New Clarion electrode with positioner: insertion studies.

A new straight thin electrode array (universal electrode) was designed to be used together with a positioner, which will place the electrode array at the medial wall (modiolus) of the cochlea. The study objectives were to demonstrate safety and ease of insertion, tissue trauma, electrode position, and depth for universal and standard electrodes in human temporal bones; to test functional properties in cats; and to determine the surgical procedure and electrophysiological benefits in a clinical study. The cadaver study demonstrated the ease of insertion for the universal electrode and the positioner without tissue damage. An average gain of insertion depth of 180 degrees was achieved with the positioner. Animal studies demonstrated a reduction in threshold of 6 dB for the electrical auditory brain stem response (EABR). Neither additional cochlear damage nor additional connective tissue formation was found. The intraoperative human study findings showed a marked reduction of threshold for both EABR and stapedius reflex thresholds. Impedances were increased. Plain x-rays demonstrated modiolus proximity of the electrode with the positioner. The new Clarion electrode with positioner is a relatively safe design for providing modiolus proximity. The electrophysiological benefits include reduction of threshold and power consumption.

Clinical results of the CLARION magnetless cochlear implant.

This paper reports initial results for the CLARION Multi-Strategy Cochlear Implant, presently under investigational study in Europe. A magnetless implantable cochlear stimulator (ICS) with an ear-mold-supported headpiece was designed in response to an increasing demand for a magnetic resonance imaging (MRI)-compatible cochlear implant. Surgical technique, accompanying magnetless headpiece, and MRI compatibility were evaluated in 11 deaf patients (ages 6 to 62 years) who were implanted with a magnetless Clarion implant. Because of the headset mechanics, the ICS was implanted closer behind the ear than a magnet-containing ICS. The ICS-MRI compatibility was investigated with 1.5- and 0.3-T MRI. Results showed that the surgery was relatively safe and easy to learn. The headset was stable and reliable. The MRI compatibility tests indicate that the ICS poses no contraindication for patients needing MRI. Overall, the results suggest that the Clarion magnetless cochlear implant is relatively safe and easy to implant, is MRI-compatible, and functions well with the ear-mold-supported headpiece.

Speech perception results for children implanted with the CLARION cochlear implant at the Medical University of Hannover.

The perception of speech of 167 children implanted with a CLARION Multi-Strategy Cochlear Implant (1.2 device) was evaluated preimplantation and at 3, 6, 12, 18, and 24 months postimplantation. The children were between 15 months and 15 years of age. The test materials consisted of 8 tests involving syllable structure, single- and 2-syllable words, differentiation of word pairs, and sentences. Two difficulty levels were used, depending on developmental age (<7, and 7 to 15 years). There was an improvement in test scores over time for both age groups. The younger children (particularly those under age 4) improved steadily over the first 2 years, while the older children tended to plateau between 12 and 18 months after implantation. These findings demonstrate that deaf children up to 15 years old benefit from cochlear implants. Children under 4 years of age may even have the ability to compensate for delays in speech development before they reach school age.

The influence of ionizing radiation on the CLARION 1.2 cochlear implant during radiation therapy.

OBJECTIVE: This study aimed to determine the maximum dose of radiation the CLARION 1.2 cochlear implant can withstand safely. INTRODUCTION: Cochlear implants restore functional hearing to patients with sensorineural deafness. Because some patients may need radiation therapy, it is important to investigate the influence of ionizing radiation on cochlear implant function. METHODS: This study tested the function of four CLARION 1.2 implants (Advanced Bionics, Sylmar, CA, U.S.A.) after varying radiation treatments with gamma rays. The first implant received a cumulative dosage of 69 Gy over nine treatments (single doses between 0.1-30 Gy). The second was irradiated with a total of 90 Gy, receiving three treatments of 30 Gy each. The third and fourth received doses more typical of patient therapy (i.e., 2 Gy) approximately 30 times, for a cumulative dosage of approximately 60 Gy. Implant function was tested after every treatment; the CLARION implant incorporates a back-telemetry system, allowing impedance and current output testing. RESULTS: Despite the type of treatment, the results were quite consistent: difficulties in function occurred when the cumulative dosage inside the implant was approximately 60 Gy. The first implant recovered completely and the second recovered partially. DISCUSSION: The CLARION 1.2 cochlear implant seems to safely withstand approximately 60 Gy of radiation before experiencing functional difficulties. In a clinical situation, the implant would not likely be in the target volume irradiated, and thus the patient's therapeutic cumulative dosage might be higher.

Age-related performance of human subjects on saccadic eye movement tasks.

We measured saccadic eye movements in 168 normal human subjects, ranging in age from 5 to 79 years, to determine age-related changes in saccadic task performance. Subjects were instructed to look either toward (pro-saccade task) or away from (anti-saccade task) an eccentric target under different conditions of fixation. We quantified the percentage of direction errors, the time to onset of the eye movement (saccadic reaction time: SRT), and the metrics and dynamics of the movement itself (amplitude, peak velocity, duration) for subjects in different age groups. Young children (5-8 years of age) had slow SRTs, great intra-subject variance in SRT, and the most direction errors in the anti-saccade task. Young adults (20-30 years of age) typically had the fastest SRTs and lowest intra-subject variance in SRT. Elderly subjects (60-79 years of age) had slower SRTs and longer duration saccades than other subject groups. These results demonstrate very strong age-related effects in subject performance, which may reflect different stages of normal development and degeneration in the nervous system. We attribute the dramatic improvement in performance in the anti-saccade task that occurs between the ages of 5-15 years to delayed maturation of the frontal lobes.

Magnetic resonance imaging compatibility testing of the Clarion 1.2 cochlear implant.

OBJECTIVE: This study aimed to investigate the compatibility of the Clarion 1.2 magnet-containing cochlear implant with a 1.5-tesla (T) and 0.3-T magnetic resonance imager. BACKGROUND: Cochlear implants restore functional hearing to patients with sensorineural deafness. With the rapidly increasing number of patients with cochlear implants, there is a need to investigate the implant's magnetic resonance imaging (MRI) compatibility. METHODS: The authors tested the potential torque and force on the metallic components of the implant, heating of the implant and surrounding tissue, unintentional output, implant damage, and image distortion. Tests were performed in both a 1.5-T and 0.3-T MRI. RESULTS: The torque experienced by the implant in the 1.5-T MRI (0.19 nm) was large enough that it could potentially cause implant movement in some patients. An acceptable amount of torque (0.04 nm) was found in the 0.3-T MRI. Image distortion occurred in the area directly around the implant with a radius of up to 60 mm in the 1.5-T MRI and 100 mm in the 0.3-T MRI. In both MRI units, there was no detectable temperature increase or unintentional output. There was no implant damage except that with worst-case conditions, the internal magnet was demagnetized by 78.5% with the 1.5-T unit and 3.36% with the 0.3-T unit. CONCLUSIONS: The authors recommend patients with cochlear implants avoid imaging in a 1.5-T MRI. The results suggest that the 0.3-T MRI poses little or no risks to patients with cochlear implants.

Combined eye-head gaze shifts to visual and auditory targets in humans.

We studied the characteristics of combined eye-head gaze shifts in human subjects to determine whether they used similar strategies when looking at visual (V), auditory (A), and combined (V + A) targets located at several target eccentricities along the horizontal meridian. Subjects displayed considerable variability in the combinations of eye and head movement used to orient to the targets, ranging from those who always aligned their head close to the target, to those who relied predominantly on eye movements and only moved their head when the target was located beyond the limits of ocular motility. For a given subject, there was almost no variability in the amount of eye and head movement in the three target conditions (V, A, V + A). The time to initiate a gaze shift was influenced by stimulus modality and eccentricity. Auditory targets produced the longest latencies when located centrally (less than 20 degrees eccentricity), whereas visual targets evoked the longest latencies when located peripherally (greater than 40 degrees eccentricity). Combined targets (V + A) elicited the shortest latency reaction times at all eccentricities. The peak velocity of gaze shifts was also affected by target modality. At eccentricities between 10 and 30 degrees, peak gaze velocity was greater for movements to visual targets than for movements to auditory targets. Movements to the combined target were of comparable speed with movements to visual targets. Despite the modality-specific differences in reaction latency and peak gaze velocity, the consistency of combinations of eye and head movement within subjects suggests that visual and auditory signals are remapped into a common reference frame for controlling orienting gaze shifts. A likely candidate is the deeper layers of the superior colliculus, because visual and auditory signals converge directly onto the neurons projecting to the eye and head premotor centers.