Numerous exploratory, proof-of-concept and interventional studies have used histaminergic and non-histaminergic human models of itch. However, no reliability studies for such surrogate models have been conducted. This study investigated the test-retest reliability for the response to histamine- and cowhage- (5, 15, 25 spiculae) induced itch in healthy volunteers. Cowhage spiculae were individually applied with tweezers and 1% histamine was applied with a skin prick test (SPT) lancet, both on the volar forearm. The intensity of itch was recorded on a visual analogue scale and self-reported area of itch was assessed 5 and 10 min after itch provocation. Reliability of the evoked itch (area under the curve and peak intensity) was assessed by the coefficient of variation (CV), intra-class correlation coefficient (ICC), and sample size estimation for parallel and cross-over designs. Cowhage (ICC = 0.57-0.77, CVbetween = 97%, CVwithin = 41%) and histamine: (ICC = 0.83-0.93, CVbetween = 97%, CVwithin = 20%) exhibited moderate-to-excellent intra-individual reliability and moderate inter-individual reliability for the itch intensity. For a test-retest observation period of one week, SPT-delivered histamine and application of cowhage-spiculae are reproducible human models of itch. The high inter-individual and low intra-individual variability suggests cross-over designed studies when applicable.

Emerging evidence suggests that some phenotypic features, such as eye or hair colour, might predict pain. We investigated if light and dark eye and hair colour would influence pain in 60 healthy subjects divided in groups of 15 according to their eye-hair colour and gender. Pressure pain thresholds (PPTs), cold pressor test (CPT), and quality of the perceived pain were assessed. Findings indicated that dark pigmentation phenotype is more sensitive in response to CPT.

No abstract

There is a dearth of knowledge about the pattern of pain and somatosensory alterations that co-exist with neuromyelitis optica spectrum disorder (NMOSD). Understanding the presence and underlying mechanisms will assist in better pain management in these patients. This study sought to identify prevalence and pattern of headache, craniofacial pain and abnormalities in somatosensory function within a group of NMOSD patients in Denmark. Six patients (two males, four females; mean age 41.2 ± 8.6 years) participated in a telephone interview. Eight questionnaires were used to assess pain, illness perception, fatigue, anxiety and depression. Pain occurred in several regions, including the head, face, neck, back and legs. Two patients experienced frequent headaches and one had headaches following neck pain. Pain occurred frequently over a 3-month period, ranging from mild to severe and described as ‘burning’ (66.7%), ‘exhausting’ (83.3%) and ‘sharp’ (50%). Correlations were found between pain severity and patients’ ‘ability to walk’ (r=0.889), ‘general activity’ (r=0.901), ‘mood’ (r=0.603), ‘normal work’ (r=0.664), ‘relations with other people’ (r=0.774) and ‘sleep’ (r=0.586). Somatosensory abnormality was only reported in legs. While fatigue had a great impact on patients’ daily life, patients did not report that for anxiety and depression. This study demonstrated that headaches and craniofacial pain occur frequently in NMOSD. Patients’ function, mobility, mood and sleep were all affected by pain. These findings highlight the value of further investigation on headaches, craniofacial and overall pain in NMOSD.