Neuromodulation : journal of the International Neuromodulation Society
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Spinal cord stimulation (SCS) was performed to test the hypothesis that pain relief data during acute (15 minute intraoperative) and prolonged (5 day) SCS screening have equivalent predictive value for long-term successful SCS control of chronic low back pain and/or lower extremity pain. A retrospective series of patients with chronic low back and/or lower extremity pain underwent either percutaneous or open (ie, laminectomy) SCS implantation during which acute intraoperative followed by prolonged screening trials for percentage pain relief (%PR) were performed. Data were analyzed for (a) correlation between positive predictive value (PPV) of acute and prolonged SCS screening for %PR and (b) PPV of acute vs. prolonged screening %PR for long-term SCS %PR. ⋯ After permanent SCS implantation, at mean follow-up = 9.4 ± 1.5 months, acute and prolonged SCS screening %PR PPV's were each statistically significant for predicting long-term SCS relief of chronic pain (n = 31/38, PPV = 82% and n = 31/36, PPV = 86%, SRCC = 0.462 and 0.433, respectively, p < 0.01). We conclude that successful pain relief during acute SCS screening is highly correlated with successful prolonged SCS screening of chronic low back and/or lower extremity pain relief. Acute and prolonged SCS screening appear to have equivalent predictive value for successful long-term SCS control of chronic low back and/or lower extremity pain. These preliminary results suggest potential justification for eliminating prolonged and retaining acute (intraoperative) SCS screening for selection of permanent SCS implantation candidates.
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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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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.