Biomedical subjects

A Quentin Summerfield

Publications and source records attributed to A Quentin Summerfield.

6 recordsLinked to original sources

PubMed2003

Health-service costs of pediatric cochlear implantation: multi-center analysis.

OBJECTIVE: Pediatric cochlear implantation (CI) entails surgery followed by lifetime maintenance, and hence incurs both initial and ongoing costs. Previous assessments of these costs were either undertaken early in the evolution of services, or were based on single hospitals, or estimated costs largely from hospital charges. The aim was to overcome these limitations by conducting a multi-center evaluation of the costs of providing unilateral CI to children in the United Kingdom (UK). METHODS: Annual numbers of implantations in all UK pediatric CI programs were monitored prospectively from 1991. Resource use was measured in 12 programs in 1998/1999 and retrospectively back to the year of inception of each program. The profile of outpatient and outreach visits was assessed in the 12 programs. Together these variables were used to estimate health-service costs for four phases of management: pre-operative assessment, implantation, tuning, and subsequent maintenance, using economic micro-costing methods. Costs were subsequently estimated for all children implanted in 1998/1999 (N=199) and were aggregated over 1, 15, and 73 years following implantation. To assess the robustness of cost estimates, parameter values were varied over plausible ranges and costs re-estimated. Total UK health-service costs were also estimated. All costs are presented in euros (1=US dollars 0.98= pound 0.65, 1st July 2002), inflated to 2000/2001 financial-year levels, and discounted at 6% per annum. RESULTS: Per-child average costs were 42972 (1-year), 73763 (15-years), and 95034 (73-years). Cost estimates were not overly sensitive to the value of any one cost component nor to the relative cost of outpatient and outreach visits. When these parameters were varied, costs ranged between 30000 and 47000 (1-year), 61000 and 83000 (15-years), and 82000 and 108000 (73-years). The total UK health-service cost of unilateral pediatric CI was estimated to be 14 million in 2000/2001 and is predicted to rise to 23 million in 2015/2016, if the present model of service-delivery continues. The cost of maintaining implanted children was estimated to account for 22% of the total in 2000/2001 and is predicted to rise to 63% by 2015/2016. CONCLUSIONS: Ongoing costs of maintaining implanted children and their implant systems are significant and should be factored into resource-allocation decisions.

Adolescent↗

PubMed2002

A cost-utility scenario analysis of bilateral cochlear implantation.

CONTEXT: Unilateral cochlear implantation is a cost-effective intervention for profound bilateral hearing loss. There is worldwide interest in providing implants bilaterally. OBJECTIVE: To use modeling to estimate the cost of gaining a quality-adjusted life-year by providing implants to both ears of profoundly postlingually deafened adults. DESIGN: Economic scenario analysis relating the costs of providing implants to estimates of the gain in health-related quality of life (utility) from unilateral and bilateral implantation. SETTING: Fourteen hospitals in the United Kingdom National Health Service and 1 Medical Research Council research unit. PARTICIPANTS: Normal-hearing adult volunteers with knowledge of implantation (n = 70). Adults undergoing unilateral implantation who either did not benefit from acoustic hearing aids preoperatively (type 1, n = 87) or benefited marginally (type 2, n = 115). MAIN OUTCOME MEASURES: Changes in utility from unilateral and bilateral implantation estimated with the time trade-off technique (volunteers) and from unilateral implantation measured with the Mark II Health Utilities Index (patients); costs of providing implants and sustaining patients who have undergone implantation (health care perspective). RESULTS: Gains in utility from unilateral implantation estimated by volunteers did not differ significantly from gains recorded by patients, giving credibility to the volunteers' estimate of the gain from bilateral compared with unilateral implantation. Cost-utility ratios, in pounds sterling per quality-adjusted life-year, based on volunteers' estimates, were pound 16,774 (type 1: unilateral implantation vs no intervention), pound 27,401 (type 2: unilateral implantation vs management with hearing aids), pound 61,734 (simultaneous bilateral implantation vs unilateral implantation), and pound 68,916 (provision of an additional implant vs no additional intervention). CONCLUSION: More quality of life is likely to be gained per unit of expenditure on unilateral implantation than bilateral implantation.

Adult↗

PubMed2002

Microelectrode and neuroimaging studies of central auditory function.

Imaging studies in humans are revealing parallels with the functional organisation of the auditory brain discovered in microelectrode studies in animals: the rate of amplitude modulation generating the strongest response declines systematically from the lower brain stem to the cortex; an increase in sound level induces a higher level and a greater extent of activity; spectra are represented tonotopically in multiple cortical areas. There are also differences: evidence of organisation reflecting the sound level of the stimulus is absent in animals, but has been found in humans. Additionally, imaging has revealed functional specialisations which have not (yet) been located in animals: areas that respond more strongly to sounds with stronger pitches and to sounds that move in space. Microelectrode studies suggest that vocalisations are represented by spatially distributed populations of neurones in secondary auditory areas. In humans, likewise, activation progressively more specific to speech is found as the search moves from primary to secondary to accessory areas.

Animals↗

PubMed2002

Spectral and temporal processing in human auditory cortex.

Hierarchical processing suggests that spectrally and temporally complex stimuli will evoke more activation than do simple stimuli, particularly in non-primary auditory fields. This hypothesis was tested using two tones, a single frequency tone and a harmonic tone, that were either static or frequency modulated to create four stimuli. We interpret the location of differences in activation by drawing comparisons between fMRI and human cytoarchitectonic data, reported in the same brain space. Harmonic tones produced more activation than single tones in right Heschl's gyrus (HG) and bilaterally in the lateral supratemporal plane (STP). Activation was also greater to frequency-modulated tones than to static tones in these areas, plus in left HG and bilaterally in an anterolateral part of the STP and the superior temporal sulcus. An elevated response magnitude to both frequency-modulated tones was found in the lateral portion of the primary area, and putatively in three surrounding non-primary regions on the lateral STP (one anterior and two posterior to HG). A focal site on the posterolateral STP showed an especially high response to the frequency-modulated harmonic tone. Our data highlight the involvement of both primary and lateral non-primary auditory regions.

Acoustic Stimulation↗

PubMed2002

Use of vocalic information in the identification of /s/ and /sh/ by children with cochlear implants.

OBJECTIVE: When a syllable such as "sea" or "she" is spoken, listeners with normal hearing extract evidence of the fricative consonant from both the fricative noise and the following vocalic segment. If the fricative noise is made ambiguous, listeners may still perceive "s" or "sh" categorically, depending on information in the vocalic segment. Do children whose auditory experience comes from electrical stimulation also display this effect, in which a subsequent segment of speech disambiguates an earlier segment? DESIGN: Unambiguous vowels were appended to ambiguous fricative noises to form tokens of the words "she," "sea," "shoe," and "Sue." A four-choice identification test was undertaken by children with normal hearing (N = 29), prelingually deaf children with the Nucleus Spectra-22 implant system using the SPEAK coding strategy (N = 13), postlingually deafened adults with the same implant system (N = 26), and adults with normal hearing (N = 10). The last group undertook the test before and after the stimuli were processed to simulate the transformations introduced by the SPEAK coding strategy. RESULTS: All four groups made use of vocalic information. Simulated processing reduced the use made by normal-hearing adults. Implanted subjects made less use than the other groups, with no significant difference between implanted children and implanted adults. The highest levels of use by implanted subjects were within one standard deviation of the mean level displayed when normal-hearing adults listened to processed stimuli. Analyses showed that the SPEAK strategy distorted formant contours in the vocalic segments of the stimuli in ways that are compatible with the errors of identification made by implanted subjects. CONCLUSIONS: Some children with implants can extract information from a following vowel to disambiguate a preceding fricative noise. The upper limit on this ability may be set by distortions introduced by the implant processor, rather than by the auditory experience of the child.

Adult↗

PubMed2002

Epidemiology of the UK population of hearing-impaired children, including characteristics of those with and without cochlear implants--audiology, aetiology, comorbidity and affluence.

This study reports epidemiological data for 17,160 children with permanent bilateral hearing impairment >40 dB in the UK in the birth cohorts 1980-95 inclusive. Children were uniquely ascertained from notifications from professionals in health and education. Results indicate a changing aetiological profile over birth cohort. The percentage of unknown aetiologies and those of prenatal or postnatal origin have decreased, while syndromal and perinatal aetiologies have increased, with no change in genetic aetiologies. Nearly 30% of hearing-impaired children have another disability in addition to their hearing impairment. Children with cochlear implants are more likely than other profoundly impaired children to have a postnatal aetiology and less likely to have disabilities concerned with learning or cognition. A proxy measure of affluence indicates that significantly more profoundly impaired children in more affluent families receive cochlear implants than do those in less affluent families. These findings provide baseline data for the UK population and raise questions of widespread relevance for future research.

Audiometry, Pure-Tone↗