Do burn injuries during infancy affect pain and sensory sensitivity in later childhood?

Studies in animals and humans suggest that neonatal and early infant pain or stress experiences can induce long-term alterations in somatosensory and pain processing. We studied pain and sensory sensitivity in school-aged children (9-16 years) who had suffered moderate (N=24) or severe (N=24) burn injuries in infancy (6-24 months of age) and 24 controls. Quantitative sensory testing entailing detection and pain thresholds for thermal and mechanical stimuli and perceptual sensitization to tonic heat and repetitive mechanical stimuli was performed. Two testing sites (thenar, trigeminal region), both not affected by the burn injury, were used to determine whether there are global changes in pain sensitivity. The result pattern suggests a differential impact of burn severity. Compared to controls, moderately burned children showed significantly higher mechanical detection thresholds (thenar) and significantly lower mechanical pain thresholds and significantly greater perceptual sensitization to repetitive mechanical stimuli (both testing sites). No significant alterations were observed for thermal stimuli. In contrast, severely burned children showed, compared to controls, primarily alterations in thermal pain sensitivity (elevated pain thresholds at both testing sites, significantly greater perceptual sensitization at the thenar). In these children, mechanical pain sensitivity and detection thresholds were not consistently altered. This differential pattern of altered sensory and pain sensitivity may reflect differences in experienced stress, pain and analgesic treatment between moderately and severely burned children. Most importantly, our findings suggest that early traumatic and painful injuries, such as burns, can induce global, long-term alterations in sensory and pain processing.