Central pain modulation in children with functional abdominal pain related disorders

Introduction:Functional abdominal pain related disorders (FAPD) are common among young individuals. To date, relatively little is known regarding the function of the central pain mechanisms in this vulnerable group. Therefore, this study aimed to compare conditioned pain modulation (CPM), pressure algometry and psychosocial variables in young children (aged 6-12 years) with FAPD and healthy controls. Methods:Thirty-nine children diagnosed with FAPD were compared with 36 age –and sex matched pain-free controls. Pressure algometry was used to assess pressure pain thresholds at both symptomatic (umbilicus) and non-symptomatic (trapezius and tibia) test sites. CPM was recorded as an increase in the pain pressure threshold at the trapezius test site in response to experimental conditioning pain imposed by the cold pressure task (12°C ± 1°C). The assessors were blinded to the type of subject assessed. Parent-proxy and/or self-reported questionnaires were used to assess pain intensity, functional disability, pain-related fear and parental pain catastrophizing. Results:Compared with pain-free controls, young children with FAPD showed lower pressure pain thresholds at all test sides (P<.5), a less efficient CPM response (P=.2), more functional disability (P<.1) and pain related fear (P<.1). Parents of children with FAPD catastrophized more about their child’s pain than parents of healthy controls (P<.1). Discussion:Young children with FAPD demonstrated less efficient central pain modulation. Future research should control for psychosocial variables while testing CPM, given their direct effect on descending pain modulation through activation of the facilitatory pathways. Process evaluation: The full-out written manuscript of this study is currently under review by all co-authors prior to the submission process. Developing a standardized CPM paradigm for our study population, as well as selecting the proper questionnaires to assess for psychosocial variables was challenging, given their young age (6-12 years). Other experienced problems related to this study can mainly be categorized as practical problems, such as patient recruitment and availability of the assessors and the testing room. References: Morris MC, Walker LS, Bruehl S, Stone AL, Mielock AS, Rao U. Impaired conditioned pain modulation in youth with functional abdominal pain. Pain [Internet]. 216;157(1):2375–81. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27389918 Williams AE, Heitkemper M, Self MM, Czyzewski DI, Shulman RJ. Endogenous inhibition of somatic pain is impaired in girls with irritable bowel syndrome compared with healthy girls. J Pain [Internet]. Elsevier Ltd; 213;14(9):921–3. Available from: http://dx.doi.org/1.116/j.jpain.213.3.3 Pas R, Ickmans K, Oosterwijck S Van, Van Der Cruyssen K, Foubert A, Leysen L, et al. Hyperexcitability of the Central Nervous System in Children with Chronic Pain: A Systematic Review. Pain Med [Internet]. 217;(January):1–11. Available from: https://academic.oup.com/painmedicine/advance-article-abstract/doi/1.193/pm/pnx32/478317