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At least 811 records · Page 45Linked to original sources
PubMed2005

Incidence of hemorrhage associated with electrophysiological studies performed using macroelectrodes and microelectrodes in functional neurosurgery.

OBJECT: The goal of this study was to analyze the incidence of intracranial bleeding in patients who underwent procedures guided by microelectrode recording (MER) rather than by macroelectrode stimulation alone. METHODS: Between March 1994 and July 2001, 178 patients underwent 248 functional neurosurgical procedures performed by the same team at the University of California at Los Angeles. The procedures included pallidotomy (122 patients), thalamotomy (19 patients), and implantation of deep brain stimulation electrodes in the subthalamic nucleus (36 patients), globus pallidus internus (17 patients), and ventralis intermedius nucleus (54 patients). One hundred forty-four procedures involved macroelectrode stimulation and 104 involved MER. Groups were analyzed according to the presence of arterial hypertension, MER or macroelectrode stimulation use, and occurrence of hemorrhage. Nineteen patients with arterial hypertension underwent 28 surgical procedures. Five cases of hemorrhage (2.02%) occurred. One patient presented with hemiparesis and dysphasia but no surgery was required. The incidence of hemorrhage in patients in whom MER was performed was 2.9%, whereas the incidence in patients in whom MER was not used was 1.4% (p = 0.6529). Bleeding occurred in 10.71% of patients with hypertension and 0.91% of those who were nonhypertensive (p = 0.0111). Among the 104 patients in whom MER was performed, 12 had hypertension. Bleeding occurred in two (16.67%) of these 12 patients. An increased incidence of bleeding in hypertensive patients who underwent MER (p = 0.034) was noticed when compared with nonhypertensive patients who underwent MER. A higher number of electrode passes through the parenchyma was observed when MER was used (p = 0.0001). A positive trend between the occurrence of hemorrhage and multiple passes was noticed. Conclusions. Based on the data the authors suggest that a higher incidence of hemorrhage occurs in hypertensive patients, and a higher incidence as well in hypertensive patients who underwent MER rather than macroeletrode stimulation. Special attention should be given to MER use in hypertensive patients and particular attention should be made to multiple passes.

Adolescent↗
PubMed2006

Microelectrode-guided implantation of deep brain stimulators into the globus pallidus internus for dystonia: techniques, electrode locations, and outcomes.

OBJECT: Deep brain stimulation (DBS) of the globus pallidus internus (GPI) is a promising new procedure for the treatment of dystonia. The authors describe their technical approach for placing electrodes into the GPI in awake patients with dystonia, including methodology for electrophysiological mapping of the GPI in the dystonic state, clinical outcomes and complications, and the location of electrodes associated with optimal benefit. METHODS: Twenty-three adult and pediatric patients with various forms of dystonia were included in this study. Baseline neurological status and DBS-related improvement in motor function were measured using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS). The implantation of DBS leads was performed using magnetic resonance (MR) imaging-based stereotaxy, single-cell microelectrode recording, and intraoperative test stimulation to determine thresholds for stimulation-induced adverse effects. Electrode locations were measured on computationally reformatted postoperative MR images according to a prospective protocol. CONCLUSIONS: Physiologically guided implantation of DBS electrodes in patients with dystonia was technically feasible in the awake state in most patients, and the morbidity rate was low. Spontaneous discharge rates of GPI neurons in dystonia were similar to those of globus pallidus externus neurons, such that the two nuclei must be distinguished by neuronal discharge patterns rather than rates. Active electrode locations associated with robust improvement (> 70% decrease in BFMDRS score) were located near the intercommissural plane, at a mean distance from the pallidocapsular border of 3.6 mm.

Adolescent↗
PubMed1998

Stereotactic microelectrode-guided posteroventral pallidotomy and pallidal deep brain stimulation for Parkinson's disease.

Three patients underwent stereotactic posteroventral pallidotomy, and 1 patient underwent pallidal deep brain stimulation, for medically intractable symptoms of advanced Parkinson's disease, characterized by peak-dose levodopa dyskinesias, wearing-off fluctuations, tremor, rigidity and bradykinesia. Surgery was performed stereotactically under local anaesthesia, with eventual target coordinates derived from a combination of magnetic resonance imaging (MRI), coregistration with an electronic brain atlas, intraoperative microelectrode neuronal recordings and microstimulation before lesioning or placement of a deep brain stimulator was done. Assessment was made at baseline preoperatively and at 3-month intervals postoperatively, with Unified Parkinson's Disease Rating Scale (UPDRS) and Core Assessment Program for Intracerebral Transplantation (CAPIT) scoring. All patients improved in dyskinesia, tremor, rigidity and bradykinesia contralateral to the lesion side, but also on the ipsilateral side to a lesser extent. The improvement was largely seen in the 'off' state: UPDRS by 41%, and CAPIT by 19% on the contralateral side. 'On' freezing was not helped. There were no deaths and no visual complications, but there was one complication of a delayed contralateral upper limb dystonia after pallidotomy. The 1 patient with pallidal deep brain stimulation (DBS) obtained similar improvement as those with pallidotomy. Posteroventral pallidotomy and pallidal stimulation improves all the cardinal features of Parkinson's disease, and effectively ameliorates levodopa dyskinesias.

Electric Stimulation Therapy↗
PubMed1976

Automatic microelectrode compensator (AMC).

A solid-state system designed for compensation of asymmetry potentials between microelectrodes, for bioelectric measurements, is described. Advantages over the manual compensator are the following: synchronic compensation of electrodes, application to automatized systems against aging effects in electordes, high speed, and elimination of general muisances of manual circuits. Besides, the system allows to measure digitally the polarization difference and resting membrane potential with precision of +/- 1 mV.

Bioelectric Energy Sources↗
PubMed2000

Quantification of acute neurotoxic effects of trimethyltin using neuronal networks cultured on microelectrode arrays.

We used spontaneously active monolayer networks in vitro, cultured on thin film microelectrode arrays as experimental platforms for the determination of trimethyltin chloride (TMT) toxicity. Two different tissues of the mouse CNS (spinal cord and auditory cortex) exhibited characteristic and dose-dependent changes of their electrophysiological activity patterns after treatment with TMT, a standard neurotoxicant. Spinal cord networks began to respond to TMT at 1-2 microM and shut off activity at 4-7 microM. Auditory cortex cultures started to respond at 2-3 microM and shut off activity at 7-8 microM. Repeated applications of low doses of TMT always influenced the electrical activity in a reversible manner, with no overt cytotoxic effects. The inhibitory concentrations for a 50% reduction of activity (IC ) were 1.5+/-0.5 microM (spinal cord) and 4.3+/-0.9 microM (auditory cortex) indicating a relatively low interculture variability within one tissue type. The non-overlapping IC50 range for cortical and spinal cord cultures may suggest tissue specificity for network responses to TMT. Shut-off concentrations were found to be within a factor of two of the lethal concentrations reported for mice in vivo. Action potential amplitude and shape did not change even when complete cessation of activity was approached, suggesting that acute TMT applications did not affect neuronal metabolism that would lead to a lowering of membrane potentials. Our results suggest that spontaneously active monolayer networks in vitro are suitable for toxicological investigations since network activity can be influenced in a dose-dependent manner. These properties allow the development of neurotoxicity biosensors based on physiological responses of spontaneously active networks.

Action Potentials↗
PubMed1998

[Study on nitric oxide in isolated cochlear neuron of chicken with chemically modified carbon fiber microelectrode].

OBJECTIVE: Nitric oxide(NO) is involved in neural signaling that is important to the physiologic and pathophysiologic activities of cochlea and vestibule. This study is to compare physiologic function of mammalian cochlea with that of chicken cochlea. METHODS: Using chemically modified carbon fiber microelectrode to measure qualitatively NO which was released from isolated cochlear neuron cluster of chicken in response to certain agonists, such as ATP, L-Arg and ACh. The presence of NO release is indicated by elevation of amplitude and lasting time of microelectric current. RESULTS: The results demonstrated that No releases stimulated by ACh and L-Arg were similar in amplitude but the lasting time stimulated by ACh was shorter than that of L-Aeg. Response to ATP, however, differred apparently in a manner which the amplitude was larger than that of ACh and L-Arg, whereas the lasting time approximated to that of L-Arg but longer than that of ACh. Before application of agonists, preapplication of L-NNA, a NOS antagonist no current changes could be monitored. CONCLUSION: These data suggested that chicken cochlear ganglion can synthesize and release NO. The effective mechanism of the agonists and possible role of NO in the cochlea is discussed.

Acetylcholine↗
PubMed1998

[Microelectrode-guided posteroventral pallidotomy for Parkinson's disease: clinical study of 100 cases].

OBJECTIVE: To evaluate the outcome of posteroventral pallidotomy (PVP) for Parkinson's disease (PD). METHOD: The data from 100 patients with PD receiving PVP were retrospectively analyzed with UPDRS. RESULT: PVP significantly improved PD symptoms. Several typical symptoms were improved:tremor in 72% patients, rigidity 81%, akinesia 71%, gait 60%, balance 64% and off state 75%. CONCLUSION: PVP improves Parkinsonian symptoms, and is superior to classical thalamotomy. Microelectrode recording is essential to surgical results and avoidance of severe complication.

Adult↗
PubMed2002

Beta-functionalised polythiophenes as microelectrode modifiers in low conductive media.

A study on polythiophene coated microelectrodes is reported, the goal being that of checking the capability of these electrochemical systems to work in low conductive media. The possibility of electrochemically p-doping the polymer in the presence of very low concentrations or even in the absence of supporting electrolyte in the solution is ascertained, opening the way to the use of similar systems in pure solvent media. This result is obtained in such conditions that the presence of residual charges--and corresponding counterions--trapped inside the film coating can be reasonably hypothesised.

Electric Conductivity↗
PubMedDate not supplied

[Determination with a microelectrode of membrane potential of giant human erythrocytes obtained by La(3+)-induced fusion].

The effect of La3+ on the fusion of erythrocytes of blood stored for a week at +4 degrees C was studied. It was shown that the fusion of erythrocytes begins after one day of storage of blood. The most intensive fusion of erythrocytes was observed on day 4 of blood storage. As a result, giant cells with a size of 100 microns and more arise. The electrical potential of giant cells was measured using a microelectrode and was -6.6 +/- 1.5 mV.

Cations↗
PubMed1975

The use of metal microelectrodes in broad-band recording.

We checked to what extent the voltage-current relationship of a microelectrode is linear. In the linear domain we measured the impedance characteristic of the electrode. We measured the frequency response curve and the phase characteristic of the electrode and amplifier system.

Electrophysiology↗
PubMed1992

[Extracellular calcium in the rat brains and the effects of nifedipine in experimental cerebral infarction using calcium ion selective microelectrodes in vivo].

Extracellular Ca2+ (Ca2+ e) changes in the cerebral infarction areas of the rats with the double-tubulus calcium ion-selective microelectrodes made of calcium active material, di-2-isooctylphenyl calcium phosphate to observe the effects of two concentrations of nifedipine given before the middle cerebral artery (MCA) occlusion. Twenty-four rats were divided into three groups: group A: with just the left MCA occlusion, Group B: with intramuscular injection of nifedipine 1mg/kg one hour before the MCA occlusion, and Group C with intramuscular injection of nifedipine 5mg/kg one hour before the MCA occlusion. The results indicated that the mean concentration of Ca2+ e in the normal brain Group A was 1.119 mM. The Ca2+ e concentrations became 0.4613 mM, 0.191 mM and 0.0654 mM, 2, 5 and 30 minutes after the MCA occlusion respectively. The other groups, Group B and Group C, receiving two kinds of dosages of nifedipine respectively showed the Ca2+ e concentrations to be 0.5262 mM and 0.5588 mM, 0.3456 mM and 0.3058 mM, 0.2156 mM and 0.1989 mM, 2, 5 and 30 minutes after the MCA occlusion respectively. There is no statistic significance between group B and group c (P greater than 0.25) By comparing Group A with Group B or C, it was found that the Ca2+ e level of Group B or C is about 3 times greater than that of Group A (P less than 0.0025) and (P less than 0.005) 30 minutes after the MCA occlusion.

Animals↗
PubMed2004

[Preoperative adverse events during stereotactic microelectrode-guided deep brain surgery in Parkinson's disease].

OBJECTIVES: To evaluate the prevalence of adverse events and complications during surgery using deep brain electrodes, mainly in the treatment of Parkinsonism. To describe the adjustment of propofol to meet the needs of neurophysiological monitoring. PATIENTS AND METHODS: A prospective study of patients undergoing stereotactic microelectrode-guided deep brain surgery (stereotactic pallidotomy, implantation of electrodes in the thalamic or subthalamic neurons of the globus pallidus). After placement of a stereotactic frame and completion of a computed tomography scan of the head, the patients were transferred to the operating room. Monitoring included electrocardiography, pulse oximetry, arterial pressure (invasive), endtidal carbon dioxide pressure, and diuresis. Anesthesia was maintained by intermittent infusion of propofol. Variables recorded were age, sex, disease and time elapsed since diagnosis, surgical complications and their treatment, total dose of propofol, duration of surgery, and place of transfer for recovery. RESULTS: One hundred twenty-eight patients (50 women, 78 men) with a mean (+/- SD) age of 59.6 +/- 10.2 years underwent the procedure from 1996 through 2003. The mean time elapsed since diagnosis of the disease was 14 +/- 6.2 years. The propofol dose was 890.6 +/- 571.4 mg and duration of surgery was 8.3 +/- 2.4 hours. Adverse events were observed for 101 patients (78.9%). The most common complications involved hemodynamics: arterial hypertension (59.4%), bradycardia (18.0%), arterial hypotension (7.9%), and tachycardia (6.2%). Other more serious complications were pneumocephalus with clinical repercussions (3 cases), globus pallidus hematoma (2), air embolism (2), epileptic seizure (3), anisocoria (1), and dyspnea and/or airway obstruction (7). CONCLUSIONS: Deep brain stimulation requires surgery of long duration. Because of frequent episodes of arterial hypertension, which increases the risk of brain hemorrhage, and other less common but potentially dangerous complications, careful clinical monitoring is necessary during the procedure. The intermittent use of propofol does not interfere with neurophysiological monitoring.

Aged↗
PubMed1979

Exteroceptive, proprioceptive, and sympathetic activity recorded with microelectrodes from human peripheral nerves.

With tungsten microelectrodes percutaneously inserted into human peripheral nerve fascicles, in vivo recordings of single-unit action potentials can be obtained from different types of myelinated and unmyelinated nerve fibers. This technique of microneurography has provided a great deal of information about (1) the sensory innervation of the human skin, with its mechanoreceptive, thermoreceptive, and nociceptive functions, (2) the proprioceptive innervation of human skeletal muscles, special attention being devoted to the motor control functions of the muscle spindles and the fusimotor system, and (3) the sympathetic innervation of autonomic effector organs in skin and muscle, with its significance for, for example, regulation of temperature and blood pressure. The technique has its main application not as a routine procedure in clinical diagnostic work but as a research tool in basic physiologic and pathophysiologic studies.

Humans↗
PubMed2005

Microelectrode recording-determined subthalamic nucleus length not predictive of stimulation-induced side effects.

OBJECT: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a popular treatment for patients with medically refractory Parkinson disease. Many surgeons believe that microelectrode recording (MER) during DBS electrode implantation is needed to optimize placement, whereas stimulation-induced side effects such as paresthesias, dystonic contractions, dyskinesias, and ocular motor signs that become apparent postoperatively may be an indicator of the proximity of the electrode to various boundaries of the STN. This study was performed to evaluate the relationship between mapping of the STN by using MER and postoperative stimulation-induced side effects. METHODS: Eighty-two electrodes implanted in 75 patients between March 1999 and March 2003 were retrospectively examined to evaluate the length of the STN defined by MER, and the number of and threshold for postoperative stimulation-induced side effects. Electrodes were typically tested with increasing stimulation amplitudes (maximum 6 V) by using a monopolar array. The 82 electrodes were associated with 97 stimulation-induced side effects. The mean time between surgery and testing stimulation-induced side effects was 3.9 months. Statistical analysis (two-tailed t-test) revealed no significant difference in the number of stimulation-induced side effects (or the mean threshold for paresthesias, the most common side effect) for electrodes associated with an STN length less than 4.5 mm (13 electrodes) compared with those associated with an STN greater than or equal to 4.5 mm (69 electrodes, p = 0.616). For every electrode, the target adjustment based on MER results was within 2 mm of the image-planned target (usually 1 mm anterior). In the x axis (medial-lateral orientation), there was no systematic difference in adjustments made for the electrodes associated with the shorter compared with the longer STN lengths. In the y axis (anterior-posterior orientation), there was a very small statistically significant difference in the mean adjustment (0.4 mm) between the two groups. CONCLUSIONS: Analysis of these results suggests that a shorter MER-determined STN length alone does not reliably predict the incidence of stimulation-induced side effects.

Chi-Square Distribution↗
PubMed2006

[Investigation on spontaneous electrical activity of murine embryonic heart using microelectrode arrays].

In our studies, we have applied a novel tool, microelectrode arrays (MEA), to investigate the electrophysiological properties of murine embryonic hearts in vitro. The electrical signals were recorded from the areas of the heart adhering to the 60 MEA electrodes, being called field potentials (FPs). As an extracelluar recording, the waveform of the FP appeared similar to a reversed action potential obtained from single cell by whole cell current clamp and the FP duration was comparable with the action potential duration. To study propagation of spontaneous electrical activity, we have compared the occurrence time of FPs recorded from different electrodes. It is shown that there was already an apparent A-V delay [(50.21+/-9.7) ms] at day 9.5 post coitum (E9.5) when heart was still tubular-like and atrium and ventricle were not separated anatomically, while occurence of FP at different electrodes of ventricular area were almost synchronous. Further, we looked into the modulation of spontaneous electrical activity during cardiac development: at E9.5 of embryonic development, 1 mumol/L of isoproterenol (Iso) increased beating frequency by (34.04+/-7.31)%, shortened the A-V delay by (20.00+/-6.44) % and prolonged FP duration. In contrast, 1 mumol/L of carbachol (CCh) slowed down beating frequency by (42.32+/-5.36) %, A-V conduction by (26.00+/-4.81) % and shortened FP duration; however at late stage (E16.5), the regulatory effect of Iso and CCh was strengthened. Therefore we conclude that cardiac conduction system is already established at E9.5 when the four-chambered heart is not formed yet and the regulation of spontaneous activity by sympathetic and para-sympathetic system is gradually matured during cardiac development.

Action Potentials↗
PubMedDate not supplied

Use of ion-sensitive microelectrodes to study intracellular free magnesium concentration and its regulation in mammalian cardiac muscle.

Ion-sensitive microelectrodes (ISEs) have been used to measure intracellular [Mg2+] ([Mg2+]i) in cardiac muscle, although most measurements have tended to overestimate the value due to the poor selectivity of the Mg2+ ionophore in the sarcoplasm and to inaccurate collation of individual ISE measurements. This paper highlights the correct method for analysis of data from multiple ISE experiments. Since [Mg2+]i is constrained at a lower concentration than would be expected by passive distribution of the ion, some of the possible mechanisms underlying Mg2+ extrusion from ferret ventricular myocardium were investigated. During elevation of the extracellular [Mg], mean [Mg2+]i rose from 1.61 to 1.91 mM. The same intervention had no significant effect on membrane potential, intracellular [Na+] or pH measured with ISEs, and there was no change in resting [Ca2+], as assessed from fura-2 fluorescence. The data are not consistent with a simple mechanism for Na(+)-Mg2+ exchange as the primary mode of Mg2+ regulation in cardiac muscle or with an Mg2+ extrusion mechanism involving steady-state ion exchange.

Animals↗
PubMed1990

Measurement with microelectrodes of intracellular Na+, K+, H+ and Cl- activities and of membrane potential in normal rat liver slices and during the 4-dimethylaminoazobenzene-induced rat hepatocarcinogenesis.

Steady-state membrane potentials (Vm) and intracellular Na+ (aiNa), K+ (aiK), H+ (aiH) and Cl- (aiCl) activities were measured with double-barrelled ion-selective microelectrodes in liver slices from normal rats and during the 4-dimethylaminoazobenzene-induced (DAB) hepatocarcinogenesis. Rats fed with the experimental regimen without the carcinogen were used as control animals. In Krebs-Henseleit bicarbonate saline containing 5.5 mM glucose as bathing solution at 37 degrees C, Vm was found to be significantly lower in neoplastic hepatocytes, compared to normal liver cells. Vm decreased also in control rat liver cells. Increased Na+/K+ ratios and Na+ + K+ activities were found in cancerous hepatocytes whereas H+ and Cl- activities decreased. Therefore, the intracellular pH increased significantly in neoplastic cells, compared to normal and control cells. This could reflect activation of the Na+/H+ exchange system during the DAB-induced hepatocarcinogenesis, leading to a stimulation of cell metabolism with increased rate of protein and DNA synthesis and loss of growth control, under these conditions.

Animals↗