Current pain and headache reports
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The hippocampus is involved in pain processing, pain-related attention and anxiety, and stress response. The present review compiles the present knowledge of hippocampal volume, activity, and connectivity regarding migraine. ⋯ For hippocampal volume, a longitudinal study discovered decreased volume in newly diagnosed migraine patients after 1 year. Two cross-sectional studies suggested an adaptive increase of volume at low headache frequency and a maladaptive decrease of volume at higher headache frequency. Patients who carried a COMT Val homozygous were found to have larger hippocampi on both sides compared with healthy controls with the same polymorphism. For hippocampal activation, one study showed greater nociceptive activation in patients with migraine compared to healthy controls, with the activity correlated to headache frequency. Another study showed greater deactivation and higher functional connectivity linked to other pain-processing regions in low frequency compared to high-frequency migraineurs. At resting state, intraregional functional connectivity of hippocampus was demonstrated to be lower, and connectivity of the hippocampus with other brain regions was different in patients carrying specific genetic variants. For structural connectivity, two studies suggest a stronger connectivity between the hippocampus and other corticolimbic regions, and the altered connectivities are responsible for migraine-associated allodynia or placebo effect of migraine. Factors including headache frequency, accumulative number of migraine attacks, anxiety score, depression score, and genetic variants are related to hippocampal morphology and functional changes in people with migraine. Future studies should select participants precisely and appropriately control for genetic variants to investigate the complex relationship between the hippocampus and migraine.
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Curr Pain Headache Rep · Feb 2018
ReviewChronification of Pain: Mechanisms, Current Understanding, and Clinical Implications.
The development of acute to chronic pain involves distinct pathophysiological changes in the peripheral and central nervous systems. This article reviews the mechanisms, etiologies, and management of chronic pain syndromes with updates from recent findings in the literature. ⋯ Chronic post-surgical pain (CPSP) is not limited to major surgeries and can develop after smaller procedures such as hernia repairs. While nerve injury has traditionally been thought to be the culprit for CPSP, it is evident that nerve-sparing surgical techniques are not completely preventative. Regional analgesia and agents such as ketamine, gabapentinoids, and COX-2 inhibitors have also been found to decrease the risks of developing chronic pain to varying degrees. Yet, given the correlation of central sensitization with the development of chronic pain, it is reasonable to utilize aggressive multimodal analgesia whenever possible. Development of chronic pain is typically a result of peripheral and central sensitization, with CPSP being one of the most common presentations. Using minimally invasive surgical techniques may reduce the risk of CPSP. Regional anesthetic techniques and preemptive analgesia should also be utilized when appropriate to reduce the intensity and duration of acute post-operative pain, which has been correlated with higher incidences of chronic pain.
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Curr Pain Headache Rep · Feb 2018
ReviewIntrathecal Drug Delivery and Spinal Cord Stimulation for the Treatment of Cancer Pain.
The purpose of the present investigation is to summarize the body and quality of evidence including the most recent studies in support of intrathecal drug delivery systems and spinal cord stimulation for the treatment of cancer-related pain. ⋯ In the past 3 years, a number of prospective studies have been published supporting intrathecal drug delivery systems for cancer pain. Additional investigation with adjuvants to morphine-based analgesia including dexmedetomidine and ziconotide support drug-induced benefits of patient-controlled intrathecal analgesia. A study has also been recently published regarding cost-savings for intrathecal drug delivery system compared to pharmacologic management, but an analysis in the Ontario, Canada healthcare system projects additional financial costs. Finally, the Polyanalgesic Consensus Committee has updated its recommendations regarding clinical guidelines for intrathecal drug delivery systems to include new information on dosing, trialing, safety, and systemic opioid reduction. There is still a paucity of clinical evidence for spinal cord stimulation in the treatment of cancer pain. There are new intrathecal drugs under investigation including various conopeptides and AYX1. Large, prospective, modern, randomized controlled studies are still needed to support the use of both intrathecal drug delivery systems as well as spinal cord stimulation for cancer pain populations. There are multiple prospective and small randomized controlled studies that highlight a potential promising future for these interventional modalities. Related to the challenge and urgency of cancer pain, the pain practitioner community is moving toward a multimodal approach that includes discussions regarding the role of intrathecal therapies and spinal cord stimulation to the individualized treatment of patients.
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Curr Pain Headache Rep · Feb 2018
ReviewComplex Regional Pain Syndrome, Current Concepts and Treatment Options.
Complex regional pain syndrome (CRPS) refers to a chronic pain condition that is characterized by progressively worsening spontaneous regional pain without dermatomal distribution. The symptomatology includes pain out of proportion in time and severity to the inciting event. The purpose of this review is to present the most current information concerning epidemiology, diagnosis, pathophysiology, and therapy for CRPS. ⋯ In recent years, discovery of pathophysiologic mechanisms of CRPS has led to significant strides in the understanding of the disease process. Continued elucidation of the underlying pathophysiological mechanisms will allow for the development of more targeted and effective evidence-based therapy protocols. Further large clinical trials are needed to investigate mechanisms and treatment of the disorder.
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Curr Pain Headache Rep · Feb 2018
Review Meta AnalysisThe Effect of Ketamine Infusion in the Treatment of Complex Regional Pain Syndrome: a Systemic Review and Meta-analysis.
Complex regional pain syndrome (CRPS) is a painful debilitating neurological condition that accounts for approximately 1.2% of adult chronic pain population. Ketamine, an NMDA receptor antagonist, is an anesthetic agent that has been used by some pain specialists for CRPS. There is a growing body of clinical evidence to support the use of ketamine in the treatment of neuropathic pain, especially CRPS. This meta-analysis study was aimed to examine the efficacy of ketamine in the treatment of CRPS. ⋯ A search of Embase, Pubmed, Web of Knowledge, Cochrane, Clinical Trial.gov , and FDA.gov between Jan 1, 1950, and August 1, 2017, was conducted to evaluate ketamine infusion therapy in the treatment of CRPS. We selected randomized clinical trials or cohort studies for meta-analyses. I 2 index estimates were calculated to test for variability and heterogeneity across the included studies. The primary outcome is pain relief. The effect of ketamine treatment for complex regional pain syndrome was assessed by 0-10 scale numerical rating pain score. The secondary outcome is the pain relief event rate, which is defined as the percentage of participants who achieved 30% or higher pain relief in each of the qualified studies. Our meta-analysis results showed that the Ketamine treatment led to a decreased mean of pain score in comparison to the self-controlled baseline (p < 0.000001). However, there is a statistical significance of between-study heterogeneity. The immediate pain relief event rate was 69% (95% confidence interval (CI) 53%, 84%). The pain relief event rate at the 1-3 months follow-ups was 58% (95% CI 41%, 75%). The current available studies regarding ketamine infusion for CRPS were reviewed, and meta-analyses were conducted to evaluate the efficacy of ketamine infusion in the treatment of CRPS. Our findings suggested that ketamine infusion can provide clinically effective pain relief in short term for less than 3 months. However, because of the high heterogeneity of the included studies and publication bias, additional random controlled trials and standardized multicenter studies are needed to confirm this conclusion. Furthermore, studies are needed to prove long-term efficacy of ketamine infusion in the treatment of CRPS.