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At least 19 recordsLinked to original sources
PubMedDate not supplied

Experience with implanted electrodes.

Implant units, manufactured by Medtronic, Inc., have been implanted in 31 patients for treatment of drop-foot. The principal problem encountered in this series was inflammatory reaction. This was observed in seven patients, and was serious enough in five to require removal of the implant. On the positive side, there have been no failures of the implanted equipment for periods of up to 7.3 years, although there is currently a question on one patient. There has also been no documented damage to the nerve from chronic stimulation. Fine wire elctrodes have been implanted intraneurally in a series of animals and in three patients. Preliminary results look encouraging, and this approach seems to hold considerable promise for a new generation of electrode design.

Amputees↗
PubMed1996

Non-invasive electrocologram: correlation between the electrical activity of the dog colonic muscle wall recorded by cutaneous and implanted electrodes.

Chronic experiments were performed on dogs with silver, bipolar, ball-shaped electrodes implanted on the colonic and of the gastric muscle wall. Cutaneous electrodes were placed on the abdominal wall, along the projection of descending colon and also of the stomach, at the beginning of each experiment. Slow waves were led off in the electrocolomyogram (EColMG), corresponding to low-amplitude waves in the non-invasive electrocologram (EColG) with a frequency of 6.39 +/- 0.58 cpm (type A). When bursts of spike potentials appeared with the slow waves in the EColMG, increase of the amplitude of the EColG waves and decrease of the frequency (1.90 +/- 0.20 cpm) was observed. There was a significant difference between the colonic wave frequency and the frequency of the gastric waves (3.96 +/- 0.28 cpm). A good correlation was found between the number and frequency of the spike potentials in a group in the EColMG and the wave amplitude in the EColG. A sequence of low-frequency, high-amplitude waves (type B) characterized an activity period, while a sequence of low-amplitude, high-frequency waves (type A) corresponded to a quiescent period of the colonic motility. Thus the functional state of the colonic muscle wall could be judged by the differences in the frequency and amplitude of the EColG waves.

Animals↗
PubMed1979

Effect of lactulose, neomycin and antacid on colonic pH recorded continuously with an implanted electrode.

Colonic pH was continuously monitored by a pH electrode implanted in the transverse colon of rats over a 24-hour period. Lactulose significantly reduced the colonic pH to 5.37 +/- .39 from a fasting value of 6.77 +/- .75. Pretreatment with neomycin or concomitant use of a nonabsorbable antacid prevented lactulose-induced reduction in the colonic pH. The clinical implication of the study is that combined use of lactulose with neomycin or high doses of non-absorbable antacids in the treatment of chronic portasystemic encephalopathy may be undesirable.

Animals↗
PubMed2002

Event-related potentials recorded from the cingulate gyrus during attentional tasks: a study in patients with implanted electrodes.

Recent neuroimaging data suggests that the cingulate gyrus is involved in a variety of cognitive tasks. In this study sensory field potentials were directly recorded from the cingulate gyrus in order to investigate its implication in attentional processes associated or not with a motor task. Evoked potentials recordings were performed in 29 epileptic patients with multilead electrodes implanted for presurgical evaluation, who agreed to participate in an experimental protocol consisting of a series of paradigms designed using a warning auditory tone, two distinct visual patterns and various attentional, memory, motor and decisional tasks. Our data shows that evoked potentials could be recorded from various parts of the cingulate gyrus. The inclusion of an instruction in the experimental paradigm resulted in an increase in the amplitude of the late, intrinsic component of the visual evoked potential culminating at about 450 ms. Several variations of response patterns across individuals were identified. We conclude that the cingulate gyrus appears to be a multimodal area involved in several types of cognitive activity, including attention. Variations in response patterns are probably related to differences in the strategy adopted by each subject when faced with a particular cognitive task.

Adult↗
PubMed1983

The role of computed tomographic and digital radiographic techniques in stereotactic procedures for electrode implantation and mapping, and lesion localization.

This paper describes a computer-based system for analyzing stereotactic CT scans and angiograms. Simple Plexiglas frames containing metallic marker pellets and rods are affixed to the sides of the frame during CT scanning and angiography. The images of these markers are recognized by the computer program and used to compute the frame coordinate system. Coordinates of a lesion on CT and angiogram images may be readily computed and coordinate sets specified by the operator may be displayed on the imager, along with positions of implanted electrodes and a numerical indication of recorded activity for each site.

Brain Diseases↗
PubMed1979

Electrode implantation and electrostimulation in rabbits.

The investigators studied functional electrostimulation by means of an implanted electrode placed around the peroneal nerve in rabbits. Current pulses were administered from a stimulating unit outside the body, via a connecting skin plug and subcutaneous leads to the electrode. It is concluded that if this form of stimulation is to be praticable without undesirable results, certain mechanical problems require further study.

Animals↗
PubMed1993

Transmitter amino acid levels in rat brain regions after amygdala-kindling or chronic electrode implantation without kindling: evidence for a pro-kindling effect of prolonged electrode implantation.

Kindling is a chronic model of epilepsy characterized by a progressive increase in response to the same regularly applied stimulus. The biological basis of the kindling phenomenon requires to be determined, but several studies indicate that alterations in amino acidergic neurotransmission may be involved. In the present experiments, levels of glutamate, aspartate, GABA, glycine, and taurine were determined in 12 brain regions by HPLC in 3 groups of animals: (a) a group which was kindled via electrical stimulation of intraamygdala electrodes and was sacrificed 36 days after the last fully kindled seizure for neurochemical determinations; (b) a group of implanted but nonstimulated rats (surgical control group) in which neurochemical measurements were done at the same time after electrode implantation as the kindled group, and (c) a group of non-implanted, naive control rats. Compared to surgical controls, kindling induced a significant reduction of glutamate, GABA, and taurine in the brain stem (pons/medulla), whereas no differences between both groups were found in any of the other regions. However, both electrode-implanted groups differed significantly from non-implanted naive rats in several regions, indicating that electrode-implantation per se induced long-lasting alterations in transmitter amino acids. The most striking difference to naive controls was an increase of glycine levels in several regions in which this amino acid is known to potentiate glutamatergic transmission. In order to examine the functional consequences of prolonged electrode implantation, seizure thresholds were determined in groups of rats with short and prolonged electrode implantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1995

Linear intracerebral calcification after depth electrode implantation.

We report linear calcifications along the trajectories of previously implanted depth electrodes in 2 patients. A 20-year-old man and a 38-year-old woman with medically intractable complex partial seizures (CPS), underwent bilateral frontal and mesiotemporal depth electrode implantation as part of their epilepsy surgery workup. Brain computed tomography (CT) at that time was normal (except for cerebrellar atrophy in one case). One patient had a left anterotemporal lobectomy (ATL), and the other declined operation. Subsequent CT scans showed linear calcifications 1-2 cm long in the occipital lobes (unilateral in 1 and bilateral in the other) that followed the trajectories of the temporal depth electrodes. This finding remained unchanged at latest follow-up (2-2.5 years), and no new pathology has appeared on subsequent scans. No abnormalities of calcium metabolism were detected. Review of all available CT scans of our patients with a history of previous depth electrode implantation showed no additional similar cases. We believe this is the first report of intracerebral calcifications after depth electrode implantation.

Adult↗
PubMedDate not supplied

[Electrode implantation for the recording of brain electrical activity causes long-term changes in rat behavior].

Comparative evaluation was carried out of behavior of rats with implanted brain electrodes and animals without electrodes. In rats with implanted electrodes the anxiety-phobic level was increased, open-field locomotor activity and rearings were decreased, novelty reactions on illumination changes and zoosocial interactions were deranged. The behavior remained altered for at least 3 weeks after surgery.

Animals↗
PubMed1992

Augmentation of the accuracy of percutaneous electrode implantation by using a modified arthroscope to guide insertion.

Using a clear polyvinyl fluoride sheath over an arthroscope, inserted through a 1-cm stab incision, we have demonstrated the feasibility of visualizing the sciatic nerve and its branches in the feline model. The purpose of this technique is to allow visual control, without a large surgical incision, of the exact site of implantation of electrodes used for functional neuromuscular stimulation. Currently, we determine the optimum site for percutaneous electrode implantation by stimulating the target nerve or muscle with a 26-gauge probe needle until maximal response is obtained. This method lacks accuracy because there is no direct visualization of the location of the tip of the probe or the electrode. With the new technique, we identified nerves by their distinctive vascular markings and we followed the nerves with minimal disruption of the soft tissues. In this way, individual branches were identified and targeted for instrumentation, allowing selective stimulation of specific muscle groups.

Animals↗
PubMed1999

Thalamic stimulation and functional magnetic resonance imaging: localization of cortical and subcortical activation with implanted electrodes. Technical note.

The utility of functional magnetic resonance (fMR) imaging in patients with implanted thalamic electrodes has not yet been determined. The aim of this study was to establish the safety of performing fMR imaging in patients with thalamic deep brain stimulators and to determine the value of fMR imaging in detecting cortical and subcortical activity during stimulation. Functional MR imaging was performed in three patients suffering from chronic pain and two patients with essential tremor. Two of the three patients with pain had undergone electrode implantation in the thalamic sensory ventralis caudalis (Vc) nucleus and the other had undergone electrode implantation in both the Vc and the periventricular gray (PVG) matter. Patients with tremor underwent electrode implantation in the ventralis intermedius (Vim) nucleus. Functional MR imaging was performed during stimulation by using a pulse generator connected to a transcutaneous extension lead. Clinically, Vc stimulation evoked paresthesias in the contralateral body, PVG stimulation evoked a sensation of diffuse internal body warmth, and Vim stimulation caused tremor arrest. Functional images were acquired using a 1.5-tesla MR imaging system. The Vc stimulation at intensities provoking paresthesias resulted in activation of the primary somatosensory cortex (SI). Stimulation at subthreshold intensities failed to activate the SI. Additional stimulation-coupled activation was observed in the thalamus, the secondary somatosensory cortex (SII), and the insula. In contrast, stimulation of the PVG electrode did not evoke paresthesias or activate the SI, but resulted in medial thalamic and cingulate cortex activation. Stimulation in the Vim resulted in thalamic, basal ganglia, and SI activation. An evaluation of the safety of the procedure indicated that significant current could be induced within the electrode if a faulty connecting cable (defective insulation) came in contact with the patient. Simple precautions, such as inspection of wires for fraying and prevention of their contact with the patient, enabled the procedure to be conducted safely. Clinical safety was further corroborated by performing 86 MR studies in patients in whom electrodes had been implanted with no adverse clinical effects. This is the first report of the use of fMR imaging during stimulation with implanted thalamic electrodes. The authors' findings demonstrate that fMR imaging can safely detect the activation of cortical and subcortical neuronal pathways during stimulation and that stimulation does not interfere with imaging. This approach offers great potential for understanding the mechanisms of action of deep brain stimulation and those underlying pain and tremor generation.

Chronic Disease↗
PubMed1999

Implantable electrode lead in a growing limb.

An implantable electrode leadwire system used to provide limb function for individuals with spinal cord injuries (SCI's) was evaluated in a series of growing dogs to determine whether it could maintain its performance in the presence of growth. Thirty implantable electrodes (15 epimysial and 15 intramuscular) were implanted in the forelimb muscles of six young dogs. The electrodes' leads were tunneled subcutaneously and anchored proximally in the shoulder with excess lead incorporated into the subcutaneous space to accommodate growth. Six of the leads had some of this excess placed in pouches made from surgical membrane while the other 24 leads had excess placed freely within the subcutaneous space. Motor responses to the electrodes were tested before and after growth with tendon force transducers and were compared to the performance of new electrodes implanted to the same muscles of the mature dog during the explant procedure. Measured were the pulse duration at which a measurable force is first produced (threshold) and the percentage of the maximum force that could be attained from the target muscle before activation of adjacent muscles (usable force range). An analysis of variance indicated that there was no difference in the usable force range (p = 0.62) of the original electrodes before and after growth and that of the new electrodes placed at maturity. There was a difference in the threshold (p = 0.001) which can be attributed to an increase in the values measured from the original electrodes after growth. However, the increase in threshold with growth averaged 6 micros which is not clinically significant and can be accommodated through stimulation programming. Growth of the limb and unwinding of excess lead were quantified by radiograph. Extension of the freely placed excess lead was comparable to growth so that the pouch enclosures were found to be unnecessary for facilitating lead expansion. By radiograph and surgical observations, only two of 30 electrodes (both intramuscular) appeared to have been subjected to lead tension, although they continued to provide adequate motor responses. Insufficient excess lead was judged to be the cause of dislodgment for one of these electrodes. Results of this study suggest that for this implantable leadwire system, excess lead placed in the subcutaneous space can unwind on demand with limb growth such that an electrode will remain in position and provide a stable motor response.

Analysis of Variance↗
PubMed2006

High resolution micro-CT scanning as an innovative tool for evaluation of the surgical positioning of cochlear implant electrodes.

X-ray microtomography (micro-CT) is a new technique allowing for visualization of the internal structure of opaque specimens with a quasi-histological quality. Among multiple potential applications, the use of this technique in otology is very promising. Micro-CT appears to be ideally suited for in vitro visualization of the inner ear tissues as well as for evaluation of the electrode damage and/or surgical insertion trauma during implantation of the cochlear implant electrodes. This technique can greatly aid in design and development of new cochlear implant electrodes and is applicable for temporal bone studies. The main advantage of micro-CT is the practically artefact-free preparation of the samples and the possibility of evaluation of the interesting parameters along the whole insertion depth of the electrode. This paper presents the results of the first application of micro-CT for visualization of the inner ear structures in human temporal bones and for evaluation of the surgical positioning of the cochlear implant electrodes relative to the intracochlear soft tissues.

Artifacts↗
PubMed1996

Thoracoscopic approach to implantable cardioverter defibrillator patch electrode implantation.

Even if transvenous lead system for automatic implantable cardioverter defibrillators (ICDs) has been one of the main surgical advances in the recent past, its major limitation is the high defibrillation thresholds in some cases. Thus, an additional patch may be required and implanted either in a subcutaneous position or in an epicardial position. We describe another possibility: the implantation of extrapericardial patch under video-thoracoscopic control. This new technique allows a deep implantation of the whole material without thoracotomy. Seven patients were included in our preliminary experience. During defibrillation threshold evaluation, two patients required 34 J with the single transvenous lead system, and five patients were not defibrillated with the single lead system; therefore, they required a 300-J external rescue shock. We decided to implant an additional patch in those seven patients with high defibrillation thresholds. This patch was inserted into the pleural cavity through a left subcostal incision. Under video thoracoscopy, it was positioned and stitched onto the pericardium. The defibrillation generator was then implanted through the left subcostal incision in a subdiaphragmatic space. As a result, preoperative defibrillation thresholds were significantly reduced (14.29 +/- 3.45 J, mean +/- SD) and remained stable during follow-up controls (eighth day and second month). Long-term follow-up (14 +/- 4.5 months) was uneventful, with an excellent tolerance for the patients. In conclusion, extrapericardial implantation of defibrillation patches under video thoracoscopy is an easy technique that allows low defibrillation thresholds.

Adult↗
PubMed1979

Long-term electrode implantation for recording cochlear electrical activity in guinea pigs.

Comparative measurements of the cochlear electrical activity over prolonged periods require long-term implantation of electrodes. During this time, changes in the electrode recording ability and/or impairment of the sound-conducting system, could erroneously be attributed to the experiment. To avoid this risk, an easy and reliable technique is described. The procedure uses the Fallopian canal as a route by which to approach the cochlear potentials' generators, while leaving the middle ear untouched.

Action Potentials↗
PubMed1978

Cerebral tissue response to electrode implantation.

Tissue response to platinum electrodes was assessed after an eight-day implantation period. The regions of study included the cortical areas at the opercular gyri and at the sulcus parieto-occipitalis externus, as well as the sub-cortical white matter in these cases. Perivascular and intraparenchymal hemorrhagic lesions as well as edematous changes characterized both by extensive intra and extracellular swelling were noted. Numerous phagocytic elements and degenerative strucutres were present at the electrode/parenchymal interface. Tissue alterations were asymmetrical as observed both around and at the tip of the implanted electrode. The parenchymal alterations extended from 0.2mm to 3.5mm distance from the electrode path/parenchymal interface. Greater tissue involvement was found in the subcortical white matter as compared to the adjacent cortical gray matter.

Animals↗