Relation of Retinopathy of Prematurity to Brain Volumes at Term Equivalent Age and Developmental Outcome at 2 Years of Corrected Age in Very Preterm Infants.

BACKGROUND: Retinopathy of prematurity (ROP) is a major complication of preterm birth and has been associated with later visual and nonvisual impairments. OBJECTIVES: To evaluate relationships between any stage of ROP, brain volumes, and developmental outcomes. METHODS: This study included 52 very preterm infants (gestational age [mean ± SD]: 26.4 ± 1.9 weeks). Total brain, gray matter, unmyelinated white matter (UWMV), and cerebellar volumes were estimated in 51 out of 52 infants by magnetic resonance imaging at term-equivalent age. Bayley Scales of Infant Development were used to assess developmental outcomes in 49 out of 52 infants at a mean corrected age of 24.6 months. RESULTS: Nineteen out of 52 infants developed any stage of ROP. Infants with ROP had a lower median (IQR) UWMV (173 [156-181] vs. 204 [186-216] mL, p < 0.001) and cerebellar volume (18.3 [16.5-20] vs. 22.3 [20.3-24.7] mL, p < 0.001) than infants without ROP. They also had a lower median (IQR) mental developmental index (72 [56-83] vs. 100 [88-104], p < 0.001) and a lower psychomotor developmental index (80 [60-85] vs. 92 [81-103], p = 0.002). Brain volumes and developmental outcomes did not differ among infants with different stages of ROP. CONCLUSION: Any stage of ROP in preterm infants was associated with a reduced brain volume and an impaired developmental outcome. These results suggest that common pathways may lead to impaired neural and neurovascular development in the brain and retina and that all stages of ROP may be considered in future studies on ROP and development.

Early Electroencephalography Suppression and Postnatal Morbidities Correlate with Cerebral Volume at Term-Equivalent Age in Very Preterm Infants.

BACKGROUND: Early brain activity is associated with long-term outcome. Establishing a relation also with postnatal brain growth may increase our understanding of early life influences on preterm brain development. OBJECTIVES: The aim of this study was to investigate whether early electroencephalography (EEG) activity in infants born very preterm is associated with brain volumes at term, and whether postnatal morbidity affects this association. METHODS: Very preterm infants (n = 38) with a median gestational age (GA) of 25.6 weeks had early recordings of single-channel EEG. The percentage of suppressed EEG, i.e., interburst intervals (IBI%) between 24 and 72 h of age, was analyzed in relation to brain volumes on magnetic resonance imaging performed at term-equivalent age, taking into account neonatal morbidities. RESULTS: Early electrocortical depression and a higher IBI% were associated with increased cerebrospinal fluid volume (CSFV) and lower total brain volume relative to intracranial volume, also after adjustment for GA, postnatal morbidities, morphine administration, and postnatal head growth. Overall, an increase in IBI% to 1 SD from the mean corresponded with an increase in CSFV to +0.7 SD and a decrease in brain volume to -0.7 SD. The presence of 2 or more postnatal morbidities were associated with around 10% lower brain volumes. CONCLUSIONS: More suppressed early EEG activity of very preterm infants is associated with lower brain volume and increased CSFV at term age, also when adjusting for postnatal morbidities. The findings indicate the importance of pre- and early postpartal determinants of postnatal brain growth, possibly also including activity-dependent mechanisms for brain growth.

Auditory event-related potentials are related to cognition at preschool age after very preterm birth.

BACKGROUND: Auditory event-related potentials (AERP) are neurophysiological correlates of sound perception and cognitive processes. Our aim was to study in very preterm born children at preschool age if AERP correlate with cognitive outcome. METHODS: Seventy children (mean ± SD gestational age 27.4 ± 1.9 wk, birth weight 996 ± 288 g) were investigated at age 4.3-5.3 y with psychological testing (WPPSI-R, four subtests of NEPSY). Electroencephalogram was recorded while they listened to a repeated standard tone, randomly replaced by one of three deviants. Latencies and amplitudes for AERP components and mean amplitudes in successive 50-ms AERP time windows were measured. RESULTS: Better cognitive test results and higher gestational age correlated with shorter P1 latencies and more positive mean amplitudes 150-500 ms after stimulus change onset. Neonatal brain damage was associated with a negative displacement of AERP curves. Neonatal morbidity had an impact on earlier time windows while gestational age and brain damage on both early and later time windows. CONCLUSION: AERP measures were associated with cognitive outcome. Neonatal morbidity mainly affects early cortical auditory encoding, while immaturity and brain damage additionally influence higher cortical functions of auditory perception and distraction. Perinatal auditory environment might play a role in development of auditory processing.

Auditory event-related potentials at preschool age in children born very preterm.

OBJECTIVE: To assess auditory event-related potentials at preschool age in children born very preterm (VP, 27.4 ± 1.9 gestational weeks, n=70) with a high risk of cognitive dysfunction. METHODS: We used an oddball paradigm consisting of a standard tone randomly replaced by one of three infrequent deviants (differing in frequency, sound direction or duration). RESULTS: The P1 and N2 latencies were inversely correlated to age (50-63 months) both in VP (r=-0.451, p<0.001, and r=-0.305, p=0.01, respectively) and term born controls (TC; n=15). VP children had smaller P1 than near-term (n=12) or TC (1.70 ± 0.17 µV vs 2.68 ± 0.41 and 2.92 ± 0.43, respectively; p<0.05). Mismatch negativity response did not differ between groups. CONCLUSIONS: Our data suggest a fast maturation of P1 and N2 responses with fast decrease in P1 and N2 latencies around the age of 5 years. Mismatch negativity response does not seem to be a robust measure for defining abnormalities in VP children. SIGNIFICANCE: In ERP studies in preschool children, even small, non-significant group differences in age at recording should be corrected for. Very preterm born children at preschool age have aERP patterns as earlier described in full-term born children with cognitive deficits.

Circulatory insulin-like growth factor-I and brain volumes in relation to neurodevelopmental outcome in very preterm infants.

BACKGROUND: To evaluate the relationships between postnatal change in circulatory insulin-like growth factor-I (IGF-I) concentrations, brain volumes, and developmental outcome at 2 y of age in very preterm infants. METHODS: IGF-I was measured weekly, and nutritional intake was calculated daily from birth until a postmenstrual age (PMA) of 35 wk. Individual ß coefficients for IGF-I, IGF-I(B), representing the rate of increase in IGF-I from birth until a PMA of 35 wk were calculated. Brain magnetic resonance imaging was performed at term age, with segmentation into total brain, cerebellar, gray matter, and unmyelinated white matter volume (UWMV). Developmental outcome was evaluated using Bayley Scales of Infant Development-II. RESULTS: Forty-nine infants, with mean gestational age (GA) of 26.0 wk, were evaluated at mean 24.6 mo corrected age. Higher IGF-I(B), UWMV, and cerebellar volume were associated with a decreased risk for a Mental Developmental Index (MDI) < 85 (odds ratio (95% confidence interval): 0.6 (0.4-0.9), 0.96 (0.94-0.99), and 0.78 (0.6-0.96), respectively). In multivariate analysis, higher IGF-I(B) and higher UWMV combined with female gender constituted the two models with the highest predictive value for MDI > 85. CONCLUSION: A higher rate of increase in circulating IGF-I is associated with a decreased risk for subnormal MDI at 2 y of corrected age. This relationship is in part dependent on brain volume at term age.

Postnatal decrease in circulating insulin-like growth factor-I and low brain volumes in very preterm infants.

CONTEXT: IGF-I and IGF binding protein-3 (IGFBP-3) are essential for growth and maturation of the developing brain. OBJECTIVE: The aim of this study was to evaluate the association between postnatal serum concentrations of IGF-I and IGFBP-3 and brain volumes at term in very preterm infants. DESIGN: Fifty-one infants with a mean (sd) gestational age (GA) of 26.4 (1.9) wk and birth weight (BW) of 888 (288) g were studied, with weekly blood sampling of IGF-I and IGFBP-3 from birth until 35 gestational weeks (GW) and daily calculation of protein and caloric intake. Magnetic resonance images obtained at 40 GW were segmented into total brain, cerebellar, cerebrospinal fluid, gray matter, and unmyelinated white matter volumes. MAIN OUTCOME MEASURES: We evaluated brain growth by measuring brain volumes using magnetic resonance imaging. RESULTS: Mean IGF-I concentrations from birth to 35 GW correlated with total brain volume, unmyelinated white matter volume, gray matter volume, and cerebellar volume [r = 0.55 (P < 0.001); r = 0.55 (P < 0.001); r = 0.44 (P = 0.002); and r = 0.58 (P < 0.001), respectively]. Similar correlations were observed for IGFBP-3 concentrations. Correlations remained after adjustment for GA, mean protein and caloric intakes, gender, severe brain damage, and steroid treatment. Protein and caloric intakes were not related to brain volumes. Infants with BW small for GA had lower mean concentrations of IGF-I (P = 0.006) and smaller brain volumes (P = 0.001-0.013) than infants with BW appropriate for GA. CONCLUSION: Postnatal IGF-I and IGFBP-3 concentrations are positively associated with brain volumes at 40 GW in very preterm infants. Normalization of the IGF-I axis, directly or indirectly, may support normal brain development in very preterm infants.