Pain
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Although depressive symptoms are common among those living with back pain, there is limited information on the relationship between postsurgical pain reduction and changes in depressive symptoms. The objective of this prospective cohort study was to examine the change in pain and depressive symptoms and to characterize the relationship between pain and depressive symptoms after lumbar spine surgery. We assessed 260 individuals undergoing lumbar spine surgery preoperatively and postoperatively (3 and 6 months) using a pain intensity numeric rating scale and the Patient Health Questionnaire depression scale. ⋯ However, at 6 months, individuals who experienced a reduction in pain (63%) were nearly twice as likely to experience a reduction in depressive symptoms (odds ratio 1.93, 95% CI 1.15 to 3.25) as those who experienced no change or an increase in pain (31%). We found that most individuals experienced clinically important reductions in pain after surgery. We concluded that those whose pain level was reduced at 6 months were more likely to experience a reduction in depressive symptoms.
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Polyneuropathy can be linked to chronic pain but also to reduced pain sensitivity. We investigated peripheral C-nociceptors in painful and painless polyneuropathy patients to identify pain-specific changes. Eleven polyneuropathy patients with persistent spontaneous pain and 8 polyneuropathy patients without spontaneous pain were investigated by routine clinical methods. ⋯ Moreover, spontaneous activity of mechanoinsensitive C-nociceptors correlated to less pronounced activity-dependent slowing of conduction (Kendall's tau=-.48, P=.009), suggesting that axons were included in the sensitization process. Hyperexcitability in mechanoinsensitive C-nociceptors was significantly higher in patients with polyneuropathy and pain compared to patients with polyneuropathy without pain, while the difference was much less prominent in mechanosensitive (polymodal) C-nociceptors. This hyperexcitability may be a major underlying mechanism for the pain experienced by patients with painful peripheral neuropathy.
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Low back pain is associated with plasticity changes and central hypersensitivity in a subset of patients. We performed a case-control study to explore the discriminative ability of different quantitative sensory tests in distinguishing between 40 cases with chronic low back pain and 300 pain-free controls, and to rank these tests according to the extent of their association with chronic pain. Gender, age, height, weight, body mass index, and psychological measures were recorded as potential confounders. ⋯ As measures of discrimination, we estimated receiver operating characteristics (ROC) and likelihood ratios. Six tests seemed useful (in order of their discriminative ability): (1) pressure pain detection threshold at the site of most severe pain (fitted area under the ROC, 0.87), (2) single electrical stimulation pain detection threshold (0.87), (3) single electrical stimulation reflex threshold (0.83), (4) pressure pain tolerance threshold at the site of most severe pain (0.81), (5) pressure pain detection threshold at suprascapular region (0.80), and (6) temporal summation pain threshold (0.80). Pressure and electrical pain modalities seemed most promising and may be used for diagnosis of pain hypersensitivity and potentially for identifying individuals at risk of developing chronic low back pain over time.