use of objective measures of stimulation levels if necessary, and consistent habilitation.

Multidimensional Voice Program Analysis in Profoundly Deaf Children: Quantifying Frequency and Amplitude Control

Characterization of the vocal profile of profoundly deaf children using an objective voice analysis was carried out in a university-based pediatric otolaryngology clinic. 21 persons ages 3.5 to 18 years were assessed. From each sustained phonation of the vowel /a/ the following acoustic variables were extracted: fundamental frequency (F0), jitter percentage, shimmer percentage, fundamental frequency variation (vF0), peak amplitude variation (vAM), and first, second, and third formant frequencies (F1, F2, F3). Mean F0 was 267.8 Hz and consistent with established normative data. Mean measurements of jitter (0.88%) and shimmer (3.5%) were also within normal limits. The notable feature of the acoustic analysis was a statistically significant elevation in vF0 (2.81%) and vAM (23.58%). With the exception of one subject, the F1, F2, and F3 formant frequencies were comparable to those for normal hearing children. Auditory deprivation results in poor long-term control of frequency and amplitude during sustained phonation. The inability to maintain a sustained phonation may represent the partial collapse of an internal model of voice and speech.

Parental and program's decision making in paediatric simultaneous bilateral cochlear implantation: Who says no and why?

OBJECTIVEnTo evaluate initial candidacy for bilateral simultaneous cochlear implantation in children.nnnDESIGNnProspective case series.nnnSETTINGnTertiary academic pediatric hospital.nnnPARTICIPANTSnAs part of our research protocol all children eligible for cochlear implantation were assessed for suitability to receive a simultaneous bilateral implant. Over a 12-month period (January to December 2007) 78 children received a total of 95 cochlear implants. Children with sequential second implants (24), revision cases (4), and out of province recipients (4) were excluded. The remaining 46 patients were assessed for bilateral simultaneous implantation.nnnMAIN OUTCOME MEASURESnTeam/parental decision to proceed with bilateral simultaneous implantation.nnnRESULTSn17 children (37%) received simultaneous bilateral implants. 29 children (63%) were not considered suitable for simultaneous bilateral implantation. Reasons included developmental delay (10), residual borderline hearing in the second ear (9), parental/patient refusal (6), abnormally poor speech development for age (2), and abnormal cochlear anatomy precluding implantation (2). None were considered unsuitable for the more prolonged operative procedure on medical grounds.nnnCONCLUSIONSnAlthough bilateral implantation is thought to produce the optimal auditory outcome, not all patients are suitable, nor do all parents wish to proceed, when assessed for simultaneous implantation. Some of these patients are likely to be candidates for sequential bilateral implantation in due course.

Tinnitus is prevalent in children with cochlear implants

OBJECTIVESnTo explore the prevalence and the perceived impact of tinnitus in children using cochlear implants.nnnMETHODnCross-sectional study of implanted children attending a cochlear implant family event organized annually by our academic tertiary pediatric care center. Children were interviewed together with their parents, using open-questioning and structured interview qualitative methodologies. The main outcome measures were the prevalence of tinnitus and any impact of these symptoms.nnnRESULTSn40 children (age range: 3-15, mean: 7 years) and their families were interviewed. These included unilateral implantees (n=21), and bilateral implantees (n=19) whose two procedures were simultaneous (n=6), within 6-12 months (n=3), or >2 years apart (n=10). Tinnitus was reported by 38% (n=15). Tinnitus occurred most commonly in the implanted ear, when the implants were not in use (e.g. in bed at night). The children were generally untroubled by the tinnitus, although two reported difficulty sleeping. Tinnitus was most frequent in children aged 6-8 years (8/17, 47%), and in bilateral implantees with an inter-procedure delay of at least 2 years (6/10, 60%). Tinnitus was least reported in those implanted bilaterally simultaneously (1/6, 17%), and in those 5 years old or younger (3/11, 27%). No obvious relationship was identified between the prevalence of tinnitus and the etiology of deafness, age of implantation, or time elapsed since implantation.nnnCONCLUSIONSnTo our knowledge this is the first study to report the widespread prevalence of tinnitus in implanted children. Further work, particularly examining the effect of inter-implant delay on tinnitus in bilateral implantees, may contribute to our understanding of the neuronal plasticity after implantation.