The relationship in neonates between clinically measured head circumference and brain volume estimated from head CT-scans

Objective: To determine if the frontal-occipital head circumference correla tes with brain volume on CT and to investigate correlations between the vol umes of different brain subdivisions in live neonates. Methods: Records were studied from 27 neonates with anatomically normal hea d CT-scans which were ordered for clinical reasons, and which were performe d at Johns Hopkins Hospital. Clinical data were abstracted from medical rec ords. Brain volumes were estimated by digitizing the structures of interest on each slice of head CT-scans. Results: In this sample of 27 infants with a mean birth weight of 3000.4+/- 668 g, mean head circumference of 33.5+/-1.8 cm, and mean gestational age o f 37 weeks and 4 days+/-24 days, the mean of total brain volume was 333.0+/ -78.3 ml. The correlation between clinically measured head circumference an d total brain volume was 0.55 (P < 0.003). Regression of total brain volume on head circumference and its second and third powers accounted for 43% of the variation in total brain volume. Other predictor variables, namely inf ant race, sex, gestational age, and maternal age, were not significant in t his regression once head circumference was included. The slope of the cubic function of head circumference as a predictor of brain volume was greatest below the mean head circumference of 33.5 cm. Brain volume leveled off at head circumferences greater than the mean. Conclusion: Head circumference is a powerful predictor of total brain volum e in the neonate: below the approximate head-circumference mean of 33.5 cm, smaller head circumference indicates smaller total brain volume. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.