Neurophysiologic Profiling of At-Risk Low and Very Low Birth-Weight Infants Using Magnetic Resonance Imaging

Abstract

Low birth-weight (LBW) and very low birth-weight (VLBW) newborns have increased risks of brain injuries, growth failure, motor difficulties, developmental coordination disorders or delay, and adult-onset vascular diseases. However, relatively little is known of the neurobiologic underpinnings. To clarify the pathophysiologic vulnerabilities of such neonates, we applied several advanced techniques for assessing brain physiology, namely T2-relaxation-under-spin-tagging (TRUST) magnetic resonance imaging (MRI) and phase-contrast (PC) MRI. This enabled quantification of oxygen extraction fraction (OEF), global cerebral blood flow (CBF), and cerebral metabolic rate of oxygen (CMRO2). A total of 50 neonates (LBW-VLBW, 41; term controls, 9) participated in this study. LBW-VLBW neonates were further stratified as those with (LBW-VLBW-a, 24) and without (LBW-VLBW-n, 17) structural MRI (sMRI) abnormalities. TRUST and PC MRI studies were undertaken to determine OEF, CBF, and CMRO2. Ultimately, CMRO2 proved significantly lower (p = 0.01) in LBW-VLBW (vs term) neonates, both LBW-VLBW-a and LBW-VLBW-n subsets showing significantly greater physiologic deficits than term controls (p = 0.03 and p = 0.04, respectively). CMRO2 and CBF in LBW-VLBW-a and LBW-VLBW-n subsets did not differ significantly (p > 0.05), although OEF showed a tendency to diverge (p = 0.15). However, OEF values in the LBW-VLBW-n subset differed significantly from those of term controls (p = 0.02). Compared with brain volume or body weight, these physiologic parameters yield higher area-under-the-curve (AUC) values for distinguishing neonates of the LBW-VLBW-a subset. The latter displayed distinct cerebral metabolic and hemodynamic, whereas changes were marginal in the LBW-VLBW-n subset (i.e., higher OEF and lower CBF and CMRO2) by comparison. Physiologic imaging may therefore be useful in identifying LBW-VLBW newborns at high risk of irreversible brain damage.

Cerebrovascular reactivity to carbon dioxide tension in newborns: data from combined time-resolved near-infrared spectroscopy and diffuse correlation spectroscopy

“…The calculated values of tCMRO 2 (0.52 mlO 2 ∕100 g∕min) were lower compared to previous studies: neonates in intensive care units at different gestational ages 20,21 (∼1.0 ml O 2 ∕ 100 g∕min) and healthy and non-sedated neonates aged between 35 and 42 gestational weeks (0.76 mlO 2 ∕100 g∕min, 18 0.60 mlO 2 ∕100 g∕min, 19 and 1.2 mlO 2 ∕100 g∕min 22 ). This difference can partly be explained by the fact that StO 2 overestimates cerebro-venous saturation due to the arterial contribution to the NIRS signal.…”

Measuring Quantitative Cerebral Blood Flow in Healthy Children: A Systematic Review of Neuroimaging Techniques

“…For the studies that reported age in gestational weeks, CBF of the whole brain appeared to be much higher—ranging from 17 to 90 mL/100 g/min in subjects aged between 34 and 114 gestational weeks 37,40 . Several studies included both full and early‐term infants and demonstrated that CBF in pre‐term infants was significantly lower than those born in full‐term 34,37,44 . Regarding the factors affecting CBF in infants, only one study found that CBF (ranging between 17 and 90 mL/100 g/min) measured by PC MRI increased with age among infants between 34 and 114 gestational weeks at the time of scan 37 …”

“…Since some of these studies included CBF values in pre-term infants, we have found that whole brain CBF in full-term infants was generally higher than those born pre-term measured by ASL and PC MRI. 34,37,39,44 Taken together, the CBF alterations between birth and early adulthood may reflect energy consumption during different stages of brain development, both structurally and cognitively.…”

“…37,40 Several studies included both full and earlyterm infants and demonstrated that CBF in pre-term infants was significantly lower than those born in full-term. 34,37,44 Regarding the factors affecting CBF in infants, only one study found that CBF (ranging between 17 and 90 mL/100 g/min) measured by PC MRI increased with age among infants between 34 and 114 gestational weeks at the time of scan. 37…”