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PubMed1996

[Indications for middle ear obliteration within the scope of cochlear implant management].

BACKGROUND: Cochlear implants have gained worldwide acceptance as a reliable method of rehabilitation of profoundly hearing-impaired patients. Due to thorough patient selection major postoperative complications rarely occur and are flap related in most cases. Deafness can develop during chronic suppurative otitis media, either coincidentally or secondary to the medical treatment; normally this condition is regarded as a contraindication for cochlear implantation. In cases with a mastoid cavity after surgical treatment for cholesteatoma, the electrode covered only by the epithelial lining will likely become exposed or extruded. Therefore we suggest the obliteration of the middle ear cleft with abdominal fat and the blindsac closure of the external ear canal before cochlear implantation in these conditions. PATIENTS: The average age of our 12 patients was 48 years, whereas the youngest was 2 1/2 years of age. Due to chronic inflammatory ear disease. 11 patients had a mastoid cavity on both ears. Eight patients had a cholesteatoma, the chronic bone destroying process in the temporal bone of two female patients was considered as a fibroinflammatory pseudotumor. The child had a congenital deafness in both ears with a Mondini dysplasia in CT scan. She had already developed two episodes of pneumococcal meningitis which was caused by a defect in the stapes footplate through which a liquor-filled cystic sac herniated in the middle ear. Because of a massive liquorrhoea after opening of the sac, we decided to obliterate the middle ear cleft after successful insertion of the electrode array. RESULTS: All active electrodes of 10 Nucleus implants (Cochlear) and two Clarion devices (Advanced Bionics Corp.) were successfully inserted in the cochlea of the 12 patients. After an average follow-up of 15 months, a temporary facial palsy in one patient and an insufficient closure of a retroauricular fistula over the mastoid cavity in two cases were observed as postoperative complications. One patient with a fibroinflammatory pseudotumor developed a massive inflammatory reaction in the implanted ear two months after cochlear implantation, which could not be controlled by conservative treatment. The implant had to be removed and local conditions settled after administration of immunosuppressive treatment with cyclophosphamide. The patient received a new implant seven months ago. CONCLUSIONS: Implantation of a foreign body in a potentially infected space which communicates intracranially means a surgical challenge which can be managed by obliteration of the middle ear after subtotal petrosectomy with abdominal wall fat combined with a reliable closure of the external ear canal. In case of massive inflammation we would prefer a two-stage procedure.

Adipose Tissue↗
PubMed2006

Four years' experience with the minimally invasive surgical approach in cochlear implant surgery.

This is a prospective study on 808 profoundly or totally deaf patients who underwent either unilateral or bilateral cochlear implantation, involving a minimally invasive surgical approach, at the Medical University of Hannover's Department of Otolaryngology between May 2001 and May 2005. Advanced Bionics, Cochlear and MED-EL devices were used, the latter having been in use at our department since the beginning of 2003. The aim of our investigation was to determine the optimal surgical technique, evaluate safety aspects and gauge patient satisfaction with this minimally invasive surgical approach during cochlear implantation. Surgical technique is analysed. Complications such as skin flap problems did not occur. The use of this minimally invasive surgical technique did not increase the surgical risk. This procedure proved both cosmetically and psychologically beneficial for patients, especially for children and their parents.

Adult↗
PubMed1996

Initial independent results with the Clarion cochlear implant.

OBJECTIVE: This paper reports some preliminary findings from patients, implanted at the University of Iowa, using the Advanced Bionics Clarion cochlear implant (version 1.0). We compared the performance of patients using both simultaneous analog and nonsimultaneous pulsatile processing strategies. The performance of Clarion patients was also compared with a group of patients who were using either the feature-extraction Nucleus cochlear implant or the compressed-analog Ineraid cochlear implant. DESIGN: One aim was to compare the analog and pulsatile stimulation in 19 patients using the Clarion implant. This aim could be accomplished only partially because of difficulties encountered in adequately fitting patients with the analog strategy. A second aim was to compare the Clarion users' performance with feature-extraction Nucleus and compressed-analog Ineraid patients. Comparisons were made with all patients having 9 mo experience postimplantation. RESULTS: Subjects performed better using the pulsatile mode compared with the analog mode. All subjects chose to use the pulsatile strategy after the first 3 mo of the study. Results comparing performance at 9 mo with our compressed-analog Ineraid and feature-extraction Nucleus patients indicated, in general, better average performance for the Clarion users. CONCLUSIONS: We conclude that the pulsatile version of the Clarion cochlear implant typically produces superior performance to the analog version of that device at this stage in its development. After 9 mo of experience, users of the Clarion implant are performing better than are users of the feature-extraction Nucleus and compressed-analog Ineraid cochlear implants with comparable amounts of experience.

Adult↗
PubMed1998

Stability of the cochlear implant array in children.

OBJECTIVE: To determine cochlear implant electrode stability in the young patient. Electrode migration due to future skull growth was a concern that led to prohibiting implantation in children less than 2 years of age. Recently, the high level of performance achieved by young implantees has led to a re-evaluation of this lower age limit, requiring an assessment of the effects of skull growth over time. STUDY DESIGN: Prospective radiographic analysis of electrode position of cochlear implants in young children. METHODS: Twenty-seven children implanted with the Nucleus (Cochlear Corp., Denver, CO) or Clarion (Advanced Bionics Inc., Sylmar, CA) multi-channel cochlear prostheses were subjects for this study. Follow-up radiographic studies were obtained for a period of 1 month to 5 years after implantation. The age at time of implantation ranged from 14 months to 5 years. An intraoperative modified Stenver's view plain radiograph was obtained as a baseline. After implantation, on a yearly basis transorbital Stenver's and base views were obtained for comparative purposes. Additional radiographs were obtained whenever a change in performance or electrode map caused suspicion for extrusion. Electrode position was determined using a computer graphics enhancement technique whereby image contrast filters enhanced the visibility of the electrode array and surrounding bony structures. RESULTS: An analysis of the data revealed no migration of the electrode array over time. CONCLUSIONS: The confirmation of the stability of the electrode array alleviates the concern of the effects of skull growth on cochlear implantation in young children.

Child, Preschool↗
PubMed2001

Cochlear reimplantation: surgical techniques and functional results.

OBJECTIVES/HYPOTHESIS: The most common indication for cochlear reimplantation is device failure. Other, less frequent indications consist of "upgrades" (e.g., single to multichannel), infection, and flap breakdown. Although the percentage of failures has decreased over time, an occasional patient requires reimplantation because of device malfunction. The varying designs of internal receiver/stimulators and electrode arrays mandate an examination of the nature and effects of reimplantation for the individual designs. The purpose of the current study was to investigate the reimplantation of several implant designs and to determine whether differences in surgical technique, anatomical findings, and postoperative performance exist. STUDY DESIGN: Retrospective chart review. METHODS: The subjects were 33 of 618 severely to profoundly deaf adults and children who had implantation at the New York University Medical Center (New York, NY) between February 1984 and December 2000. The subjects had previously had implantation with either a single-channel 3M/House (House Ear Institute, Los Angeles, CA) or 3M/Vienna (Technical University of Vienna, Vienna, Austria) device or with one of the multichannel Clarion (Advanced Bionics, Sylmar, CA), Ineraid (Smith & Nephew Richards, TN), or Nucleus (including the Contour) devices (Cochlear Corp., Englewood, CO) before reimplantation. RESULTS: Length of use before reimplantation ranged from 1 month to 13 years and included traumatic and atraumatic (electronic) failures, as well as device extrusion or infection. Results indicated that postoperative performance was either equal to or better than scores before failure. None of the devices explanted caused damage that precluded the implantation of the same or an upgraded device. These findings support the efficacy and safety of internal implant designs as related to the maintenance of a functional cochlea for the purpose of reimplantation. CONCLUSIONS: Cochlear reimplantation can be performed safely and without decrement to performance. The number of implanted electrodes at reinsertion were either the same or greater in all cases.

Adult↗
PubMed2002

Cochlear implantation with large vestibular aqueduct syndrome.

OBJECTIVES: In this investigation, we report the outcomes of 14 adults (age >18 y) and 9 children (age <18 y) with radiographically proven large vestibular aqueduct syndrome (LVAS) who received cochlear implants at Indiana University School of Medicine. STUDY DESIGN: This is a retrospective case-control study detailing the outcomes of 23 patients with LVAS and 46 control patients implanted with Nucleus (Cochlear Corp., Englewood, CO), Clarion (Advanced Bionics Corp., Sylmar, CA), or Med-El (MED-EL Corp., Innsbruck, Austria) cochlear implants. METHODS: Performance data on pure-tone averages, speech detection thresholds, and a variety of auditory and speech recognition tasks from these patients with LVAS were compared with performance data obtained from a matched group of 46 cochlear implant users who did not have LVAS. Specific patient characteristics used in matching included the age of the patient, the age at implant of the patient, and whether the patient was pre- or postlingually deafened. Data for the adult group was analyzed using the Student t test, and data for the pediatric patient group was compared using a chi2 test. RESULTS: The results indicated positive outcomes for both pediatric and adult groups. With both adult and pediatric groups, auditory and speech recognition performance did not differ significantly between those patients with LVAS and control subjects. CONCLUSIONS: This study adds further support for the use of cochlear implantation in patients with LVAS. Cochlear implantation is beneficial and can be offered as an eventual treatment of LVAS if hearing loss progresses to profound levels in these patients.

Audiometry↗
PubMed2002

Biophysics of cochlear implant/MRI interactions emphasizing bone biomechanical properties.

OBJECTIVE/HYPOTHESIS: The forces exerted during a 1.5-Tesla MRI evaluation on the internal magnet of a cochlear implant (CI) raise concern about the safety for CI recipients. This study determines the magnitude of force required to fracture the floor of a CI receiver bed. METHOD: Recessed CI beds were drilled to maximum uniform thinness into formalin-fixed and fresh-frozen human calvaria specimens. A Med-El stainless steel CI template mounted to the piston of an electrohydraulic testing device was used to fracture the floor of the implant beds. Force and displacement were measured as a function of time using a digital data acquisition system. RESULTS: Mean force to first failure, displacement to first failure, and minimum thickness, respectively, were: group 1 (formalin-fixed, 0.3-0.4-mm thick [n = 22]), 34.08 N (8.21-59.64 N, standard deviation [SD] 15.41 N), 1.09 mm (0.40-2.16 mm, SD 0.51 mm), 0.36 mm (0.3-0.4 mm, SD 0.05 mm); group 2 (formalin-fixed, 0.5-0.9 mm thick [n = 21]), 52.82 N (20.28-135.53 N, SD 25.29 N), 1.08 mm (0.50-2.28 mm, SD 0.47 mm), 0.58 mm (0.5-0.9 mm, SD 0.12 mm); group 3 (fresh-frozen [n = 9]), 134.13 N (86.44-190.70 N, SD 34.92 N), 1.96 mm (1.47-2.46 mm, SD 0.35 mm), 0.42 mm (0.3-0.6 mm, SD 0.11 mm). CONCLUSIONS: The mean magnitude of force required to fracture the floor of a CI bed is significantly greater than those that are generated when a Med-El Combi 40+, CII Bionic Ear CI, or Nucleus Contour CI is placed into a 1.5-Tesla MRI unit.

Adult↗
PubMed2003

Comparative study of cochlear damage with three perimodiolar electrode designs.

OBJECTIVE: To describe intracochlear insertion trauma caused by three perimodiolar cochlear implant electrodes. STUDY DESIGN: Descriptive histological study of 15 human cadaver temporal bones. METHODS: Fifteen cadaver temporal bones underwent surface preparation and were implanted with one of the following perimodiolar electrode arrays: Combi 40+PM (MedEl Corporation), HiFocus II (Advanced Bionics Corporation), or Contour (Cochlear Corporation). A cryosectioning technique was used to study horizontal sections at 200 microm intervals with the electrode in place. Image-enhanced videofluoroscopy and computer-assisted morphometrics were used to assess the mechanism of insertion trauma and to determine electrode position within the modiolus. RESULTS: Histological examination revealed varying degrees of damage to the spiral ligament, basilar membrane, and osseous spiral lamina. Using a novel grading system for electrode trauma, there was no statistically significant difference among the three electrodes. A literature search of histological studies of a commonly used "standard" electrode showed damage equal to or greater than that seen in the current study. CONCLUSIONS: Insertion trauma caused by periomodiolar electrodes occurs to an acceptable degree. Refinement of electrodes based on mechanisms of trauma may be able to further reduce damage.

Basilar Membrane↗
PubMed2003

The genesis of neurosurgery and the evolution of the neurosurgical operative environment: part II--concepts for future development, 2003 and beyond.

The future development of the neurosurgical operative environment is driven principally by concurrent development in science and technology. In the new millennium, these developments are taking on a Jules Verne quality, with the ability to construct and manipulate the human organism and its surroundings at the level of atoms and molecules seemingly at hand. Thus, an examination of currents in technology advancement from the neurosurgical perspective can provide insight into the evolution of the neurosurgical operative environment. In the future, the optimal design solution for the operative environment requirements of specialized neurosurgery may take the form of composites of venues that are currently mutually distinct. Advances in microfabrication technology and laser optical manipulators are expanding the scope and role of robotics, with novel opportunities for bionic integration. Assimilation of biosensor technology into the operative environment promises to provide neurosurgeons of the future with a vastly expanded set of physiological data, which will require concurrent simplification and optimization of analysis and presentation schemes to facilitate practical usefulness. Nanotechnology derivatives are shattering the maximum limits of resolution and magnification allowed by conventional microscopes. Furthermore, quantum computing and molecular electronics promise to greatly enhance computational power, allowing the emerging reality of simulation and virtual neurosurgery for rehearsal and training purposes. Progressive minimalism is evident throughout, leading ultimately to a paradigm shift as the nanoscale is approached. At the interface between the old and new technological paradigms, issues related to integration may dictate the ultimate emergence of the products of the new paradigm. Once initiated, however, history suggests that the process of change will proceed rapidly and dramatically, with the ultimate neurosurgical operative environment of the future being far more complex in functional capacity but strikingly simple in apparent form.

Forecasting↗
PubMed2001

Comparison of pediatric Clarion recipients with and without the electrode positioner.

OBJECTIVE: To compare surgical experience and measures of electrode and patient performance of children who were implanted with the Clarion (Advanced Bionics, Sylmar, CA, U.S.A.) device with and without the new electrode positioner (EP). STUDY DESIGN: Prospectively and retrospectively collected data were compared between two independent groups. SETTING: Tertiary care children's hospital. PATIENTS: Twenty-four children (mean age, 3.0 years) implanted during the original Food and Drug Administration (FDA) clinical trial required for commercial approval of the Clarion and 15 children (mean age, 3.4 years) implanted with the EP as part of an ongoing FDA trial. INTERVENTION: Cochlear implant with and without EP. MAIN OUTCOME MEASURES: Electrical psychophysical threshold, most comfortable loudness level (MCL), electrode impedance, and speech perception measures were compared at 3 and 6 months after initial stimulation. RESULTS AND CONCLUSION: All children had complete insertion of electrodes. No difficulty inserting the EP occurred nor did subsequent related complications. Subjects with the EP had significantly lower threshold and MCL levels. Electrode impedance declined on stimulated electrodes in both groups. Meaningful Auditory Integration Scale scores significantly improved in both groups; the EP group appeared to receive as much benefit as the non-EP group.

Auditory Threshold↗
PubMed2001

Adult cochlear implant patient performance with evolving electrode technology.

OBJECTIVE: In 1998, clinical trials were initiated to evaluate the CLARION Multi-Strategy Cochlear Implant (Advanced Bionics Corp., Sylmar, CA, U.S.A.), a precurved electrode with an electrode positioning system (EPS) in adults with severe to profound hearing impairments. In 1999, clinical trials were initiated to assess the CLARION HiFocus electrode with EPS in a similar group of adults. The purpose of this retrospective study was to evaluate and compare the preoperative and 1-, 3-, and 6-month postoperative speech perception scores obtained by the first 56 patients implanted with the precurved electrode with EPS and the first 56 patients implanted with the HiFocus electrode with EPS. Speech strategy preferences were additionally noted and compared at each test interval for each group. STUDY DESIGN: All subjects participated in preoperative testing with hearing aids and postoperative (1, 3 and 6 months) testing with either the precurved electrode with EPS or the HiFocus electrode with EPS. Demographic characteristics and preoperative and postoperative speech perception results were compared within and between the 2 groups. SETTING: Data presented here were collected at cochlear implant programs affiliated with tertiary medical centers located in the United States and Canada that participated in the clinical trials. PATIENTS: Patients were postlinguistically deafened adults who received a CLARION cochlear implant. RESULTS AND CONCLUSION: Within-group evaluations revealed that both groups demonstrated significant improvements on all speech perception measures when 1-month postoperative scores were compared with scores obtained preoperatively with hearing aids. Between-group comparison of demographic data showed that the HiFocus group had a significantly higher mean age at implant and a significantly longer mean duration of deafness than the precurved electrode with EPS group. Statistical comparison of mean speech perception scores showed no significant difference between subjects using the precurved electrode with EPS versus the HiFocus electrode with EPS at the preoperative, 1-, and 3-month test intervals. At the 6-month test interval, the mean CNC Monosyllabic Word Test score obtained by the HiFocus with EPS group was significantly better than the mean score obtained by the group with the precurved electrode with EPS (p < 0.05).

Audiometry↗
PubMed2004

Histologic evaluation of the tissue seal and biologic response around cochlear implant electrodes in the human.

HYPOTHESIS: Histopathologic study of the tissue seal and biologic response around cochlear implant electrodes in patients who had received a cochlear implant during life could provide clues concerning the pathogenesis of meningitis after cochlear implantation. BACKGROUND: Bacterial meningitis has been reported as an infrequent complication of cochlear implantation using a variety of electrode designs. The cause of meningitis in cochlear implant recipients has not been firmly established. In an analogous surgical situation, namely stapedectomy, delayed meningitis could occur as a complication of ipsilateral acute suppurative otitis media in which there was open communication between the middle ear and perilymph. METHODS: Twenty-one temporal bones from 20 individuals who had undergone cochlear implantation during life were studied by light microscopy. All sections passing through the cochleostomy site and electrode track were examined to evaluate the tissue seal at the cochleostomy, the presence or absence of an extracochlear electrode sheath, and finally, to seek evidence of a cellular inflammatory response near the electrode. These data were compared with clinical data, including electrode system used, the number of years between implantation and death, type of tissue used at surgery, and the age and sex of the patients. RESULTS: The 21 specimens included cases implanted with the Symbion Ineraid, Cochlear Corporation Nucleus 22-channel, Cochlear Corporation Nucleus 24-channel, a Cochlear Corporation Nucleus single channel, and Advanced Bionics Clarion C1 devices. At the cochleostomy site, and just within the cochlea, there was a robust fibrous and bony tissue response in all 21 ears and in most cases, there was a fibrous sheath surrounding the electrode in the middle ear. No recognizable open communication or potential communication between the middle ear and the inner ear was seen in any of the 21 ears. An inflammatory cellular response, including mononuclear leukocytes, histiocytes, and foreign body giant cells, were present in 12 of the 21 temporal bones (57%) and was most intense at the cochleostomy site. No statistically significant relationship was found between the presence or absence of inflammatory cells and the type of tissue graft used at surgery. CONCLUSIONS: The histologic evidence presented in this study does not support open communication between the middle and the inner ear as part of the pathogenesis of bacterial meningitis as a late complication after cochlear implantation. Rather, the finding of a cellular inflammatory response in 12 of 21 temporal bones suggests that late hematogenous contamination and colonization of the implant is a much more likely pathogenic mechanism. This putative mechanism has implications for possible strategies to prevent meningitis after cochlear implantation.

Aged↗
PubMed2004

Labyrinth dysfunction 8 months after cochlear implantation: a case report.

OBJECTIVE: Investigate whether the cochleostomy is a possible port of entry for pneumolabyrinth and a resulting vertigo in patients provided with a cochlear implant. STUDY DESIGN: Retrospective case review. SETTING: Ludwig-Maximilians University of Munich, Hospital Grosshadern. PATIENT: 62-year-old patient who underwent implantation of a HiFocus II cochlear implant with positioner from Advanced Bionics (CLARION). Eight months postoperatively, the patient reported rotatory vertigo and right-side tinnitus after he had blown his nose harder than usual during an episode of rhinitis. INTERVENTIONS: Preoperative and postoperative testing of both the petrosal bone with a CT scan and of balance function. MAIN OUTCOME MEASURE: Air inclusion in the labyrinth. RESULTS: In contrast to the preoperative high resolution computed tomography (CT) scan, air inclusion was seen in the labyrinth during the episode of vertigo. At the same time, balance function tests with Frenzel glasses revealed both spontaneous and provoked horizontal nystagmus to the right side. At follow-up 8 weeks later, the level of vertigo had significantly decreased. Twelve months later, the control CT showed the cochlear implant positioned correctly and no visible air in the labyrinth. CONCLUSION: It is known that placement of the HiFocus II with Positioner from CLARION requires a relatively large cochleostomy of 1.5 mm. Moreover, in the connective tissue seal between the electrode and the positioner, the latter reaches into the tympanic cavity, and this is possibly the weak point. Further investigation will be needed to determine whether the large cochleostomy with the HiFocus II with positioner increases the predisposition to labyrinth dysfunction.

Cochlear Implantation↗
PubMed2005

Speech perception with mono- and quadrupolar electrode configurations: a crossover study.

OBJECTIVE: To study the effect of two multipolar electrode configurations on speech perception, pitch perception, and the intracochlear electrical field. STUDY DESIGN: Crossover design; within subject. SETTING: Tertiary referral center. PATIENTS: Eight experienced adult cochlear implant users. INTERVENTION: Each subject used each of three experimental processors for 3 weeks. The following processors were compared that differed only in electrode configuration: 1) monopolar; 2) hybrid quadrupolar, in which half of the current returned to the extracochlear reference electrode and half to two electrodes immediately to the left and right of the active electrode; and 3) flat tripolar +2, which directed all the current to four reference electrodes (two on each side), separated from the active electrode by two inactive electrodes. All the processors used the standard Advanced Bionics HiRes speech-processing strategy, 12 channels, 1,220 pulses per second per channel, and with a pulse width of 33 (micros/phase). RESULTS: The monopolar processors had the largest stimulation efficiency and the smallest dynamic range in linear current units. The reverse was true of flat tripolar +2 processor, whereas the hybrid quadrupolar processor fell in between. Insufficient loudness growth prevented the use of the flat tripolar +2 processor in three subjects. Word recognition did not differ between the clinically used 16-channel monopolar processor and the experimental monopolar processor, regardless of the differences in the number of channels, pulse rate, and duration of experience. Word recognition with the flat tripolar +2 processor was significantly poorer than with the monopolar and hybrid quadrupolar processors; monopolar and quadrupolar processors did not differ. There was no significant interaction between processor type and competing noise type (stationary or fluctuating), but performance at the higher level of fluctuating noise was best with the hybrid quadrupolar processor in almost all the subjects. Pitch scaling showed ceiling performance in five subjects and differed between processors in the two other subjects with imperfect tonotopy. Intracochlear current spread was considerable with the monopolar configuration; it was reduced with the hybrid quadrupolar configuration and virtually absent beyond the active electrodes with the tripolar configuration. CONCLUSION: More confined configurations reduced the longitudinal width of the electrical field, which was expected to enhance channel separation, but no improvement in word recognition was found. More research is needed to test confined configurations that have enhanced efficiency and to evaluate the fundamental effects of configuration on channel discriminability.

Acoustic Stimulation↗
PubMed2005

Facial nerve stimulation after cochlear implantation.

OBJECTIVES: This study was designed to compare the incidence and nature of facial nerve stimulation (FNS) in patients receiving cochlear implants (CI) manufactured by Cochlear Corporation, Advanced Bionics Corporation, and MedEl. STUDY DESIGN: Retrospective chart review at a tertiary referral center. METHODS: The charts of 600 patients who received CIs from 1993 to 2003 with at least 1 year of follow-up were reviewed for significant FNS (FNS on at least 1 channel at functional stimulation levels). Data collected included age, sex, etiology of deafness, device type, electrode, FNS onset after initial stimulation, number and location of electrode contacts causing FNS, and loudness level at which FSN occurred. Nucleus straight and perimodiolar electrodes were also compared. RESULTS: Thirty-nine of 600 (6.5%) patients had FNS on at least one channel, (MedEl 3 of 43 [7.0%], Nucleus 29 of 440 [6.6%], and Clarion 7 of 117 [6.0%]). The incidence of FNS in Nucleus perimodiolar electrodes (16 of 250 [6.4%]) was similar to straight electrodes (13 of 190 (6.8%]), as was the mean number of electrodes causing FNS per patient (11 vs. 12). However, straight electrodes caused stimulation at significantly softer perceived loudness levels than perimodiolar electrodes (P < .0001). CONCLUSIONS: In this large series of CI FNS, the overall incidence of FNS is consistent with previous reports. All devices had a similar incidence of FNS, but perimodiolar electrodes produced FNS only at significantly higher loudness levels than straight electrodes, making them preferable for patients at risk for FNS receiving Nucleus devices.

Adolescent↗
PubMed2006

Biomechanical characterization of needle piercing into peripheral nervous tissue.

Several neural interfaces have been developed to control neuroprostheses and hybrid bionic systems. Among them, intraneural electrodes are very promising because they represent an interesting trade-off between the needs for high selectivity and for reduced invasiveness. However, in most of the cases, no particular attention has been devoted so far to the design of these systems starting from the mechanical properties of the system to be interfaced. The aim of this paper was to study and characterize in a quantitative way the piercing of peripheral nervous tissue in order to gather useful information to design intraneural interfaces able to reduce (as much as possible) the damages provoked by this task. In particular, attention has been paid to determine the values of force and pressure to carry out the piercing task in different velocity conditions. From the experimental data it was possible to characterize indirectly the tissue sinking under the needle tip. For each experimental velocity (ranging from 1 to 2000 mm/min) a threshold, under which the tissue cannot be pierced, has been calculated. The force magnitude required for piercing was shown to be in the range 0.3-25 mN for the different velocities. Moreover, differences between piercing carried out at very low velocity (multi-piercing) and at low velocity (mono-piercing) have been characterized and correlated with the physical characteristics of the nervous tissue. Experimental data have been integrated with a theoretical analysis of the neural interfaces piercing structures. The problem of buckling, representing for these structures the main cause of tissue piercing impossibility, has been analyzed. The nonlinear theoretical model allows to compare different needle geometries and materials with regard to piercing possibility at different velocities. Moreover, an optimization of piercing elements geometry with regard to amount of used material and space has been provided.

Animals↗
PubMed2006

Limits of capacity for the exchange of information in the human nervous system.

An approximation to the maximum capacity of exchange of information in the central nervous system of the human body is carried out. The maximum possible quantity in bits per second that the brain possibly exchanges with the rest of the body is sought for. This value could be useful for the designing of bionic systems, the analysis of the operation of the brain and consciousness, as well as the designing of future communication systems.

Brain↗
PubMed2005

Reliability of signals from a chronically implanted, silicon-based electrode array in non-human primate primary motor cortex.

Multiple-electrode arrays are valuable both as a research tool and as a sensor for neuromotor prosthetic devices, which could potentially restore voluntary motion and functional independence to paralyzed humans. Long-term array reliability is an important requirement for these applications. Here, we demonstrate the reliability of a regular array of 100 microelectrodes to obtain neural recordings from primary motor cortex (MI) of monkeys for at least three months and up to 1.5 years. We implanted Bionic (Cyberkinetics, Inc., Foxboro, MA) silicon probe arrays in MI of three Macaque monkeys. Neural signals were recorded during performance of an eight-direction, push-button task. Recording reliability was evaluated for 18, 35, or 51 sessions distributed over 83, 179, and 569 days after implantation, respectively, using qualitative and quantitative measures. A four-point signal quality scale was defined based on the waveform amplitude relative to noise. A single observer applied this scale to score signal quality for each electrode. A mean of 120 (+/- 17.6 SD), 146 (+/- 7.3), and 119 (+/- 16.9) neural-like waveforms were observed from 65-85 electrodes across subjects for all recording sessions of which over 80% were of high quality. Quantitative measures demonstrated that waveforms had signal-to-noise ratio (SNR) up to 20 with maximum peak-to-peak amplitude of over 1200 microv with a mean SNR of 4.8 for signals ranked as high quality. Mean signal quality did not change over the duration of the evaluation period (slope 0.001, 0.0068 and 0.03; NS). By contrast, neural waveform shape varied between, but not within days in all animals, suggesting a shifting population of recorded neurons over time. Arm-movement related modulation was common and 66% of all recorded neurons were tuned to reach direction. The ability for the array to record neural signals from parietal cortex was also established. These results demonstrate that neural recordings that can provide movement related signals for neural prostheses, as well as for fundamental research applications, can be reliably obtained for long time periods using a monolithic microelectrode array in primate MI and potentially from other cortical areas as well.

Action Potentials↗