Pain activates cortical areas in the preterm newborn brain

To Study the patterns of supraspinal pain processing in neonates, we hypothesized that acute pain causes haemodynamic changes associated with activation of the primary somatosensory cortex. Forty preterm neonates at 28-36 weeks of gestation (mean = 32.0) and at 25-42 h (rnean = 30.7) of age were studied following standardized tactile (skin disinfection) and painful (venipuncture) stimuli. Changes in regional cerebral haemodynamics were monitored by near infrared spectroscopy (NIRS) over both somatosensory cortices in 29 newborns, and over the contralateral somatosensory and occipital areas in I I newborns. Heart rate (HR) and peripheral oxygen saturation (SaO(2)) were recorded simultaneously with MRS parameters: oxygenated [HbO(2)], deoxygenated, and total hemoglobin. Tactile stimulation produced no changes in HR or SaO(2). HR increased in the first 20 s (p < 0.001), while SaO(2) decreased during the 40 s after venipuncture (p, < 0.0001). Following tactile or painful stimulation, [HbO(2)] increased bilaterally regardless of which hand was stimulated (p < 0.0001). Pain-induced [HbO(2)] increases in the contralateral somatosensory cortex (p < 0.05) were not mirrored in the occipital cortex (p > 0.1). Pain-related [HbO(2)] increases were more pronounced in male neonates (p < 0.05 on left, p < 0.00 1 on right), inversely correlated with gestational age (r = -0.53 on left, p < 0.01; r = -0.42 on right, p < 0.05) and directly correlated with postnatal age (r = 0.75 on left, P < 0.0001; r = 0.67 on right, p < 0.0001). Painful and tactile stimuli elicit specific haemodynamic responses in the somatosensory cortex, implying conscious sensory perception in preterm neonates. Somatosensory cortical activation occurs bilaterally following unilateral stimulation and these changes are more pronounced in male neonates or preterm neonates at lower gestational ages. (c) 2006 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.