PubMed · 10786382
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E Palacios, G Valvassori. 2000. Osteogenesis imperfecta.. https://pubmed.ncbi.nlm.nih.gov/10786382/
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OBJECTIVE: To examine the feasibility of cochlear implantation in children younger than 2 years regarding surgery and functional outcomes. DESIGN: Prospective study. SETTING: Tertiary pediatric cochlear implant center. PATIENTS: A consecutive sample of 12 children younger than 2 years at the time of cochlear implantation (8 boys and 4 girls). The cause of hearing loss was meningitis in 6 children and congenital in 6. INTERVENTIONS: Multichannel cochlear implantation using the Nucleus C124M (Cochlear Co, Sydney, Australia) device. Functional outcome was assessed using the Listening Progress Profile and the Categories of Auditory Performance. MAIN OUTCOME MEASURES: Perioperative and postoperative surgical complications and functional outcome. RESULTS: Eight children had a completely patent cochlea. Four children required a 3- to 5-mm drilling to reach the scala tympani because of ossification after meningitis. Full insertion was achieved in 11 patients; the other child received 18 electrodes. One patient had temporary facial nerve weakness; 2 others had wound edema and serous discharge that resolved with conservative management. In the longer term, 1 child experienced a single episode of acute otitis media; another had recurrent episodes of otitis media. Mean Listening Progress Profile scores increased from 1 to 42 and median Categories of Auditory Performance scores increased from 0 to 5 at 2 years postsurgery. Comparison with the scores in the 2- to 5-year group showed no significant differences. No significant tuning difficulties were experienced with all children. CONCLUSIONS: Cochlear implantation is feasible in children younger than 2 years without significant surgical complications or particular tuning difficulties. Functional results 2 years after implantation were as good as or better than those of children who underwent implantation between ages 2 and 5 years.
The cochlea uses active amplification to capture faint sounds. It has been proposed that the amplifier comprises a set of self-tuned critical oscillators: each hair cell contains a force-generating dynamical system that is maintained at the threshold of an oscillatory instability, or Hopf bifurcation. While the active response to a pure tone provides frequency selectivity, exquisite sensitivity, and wide dynamic range, its intrinsic nonlinearity causes tones of different frequency to interfere with one another in the cochlea. Here we determine the response to two tones, which provides a framework for understanding how the ear processes the more complex sounds of speech and music. Our calculations of two-tone suppression and the spectrum of distortion products generated by a critical oscillator accord with experimental observations of basilar membrane motion and the nervous response. We discuss how the response of a set of self-tuned oscillators, covering a range of characteristic frequencies, represents the structure of a complex sound. The frequency components of the stimulus can be inferred from the timing of neural spikes elicited by the vibrating hair cells. Passive prefiltering by the basilar membrane improves pitch discrimination by reducing interference between tones. Our analysis provides a general framework for examining the relation between the physical nature of the peripheral detection apparatus and psychophysical phenomena such as the sensation of dissonance and auditory illusions.
BACKGROUND: Deafness and handicapping sensorineural hearing impairment occur frequently in neonatal intensive care unit survivors for unknown reasons. PATIENTS AND METHODS: Hearing was tested early and repeatedly in neonatal intensive care unit patients with an auditory brainstem response (ABR) screener. The temporal bones of 15 nonsurvivors (30 ears) were fixed promptly (average, 5 hours) after death for histological evaluation. RESULTS: Among these patients, 12 failed the ABR screen bilaterally, 1 passed unilaterally, and 2 passed bilaterally. Cochlear histopathologic conditions that could contribute to hearing loss included bilateral selective outer hair cell loss in 2 patients, bilateral selective inner hair cell loss in 3 (all premature), and a combination of both outer and inner hair cell loss in 2. Other hair cell abnormalities were noted; the 2 infants who had passed the ABR screen demonstrated normal histological features. Neuronal counts were normal. CONCLUSIONS: Auditory brainstem response failure among these neonatal intensive care unit infants who died was extremely common in part owing to an unexpected histological alteration, selective inner hair cell loss among premature newborns, that should be detectable uniquely by the ABR testing method. Additional histological patterns suggest more than one cause for neonatal intensive care unit hearing loss. Hair cell loss patterns seem frequently compatible with in utero damage.