The journal of pain : official journal of the American Pain Society
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The aim of the study is to test if sustained nociceptive mechanical stimulation (SNMS) of latent myofascial trigger points (MTrPs) induces widespread mechanical hyperalgesia. SNMS was obtained by inserting and retaining an intramuscular electromyographic (EMG) needle within a latent MTrP or a nonMTrP in the finger extensor muscle for 8 minutes in 12 healthy subjects. Pain intensity (VAS) and referred pain area induced by SNMS were recorded. Pressure pain threshold (PPT) was measured immediately before and after, and 10-, 20-, and 30-minutes after SNMS at the midpoint of the contralateral tibialis anterior muscle. Surface and intramuscular EMG during SNMS were recorded. When compared to nonMTrPs, maximal VAS and the area under VAS curve (VASauc) were significantly higher and larger during SNMS of latent MTrPs (both, P < .05); there was a significant decrease in PPT 10 minutes, 20 minutes, and 30 minutes postSNMS of latent MTrPs (all, P < .05). Muscle cramps following SNMS of latent MTrPs were positively associated with VASauc (r = .72, P = .009) and referred pain area (r = .60, P = .03). Painful stimulation of latent MTrPs can initiate widespread central sensitization. Muscle cramps contribute to the induction of local and referred pain. ⋯ This study shows that MTrPs are one of the important peripheral pain generators and initiators for central sensitization. Therapeutic methods for decreasing the sensitivity and motor-unit excitability of MTrPs may prevent the development of muscle cramps and thus decrease local and referred pain.
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Our aim was to describe the referred pain patterns and size of areas of trigger points (TrPs) in the masticatory and neck-shoulder muscles of women with myofascial temporomandibular disorders (TMD). Twenty-five women with myofascial TMD and 25 healthy matched women participated. Bilateral temporalis, deep masseter, superficial masseter, sternocleidomastoid, upper trapezius and suboccipital muscles were examined for TrPs by an assessor blinded to the subjects' condition. TrPs were identified with manual palpation and categorized into active and latent according to proposed criteria. The referred pain areas were drawn on anatomical maps, digitalized, and measured. The occurrence of active (P < .001) and latent TrPs (P = .04) were different between groups. In all muscles, there were significantly more active and latent TrP in patients than controls (P < .001). Significant differences in referred pain areas between groups (P < .001) and muscles (P < .001) were found: the referred pain areas were larger in patients (P < .001), and the referred pain area elicited by suboccipital TrPs was greater than the referred pain from other TrPs (P < .001). Referred pain areas from neck TrPs were greater than the pain areas from masticatory muscle TrPs (P < .01). Referred pain areas of masticatory TrPs were not different (P > .703). The local and referred pain elicited from active TrPs in the masticatory and neck-shoulder muscles shared similar pain pattern as spontaneous TMD, which supports the concept of peripheral and central sensitization mechanisms in myofascial TMD. ⋯ The current study showed the existence of multiple active muscle TrPs in the masticatory and neck-shoulder muscles in women with myofascial TMD pain. The local and referred pain elicited from active TrPs reproduced pain complaints in these patients. Further, referred pain areas were larger in TMD pain patients than in healthy controls. The results are also in accordance with the notion of peripheral and central sensitization mechanisms in patients with myofascial TMD.
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Multicenter Study Clinical Trial
Initial Psychometric Properties of the Pain Care Quality Survey (PainCQ).
This study examined the psychometric properties of the Pain Care Quality (PainCQ) survey, a new instrument to measure the quality of nursing and interdisciplinary care related to pain management. Hospitalized medical/surgical oncology patients with pain from 3 states completed the 44-item version of the PainCQ survey following completion of a nursing shift. Interdisciplinary items were evaluated over the entire hospital stay; nursing care was evaluated during the previous shift. The sample included 109 patients ranging in age from 20 to 84 (mean = 53.09). The sample was 58.7% female, 88% non-Hispanic white. Principal Axis Factoring with an oblimin rotation was used as factors were correlated. Two scales resulted. The PainCQ-Interdisciplinary scale included 11 items representing 2 constructs and explaining 47.1% of shared item variance: partnership with the health care team (k = 6 items; α = .85) and comprehensive interdisciplinary pain care (k = 5 items; α = .76). The PainCQ-Nursing scale measured three constructs and explained 60.8 % of shared item variance: being treated right (k = 15 items; α = .95), comprehensive nursing pain care (k = 3 items; α = .77), and efficacy of pain management (k =4 items; α = .87). Results supported the internal consistency reliability and structural validity of the PainCQ survey with 33 items. ⋯ This article presents the psychometric properties of a new tool to measure interdisciplinary and nursing care quality related to pain management from the patient's perspective. This tool can be used for research and as a clinical performance measure to monitor and improve quality of care and patient outcomes.
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Central sensitization is one form of long-term plasticity in the central nervous system. Sustained activation of primary sensory fibers supplying dorsal horn can induce long-lasting increases in the discharge amplitude of primary afferent synapses. This is similar to the long-term potentiation that occurs in many other CNS regions. Drugs that limit the short-duration wind-up component of central sensitization include sodium channel blockers, NMDA antagonists, fast-acting opioids and the calcium-channel ligands gabapentin and pregabalin (S-3-(aminomethyl)-5-methylhexanoic acid). Pregabalin, like gabapentin, binds selectively to the Ca(V)α₂δ auxiliary subunit of presynaptic voltage-gated calcium channels. The conformational changes induced by this binding inhibit abnormally intense neuronal activity by reducing the synaptic release of glutamate and other neurotransmitters. Recent identification in animal models of increased Ca(V)α₂δ protein expression in chronic pain, allodynia, and hyperalgesia have drawn additional interest to drugs that bind the Ca(V)α₂δ site. Experimental studies with animal models and healthy human volunteers have shown that pregabalin reduces nociceptive responses, particularly in conditions involving central sensitization. Since these actions occur with relatively modest effects on physiological and cognitive functions, pregabalin may be an important consideration in the pharmacotherapy of otherwise difficult-to-treat pain syndromes. ⋯ This focus article discusses how the central nervous system plasticity phenomenon, central sensitization, is established in the induction and maintenance of chronic pain, allodynia, and hyperalgesia. In addition, it explores the neurophysiologic actions of the calcium-channel ligands gabapentin and pregabalin in limiting pathological manifestations of central sensitization.
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Emerging evidence suggests that some individuals with regional pain disorders go on to develop chronic widespread pain (CWP). However, the mechanism behind this transition and the nature of risk factors that predispose a person to develop CWP remain to be elucidated. The purpose of this study was to describe the frequency with which participants with chronic back or neck pain develop CWP and to determine the risk factors associated with this development. In a sample of 512 individuals, we found that nearly a quarter (22.6%) of subjects who presented with regional back or neck pain in 2001/2002 had developed CWP by 2007. Logistic regression indicated that 7 factors were associated with the transition to CWP: moderate or severe pain intensity, female gender, history of abuse, family history of CWP, severe interference with general activity, having 1 or more central sensitivity syndromes, and using more pain management strategies. History of abuse was not significant in multivariate analysis. Notably, number of depressive symptoms endorsed, pain duration, age, body mass index, number of medication classes used, and receipt of disability benefits were not significantly associated with this transition. ⋯ This study offers insight into risk factors associated with the development of CWP. This information not only offers clues as to the mechanism behind the expansion of pain sensitivity from a regional pain locus to a widespread pain disorder but also provides insight as to how clinicians might mitigate this transition.