Pain
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Chronic deep brain stimulation (DBS) of the periventricular gray (PVG) has been used for the treatment of chronic central pain for decades. In recent years motor cortex stimulation (MCS) has largely supplanted DBS in the surgical management of intractable neuropathic pain of central origin. However, MCS provides satisfactory pain relief in about 50-75% of cases, a range comparable to that reported for DBS (none of the reports are in placebo-controlled studies and hence the further need for caution in evaluating and comparing these results). ⋯ We have found an interesting and consistent correlation between thalamic electrical activity and chronic pain. This low frequency potential may provide an objective index for quantifying chronic pain, and may hold further clues to the mechanism of action of PVG stimulation. It may be possible to use the presence of these slow FPs and the effect of trial PVG DBS on both the clinical status and the FPs to predict the probable success of future pain control in individual patients.
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Complex regional pain syndrome type 1 (CRPS1) often leads to serious activity limitations in everyday life. To date, however, limitations in patients with CRPS1 of an upper limb have not been objectively measured. Therefore, the aim of this study was to determine the long-term impact of upper limb CRPS1 on general mobility and upper limb usage during everyday life, as measured with a novel upper limb-activity monitor (ULAM). ⋯ For upper limb usage outcome measures during sitting, there was a marked difference between CRPS1 patients and controls. Especially patients with dominant side involvement clearly showed less activity of their involved limb during sitting, indicated by significant differences for the mean intensity (P=0.014), percentage (P=0.004), and proportion (P=0.032) of upper limb activity. It is concluded that these ten chronic CRPS1 patients still had limitations in upper limb usage during everyday life, 3.7 years (average) after the causative event.
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Neuropathic pain models, such as the chronic constriction injury (CCI) model, are partial nerve injury models where there exist both intact and injured peripheral axons. Recent studies suggested that dorsal root ganglion (DRG) neurons with intact axons also show the alteration of excitability and gene expression and might have some role in the pathophysiological mechanisms of neuropathic pain. The incidence of pain-related behavior after the CCI is unstable and variable. ⋯ The CCI induced an increased number of BDNF-labeled neurons in the ipsilateral DRG and the increase in BDNF expression was observed mainly in small- and medium-sized neurons that were mainly ATF3-negative. On the other hand, the number of GABA(A)-Rgamma2 subunit mRNA-positive neurons decreased in the ipsilateral DRG and GABA(A)-R- and ATF3-labeled neurons rarely overlapped. These changes in molecular phenotype in intact and injured primary afferents may be involved in the pathophysiological mechanisms of neuropathic pain produced by partial nerve injury.