Neuromodulation : journal of the International Neuromodulation Society
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In the not-too-distant past, the dorsal root ganglion (DRG) was portrayed as a passive neural structure without involvement in the development or maintenance of chronic neuropathic pain (NP). The DRG was thought of as a structure that merely "supported" physiologic communication between the peripheral nervous system (PNS) and the central nervous system (CNS). Newer scientific information regarding the anatomic and physiologic changes that occur within the DRG as a result of environmental pressures has dispelled this concept and suggests that the DRG is an active participant in the development of NP. This new information, along with new clinical data showing that stimulation of the DRG reduces intensity of pain, suggests that the DRG can be a robust target for neuromodulation therapies. ⋯ The DRG is an active participant in the development of NP. DRG stimulation has multiple effects on the abnormal changes that occur within the DRG as a result of peripheral afferent fiber injury. The sum total of these stimulation effects is to stabilize and decrease hyperexcitability of DRG neurons and thereby decrease NP.
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Recent clinical studies suggest that neurostimulation at the dorsal root entry zone (DREZ) may alleviate neuropathic pain. However, the mechanisms of action for this therapeutic effect are unclear. Here, we examined whether DREZ stimulation inhibits spinal wide-dynamic-range (WDR) neuronal activity in nerve-injured rats. ⋯ Attenuation of WDR neuronal activity may contribute to DREZ stimulation-induced analgesia. This finding supports the notion that DREZ may be a useful target for neuromodulatory control of pain.
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Sacral neuromodulation has been considered as an effective treatment option for various types of chronic voiding dysfunction, but the mechanism of action has not been well understood. The aim of this study was to evaluate the effect of chronic sacral neuromodulation on isolated bladder functions in a rat model of spinal cord injury. ⋯ In our rat model of SCT, SNM seemed to alter adrenergic receptor function in the urinary bladder. Further studies are required to clarify the mechanism of these alterations at the level of bladder receptors following sacral neuromodulation.
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Clinical Trial
Lack of body positional effects on paresthesias when stimulating the dorsal root ganglion (DRG) in the treatment of chronic pain.
One prominent side effect from neurostimulation techniques, and in particular spinal cord stimulation (SCS), is the change in intensity of stimulation when moving from an upright (vertical) to a recumbent or supine (horizontal) position and vice versa. It is well understood that the effects of gravity combined with highly conductive cerebrospinal fluid provide the mechanism by which changes in body position can alter the intensity of stimulation-induced paresthesias. While these effects are well established for leads that are placed within the more medial aspects of the spinal canal, little is known about these potential effects in leads placed in the lateral epidural space and in particular within the neural foramina near the dorsal root ganglion (DRG). ⋯ Neuromodulation of the DRG produces paresthesias that remain consistent across body positions, suggesting that this paradigm may be less susceptible to positional effects than dorsal column stimulation.
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Comparative Study
Is preoperative pain duration important in spinal cord stimulation? A comparison between tonic and burst stimulation.
Conflicting data have been published as to whether the success rate of spinal cord stimulation (SCS) is inversely proportional to the time interval from the initial onset of symptoms to implantation. Recently, a new stimulation design called burst stimulation has been developed that seems to exert its effect by modulating both the medial and lateral pain pathways and has a better effect than tonic stimulation on global pain, back pain, and limb pain. ⋯ These results suggest that the duration of pain is not an exclusion criterion for SCS and that similar success rates can be obtained for longstanding pain and pain of more recent onset.