Other: Cutaneous sensory abnormalities in children with complex regional pain syndromes (CRPS)

Abstract

Diagnostic criteria for CRPS types I and II, while standardized in adults, are yet to be validated in children. We prospectively evaluated characteristics of pain and cutaneous sensitivity in children who met the modified adult IASP criteria for CRPS using standardized neurologic examinations and quantitative sensory testing (QST). After IRB approval, parental consent, and patient assent, 55 children with unilateral CRPS (52 females, 3 males) ages 7-17 years underwent neurologic examination and QST by a single blinded investigator. Differences in mechanical and thermal thresholds between the affected limb and an identical area of the contralateral asymptomatic limb were measured. Variables were compared using the Mann-Whitney U-test with a Bonferroni-corrected significance level of P < 0.01. Results: All patients developed pain and altered skin sensitivity after trauma. Two distinct groups were apparent: those with brush Allodynia (WA) and those with no brush Allodynia (NA) (median thresholds 6.6 vs. 0, P < 0.01). Groups had similar demographics, duration and type of pain, skin temperature and autonomic signs. All patients had spontaneous pain, median visual analog pain scores were similar between the WA and NA groups (6.4 vs. 5.6, P = 0.21). Cold and warm temperature sensation thresholds were slightly elevated but not significantly different between WA and NA (0.7 vs. -1.5°C; 0.2 vs. 0.6 °C, P < 0.05). Median thresholds for mechanical and thermal hyperalgesia and temporal summation of pricking pain were significantly lower in WA compared to NA group: pricking pain (6.3 vs. 0), temporal summation (8.2 vs. 0), cold pain (5.6 vs. 0.2°C)) and heat pain (-2.2 vs. 1.2°C) (all P < 0.01) Altered cutaneous sensitivity occurred more commonly in the symptomatic area of children with CRPS having mechanical allodynia compared to those with no allodynia and may reflect peripheral and/or central sensitization. Additional studies are needed to elucidate the pain mechanisms of CRPS in children.