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Results for “Electrodes, Implanted”

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At least 127 records · Page 7Linked to original sources
PubMed1998

Degeneration and regeneration in rabbit peripheral nerve with long-term nerve cuff electrode implant: a stereological study of myelinated and unmyelinated axons.

Selective and dynamically co-ordinated functional electrical stimulation (FES) of paralysed/paretic limbs in upper motor neuron lesioned people depends on optimal contact at the neural interface. Implanted nerve cuff electrodes may form a stable electrical neural interface, but may also inflict nerve damage. In this study the immediate and long-term effects of cuff implantation on the number and sizes of myelinated and unmyelinated axons have been evaluated with unbiased stereological techniques. Cuff electrodes were implanted in rabbit tibial nerves just below the knee joint, and the stereological analyses were carried out 2 weeks and 16 months after implantation. Myelinated axons were analysed at standardised levels proximal to, underneath, and distal to the cuff; unmyelinated axons underneath the cuff. A 27% loss of myelinated axons was found underneath and distal to the nerve cuff 2 weeks post surgery. All axonal sizes were equally lost except for the very smallest. At 16 months post surgery the number of myelinated axons was restored to control values at both levels. Except for the presence of regenerative sprouts at 2 weeks post surgery, no changes in the number or sizes of unmyelinated axons were revealed at either 2 weeks or 16 months post surgery. Our study demonstrates that implanted cuff electrodes may cause an initial loss of myelinated axons but with subsequent regeneration.

Anatomy, Artistic↗
PubMed2002

Thoracoscopic electrode implantation for diaphragm pacing in dogs.

BACKGROUND: Diaphragm pacing is an attractive method of ventilatory support; however, it requires electrode implantation to the phrenic nerve or diaphragm. The thoracic approach is favored for several reasons, and it usually accompanies invasive bilateral thoracotomy. OBJECTIVES: This study was conducted to develop a new electrode suitable for video-assisted thoracoscopic implantation, which is less invasive than the conventional thoracic approach. METHODS: The feasibility of video-assisted thoracoscopic implantation was tested with newly designed electrodes using 5 mongrel dogs. Furthermore, diaphragm pacing was performed for 60 min to test whether or not the implanted electrodes were functional. RESULTS: Video-assisted electrode implantation was successful in all 5 cases. No complications occurred during the implantation procedure. In acute-phase pacing trials, the electrodes stimulated the phrenic nerves for 60 min without any pacing failures. The mean value of PaCO(2) increased gradually from 32.2 +/- (SEM) 1.52 to 54.6 +/- 4.58 mm Hg, and the value of tidal volume decreased gradually from 242.9 +/- 31.3 to 147.5 +/- 24.5 ml in 60 min pacing. CONCLUSIONS: The thoracoscopic implantation of new electrodes was less invasive, and was a safe procedure for diaphragm pacing. Meticulous care should be taken to avoid muscle fatigue.

Analysis of Variance↗
PubMed1976

Implantable electrode for recording nerve signals in awake animals.

An implantable electrode assembly consisting of collagen and metallic electrodes was constructed to measure simultaneously neural signals from the intact nerve and bioelectrical noises in awake animals. Mechanical artifacts, due to bodily movement, were negligibly small. The impedance of the collagen electrodes, measured in awake cats 6-7 days after implantation surgery, ranged from 39.8-11.5 komega at a frequency range of 20-5 kHz. Aortic nerve activity and renal nerve activity, measured in awake conditions using the collagen electrode, showed grouped activity synchronous with the cardiac cycle. Results indicate that most of the remal nerve activity was from postganglionic sympathetic fibers and was inhibited by the baroceptor reflex in the same cardiac cycle.

Animals↗
PubMed2005

A model for cochlear implant electrode insertion and force evaluation: results with a new electrode design and insertion technique.

OBJECTIVES AND HYPOTHESIS: This study has the specific aim of evaluating the insertion characteristics of a new cochlear implant electrode. Techniques for evaluation of fluoroscopic real time mechanical insertion dynamics, histologic electrode position and trauma results, hydraulic force, and mechanical insertion forces are presented. In addition, this study should serve to present a novel model for cochlear implant electrode insertion evaluations. STUDY DESIGN: Prospective analysis using a series of analytical techniques. METHODS: All studies are conducted in fixed cadaveric temporal bones. Real time fluoroscopic insertion evaluations, histologic evaluations for trauma and electrode position in embedded bones, hydraulic measures, and mechanical intracochlear force measurements are conducted with a current and new electrode. RESULTS: The Contour Advance electrode provides a more reliable and less traumatic insertion when deployed with the Advance Off Stylet technique. This is largely because of a reduction in intracochlear outer wall force generation. Fluoroscopic and histologic analysis reveal a smooth insertion without reliance on cochlear outer wall contact. No hydraulic forces were detected when measured from the superior semicircular canal ampulla. CONCLUSION: The model used for this study provides valuable information to cochlear implant surgeons and design engineers. The Contour Advance electrode, inserted with the Advance Off Stylet technique, represents an improvement over the Contour electrode inserted with the standard insertion technique.

Cadaver↗
PubMed1989

Facial nerve electroneurography with implanted electrodes. Experimental study in the rabbit.

Facial nerve function was evaluated with permanently implanted electrodes for registration of electroneurography in an experimental model. The test-retest reproducibility was analyzed under normal conditions, as well as after facial nerve section. The mean observed intraindividual variation obtained at different sessions was 4%. We believe that the method is well suited for studies of experimental facial palsy.

Animals↗
PubMed1985

Psychological factors and outcome of electrode implantation for chronic pain.

The utility of using psychological assessments as a basis for predicting pain relief after electrode implantation is examined. Two raters independently reviewed the functional pain protocols of chronic pain patients who were candidates for deep brain (n = 13) or spinal cord (n = 17) electrode implants and predicted whether each would have a good or poor treatment response. At follow-up, five deep brain (39%) and four spinal cord (24%) patients were classified as having good responses to treatment. Predictions of outcome based on psychological data were accurate for 80% of the patients. These results suggest that functional pain assessment is useful as a part of preimplantation screening and emphasize the importance of psychological factors in the outcome of treatment for chronic pain.

Electrodes, Implanted↗
PubMed1999

The parafascicular nucleus and two-way active avoidance: effects of electrical stimulation and electrode implantation.

To evaluate whether electrical stimulation of the parafascicular nucleus (PF) can improve short-term (24 h) and/or long-term (21 days) retention of two-way active avoidance, rats were implanted with an electrode at this nucleus (experimental groups) or above it (control groups). After a single 30-trial acquisition session, experimental groups were submitted to a 10-min session of electrical stimulation. Results showed that the simple implantation of an electrode at the posterior PF enhanced by itself the acquisition of two-way active avoidance, in such a way that the subsequent stimulation of this region may have been unable to further improve the performance of the rats. On the other hand, parafascicular stimulation improved the 24-h retention of the task in a site-specific way, since this effect was mainly seen after stimulation of the central PF region. The facilitative effect on 24-h retention could also depend on the level of performance achieved during the acquisition session, because this improvement was only evidenced in poorly learning animals. No effects were found on 21-day retention. The present results confirm the involvement of the PF in learning and memory and the functional heterogeneity of this nucleus.

Analysis of Variance↗
PubMed2005

A temporal bone study of insertion trauma and intracochlear position of cochlear implant electrodes. II: Comparison of Spiral Clarion and HiFocus II electrodes.

In recent years, several new designs of cochlear implant electrodes have been introduced clinically with the goal of optimizing perimodiolar placement of stimulation sites. Previous studies suggest that perimodiolar electrodes may increase both the efficiency and performance of a cochlear implant. This is the second of two studies designed to examine the positioning of electrodes and the occurrence of insertion-related injury with these newer designs and to directly compare two perimodiolar electrodes to their predecessors. In our previous report we compared the Nucleus banded electrode with the Nucleus Contour perimodiolar electrode. In the present study, using the same protocol, we examine the Spiral Clarion electrode and its successor, the HiFocus II electrode with attached positioner. Eight Spiral Clarion arrays and 20 HiFocus II electrodes with positioners were inserted into human cadaver temporal bones. Following insertion, the specimens were embedded in acrylic resin, cut in quarters with a diamond saw and polished. Insertion depth, proximity to the modiolus and trauma were evaluated in X-ray images and light microscopy. The newer electrode was consistently positioned closer to the modiolus than the previous device whereas the angular depth of insertion measured for the two electrodes was similar. The incidence of trauma was minimal when either electrode was inserted to a depth of less than 400 degrees . However, severe trauma was observed in every case in which the HiFocus II with positioner was inserted beyond 400 degrees and in some cases in which the Spiral Clarion was inserted beyond 400 degrees . To evaluate the possible role of electrode size in the trauma observed we modeled both devices relative to the dimensions of the scala tympani. We found that the fully inserted HiFocus II electrode with positioner was larger than the scala tympani in approximately 70% of temporal bones measured. The results suggest that both the Clarion spiral and HiFocus II with positioner can be inserted with minimal trauma, but in many cases not to the maximum depth allowed by the design.

Cadaver↗