Neurobehavior at term and white and gray matter abnormalities in very preterm infants.

OBJECTIVE: To examine the relationship between very preterm infant neurobehavior at term and concurrent magnetic resonance-defined cerebral abnormalities. STUDY DESIGN: 168 very preterm infants (birth weight <1250 g or gestation <30 weeks) were examined at term with 2 standardized neurobehavioral assessments, the Revised Hammersmith Neonatal Neurological Examination and the Neonatal Intensive Care Unit Network Neurobehavioral Scale. The relationship between composite neurobehavioral scores and qualitative white and gray matter abnormalities on magnetic resonance imaging was determined. RESULTS: Poorer neurobehavioral performance related to magnetic resonance-defined cerebral abnormalities. Composite neurobehavioral scores related to the total grade of white matter abnormality, and worse neurobehavior related most strongly to 2 components of this grade: white matter signal abnormalities and reduction in white matter volumes. Neurobehavior was not related to the total grade of gray matter abnormality. However, delayed gyral maturation, a component of the total gray matter grade, was related to poorer performance on both neurobehavioral scales. CONCLUSION: Very preterm infant neurobehavior at term is related to concurrent cerebral abnormalities in both white and gray matter defined by qualitative magnetic resonance imaging.

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. 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.

Alterations in neurobehavior at term reflect differing perinatal exposures in very preterm infants.

OBJECTIVES: Preterm infants have higher rates of cognitive and behavioral difficulties at school age than their term-born peers. We hypothesized that neurobehavior at term would be different in very preterm infants compared with term infants and that perinatal exposures would be associated with these alterations in neurobehavior. PATIENTS AND METHODS: Two standardized neurobehavioral evaluations were completed on 207 infants at term equivalent, including 168 very preterm infants (<1250 g or <30 weeks' gestation) and 39 term control infants. The assessments used were the Neonatal Intensive Care Unit Network Neurobehavioral Scale and the revised Hammersmith Neonatal Neurologic Examination. The relationship of perinatal variables to preterm infant neurobehavioral scores for both evaluations was examined. RESULTS: Compared with term-born infants, preterm infant neurobehavior was significantly altered for the Hammersmith Neonatal Neurologic Examination total score and all of the subtotals. Similarly, preterm infants displayed altered neurobehavior for the majority of the Neonatal Intensive Care Unit Network Neurobehavioral Scale summary scores. Complete perinatal data were available for 157 of 168 very preterm infants. The perinatal variables most strongly associated with altered preterm infant neurobehavior on multivariate regression analysis included the total number of days of assisted ventilation, intraventricular hemorrhage, and necrotizing enterocolitis. Positive perinatal influences on neurobehavioral performance at term on multivariate analysis included maternal antenatal steroids, female gender, and infants receiving breast milk at discharge home. CONCLUSIONS: Preterm infants at term equivalent showed alterations in motor behavior and higher cortically integrated functions. The pattern of abnormality in neurobehavior differed in relation to perinatal exposures. Neurobehavioral examination at term equivalent age is useful in evaluating the impact of neonatal intensive care.