PEDIATRICS Vol. 121 No. 6 June 2008, pp. e1534-e1540 (doi:10.1542/peds.2007-2671)
ARTICLE |
Head Growth in Preterm Infants: Correlation With Magnetic Resonance Imaging and Neurodevelopmental Outcome
a Victorian Infant Brain Studies, Murdoch Childrens Research Institute, Parkville, Victoria, Australia
b Department of Neonatal Services, Royal Women's Hospital, Melbourne, Australia
c Department of Neonatal Medicine, Royal Children's Hospital, Melbourne, Australia
d Department of Obstetrics & Gynaecology, University of Melbourne, Melbourne, Australia
e Neuroimaging & Neuroinformatics, Howard Florey Institute, Melbourne, Australia
f Department of Pediatrics, St Louis Children's Hospital, Washington University, St Louis, Missouri
OBJECTIVE. Extremely preterm birth is associated with adverse neurodevelopmental sequelae. Head circumference has been used as a measure of brain growth. There are limited data relating head circumference to MRI. The purpose of this work was to establish the relationship between head circumference with brain MRI at term-equivalent age and to relate head circumference with neurodevelopmental outcome at 2 years.
PATIENTS AND METHODS. Two hundred and twenty-seven preterm infants (birth weight of <1250 g or <30 weeks gestation) were recruited. Head circumference was measured at birth, term, and 2 years corrected age, and z scores were computed. Microcephaly was defined as a head circumference z score of less than –2 SDs for age and gender. MRI scans at term (n = 214) were graded for white and gray matter abnormalities, and segmented volumes were calculated for different tissue types. Outcome at 2 years corrected age (n = 202) included scores on the Bayley Scales of Infant Development II.
RESULTS. Microcephaly increased from 7.5% at term to 29.7% at 2 years. There was no significant relationship between head circumference and white or gray matter abnormalities on MRI. There was a strong correlation between head circumference and brain volume at term. At term, microcephalic infants had significantly decreased volumes for total brain tissue and most segmented volumes compared with infants with normal head circumference, but only deep nuclear gray matter volume remained significantly lower when adjusted for total intracranial volume. At 2 years, microcephaly was associated with poorer cognitive and motor development and an increased rate of cerebral palsy.
CONCLUSIONS. Brain volume is a determinant of head size at term. Microcephaly is associated with a reduction of brain tissue volumes, especially deep nuclear gray matter, which suggests a selective vulnerability. Poor postnatal head growth in preterm infants becomes more evident by 2 years and is strongly associated with poor neurodevelopmental outcome and cerebral palsy.
Key Words: head circumference MRI neurodevelopmental outcome preterm infant
Abbreviations: HC—head circumference MR—magnetic resonance CSF—cerebrospinal fluid CGM—cortical gray matter DNGM—deep nuclear gray matter MWM—myelinated white matter unMWM—unmyelinated white matter MDI—Mental Developmental Index PDI—Psychomotor Developmental Index CI—confidence interval
Accepted Dec 13, 2007.
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