Background : Pain in infancy is poorly understood, and medical staff often have difficulty assessing\r\nwhether an infant is in pain. Current pain assessment tools rely on behavioural and\r\nphysiological measures, such as change in facial expression, which may not accurately reflect\r\npain experience. Our ability to measure cortical pain responses in young infants gives us the\r\nfirst opportunity to evaluate pain assessment tools with respect to the sensory input and\r\nestablish whether the resultant pain scores reflect cortical pain processing.\r\nMethods and Findings : Cortical haemodynamic activity was measured in infants, aged 25ââ?¬â??43 wk postmenstrual,\r\nusing near-infrared spectroscopy following a clinically required heel lance and compared to the\r\nmagnitude of the premature infant pain profile (PIPP) score in the same infant to the same\r\nstimulus (nÃ?¼12, 33 test occasions). Overall, there was good correlation between the PIPP score\r\nand the level of cortical activity (regression coefficientÃ?¼0.72, 95% confidence interval [CI] limits\r\n0.32ââ?¬â??1.11, p Ã?¼ 0.001; correlation coefficient Ã?¼ 0.57). Of the different PIPP components, facial\r\nexpression correlated best with cortical activity (regression coefficient Ã?¼ 1.26, 95% CI limits\r\n0.84ââ?¬â??1.67, p , 0.0001; correlation coefficient Ã?¼ 0.74) (n Ã?¼ 12, 33 test occasions). Cortical pain\r\nresponses were still recorded in some infants who did not display a change in facial expression.\r\nConclusions : While painful stimulation generally evokes parallel cortical and behavioural responses in\r\ninfants, pain may be processed at the cortical level without producing detectable behavioural\r\nchanges. As a result, an infant with a low pain score based on behavioural assessment tools\r\nalone may not be pain free.
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