Perimodiolar Arrays Research Articles

Comparison of speech perception performance between the nucleus 24 and nucleus 24 contour cochlear implant systems

Objective—To compare the 1-, 3-, and 6-month postoperative speech perception scores obtained by a group of subjects who received the new perimodiolar array (Nucleus Contour) cochlear implant with those obtained by a group of subjects implanted with the straight electrodes of the previous-generation Nucleus 24 device.Material and Methods—The speech performance of 10 postlingually deafened adults implanted with the Nucleus Contour device was compared with that of matched controls who received the Nucleus 24 model. Objective measures included word and sentence speech recognition scores.Results—Patients implanted with the Nucleus Contour device obtained significantly higher word and sentence recognition scores after short-term use of the implant compared to those obtained by patients implanted with the Nucleus 24 model.Conclusion—Further long-term studies are required to determine whether the Nucleus Contour CI recipients continue to improve over time.

Comparison of psychophysical and T-NRT levels in children using N24 Contour™ vs. children using N24 M or K. Phonemic development

Objective To compare intraoperative T-NRT (neural response telemetry) using perimodiolar Nucleus 24 Contour™ Cochlear Implant (C.I.) with the ones obtained using straight Nucleus 24 M or K. To compare the levels T (threshold) and C (comfort) in the psychofisic measurements made at the first fitting and 3 months later. To determine differences in phonological development. Study design Retrospective, observational, descriptive. Statistical analysis: Student t-test. A sample of 22 children was taken: Intrasurgical T-NRT was obtained by visual technique. The stimulus electrodes were 15, 10 and 5. T and C levels were obtained using the SPEAK strategy. Analysis of phoneme accuracy was obtained at 12 and 24 months of C.I. use in children under 6 years old. Results For the perimodiolar group T-NRT was obtained between 6 and 13 levels below the obtained for the group with straight electrode. For the selected electrodes, T and C level at the first fitting was obtained between 10 and 18 levels below and 3 months later the C levels remain 10 units below the one obtained with straight electrode. These group had higher growth rate of phonemes recognition at 24 months of C.I. use. Conclusions Intrasurgical T-NRT was obtained with smaller level of stimulation using perimodiolar electrode than using straight electrode ( p<0.05) The T and C level at the first fitting and after 3 months later were smaller for the perimodiolar group in relation to the straight group ( p<0.05). The dynamic range was similar in both groups. The development of higher growth rate of phoneme recognition was found in young children using perimodiolar array at 24 months of C.I. use; being necessary to carry out this analysis in a bigger population.

Cochlear implants in children: safety as well as speech and language

The development of cochlear implants for children at the University of Melbourne and the Bionic Ear Institute, has consisted of a routine of biological and engineering safety followed by evaluation of speech processing strategies on adults before they are undertaken on children. The initial safety studies were to ensure that insertion was atraumatic, the electrical stimulus parameters did not lead to loss of ganglion cells and that the electrode could be inserted without the risk of middle ear infection leading to meningitis. The initial second formant extraction scheme was shown to produce significant open-set speech understanding in adults and was approved by the US Food and Drug Administration (FDA) in 1985. Following this, an international study was undertaken for the FDA on children using a strategy that also included the first formant, and was approved in 1990. Additional advances in speech processing have been evaluated on adults. However, before using one with high rates of stimulation, it was tested for safety on experimental animals. Further advances have been anticipated in particular through the development of a peri-modiolar array, the Nucleus Contour. Prior to its use on adults, it was tested in the human temporal bone and found to lead to minimal trauma. It was evaluated in adults and found to lead to better current localization and lower thresholds. A study was undertaken in children using a spectral maxima scheme at high rates (advanced combination encoder (ACE)) and the Contour array as it had given best results in adults. It was approved as safe and effective for use in children in 2000. Studies were also undertaken to look at plasticity and visual dominance particularly through cognitive studies and the use of the McGurk effect. This demonstrated that deaf children with implants rely heavily on visual information and there is a great need to have unambiguous auditory stimuli to get best results.

Cochlear implants in Children: safety as well as speech and language

The development of cochlear implants for children at the University of Melbourne/Bionic Ear Institute has consisted of a routine of biological and engineering safety followed by evaluation of speech processing strategies on adults before they are undertaken on children. The initial safety studies were to ensure that insertion was atraumatic, the electrical stimulus parameters did not lead to loss of ganglion cells and that the electrode could be inserted without the risk of middle ear infection leading to meningitis.The initial second formant extraction scheme was shown to produce significant open set speech understanding in adults and was approved by the U.S. Food and Drug Administration (FDA) in 1985. Following this, an international study was undertaken for the FDA on children using a strategy that also included the first formant, and was approved in 1990.Additional advances in speech processing have been evaluated on adults. However, before using one with high rates os stimulation it was tested for safety on experimental animals. Further advances have been anticipated in particular through the development of a perimodiolar array, the Nucleus “Contour.” Prior to its use on adults, it was tested in the human temporal bone and found to lead to minimal trauma. It was evaluated in adults and found to lead to better current localization and lower thresholds. A study was undertaken in children using a spectral maxima scheme at high rates (ACE) and the contour array as it had given best results in adults. It was approved as safe and effective for use in children in 2000.Studies have also been undertaken to look at plasticity and visual dominance particularly through cognitive studies and the use of the McGurk effect. This demonstrated that deaf children with implants rely heavily on visual information and there is a great need to have unambiguous auditory stimuli to get best results.

The nucleus contour electrode array: an electrophysiological study.

Positioning intracochlear electrodes adjacent to the modiolus would lead to a reduction in threshold levels and latencies, as measured with electrically evoked auditory brainstems responses. Recently, Cochlear Corporation introduced a new perimodiolar array (Contour electrode) characterized by a platinum stylet inserted into the array's silicone carrier that keeps the electrode in a straightened configuration before insertion. After completion of the insertion, the withdrawal of the stylet allows the array to coil within the cochlea positioning electrodes closer to the modiolus. The purpose of the study was to analyze the stimulation properties of the Contour electrode by evaluating the effects of the withdrawal of the stylet on electrical auditory brainstem response (EABR) characteristics. Electrical auditory brainstem response registrations were performed intraoperatively on three electrodes (1 apical, 1 medial, 1 basal) before and after the removal of the stylet in 10 patients implanted with the Nucleus 24 Contour device. A within-patient comparison of EABR characteristics was performed. The Student test was used to assess differences in EABR measures obtained before and after the stylet removal. Mean EABR thresholds were significantly lower after the removal of the stylet than with the stylet in situ for all three electrodes tested. After the removal of the stylet, latencies of waves III and V significantly decreased, whereas amplitudes significantly increased. Reduction in EABR threshold levels and latencies as well as an increase in waves III and V amplitudes after the stylet removal all demonstrate the effectiveness of the Contour system in positioning intracochlear electrodes closer to auditory neurons.