Neuromodulation : journal of the International Neuromodulation Society
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Spinal cord compression from catheter tip granulomatous masses following intrathecal drug administration may produce devastating permanent neurologic deficits. Some authors have advocated intrathecal catheter placement below the conus medullaris to avoid the possibility of spinal cord involvement. Multiple cases of catheter tip granulomas in the thoracolumbar region have been reported. ⋯ Histologic examination of the mass confirmed a sterile inflammatory mass. It has been suggested that intrathecal catheters be placed below the conus medullaris to avoid the possibility of spinal cord involvement. We present an unusual case documenting devastating permanent neurologic deficits from a catheter tip granuloma in the sacral region.
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The performance of cathode-anode configurations in a cuff electrode to stimulate a single fascicle in a nerve trunk has been investigated theoretically. A three-dimensional volume conductor model of a nerve trunk with four fascicles in a cuff electrode and a model of myelinated nerve fiber stimulation were used to calculate the recruitment of 15 m fibers in each fascicle. The effect of a monopole, a transverse bipole (anode opposite the cathode), and a narrow transverse tripole (guarded cathode) in selectively stimulating 15 m fibers in each fascicle has been quantified and presented as recruitment curves. ⋯ As compared to monopolar and longitudinal tripolar stimulation, the slope of the recruitment curves in transverse bipolar stimulation is reduced considerably, thus allowing improved fine tuning of nerve (and thus force) recruitment. Another advantage of this method is a minimal number of cable connections to the cuff electrode. The cost of the improved selectivity is an increased stimulation current.
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The aim of this study was to investigate the causation of an insufficient clinical response to acute external stimulation after implantation of brain stimulating electrodes in patients with idiopathic Parkinson's disease (IPD). This study represents to our knowledge the first consecutive postoperative monitoring of the electrical properties of electrodes and tissue in this patient cohort. We hypothesized that changes in brain tissue resistance would be etiologic for this clinically observed phenomenon. ⋯ The changes of the voltage drop on the electrodes and the tissue were insignificant over the time course. We conclude that the decline of the clinical benefit is not due to an alteration of tissue resistivity. As an explanation, we postulate that the reactive formation/resolution of edema around the electrode has the same resistivity as the target and is therefore not detectable by our measurements or modulated by a still unknown mechanism.