European journal of pain : EJP
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Plasma neurofilament light chain (NFL) has been measured as a biomarker of neuronal damage in various neurological disorders. Elevated tau and β-amyloid levels have been found in patients with fibromyalgia (FM). The aim of the present study was to compare plasma neurofilament levels in fibromyalgia patients with normal controls and to investigate the correlation with clinical features and cognitive tests. ⋯ Plasma neurofilament levels are elevated in patients with fibromyalgia, regardless of disease severity and duration. Neurofilament levels are higher in patients with mild working memory impairment and sleep disorders. Subgroups of patients with primary neuronal damage phenomena could be individualized for prospective evaluation with regard to the possible development of cognitive decline and sleep disturbances, which would justify a tailored therapeutic approach.
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Neuropathic pain is pain due to a disease or lesion of the somatosensory system, and can be either spontaneous, evoked or both. Hyperpathia is a type of evoked pain defined by IASP as 'a painful syndrome characterized by an abnormally painful reaction to a stimulus, especially a repetitive stimulus, as well as an increased threshold'. The literature is sparse, and definitions are unclear and inconsistent. ⋯ Hyperpathia is a syndrome of evoked pain. It is poorly defined and little is known about its clinical presentation. Since it is part of pain symptomatology it is important to have a clear definition and understand the pathophysiology behind. This study explored signs of hyperpathia in a heterogeneous group of patients with peripheral neuropathic pain. We used stimulus-response function and repetitive pinprick stimulation to group patients based on the IASP definition. More studies are needed to understand how symptoms and signs coincide.
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Insomnia is a highly prevalent condition that predisposes individuals to many chronic pain disorders, with most of them showing pronounced sexual dimorphism. We investigated whether experimental insomnia-like sleep disturbances (ESD) affect spontaneous pain and pain sensitivity, and whether sex modulates pain responses. ⋯ Exploration of sex as a modulator suggest that sleep disturbances amplify spontaneous pain and pressure pain sensitivity to a greater extent in females than in males, and this may contribute to females' overrepresentation and disproportionate symptom burden observed for many pain-related disorders for which insomnia is comorbid or a risk factor.
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Danger signals modulate pain perception. Both amplification and attenuation of perceived pain are observed in healthy subjects exposed to danger signals, such as transient threats of an imminent electrical shock. However, exposure to danger signals in real life typically is not transient but constant over minutes to hours. Here, this was experimentally achieved by administering hypercapnic air (7.5% CO2). The primary objective was to investigate whether perceived heat pain would be differentially modulated during this intervention compared to regular air administration. The secondary objective assessed the potential differences of such a modulation with respect to heat intensity level. ⋯ It was shown that hypercapnia leads to reduced perception of noxious heat stimuli. If confirmed by neural data in future studies this could help to better understand the interaction of pain perception and continuous physiological danger signals in clinical pain conditions, potentially allowing for improved treatment of affected individuals.
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This experiment aimed at confirming our incidental observation that, when capsaicin is applied on the volar forearm, raising the arm to a vertical position leads to a dramatic increase in capsaicin-evoked pain and to explore possible underlying mechanisms. ⋯ Capsaicin-evoked pain can be strongly modulated by limb posture and this effect may be caused by an interplay between vascular and nociceptive systems.