Head growth in preterm infants: correlation with magnetic resonance imaging and neurodevelopmental outcome.
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.


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.
Royal Women's Hospital, Department of Neonatal Services, 132 Grattan St, Carlton 3053, Melbourne, Australia. jeanie.cheong@rwh.org.au
Jeanie L Y
JL
Cheong
Rod W
RW
Hunt
Peter J
PJ
Anderson
Kelly
K
Howard
Deanne K
DK
Thompson
Hong X
HX
Wang
Merilyn J
MJ
Bear
Terrie E
TE
Inder
Lex W
LW
Doyle
D001921:Brain / Q000473:pathology*; D002508:Cephalometry; D005260:Female; D006257:Head / Q000254:growth & development*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development*; D008279:Magnetic Resonance Imaging; D008297:Male; D009420:Nervous System / Q000254:growth & development*; D009929:Organ Size