Offset Analgesia as a Measure of Central Sensitization in Children

Study Summary

Pediatric chronic pain disorders are common and consequential in Western societies, occurring in 25-80% of population-based samples with a median prevalence of 11-38% and significant pain-related disability in 3-5% of these children. Pediatric chronic pain disorders have a negative impact on many aspects children's lives including mobility, night sleep, school attendance, peer relationships, family functioning, and overall quality of life. Parents caring for these children risk loss of parental earnings, and these disorders place a high financial burden on healthcare. In a nationally representative sample in the United States, costs related to health care were significantly higher ($1,339 per capita) for children with chronic pain disorders compared to children with common pediatric health conditions of ADHD, asthma and obesity. In children with clinical chronic pain conditions, such as daily headaches or fibromyalgia, chronic pain is presumably a persistent state of an overly excitable nervous system. This phenomenon known as central sensitization is characterized by excessive pain sensitivity that occurs in response to non-painful stimuli, such as light touch or contact with clothing, and slightly painful stimuli, such as a light pinprick. This hypersensitivity results from peculiar changes in the working of the central nervous system, including the spinal cord and brain, and leads to unusual intensification of pain that is out of proportion to the inciting stimulus. For example, light touch from clothing on the skin is perceived as intensely painful. Central sensitization is also thought to contribute to the spreading of pain to other body sites in several chronic pain disorders. In chronic pain disorders, the function of the central descending inhibitory modulating system is likely impaired and is traditionally measured by a phenomenon identified as "conditioned pain modulation (CPM)" and more recently measured by a phenomenon of "offset analgesia" (OA). The O

Primary Outcome

A reduction in self-reported pain intensity when a moderate heat-pain stimulus is applied for 5 seconds, raised by 1 degree C for 5 seconds, reduced by 1 degree C, and held for 20 seconds. During all tests, patients will rate heat pain intensity continuously in real time using the linear, electronic visual analogue scale (eVAS). Patients will use their dominant hand to operate sliding knob of the eVAS with the following two anchors on 0 to 100 mm line. The left endpoint designated as "no pain se

Interventions

• OTHER Offset analgesia