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Biomedical subjects

J K Niparko

Publications and source records attributed to J K Niparko.

At least 19 recordsLinked to original sources
PubMed2000

Intracanalicular schwannoma of the facial nerve: a manifestation of neurofibromatosis type 2.

Primary facial nerve tumors, which are relatively uncommon, can present a diagnostic dilemma based on their location and variable pattern of symptoms. Of primary cranial nerve tumors, schwannomas of the facial nerve rank third in frequency after those of the eighth and fifth cranial nerves. We report an illustrative case of an intracanalicular schwannoma associated with several central nervous system tumors, consistent with neurofibromatosis type 2. Initially assumed to be an eighth cranial nerve tumor, the schwannoma was found intraoperatively to arise from the facial nerve. Early diagnosis and treatment enabled excision of the tumor without sacrifice of the facial nerve. Facial nerve schwannomas can resemble acoustic schwannomas in their clinical presentation. Only a heightened level of clinical vigilance will point to the correct diagnosis and result in an optimal therapeutic outcome for patients with these rare tumors.

Cranial Nerve Neoplasms↗
PubMed1999

Cost-utility of the cochlear implant in adults: a meta-analysis.

OBJECTIVE: To conduct a meta-analysis of the cost-utility of the cochlear implant in adults. DATA SOURCES: MEDLINE literature search, review of article bibliographies, and consultation with experts. STUDY SELECTION: Studies that reported (1) data on adults (age > or = 18 years) with bilateral, postlingual, profound deafness; (2) a health-utility gain from cochlear implantation on a scale from 0.00 (death) to 1.00 (perfect health); (3) a cost-utility ratio in terms of dollars per quality-adjusted life-year (QALY); and (4) at least 1 conventional statistical parameter (ie, SD, 95% confidence interval [CI], or P value). DATA EXTRACTION: From each study, we extracted the number of subjects, study design, health-utility instrument used, health-utility associated with profound deafness, health-utility gain from cochlear implantation, cost-utility of cochlear implantation, and reported statistical parameters. DATA SYNTHESIS: Weighted averages were calculated using a statistical weight of 1 per variance. Pooling 9 reports (n = 619), the health-utility of profoundly deaf adults without cochlear implants was 0.54 (95% CI, 0.52-0.56). Pooling 7 studies (n = 511), the health-utility of profoundly deaf adults after cochlear implantation was 0.80 (95% CI, 0.78-0.82). This improvement of 0.26 in health-utility resulted in a cost-utility ratio of $12,787 per QALY. CONCLUSIONS: Profound deafness in adults results in a substantial health-utility loss. Over half of that loss is restored after cochlear implantation, yielding a cost-utility ratio of $12,787 per QALY. This figure compares favorably with medical and surgical interventions that are commonly covered by third-party payers in the United States today.

Adult↗
PubMed1999

A prospective study of the cost-utility of the multichannel cochlear implant.

CONTEXT: Prior clinical studies have indicated that cochlear implantation provides benefits to individuals with advanced sensorineural hearing loss who are unable to gain effective speech recognition with hearing aids. OBJECTIVE: To determine the cost per quality-adjusted life-year (QALY) for adults receiving multichannel cochlear implants. DESIGN: Prospective 12-month multicenter study using preference-based quality-of-life measures and total cost determinations, comparing profoundly hearing-impaired adult subjects with and without cochlear implants. SETTING: Hospital-based and patient-resource clinics. PATIENTS: Severely to profoundly hearing-impaired adult recipients of a cochlear implant and adults eligible for the device who had not yet received it. MAIN OUTCOME MEASURE: Clinical assessment of implant participants included medical and audiologic (speech understanding) data at the time of enrollment, 6 months, and 12 months. All participants' health-utility was assessed at the time of enrollment, 6 months, and 12 months using the Health Utility Index. One-year medical resource utilization and cost data included bills related to implants, patient diaries, charge estimates from clinical sites, and published literature. A decision model was developed to determine cost per QALY. RESULTS: Of the 84 enrolled adults, 62 (75%) completed the study. Mean health-utility scores at the time of enrollment were identical between groups. The marginal 12-month health-utility gain for implant recipients was 0.20; 90% of this improvement was achieved within 6 months. For patients with a mean 22-year life expectancy, the marginal cost per QALY was $14,670. CONCLUSIONS: Overall, multichannel cochlear implants significantly improved recipients' performance on measures of speech understanding and ratings of health-utility within 6 months of implantation. The multichannel cochlear implant yielded a very favorable cost per QALY.

Adult↗
PubMed1999

Trends in educational placement and cost-benefit considerations in children with cochlear implants.

OBJECTIVES: To study the effect of cochlear implantation on the use of educational resources by profoundly hearing-impaired children and to determine trends in educational cost vs benefit. DESIGN: Retrospective study and cost-benefit analysis. SETTING: Outpatient pediatric cochlear implant program in an academic institution (The Listening Center at Johns Hopkins University School of Medicine, Baltimore, Md), in collaboration with public schools in Maryland and surrounding states. PATIENTS OR OTHER PARTICIPANTS: School-aged children with profound prelingual hearing impairment without other clearly defined disabilities. Thirty-five children with multiple-channel cochlear prostheses and a comparison group of 10 children without implants from 'total communication' programs in the Maryland public school system. INTERVENTIONS: Multiple-channel cochlear implantation and at least 1 year of a systematic auditory skill development program at the Listening Center, compared with standard educational management of children with conventional amplification. MAIN OUTCOME MEASURES: Classroom placement and number of hours of special educational support used. RESULTS: A correlation was observed between the length of cochlear implant experience and the rate of full-time placement in mainstream classrooms (r = 0.10; P= .04). There was also a negative correlation between the length of implant experience and the number of hours of special educational support used by fully mainstreamed children (Pearson product moment correlation = -0.10; P = .03). Children with greater than 2 years of implant experience were mainstreamed at twice the rate or more of age-matched children with profound hearing loss who did not have implants. They were also placed less frequently in self-contained classrooms and used fewer hours of special education support. A cost-benefit analysis based on conservative estimates of educational expenses from kindergarten to 12th grade shows a cost savings of cochlear implantation and appropriate auditory (re)habilitation that ranges from $30000 to $200000. CONCLUSIONS: Cochlear implantation accompanied by aural (re)habilitation increases access to acoustic information of spoken language, leading to higher rates of mainstream placement in schools and lower dependence on special education support services. The cost savings that results from a decrease in the use of support services indicates an educational cost benefit of cochlear implant (re)habilitation for many children.

Adolescent↗
PubMed1999

Activity influences on neuronal connectivity within the auditory pathway.

HYPOTHESIS: Sensorineural hearing loss may be associated with altered patterns of neuronal connections within the central auditory pathway. STUDY DESIGN: The cat auditory system was used to address the relative importance of impulse traffic within the auditory nerve in maintaining central nervous system connections. METHODS: Acute, unilateral deafness was induced by tetrodotoxin intoxication of cochlear hair cells. Analysis focused on the structural patterns of contact between auditory nerve endings called end bulbs of Held and their target neurons. Specifically, end bulb morphology and target cell size within the cochlear nucleus were examined. Highly specialized synaptic contacts at this junction provide a powerful site for study. RESULTS: The principal finding was that abolished activity in the auditory nerve caused nerve endings to assume a different shape, typified by more branching and smaller terminal swellings. The new shape is one typically associated with only a subpopulation of fibers in normal-hearing cats--those exhibiting a high-threshold, low-spontaneous activity profile. This result implies that abolished activity alters patterns of nerve fiber contact with second-order neurons. Tetrodotoxin produced differential effects on subpopulations of target neurons within the brainstem and is interpretable on the basis of "weighing" synaptic inputs. Second-order neurons that receive large axosomatic inputs from their parent fiber were significantly smaller than neurons that receive small, axodendritic terminals. Thus, attenuated auditory activity may produce differential effects across the auditory pathway, thereby disrupting the normal balance of inputs into synaptic stations. CONCLUSIONS: Impulse traffic is a critical factor in the interaction between the ear and central auditory stations and appears necessary for the maintenance of key synapses. As hearing disorders with impaired comprehension may be modeled by studies of auditory deafferentation, these observations extend the possibility that changes in central neuronal connections underlie reduced capabilities for processing restored auditory input.

Animals↗
PubMed1999

Meta-analysis of pediatric cochlear implant literature.

We analyzed published reports of the effect of age at implantation and the cause of and age at onset of deafness on speech perception benefit in children with cochlear implants, and compared these results with those of unreported trials of multichannel cochlear implants. Combining data from published and unpublished patient series was constrained by differences in test protocols between studies, but was made feasible by employing a meta-analysis in which data were converted into an ordinal classification scale that represented levels of communicative benefit. Results showed that more rapid gains in speech perception are associated with earlier age at implantation, and that speech perception results are independent of cause of or age at onset of deafness after 1 year of implant use. Moreover, with minor exceptions, there was no statistical difference between published and unpublished data, thereby indicating no publication bias in the literature. A meta-analytic approach is useful because it can clarify the quality of reported data and the direction of future research and, hopefully, foster collaboration in conducting and reporting future research. A standardized approach to reporting results in children is advised in order to produce a balanced interpretation of implant benefit and to facilitate wider understanding and dissemination of study conclusions.

Age Factors↗
PubMed1998

Single unit recordings in the auditory nerve of congenitally deaf white cats: morphological correlates in the cochlea and cochlear nucleus.

It is well known that experimentally induced cochlear damage produces structural, physiological, and biochemical alterations in neurons of the cochlear nucleus. In contrast, much less is known with respect to the naturally occurring cochlear pathology presented by congenital deafness. The present study attempts to relate organ of Corti structure and auditory nerve activity to the morphology of primary synaptic endings in the cochlear nucleus of congenitally deaf white cats. Our observations reveal that the amount of sound-evoked spike activity in auditory nerve fibers influences terminal morphology and synaptic structure in the anteroventral cochlear nucleus. Some white cats had no hearing. They exhibited severely reduced spontaneous activity and no sound-evoked activity in auditory nerve fibers. They had no recognizable organ of Corti, presented >90% loss of spiral ganglion cells, and displayed marked structural abnormalities of endbulbs of Held and their synapses. Other white cats had partial hearing and possessed auditory nerve fibers with a wide range of spontaneous activity but elevated sound-evoked thresholds (60-70 dB SPL). They also exhibited obvious abnormalities in the tectorial membrane, supporting cells, and Reissner's membrane throughout the cochlear duct and had complete inner and outer hair cell loss in the base. The spatial distribution of spiral ganglion cell loss correlated with the pattern of hair cell loss. Primary neurons of hearing-impaired cats displayed structural abnormalities of their endbulbs and synapses in the cochlear nucleus which were intermediate in form compared to normal and totally deaf cats. Changes in endbulb structure appear to correspond to relative levels of deafness. These data suggest that endbulb structure is significantly influenced by sound-evoked auditory nerve activity.

Animals↗
PubMed1997

Ultrastructural analysis of primary endings in deaf white cats: morphologic alterations in endbulbs of Held.

Changes in structure and function of the auditory system can be produced by experimentally manipulating the sensory environment, and especially dramatic effects result from deprivation procedures. An alternative deprivation strategy utilizes naturally occurring lesions. The congenitally deaf white cat represents an animal model of sensory deprivation because it mimics a form of human deafness called the Scheibe deformity and permits studies of how central neurons react to early-onset cochlear degeneration. We studied the synaptic characteristics of the endbulb of Held, a prominent auditory nerve terminal in the cochlear nucleus. Endbulbs arise from the ascending branch of the auditory nerve fiber and contact the cell body of spherical bushy cells. After 6 months, endbulbs of deaf white cats exhibit alterations in structure that are clearly distinguishable from those of normal hearing cats, including a diminution in terminal branching, a reduction in synaptic vesicle density, structural abnormalities in mitochondria, thickening of the pre- and postsynaptic densities, and enlargement of synapse size. The hypertrophied membrane densities are suggestive of a compensatory response to diminished transmitter release. These data reveal that early-onset, long-term deafness produces unambiguous alterations in synaptic structure and may be relevant to rehabilitation strategies that promote aural/oral communication.

Animals↗
PubMed1997

A model of educational resource use by children with cochlear implants.

We have tracked patterns of use of educational and rehabilitative resources as part of an initial assessment of cost-benefit ratios of cochlear implants in children. Forty-two children with cochlear implants in the Listening Center at Johns Hopkins program of aural rehabilitation have served as our study cohort to develop the measures to be assessed. An educational resource matrix stratifies school setting (residential vs special education vs non-specialized "mainstream" setting) and levels of rehabilitative support (speech and language therapy and interpreter use) to map past and current use of these services. Initial cost-benefit projections based on observed advancement toward educational independence in the educational resource matrix indicate an extremely favorable net present value of the implant (cost savings minus cost). These cost-benefit projections will need to be supplemented with measures of the impact on quality of life and future educational and vocational options to determine the overall cost-effectiveness of cochlear implants in children.

Baltimore↗
PubMed1997

Cochlear nucleus cell size changes in the dalmatian: model of congenital deafness.

We assessed cellular changes in one population of neurons of the cochlear nucleus associated with a form of genetic deafness in deaf dalmatians. Spheric cells from deaf dalmatians and age-matched control (hearing) dogs were analyzed morphometrically. The somatic silhouette of these cells was reduced by 22.1% to 38.1%. The effect on cell size was greater with increased duration of deafness. Because the deaf dalmatian exhibits progressive degeneration of the auditory periphery, shrinkage of spheric cells may reflect the initial influence of attenuated activity of auditory nerve fibers, and sensorineural degeneration with longer periods of deafness.

Age Factors↗