Clinical Factors That Affect the Relationship between Head Circumference and Brain Volume in Very-Low-Birth-Weight Infants

BACKGROUND AND PURPOSE: Measuring head circumference (HC) in infants is an easy screening procedure with which to detect abnormalities in brain growth. It has been demonstrated that HC can predict total brain volume (TBV) in very-low-birth-weight (VLBW) infants. However, the correlation between HC and TBV was weaker than that observed in healthy term-born toddlers, suggesting that there are factors that influence the relationship between HC and TBV. The aim of this study was to identify the clinical risk factors that caused a deviation from the regression line obtained between HC and TBV. METHODS: The study population was based on 37 VLBW infants, who underwent a clinical magnetic resonance imaging (MRI) examination at a term-equivalent age, during 2013–2015, at Toyama University Hospital. The HC and the TBV were both adjusted for sex, multiple births, and postmenstrual age. The relationship between TBV/HC and clinical characteristics was evaluated. RESULTS: There was a positive correlation between HC and TBV (r =.58, P =.000168). Two clinical factors, the lower birth body weight (BBW) (r =.38, P =.02) and dolichocephaly (r = 0.46, P =.006), were identified as factors that negatively affected the TBV/HC ratio. After excluding infants with low BBW or with dolichocephaly, the correlation between HC and TBV was higher (r =.63). CONCLUSIONS: Although HC has predictive value for TBV in VLBW infants, care should be taken in infants with low BBW (BBW less than 600 g) or dolichocephaly (MRI-based cranial index less than.68), which were related to overestimation of TBV.