NeuroSci, Volume 5, Issue 3 (September 2024) – 2 articles

Background: Chronic pain is highly burdening and multifactorial in etiology. The endogenous-pain-healing system restores body tissue to a non-painful state after an injury leading to pain, and its disruption could represent a relevant mechanism, especially for nursing interventions. Aim: To review the literature and summarize the results that support this hypothesis. Methods: We hypothesized that the mechanism behind this system mainly depends on the endogenous pain modulatory system (EPMS), which is responsible for inhibiting pain after tissue healing is complete and facilitating it when tissue damage is still present. Different biomarkers can quantify EPMS functioning. We reviewed the literature and included relevant information regarding this hypothesis. Results: First, conditioned pain modulation (CPM) measures pain inhibition and is a possible predictor for pain chronification. Second, motor cortex excitability measures the cortical control of the EPMS, which can be assessed through transcranial magnetic stimulation (using intracortical inhibition) or electroencephalography. Modifiable factors disrupt its functioning, such as sleep deprivation, medication overuse, and mental health status, but could be protective, such as exercise, certain medications, mind–body techniques, and non-invasive neuromodulation therapies. The acquisition of neurophysiological knowledge of how the chronicity of pain occurs and the EPMS involvement in this process may allow for better management of these patients. Conclusions: We raised the hypothesis that the impairment of the EPMS (altered cortical excitability and descendent pain modulation pathways) seems to be related to the disruption of the pain healing process and its chronicity. Further longitudinal studies evaluating the relationship between these biomarkers and chronic pain development are necessary. Full article

Background: We have previously shown that static and dynamic resting-state functional connectivity differ between migraineurs with and without photophobia, phonophobia, or osmophobia. Furthermore, some patients with photophobia also experience phonophobia or osmophobia. To investigate the functional connectivity specific to migraineurs with photophobia, we examined the differences in static and dynamic resting-state functional connectivity between patients with and without photophobia, with no phonophobia or osmophobia. Methods: Fifteen migraineurs with photophobia but without phonophobia or osmophobia, as well as 15 sex- and age-matched migraineurs without photophobia, phonophobia, or osmophobia, underwent 3-T functional magnetic resonance imaging during the interictal phase. Static and dynamic resting-state functional connectivity were compared using region-of-interest analyses of 91 cortical, 15 subcortical, and 26 cerebellar areas. Results: Static resting-state functional connectivity analysis revealed ten significant connectivity pairs in patients with photophobia, while dynamic resting-state functional connectivity analysis revealed six significant connectivity pairs in patients with photophobia. Migraineurs with photophobia had significantly lower connectivity between the cerebellar hemisphere and the temporal region than those without photophobia in both static and dynamic studies. Conclusions: Our results show that lower resting-state functional connectivity between the cerebellar hemisphere and the temporal region is specific to migraineurs with photophobia. Full article