Brain Stimul
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Chronic pain resulting from injury of the peripheral or central nervous system may be associated with a significant dysfunction of extensive neural networks. Noninvasive stimulation techniques, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) may be suitable to treat chronic pain as they can act on these networks by modulating neural activities not only in the stimulated area, but also in remote regions that are interconnected to the site of stimulation. Motor cortex was the first cortical target that was proved to be efficacious in chronic pain treatment. ⋯ Therapeutic applications of rTMS in pain syndromes are limited by the short duration of the induced effects, but prolonged pain relief can be obtained by repeating rTMS sessions every day for several weeks. Recent tDCS studies also showed some effects on various types of chronic pain. We review the evidence to date of these two techniques of noninvasive brain stimulation for the treatment of pain.
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Randomized Controlled Trial
Significant analgesic effects of one session of postoperative left prefrontal cortex repetitive transcranial magnetic stimulation: a replication study.
In a recent preliminary trial in 20 patients after gastric bypass surgery, 20 minutes of repetitive transcranial magnetic stimulation (TMS) over the left prefrontal cortex was associated with a 40% reduction in postoperative patient-controlled morphine use. As is the case with all novel scientific findings, and especially those that might have an impact on clinical practice, replicability is paramount. This study sought to test this finding for replication and to more accurately estimate the effect size of this brief intervention on postoperative morphine use and postoperative pain and mood ratings. ⋯ Although more research is needed to verify these observed effects independently, findings from the original postoperative TMS trial were replicated. TMS may have the potential to significantly improve current standards of postoperative care among gastric bypass patients, and further studies may be warranted on other surgical populations. Future investigations should use methodology that permits more definitive conclusions about causal effects of TMS on postoperative pain (for example, double-blinding, sham stimulation that is matched with real TMS with respect to scalp discomfort).
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Vagus nerve stimulation (VNS) is an effective anticonvulsant device and has shown antidepressant effects in chronic treatment resistant depression. Because the vagus nerve sends information to brain regions important in anxiety regulation (locus coeruleus, orbitofrontal cortex, insula, hippocampus and amygdala), this pathway might be involved in perceiving or manifesting various somatic and cognitive symptoms that characterize anxiety disorders. On the basis of this reasoning and reports of anxiolytic effects of VNS in patients treated for epilepsy and depression, we organized an open-label pilot acute trial of adjunctive VNS on top of stable medications, followed by long-term follow-up, to assess the safety and potential efficacy of VNS for patients with treatment resistant anxiety disorders. ⋯ These patients with treatment-resistant anxiety disorders generally tolerated VNS treatment, and there was evidence of acute and long-term improvement in some patients. These open data suggest that further double-blind studies assessing the VNS role in treating anxiety disorders, particularly OCD, may be warranted.