Pain
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The primary aim of this study was to evaluate activity rhythms in fibromyalgia syndrome (FMS) and their association with FMS-related symptoms. We hypothesized that stronger and more consistent activity rhythms would be associated with reduced symptom severity and presentation in FMS. Two hundred ninety-two patients with FMS (mean age = 45.1 ± 11.1; 272 women) provided a 7-day actigraphy recording and responses to questionnaires addressing degree of pain, fatigue, mood, and physical impairment. ⋯ Each activity parameter provided unique discrimination of the clinical set by multivariate test (P = 0.003, 0.018, and 0.007 for Amplitude, Phi, and Mesor, respectively). These results revealed that better pain, fatigue, mood, physical impairment, and sleep outcomes were associated with higher activity range and more rhythmicity (Amplitude), increased mean activity (Mesor), and with earlier timing of peak activity (Phi). Exploratory analyses revealed significantly worse sleep for individuals with low Amplitude and more delayed Phi.
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Chronic pain has a significant impact on quality of life. Measurement of health-related quality of life (HRQoL) is essential in the assessment of pain management outcomes, but different instruments have produced varying results. We assessed the validity of 2 HRQoL instruments, EuroQol 5 dimensions questionnaire (EQ-5D) and 15-dimensional health-related quality of life measure (15D), in patients with challenging chronic pain. ⋯ The principal component explained more variance in the 15D (R = 0.65) than in the EQ-5D (R = 0.43). The study identified differences in the pain-related variables between the EQ-5D and the 15D. In patients with chronic pain, both instruments are valid, but 15D appears somewhat more sensitive than EQ-5D.
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Pain spontaneously activates adaptive and dynamic learning processes affecting the anticipation of, and the responses to, future pain. Computational models of associative learning effectively capture the production and ongoing changes in conditioned anticipatory responses (eg, skin conductance response), but the impact of this dynamic process on unconditional pain responses remains poorly understood. Here, we investigated the dynamic modulation of pain and the nociceptive flexion reflex by fear learning in healthy human adult participants undergoing a classical conditioning procedure involving an acquisition, reversal and extinction phase. ⋯ Moderation analyses further showed that hyperalgesic effects of associability were larger in individuals reporting more harm vigilance and less emotional detachment. Higher harm vigilance was also associated with a stronger mediation of hyperalgesic effects by spinal processes. These results demonstrate how dynamic changes in pain can be explained by associative learning theory and that resilient attitudes towards fear/pain can attenuate the adverse impact of adaptive aversive learning processes on pain.
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Migraine pathophysiology includes altered brainstem excitability, and recent neuromodulatory approaches aimed at controlling migraine episodes have targeted key brainstem relay and modulatory nuclei. In this study, we evaluated the impact of respiratory-gated auricular vagal afferent nerve stimulation (RAVANS), a novel neuromodulatory intervention based on an existing transcutaneous vagus nerve stimulation approach, in the modulation of brainstem activity and connectivity in migraine patients. We applied 3T-functional magnetic resonance imaging with improved in-plane spatial resolution (2.62 × 2.62 mm) in episodic migraine (interictal) and age- and sex-matched healthy controls to evaluate brain response to RAVANS (gated to either inhalation or exhalation) and sham stimulation. ⋯ Increased connectivity was inversely correlated with relative time to the next migraine attack, suggesting clinical relevance to this change in connectivity. Poststimulation effects were also noted immediately after eRAVANS, as we found increased activation in putative pontine serotonergic (ie, nucleus raphe centralis) and noradrenergic (ie, locus coeruleus) nuclei in response to trigeminal sensory afference. Regulation of activity and connectivity of brainstem and cortical regions involved in serotonergic and noradrenergic regulation and pain modulation may constitute an underlying mechanism supporting beneficial clinical outcomes for eRAVANS applied for episodic migraine.
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Considerable research links chronic pain to autonomic nervous system (ANS) dysfunction, specifically low heart rate variability (HRV) mediated by reduced parasympathetic activity. However, little is known about factors that influence ANS function in chronic pain. The ANS is the primary pathway for brain-gut communication, making it of particular interest in gastrointestinal disorders, such as irritable bowel syndrome, characterized by functional abdominal pain (FAP). ⋯ Spectral analysis of electrocardiogram showed that Pain-Persist females had reduced power in the high frequency domain of cardiac activity, ie, reduced parasympathetic "braking" of sympathetic activity, both at rest and during stress. Pain-Remit females exhibited levels of autonomic imbalance intermediate between those of females with persistent FAP and all other participants. Parasympathetically mediated low HRV in young women with persistent FAP may reflect a peripheral mechanism (eg, gut dysfunction) or a central nervous system mechanism (eg, pain amplification or poor emotion self-regulation) involving prolonged sympathetic activation.