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The biopsychosocial model (BPS) of chronic pain aspires to be comprehensive, incorporating psychological and social factors omitted from biomedical models. Although psychosocial factors are viewed as highly influential in understanding behavioral and psychological responses to pain, these factors are usually viewed as modifiers of biological causes of the experience of pain itself, rather than as equal contributors to pain. To further advance the BPS model, we re-examine a classic 1994 paper by Wilbert "Bill" Fordyce, "Pain and suffering: what is the unit?" In this paper, Fordyce suggested that pain-related disability and suffering should be viewed as "transdermal", as having causes both inside and outside the body. We consider Fordyce's paper theoretically important because this concept allows us to more fully break free of the medical model of chronic pain than customary formulations of the BPS model. It makes it possible to place psychological and social factors on an equal footing with biological ones in explaining pain itself and to remove distinctions between pain mechanisms and pain meanings. The brain's salience network now offers a platform on which diverse influences on pain experience-from nociception to multisensory indicators of safety or danger-can be integrated, bridging the gap between impersonal nociceptive mechanisms and personal meanings. We also argue that Fordyce's article is practically important because this concept expands the BPS model beyond the bounds of the clinical encounter, opening the door to the full range of social, psychological, and biological interventions, empowering patients and non-medical providers to tackle chronic pain.
Learn More >The thermal grill illusion of pain (TGIP) is a paradoxical burning pain sensation elicited by the simultaneous application of innocuous cutaneous warm and cold stimuli with a thermode ('thermal grill') consisting of interlaced heated and cooled bars. Its neurophysiological mechanisms are unclear, but TGIP may have some mechanisms in common with pathological pain, including central sensitization in particular, through the involvement of N-methyl-D-aspartate (NMDA) receptors. However, few studies have investigated TGIP in chronic pain patients and its clinical relevance is uncertain. We hypothesized that the TGIP would be increased in comparison with controls in patients with fibromyalgia or irritable bowel syndrome (IBS), which are regarded as typical "nociplastic" primary pain syndromes related to changes in central pain processing. We compared the sensations elicited by a large range of combinations of temperature differentials between the warm and cold bars of a thermal grill applied to the hand between patients with fibromyalgia (n = 30) or IBS (n= 30) and controls (n = 30). The percentage of TGIP responses, and the intensity and unpleasantness of TGIP were significantly greater in patients than controls. Furthermore, positive correlations were found between TGIP intensity and clinical pain intensity, and between TGIP intensity and the cold pain threshold measured on the hand. These results are consistent with our working hypothesis of shared mechanisms between TGIP and clinical pain mechanisms in patients with nociplastic chronic pain syndromes and suggest that TGIP might represent a clinical marker of central sensitization in these patients.
Learn More >Current research indicates that spinal cord stimulation (SCS) has a positive short-term impact on outcomes such as quality of life, pain, and productivity in patients with chronic neuropathic pain. However, there is a need for studies on larger population samples. This study utilized data from Swedish national registers to analyze change and predictors of sick leave and disability pension two years before and after SCS treatment. Patients with SCS implanted between 2006-2017, and a reference group consisting of 5 individuals matched to each SCS patient without replacement with respect to age, sex, and region of residence, were included. A difference-in-difference approach was used to compare the average change (two years after treatment versus two years before treatment) in net disability days and indirect cost related to disability days for the SCS group, compared to the average change for the reference group. The results showed that SCS treatment in Sweden is associated with a decrease of 21 disability days and consequent decrease in indirect cost of €3,372 in working age patients. Large work loss prior to index date was also demonstrated (average 214 days one year prior), indicating a significant burden on the patient, employers, and the society at large. The number of disability days varied considerably depending on age, sex, socioeconomic variables, and comorbidities, however, the effect of SCS appeared to have little association with patient characteristics. This economic benefit needs to be considered, as well as the clinical outcome, when evaluating the full societal value of SCS.
Learn More >Leprosy-related multiple mononeuropathy offers a pattern of impairment where neuropathy with and without neuropathic pain (NeP) are present in the same individual, thus allowing to investigate peripheral sensory and innervation in both conditions. This cross-sectional study collected data on clinical and neurological examination, pain-assessment questionnaires, quantitative sensory test, and intraepidermal nerve fiber density (IENFD) of patients with leprosy and divided the cohort into two groups: with (P+) and without NeP (P-). Further, we assessed mirror body areas in the same NeP individuals with bilateral neuropathy also presenting unilateral NeP. Pain-free patients having unilateral neuropathy were controls. A total of 37 P+ patients and 22 P- patients were evaluated. Limb areas with NeP had signs of C-fiber dysfunction and hyperesthesia on QST compared with limb areas having neuropathy without NeP. Skin denervation was found in all leprosy patients. Comparisons of limbs with and without neuropathy, and with and without NeP revealed that higher heat pain thresholds (HPT) were associated with neuropathic pain areas, whereas less altered HPT was correlated with higher fiber density. Furthermore, a relationship was found between time of leprosy treatment termination and more intense neuropathy, expressed by HPT increasing 0.03 °C each month. As expected, interindividual comparisons failed to show differences in IENFD and subepidermal plexus areas between patients P+ and P- (p=0.2980, p = 0.9044; respectively). Higher HPT and lower mechanical detection threshold were related to NeP. The present study pointed out the relevance of intra-individual comparisons including mirror areas when assessing local changes in peripheral NeP.
Learn More >The aim of this systematic review is to summarize the data obtained from randomized controlled trials looking at new pharmacologic treatments for endometriosis published over the last decade with a focus on hormonal therapeutic options for endometriosis-associated pelvic pain (EAPP), excluding studies focusing on fertility.
Learn More >This brief review describes the etiology, pathophysiology, clinical features, therapy and prognosis of the diabetic mononeuropathies and diabetic amyotrophy and neuropathic cachexia. Mononeuropathies include cranial neuropathies, of which the oculomotor nerve is most commonly affected, and are thought to be due to microvascular occlusion. Peripherally, entrapment neuropathies occur in both the upper and lower limbs and are due to compression of an already damaged nerve in anatomically restricted channels. Diabetic radiculopathies occur in the dermatones of the thorax and abdomen, mimicking intraabdominal or intrathoracic pathology. I also describe the features of the rare but very distinctive diabetic amyotrophy and neuropathic cachexia. Overall, the prognosis from these conditions is excellent with residual pain or muscle weakness being rare with the exception of diabetic amyotrophy where the prognosis is dependent upon cooperation with intensive rehabilitation. Therapies include "watchful waiting," physical therapy and rarely surgical intervention, which may be urgently needed for nerve decompression and reversal of motor defects.
Learn More >(1) Background: Vestibular migraine (VM) and Meniere's disease (MD) share multiple features in terms of clinical presentations and auditory-vestibular dysfunctions, e.g., vertigo, hearing loss, and headache. Therefore, differentiation between VM and MD is of great significance. (2) Methods: We retrospectively analyzed the medical records of 110 patients with VM and 110 patients with MD. We at first established a regression equation by using logistic regression analysis. Furthermore, sensitivity, specificity, accuracy, positive predicted value (PV), and negative PV of screened parameters were assessed and intuitively displayed by receiver operating characteristic curve (ROC curve). Then, two visualization tools, i.e., nomograph and applet, were established for convenience of clinicians. Furthermore, other patients with VM or MD were recruited to validate the power of the equation by ROC curve and the Gruppo Italiano per la Valutazione degli Interventi in Terapia Intensiva (GiViTI) calibration belt. (3) Results: The clinical manifestations and auditory-vestibular functions could help differentiate VM from MD, including attack frequency (X5), phonophobia (X13), electrocochleogram (ECochG) (X18), head-shaking test (HST) (X23), ocular vestibular evoked myogenic potential (o-VEMP) (X27), and horizontal gain of vestibular autorotation test (VAT) (X30). On the basis of statistically significant parameters screened by Chi-square test and multivariable double logistic regression analysis, we established a regression equation: P = 1/[1 + e] (P, predictive value; e, natural logarithm). Nomographs and applets were used to visualize our result. After validation, the prediction model showed good discriminative power and calibrating power. (4) Conclusions: Our study suggested that a diagnostic algorithm based on available clinical features and an auditory-vestibular function regression equation is clinically effective and feasible as a differentiating tool and could improve the differential diagnosis between VM and MD.
Learn More >Obstructive sleep apnea (OSA) is a relatively common disease in the general population. Besides its interaction with many comorbidities, it can also interact with potentially painful conditions and modulate its course. The association between OSA and pain modulation has recently been a topic of concern for many scientists. The mechanism underlying OSA-related pain connection has been linked with different pathophysiological changes in OSA and various pain mechanisms. Furthermore, it may cause both chronic and acute pain aggravation as well as potentially influencing the antinociceptive mechanism. Characteristic changes in OSA such as nocturnal hypoxemia, sleep fragmentation, and systemic inflammation are considered to have a curtailing impact on pain perception. Hypoxemia in OSA has been proven to have a significant impact on increased expression of proinflammatory cytokines influencing the hyperalgesic priming of nociceptors. Moreover, hypoxia markers by themselves are hypothesized to modulate intracellular signal transduction in neurons and have an impact on nociceptive sensitization. Pain management in patients with OSA may create problems arousing from alterations in neuropeptide systems and overexpression of opioid receptors in hypoxia conditions, leading to intensification of side effects, e.g., respiratory depression and increased opioid sensitivity for analgesic effects. In this paper, we summarize the current knowledge regarding pain and pain treatment in OSA with a focus on molecular mechanisms leading to nociceptive modulation.
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