Neuromodulation : journal of the International Neuromodulation Society
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It has been known for decades that neurons in vitro and in vivo respond in a polarity-specific manner to changes in their electrical environment. Likewise, investigators have passed direct current (DC) across the human head for decades in attempts to alter brain function and behavior. Recent human data, however, have put this technique on a more solid empirical footing and it has re-emerged from obscurity as a "new," noninvasive means of neuromodulation, called transcranial direct current stimulation (TDCS). ⋯ The field is very young and many findings will require replication. Nevertheless, TDCS appears to have the potential to be a simple and safe means of neuromodulation.
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Rechargeable spinal cord stimulation (RSCS) systems have been advocated as a way to reduce replacement surgeries, overall costs, and the morbidity of therapy. However, little data exist as to patients' experiences with these devices, which require more care and maintenance than prior primary cell systems. We analyzed patient experiences with RSCS. ⋯ RSCS systems benefit most patients. However, in some patients, the lifestyle costs of recharging may not make RSCS an appropriate means of pain management. Several areas of improvement exist for the design of future devices.
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The excitability of sensorimotor cortex and spinal motoneurones can be modulated by afferent signals arising from the periphery. Low- and high-frequency vibrations activate separate classes of afferent units in the periphery. Low-frequency vibrations (2-100 Hz) activate the type I fast adapting afferent units (FA-I), whereas high-frequency vibrations (60-1000 Hz) preferentially activate the type II units (FA-II). Muscle spindles are also sensitive to high-frequency mechanical vibrations. Motor-evoked potentials (MEP) generated in response to transcranial magnetic stimulation (TMS) can be modulated by afferent signals. However, it is not clear whether these interactions take place at cortical or spinal cord levels. ⋯ The results suggest that a cerebrovascular accident influences the modulatory effects of afferent inputs at both spinal and cortical levels, and in time, as reorganization takes place, these altered influences settle towards normal levels.