Pain
-
Randomized Controlled Trial
Cortico-subcortical activation patterns for itch and pain imagery.
The imagery of itch and pain evokes emotional responses and covert motor responses (scratching to itch and withdrawal to pain). This suggests some similarity in cerebral mechanisms. However, itch is more socially contagious than pain, as evidenced by the fact that scratching behaviors can be easily initiated by watching itch-inducing situations, whereas withdrawal is less easily initiated by watching painful situations. ⋯ Connectivity with the aIC was stronger in the primary motor and premotor cortices during pain imagery and stronger in the globus pallidus during itch imagery. These findings indicate that brain regions associated with imagery of itch are the same as those involved in imagery of pain, but their functional networks differ. These differences in brain networks may explain why motor responses to itch are more socially contagious than those related to pain.
-
Recovery following a whiplash injury is varied: approximately 50% of individuals fully recover, 25% develop persistent moderate/severe pain and disability, and 25% experience milder levels of disability. Identification of individuals likely to develop moderate/severe disability or to fully recover may help direct therapeutic resources and optimise treatment. A clinical prediction rule (CPR) is a research-generated tool used to predict outcomes such as likelihood of developing moderate/severe disability or experiencing full recovery from whiplash injury. ⋯ The probability of full recovery was increased in younger individuals with initially lower levels of neck disability (PPV=71%). This study provides initial evidence for a CPR to predict both chronic moderate/severe disability and full recovery following a whiplash injury. Further research is needed to validate the tool, determine the acceptability of the proposed CPR by practitioners, and assess the impact of inclusion in practice.
-
Stressful experiences seem to negatively influence pain perception through as yet unknown mechanisms. As the noradrenergic locus coeruleus (LC) nucleus coordinates many components of the stress response, as well as nociceptive transmission, we evaluated whether the sensory and affective dimension of chronic neuropathic pain worsens in situations of stress due to adaptive changes of LC neurons. Accordingly, male rats were socially isolated for 5 weeks, and in the last 2 weeks, neuropathic pain was induced by chronic constriction injury. ⋯ These changes were accompanied by an increase in tyrosine hydroxylase and gephyrin expression in the LC. Furthermore, intra-LC administration of bicuculline, a γ-aminobutyric acid-A receptor antagonist, attenuated the negative affective effects of pain. These data show that changes in the LC are greater than those expected from the simple summation of each independent factor (pain and stress), revealing mechanisms through which stressors may exacerbate pain perception without affecting the sensorial dimension.
-
Recent studies have indicated an important role of chemokines such as CCL2 in the development of chronic pain. However, the distinct roles of different chemokines in the development and maintenance of neuropathic pain and in their interactions with neurons have not been clearly elucidated. We found that spinal nerve ligation (SNL) not only induced persistent neuropathic pain symptoms, including mechanical allodynia and heat hyperalgesia, but also produced sustained CXCL1 upregulation in the spinal cord. ⋯ SB225002 also attenuated SNL-induced pain hypersensitivity. Collectively, our results have demonstrated a novel form of chemokine-mediated glial-neuronal interaction in the spinal cord that can drive neuropathic pain. Inhibition of the CXCL1-CXCR2 signaling may offer a new therapy for neuropathic pain management.
-
Randomized Controlled Trial
Efficacy, safety, and tolerability of fulranumab, an anti-nerve growth factor antibody, in the treatment of patients with moderate to severe osteoarthritis pain.
Nerve growth factor (NGF) is increased in chronic pain conditions. This study examined analgesic efficacy and safety of fulranumab, a fully human monoclonal anti-NGF antibody, in adults with chronic osteoarthritis pain. Patients (n=466, intent-to-treat) were randomized to receive, in addition to their current pain therapy, subcutaneous injections in 1 of 6 parallel treatment groups: placebo (n=78), fulranumab 1 mg (n=77) or 3 mg (n=79) every 4 weeks (Q4wk), 3 mg (n=76), 6 mg (n=78), or 10 mg (n=78) every 8 weeks (Q8wk). ⋯ Most neurologic-related treatment-emergent adverse events were mild or moderate and resolved at the end of week 12. Serious adverse events occurred in 3 patients, but they were not neurologically related and resolved before study completion. Fulranumab treatment resulted in statistically significant efficacy in pain measures and physical function versus placebo and was generally well tolerated.