MRI Changes in the Thalamus and Basal Ganglia of Full-Term Neonates with Perinatal Asphyxia.

BACKGROUND: Magnetic resonance imaging (MRI) is the standard neuroimaging technique to assess perinatal asphyxia-associated brain injury in full-term infants. Diffusion-weighted imaging (DWI) is most informative when assessed during the first week after the insult. OBJECTIVES: To study the DWI abnormalities of the thalamus and basal ganglia in full-term infants with perinatal asphyxia. METHODS: Fifty-five (near) term infants (normothermia n = 23; hypothermia n = 32) with thalamus and/or basal ganglia injury were included. MRI findings were assessed visually and quantitatively calculating apparent diffusion coefficient (ADC) values. Thalamus/basal ganglia ADC ratios were calculated to analyze the differences between these areas. Infants with an early MRI (days 1-3) or later MRI (days 4-7) were compared. RESULTS: Isolated extensive thalamic injury was seen early, and focal thalamic and basal ganglia injury was seen later. On the early MRI, visual assessment underestimated abnormalities in the basal ganglia (59% abnormal vs. 90% abnormal on quantitative assessment; p = 0.015), suggesting the need for quantitative assessment. In infants treated with hypothermia, the thalamus/basal ganglia ADC ratio was lower. CONCLUSIONS: Both visual analysis and quantitative evaluation of cerebral MRI after perinatal asphyxia are needed, especially during the first few days after birth. Timing of ADC changes is influenced by therapeutic hypothermia.

Corticospinal Tract Injury Precedes Thalamic Volume Reduction in Preterm Infants with Cystic Periventricular Leukomalacia.

OBJECTIVES: To measure both fractional anisotropy (FA) values in the corticospinal tracts (CSTs) and volume of the thalami in preterm infants with cystic periventricular leukomalacia (c-PVL) and to compare these measurements with control infants. STUDY DESIGN: Preterm infants with c-PVL and controls with magnetic resonance imaging data acquired between birth and term equivalent age (TEA) were retrospectively identified in 2 centers. Tractography of the CST and segmentation of the thalamus were performed, and values from infants with c-PVL and controls were compared. RESULTS: Thirty-three subjects with c-PVL and 31 preterm controls were identified. All had at least 1 scan up to TEA, and multiple scans were performed in 31 infants. A significant difference in FA values of the CST was found between cases and controls on the scans both before and at TEA. Absolute thalamic volumes were significantly reduced at TEA but not on the earlier scans. Data acquired in infancy showed lower FA values in infants with c-PVL. CONCLUSIONS: Damage to the CST can be identified on the early scan and persists, whereas the changes in thalamic volume develop in the weeks between the early and term equivalent magnetic resonance imaging. This may reflect the difference between acute and remote effects of the extensive injury to the white matter caused by c-PVL.