Neuromodulation : journal of the International Neuromodulation Society
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Neuroprostheses enabling patients to ascend and descend stairs can provide real functional gain. A novel finite state control scheme is presented and validated experimentally. The motion tasks Ascent and Descent are specified by sequences of motion phases for each leg separately. ⋯ Feasibility of the approach has been successfully demonstrated. Future work will concentrate on improved foot clearance during Ascent and closed loop controlled muscle activation in selected motion phases of both Ascent and Descent. The approach is also suited for implanted lower extremity neuroprostheses.
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The objectives of this study were to assess the effectiveness of cervical spinal cord stimulation in the management of intractable pain syndromes affecting the upper limb and face and to assess the reliability of a specific electrode system in this mobile environment. Forty-one patients, aged 26-76 years (median 48) with neuropathic or ischemic pain underwent the cervical epidural implantation of identical dual two-contact paddle (four contacts per system) laminectomy electrodes. Follow-up (from 5 months to 11 years, 3 months; median 4 years, 7 months) was by multiple consultations carried out by the surgeon and/or in a nurse-led specialist clinic. ⋯ Lead fracture rate was 15% of the original (11% of the total including replacements) and only 7% (5%) became dislodged. We conclude that the electrode system described provides reliable and sustained cervical cord stimulation. The outcomes are comparable with thoracic cord stimulation for neuropathic and ischemic syndromes.
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Individual electric and geometric characteristics of neural substructures can have surprising effects on artificially controlled neural signaling. A rule of thumb approved for the stimulation of long peripheral axons may not hold when the central nervous system is involved. This is demonstrated here with a comparison of results from the electrically stimulated cochlea, retina, and spinal cord. ⋯ Bipolar cells in the retina are expected to respond with neurotransmitter release before a spike is generated in the ganglion cell, even when they are far away from the electrode. Epidural stimulation of the lumbar spinal cord predominantly stimulates large sensory axons in the dorsal roots which induce muscle reflex responses. Analysis with the generalized activating function, computer simulations of the nonlinear neural membrane behavior together with experimental and clinical data analysis enlighten our understanding of artificial firing patterns influenced by neural prostheses.
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The objective of this research was to demonstrate the potential of using peroneal nerve activity to derive timing control for stimulation in foot drop correction and to attempt recording and stimulation through the same electrode. Two subjects were implanted with cuff electrodes on the peroneal nerve. ⋯ The switching circuit successfully allowed for simultaneous recording and stimulation through the same cuff electrode. We conclude that the peroneal nerve can potentially be used to record sensory information for derivation of a stimulator control signal in a foot drop application, while at the same time being stimulated to activate foot dorsiflexors.