6 results found
Hughes S, Zhao H, Auvinet E, et al., Attenuation of capsaicin-induced ongoing pain and secondary hyperalgesia during exposure to an immersive virtual reality environment, PAIN Reports, ISSN: 2471-2531
Introduction: There is growing evidence that virtual reality (VR) can be used in the treatment of chronic pain conditions. However, further research is required in order to better understand the analgesic mechanisms during sensitised pain states. Objectives: We examined the effects of an immersive polar VR environment on capsaicin-induced ongoing pain and secondary hyperalgesia. We also investigated whether the degree of analgesia was related to baseline conditioned pain modulation (CPM) responses. Methods: Nineteen subjects had baseline CPM and electrical pain perception (EPP) thresholds measured prior to the topical application of capsaicin cream. Visual analogue scale (VAS) ratings were measured to track the development of an ongoing pain state and EPP thresholds were used to measure secondary hyperalgesia. The effects of a passive polar VR environment on ongoing pain and secondary hyperalgesia were compared to sham VR (i.e. 2D monitor screen) in responders to capsaicin (n=15). Results: VR was associated with a transient reduction in ongoing pain and an increase in EPP thresholds in an area of secondary hyperalgesia. Baseline CPM measurements showed a significant correlation with VR-induced changes in secondary hyperalgesia, but not with VR-induced changes in ongoing pain perception. There was no correlation between VR-induced changes in pain perception and VR-induced changes in secondary hyperalgesia. Conclusions: Virtual reality can reduce the perception of capsaicin-induced ongoing pain perception and secondary hyperalgesia. We also show that CPM may provide a means by which to identify individuals likely to respond to VR therapy.
Hughes SW, Hellyer PJ, Sharp DJ, et al., 2019, Diffusion tensor imaging reveals changes in microstructural integrity along compressed nerve roots that correlate with chronic pain symptoms and motor deficiencies in elderly stenosis patients, NeuroImage: Clinical, Vol: 23, ISSN: 2213-1582
Age-related degenerative changes in the lumbar spine frequently result in nerve root compression causing severe pain and disability. Given the increasing incidence of lumbar spinal disorders in the aging population and the discrepancies between the use of current diagnostic imaging tools and clinical symptoms, novel methods of nerve root assessment are needed. We investigated elderly patients with stenosis at L4-L5 or L5-S1 levels. Diffusion tensor imaging (DTI) was used to quantify microstructure in compressed L5 nerve roots and investigate relationships to clinical symptoms and motor neurophysiology. DTI metrics (i.e. FA, MD, AD and RD) were measured at proximal, mid and distal segments along compressed (i.e. L5) and intact (i.e. L4 or S1) nerve roots. FA was significantly reduced in compressed nerve roots and MD, AD and RD were significantly elevated in the most proximal segment of the nerve root studied. FA was significantly correlated with electrophysiological measures of root function: minimum F-wave latency and peripheral motor conduction time (PMCT). In addition, FA along the compressed root also correlated with leg pain and depression score. There was also a relationship between RD and anxiety, leg pain and disability score and AD correlated with depression score. Taken together, these data show that DTI metrics are sensitive to nerve root compression in patients with stenosis as a result of age-related lumbar degeneration. Critically, they show that the changes in microstructural integrity along compressed L5 nerve roots are closely related to a number of clinical symptoms associated with the development of chronic pain as well as neurophysiological assessments of motor function. These inherent relationships between nerve root damage and phenotype suggest that the use DTI is a promising method as a way to stratify treatment selection and predict outcomes.
Hughes S, Grimsey S, Strutton PH, 2018, Primary Motor Cortex Transcranial Direct Current Stimulation Modulates Temporal Summation of the Nociceptive Withdrawal Reflex in Healthy Subjects., Pain Med
Objective: Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) has shown efficacy in a number of chronic pain conditions. Despite attempts to dissect the analgesic mechanisms, it is unknown whether M1 tDCS modulates the central integration of spinal nociception. To test this, we investigated the top-down modulation of spinal excitability using temporal summation (TS) of the nociceptive withdrawal reflex (NWR). Methods: In this randomized, blinded, cross-over study, eight healthy subjects received electrically evoked TS of the NWR, which was delivered at 5 Hz at a threshold and a suprathreshold (1.1× threshold) to elicit TS resulting in different levels of pain. Subjects were asked to rate their pain after each stimulation. Changes in the TS of the NWR and pain ratings were investigated following 20 minutes of 2-mA anodal tDCS or sham stimulation applied over M1. Results: Baseline recordings showed that TS of the NWR was induced with both threshold and suprathreshold stimulation. Suprathreshold stimulation was also associated with a higher pain intensity rating. After brain stimulation, there was no effect over the lower-intensity TS of the NWR or pain ratings in both the tDCS and sham conditions. However, tDCS reduced TS of the NWR and associated pain ratings following higher-intensity suprathreshold stimulation. Conclusions: These results indicate that M1 tDCS can indirectly modulate the central integration of suprathreshold nociceptive processing in the spinal cord. It is possible that the analgesic efficacy of tDCS is dependent on plasticity induced within pain pathways following repeated, high-intensity stimulation, which may explain the beneficial effects seen in chronic pain patients.
Hughes SW, Ali M, Sharma P, et al., 2018, Frequency-dependent top-down modulation of temporal summation by anodal transcranial direct-current stimulation of the primary motor cortex in healthy adults, EUROPEAN JOURNAL OF PAIN, Vol: 22, Pages: 1494-1501, ISSN: 1090-3801
Hughes S, Hickey L, Donaldson LF, et al., 2015, Intrathecal reboxetine suppresses evoked and ongoing neuropathic pain behaviours by restoring spinal noradrenergic inhibitory tone, Pain, Vol: 156, Pages: 328-334, ISSN: 0304-3959
Abstract: The descending noradrenergic (NAergic) projection to the spinal cord forms part of an endogenous analgesic system. After nerve injury, a localised failure in this compensatory system has been implicated as a permissive factor in the development of neuropathic sensitisation. We investigated whether restoring descending NAergic tone with intrathecal reboxetine can oppose the development of the neuropathic pain phenotype after tibial nerve transection (TNT). Rats had a lumbar intrathecal catheter implanted at the time of nerve injury for administration of reboxetine (10 µg) in both acute and chronic dosing experiments. In acute dosing experiments, both intrathecal and systemic (30 mg/kg) reboxetine partially reversed mechanical allodynia. This antiallodynic effect of intrathecal reboxetine was blocked by prior administration of yohimbine ([alpha]2-adrenoceptor antagonist, 30 µg) but not by prazosin ([alpha]1-adrenoceptor antagonist, 30 µg) or propranolol ([beta]-adrenoceptor antagonist, 100 µg). Chronic intrathecal reboxetine (10 µg, intrathecally, twice daily for 2 weeks) suppressed the development of cold and mechanical allodynia. Nerve-injured animals demonstrated a place preference for intrathecal reboxetine, suggesting that it also reduced spontaneous pain. In contrast, an equivalent antiallodynic dose of systemic reboxetine (30 mg/kg) was aversive in both naive and TNT rats. On cessation of chronic intrathecal reboxetine, there was a gradual development of allodynic sensitisation that was indistinguishable from control TNT animals by 7 days after the end of dosing. Our results suggest that pharmacological restoration of spinal NAergic tone with intrathecal reboxetine can suppress both allodynia and spontaneous pain in the TNT model.
Hughes SW, Hickey L, Hulse RP, et al., Endogenous analgesic action of the pontospinal noradrenergic system spatially restricts and temporally delays the progression of neuropathic pain following tibial nerve injury, PAIN
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