An insight into electrical resistivity of white matter and brain tumors

BackgroundThere is a lack of information regarding electrical properties of white matter and brain tumors.ObjectiveTo investigate the feasibility of in-vivo measurement of electrical resistivity during brain surgery and establish a better understanding of the resistivity patterns of brain tumors in correlation to the white matter.MethodsA bipolar probe was used to measure electrical resistivity during surgery in a prospective cohort of patients with brain tumors. For impedance measurement, the probe applied a constant current of 0.7 μA with a frequency of 140 Hz. The measurement was performed in the white matter within and outside peritumoral edema as well as in non-enhancing, enhancing and necrotic tumor areas. Resistivity values expressed in ohmmeter (Ω1m) were compared between different intracranial tissues and brain tumors.ResultsNinety-two patients (gliomas WHO II:16, WHO III:10, WHO IV:33, metastasis:33) were included. White matter outside peritumoral edema had higher resistivity values (13.3 ± 1.7 Ω1m) than within peritumoral edema (8.5 ± 1.6 Ω1m), and both had higher values than brain tumors including non-enhancing (WHO II:6.4 ± 1.3 Ω1m, WHO III:6.3 ± 0.9 Ω1m), enhancing (WHO IV:5 ± 1 Ω1m, metastasis:5.4 ± 1.3 Ω1m) and necrotic tumor areas (WHO IV:3.9 ± 1.1 Ω1m, metastasis:4.3 ± 1.3 Ω1m), p=<0.001. No difference was found between low-grade and anaplastic gliomas, p = 0.808, while resistivity values in both were higher than the highest values found in glioblastomas, p = 0.003 and p = 0.004, respectively.ConclusionsThe technique we applied enabled us to measure electrical resistivity of white matter and brain tumors in-vivo presumably with a significant effect with regard to dielectric polarization. Our results suggest that there are significant differences within different areas and subtypes of brain tumors and that white matter exhibits higher electrical resistivity than brain tumors.     

Adding transcutaneous electrical nerve stimulation to visual scanning training does not enhance treatment effect on hemispatial neglect: a randomized,controlled, double-blind study

Background: Left-sided transcutaneous electrical nerve stimulation (TENS) increases right hemispheric activity, which may improve the rehabilitative outcome of hemispatial neglect.

Objective: To examine the behavioral effect of electrical stimulation of the nerve afferents of the left hand during early neuropsychological rehabilitation of post-stroke patients with hemispatial neglect.

Methods: This randomized, controlled, double-blind study included 29 patients (enrolled in the experimental or control group) with left hemispatial neglect after right hemispheric stroke. For 3 weeks, patients received 15 therapeutic sessions involving TENS (active or sham) with a mesh glove applied on the entire left hand during the first 30 minutes of a 45-minute conventional visual scanning training (VST). Signs of hemispatial neglect were assessed using a psychometric test before and after treatment.

Results: Univariate analysis of covariance revealed that differences between the control and experimental groups were not significant after treatment (F(1, 22)?=?0.294, P?=?0.593) when adjusted for pre-treatment scores and time since stroke onset. This suggested that electrical stimulation failed to mitigate the severity of hemispatial neglect symptoms.

Conclusion: Our study did not provide evidence of the effectiveness of TENS when added to VST during early rehabilitation for patients with post-stroke hemispatial neglect. Other techniques (applied alone or together) should be sought to improve recovery in this population.     

An integrated multifunctional platform based on biotin-doped conducting polymer nanowires for cell capture,release, and electrochemical sensing

Here, we propose an integrated multifunctional system constructed by conductive disulfide-biotin-doped polypyrrole nanowires (SS-biotin-Ppy NWs) for capture, release, and in situ quantification of circulating tumor cells (CTCs). A well-ordered three-dimensional nanowire structure equipped with a monoclonal antibody offers a significant impact on the cell-capture efficiency, as well as on electrical- or glutathione (GSH)-mediated release of the captured cells. In addition, the electrochemical identification/detection of the captured cancer cells can be directly conducted on the same Ppy NW platform by using horseradish peroxidase (HRP)-labeled and anti-EpCAM-conjugated nanoparticles (HRP/anti-EpCAM Ppy NPs), showing very high sensitivity and specificity. The signal amplification can be clearly attributed to the catalytic response resulting from enzymatic reduction of hydrogen peroxide on Ppy NWs, consequently generating a greatly increased amperometric response with a detection range of 10 to 1 × 10⁴ cells and a detection limit of as low as 10 cells. Overall, the proposed Ppy NWs not only present a promising platform for effective cell capture and release but also permit cytosensing capability for on-site analysis.     

THE EFFECT OF REPETITIVE ELECTRICAL STIMULATION ON THE MOTOR EVOKED HEMODYNAMIC RESPONSES

The aim of this study was to investigate the influence of short-term repetitive electrical stimulation (rES training session) on the motor-evoked hemodynamic responses. The fMRI echo-planar images (EPI) were recorded before and after the rES training. The right median nerve (MN) was stimulated during rES. The rES training resulted in a significant increase in activity in a number of supraspinal regions, including sensorimotor and associative cortical areas. On the subcortical level, the effect was also found in the cerebellum, the midbrain, and the thalamus. Possible mechanisms of the neuronal plastic changes observed after rES, and memory processes involved in learning are discussed.     

Saliency-guided neural prosthesis for visual attention: Design and simulation

Recently the authors showed that a computational model of visual saliency could account for changes in gaze behavior of monkeys with damage in the primary visual cortex. Here we propose a neural prosthesis to restore eye gaze behavior by electrically stimulating the superior colliculus to drive visual attention. The saliency computational model is used to calculate the stimulation parameters from a real-time camera stream. Our simulations demonstrate that electrodes implanted in the superior colliculus at 1.0 mm spacing are, in principle, able to recover specifically those visual attention behaviors which are lost when the primary visual cortex is damaged.     

心律转复除颤器植入术后电风暴的发生及其对预后的影响

目的调查单中心心律转复除颤器（ICD）植入术后电风暴（ES）的发生率、发作特征和危险因素，并探讨其对患者预后的影响。方法对本中心123例植入ICD的患者进行随访。Es定义为24h内出现3次或3次以上的快速室性心律失常（VA）导致ICD治疗，或ICD监测到持续30s以上的VA但未发放治疗。结果在（26．9±21．3）个月的随访期间，共有41（33．3％）例患者（ES组）发作139次ES（3．4±3．9）次／例，其中29（70．7％）例患者的首次发作在植入后1年内出现，Es发作呈现出6：00—10：00和14：00～17：00两个高峰。多因素Logistic回归分析表明植入ICD作为心脏性猝死二级预防是ES发生的独立危险因素（OR=4．797，P=0．044）。本组共15（12．2％）例患者死亡，Es组死亡率较无Es组（24．4％对6．1％，P=0．003）显著增高，Kaplan—Meier生存曲线分析显示Es组累计生存概率明显低于无Es组（Log—rank检验P〈0．001）。结论Es发作表现为上午和下午两个高峰，可导致死亡率增高，其首次发作多在ICD植入后1年内。植入ICD作为心脏性猝死二级预防是Es发生的独立危险因素。     

Is vernakalant better or not compared with other treatments for conversion acute atrial fibrillation?

Vernakalant has proved to be more rapid in converting recent onset AF to sinus rhythm compared to placebo, amiodarone, propafenone and flecainide.     

Age-related decrease in sensitivity to electrical stimulation is unrelated to skin conductance: An evoked potentials study

ObjectiveWith aging, skin is likely to become less hydrated, thereby increasing its resistance to electrical current. This, rather than sensorial/perceptual differences per se, may be the primary cause of differences between younger and older adults in somatosensorial perception in response to electrical stimuli.MethodsTo assess whether aging alters the perception of electrical stimulation, we compared the perceived intensity of electrical stimuli in younger and older subjects, considering both setpoint intensities and the actual intensities of the current passing through subjects’ skin. This resulted in reliable information about electrical somatosensory perception in both groups at equivalent received amounts of current. Somatosensory evoked potentials (SEPs) enabled the objective evaluation of somatosensitivity in both groups.ResultsAt equivalent received intensities, the mean ratings were significantly lower in older than in younger subjects. SEPs confirmed these results, with older adults having longer latencies and reduced amplitudes.ConclusionsOur results suggest that age-related decreases in somatosensitivity to electrical stimuli are not due to cutaneous physiological changes.SignificanceAge-related increases in electrical somatosensorial and pain thresholds seem to be more attributable to dysfunctions of the peripheral and/or central nervous system, than to non-optimal activation of somatosensorial receptors/nerve fibers due to cutaneous physiological changes.