Biomedical subjects

Richard C Dowell

Publications and source records attributed to Richard C Dowell.

7 recordsLinked to original sources

PubMed2006

Speech perception for adults who use hearing aids in conjunction with cochlear implants in opposite ears.

This study aimed to (a) investigate the effect of using a hearing aid in conjunction with a cochlear implant in opposite ears on speech perception in quiet and in noise, (b) identify the speech information obtained from a hearing aid that is additive to the information obtained from a cochlear implant, and (c) explore the relationship between aided thresholds in the nonimplanted ear and speech perception benefit from wearing a hearing aid in conjunction with a cochlear implant in opposite ears. Fourteen adults who used the Nucleus 24 cochlear implant system in 1 ear participated in the study. All participants had either used a hearing aid in the nonimplanted ear for at least 75% of waking hours after cochlear implantation, and/or, hearing loss less than 90 dB HL in the low frequencies in the nonimplanted ear. Speech perception was evaluated in 3 conditions: cochlear implant alone (CI), hearing aid alone (HA), and cochlear implant in conjunction with hearing aid in opposite ears (CIHA). Three speech perception tests were used: consonant-vowel nucleus-consonant (CNC) words in quiet, City University of New York style (CUNY) sentences in coincident signal and noise, and spondees in coincidental and spatially separated signal and noise. Information transmission analyses were performed on the CNC responses. Of the 14 participants tested, 6 showed significant bimodal benefit on open-set speech perception measures and 5 showed benefit on close-set spondees. However, 2 participants showed poorer speech perception with CIHA than CI in at least 1 of the speech perception tests. Results of information transmission analyses showed that bimodal benefit (performance with CIHA minus that with CI) in quiet arises from improved perception of the low frequency components in speech. Results showed that participants with poorer aided thresholds in the mid-to-high frequencies demonstrated greater bimodal benefit. It is possible that the mid-to-high frequency information provided by the hearing aids may be conflicting with the cochlear implants.

Adult↗

PubMed2006

Cochlear implant and vestibular function.

OBJECTIVES: To document incidences of vestibular dysfunction after cochlear implantation and investigate why it occurs. This work was also motivated by a desire to provide the basis for better preoperative counseling and postoperative vestibular therapy to cochlear implant patients. SETTING: Melbourne Cochlear Implant Clinic at a tertiary referral hospital. STUDY DESIGN: Prospective observational study. PATIENTS: One hundred forty-six adult implant recipients, mean age, 60 years (range, 20-90 yr). MAIN OUTCOME MEASURES: Postoperative vestibular disturbance was defined as symptoms lasting for 1 week or longer after surgery. The differences in preoperative and postoperative vestibular function were measured from subjective assessments (Dizziness Handicap Inventory and Activity Balance Confidence questionnaires) and objective assessments (bithermal caloric tests). The position of the postoperative electrode was classified as "loose", "regular", or "tight" fitting. RESULTS: Thirty-two percent of patients reported vestibular disturbance and had poorer Dizziness Handicap Inventory, Activity Balance Confidence, and caloric results in the implanted ear after surgery. Patient age, cause, and preoperative caloric result did not predict postoperative vestibular symptoms. Recipients aged 70 years or older had significantly poorer caloric results on the implanted side after surgery that was not related to the intracochlear electrode position or surgical team. CONCLUSION: One-third of recipients can expect to experience a significant vestibular disturbance after surgery, regardless of age, cause, or preoperative caloric result. "Older" ears seem more prone to permanent injury after cochlear implantation.

Adult↗

PubMed2005

Benefits of audibility for listeners with severe high-frequency hearing loss.

A consonant identification test was carried out with 10 hearing-impaired listeners under various low-pass filter conditions. Subjects were also tested for cochlear dead regions with the TEN test. All subjects had moderate-to-severe high-frequency hearing losses. Consonant recognition was tested under conditions in which the speech signals were highly audible to subjects for frequencies up to the low-pass filter cut-off. Extensive dead regions were found for one subject with the TEN test. The remaining subjects may have had dead regions above 3 kHz, because of the severity of their hearing losses, but these could not be demonstrated with the TEN test. Average consonant scores for the subject group improved significantly (p<0.05) with increasing audibility of high-frequency components of the speech signal. There were no cases of speech perception being reduced with increasing bandwidth. Nine of the subjects showed improvements in scores with increasing audibility, whereas the remaining subject showed little change in scores. For this subject, speech perception results were consistent with the TEN test findings. In general, the results suggest that listeners with severe high-frequency losses are often able to make some use of high-frequency speech cues if these cues can be made audible.

Acoustic Stimulation↗

PubMed2004

Outcomes for cochlear implant users with significant residual hearing: implications for selection criteria in children.

OBJECTIVES: To develop an evidence-based technique for providing recommendations to candidates for cochlear implantation with significant residual hearing and to assess the efficacy of the approach. DESIGN: Modified selection criteria were derived from an analysis of the postoperative performance for a large group of adult cochlear implant users. In particular, the distributions of results for implant users with significant preoperative open-set speech perception were reviewed. This suggested that the candidates had a good chance (>75%) of overall improvement if they obtained open-set sentence scores in quiet of up to 70% in the best-aided condition and scores of up to 40% in the ear to undergo implantation. PATIENTS: A group of 45 adult implantation candidates who fit the modified criteria and who underwent preimplantation and postimplantation assessment to compare actual results with those predicted from the distributions. RESULTS: The speech perception results showed that 36 subjects (80%) had improved open-set sentence scores with the cochlear implant compared with their best-aided preoperative performance (mean improvement, 20.5%). Forty-four (98%) had improved open-set sentence scores for the ear undergoing implantation (mean improvement, 65.3%). CONCLUSIONS: The general concept of using the distribution of speech perception results to make evidence-based recommendations for candidates for cochlear implants is supported by this study. The approach can be used across different subpopulations, including older children with significant residual auditory skills, and for different outcome measures. It is important that the data used to provide recommendations and modify selection criteria are from an unselected sample of implant users of adequate size. This study highlights the continuing need to evaluate speech perception performance carefully before and after cochlear implantation.

Adult↗

PubMed2004

Cochlear implants for children with significant residual hearing.

BACKGROUND: Previous research suggests that children with pure-tone averages of greater than 90 dB hearing level and/or open-set sentence perception of less than 30% may derive significant benefit from cochlear implantation. OBJECTIVE: To evaluate postoperative speech perception benefit and bilateral-bimodal benefit for 16 children whose preimplant speech perception scores exceeded conservative candidacy guidelines. STUDY DESIGN: Preimplant and postimplant repeated-measure design. METHODS: Sixteen child subjects who obtained 30% or greater on preimplant open-set sentence material, presented live voice audition alone, were selected for this study. Preimplant pure-tone averages ranged from 73 to 110 dB in the better aided ear. Preimplant and postimplant open-set word and sentence testing was completed in quiet and with competing background noise for separate ear and binaural conditions. RESULTS: Fourteen of 16 subjects had improved speech perception scores across all test materials after implantation. Group means were significantly higher for all test materials. Results in the bimodal-bilateral condition were significantly higher than implant alone for open-set word tests (scored for phonemes) and open-set sentences in quiet. CONCLUSION: The results of this study suggest that, with appropriate counseling and management, some children with significant residual hearing benefit from cochlear implantation, in particular improved speech understanding due to bimodal-bilateral hearing.

Adolescent↗

PubMed2002

Speech perception outcomes in older children who use multichannel cochlear implants: older is not always poorer.

Speech perception outcomes for early-deafened children who undergo implantation as teenagers or young adults are generally reported to be poorer than results for young children. It is important to provide appropriate expectations when counseling adolescents and their families to help them make an informed choice regarding cochlear implant surgery. The considerable variation of results in this group makes this process more difficult. This study considered a number of factors in a group of 25 children who underwent implantation in Melbourne between the ages of 8 and 18 years. Each subject completed open-set speech perception testing with Bamford-Kowal-Bench sentences before and after implantation and preoperative language testing with the Peabody Picture Vocabulary Test. Data were collected regarding the type of hearing loss, age at implantation, age at hearing aid fitting, audiometric details, and preoperative and postoperative communication mode. Results were submitted to a stepwise multiple linear regression analysis with postoperative open-set sentence scores as the dependent variables. The analysis suggested that 3 factors have a significant predictive value for speech perception after implantation: preoperative open-set sentence score, duration of profound hearing loss, and equivalent language age. These 3 factors accounted for 66% of the variance in this group. The results of this study suggest that children who have useful speech perception before implantation, and higher age-equivalent scores on language measures, would be expected to do well with a cochlear implant. Consistent with other studies, a shorter duration of profound hearing loss is also advantageous. The mean sentence score for this group, 47%, was not significantly different from the mean result across all children in the Melbourne program.

Adolescent↗

PubMed2002

The auditory steady-state response: comparisons with the auditory brainstem response.

Two studies are reported in which the threshold estimates from auditory steady-state response (ASSR) tests are compared to those of click- or toneburst-evoked auditory brainstem responses (ABRs). The first, a retrospective review of 51 cases, demonstrated that both the click-evoked ABR and the ASSR threshold estimates in infants and children could be used to predict the pure-tone threshold. The second, a prospective study of normal-hearing adults, provided evidence that the toneburst-evoked ABR and the modulated tone-evoked ASSR thresholds were similar when both were detected with an automatic detection algorithm and that threshold estimates varied with frequency, stimulus rate, and detection method. The lowest thresholds were obtained with visual detection of the ABR. The studies illustrate that ASSRs can be used to estimate pure-tone threshold in infants and children at risk for hearing loss and also in normal-hearing adults.

Adult↗