White matter changes in extremely preterm infants, a population-based diffusion tensor imaging study.

AIM: To investigate cerebral white matter (WM) abnormalities (J Pediatr 2003; 143: 171) and diffuse and excessive high signal intensities (DEHSI), (J Pediatr 1999; 135: 351) in a cohort of extremely preterm infants born in Stockholm during a 3-year period, using magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI).

METHODS: MRI at term-equivalent age was performed in 109 infants and DTI data were acquired in 54 infants. Survival rate in the entire cohort was 67%. Sixteen term-born healthy control infants were scanned for comparison.

RESULTS: No or mild WM abnormalities were seen in 86% of infants and 14% had moderate or severe WM abnormalities. DEHSI were seen in infants with all grades of white matter abnormalities and were present in 56% of infants. In the WM at the level of centrum semiovale, infants with any WM abnormalities or DEHSI had lower Fractional Anisotropy and higher Apparent Diffusion Coefficient compared with control infants. No significant differences in diffusion were seen in infants without DEHSI compared with the controls in this region. Compared with controls, the preterm infants had significantly altered diffusion in the corpus callosum.

CONCLUSION: Only 14% of the extremely preterm infants had moderate or severe WM abnormalities on MRI. However, the incidence of DEHSI was high. In the DEHSI regions, changes in diffusion parameters were detected, indicating altered WM organization.