Is sequential cranial ultrasound reliable for detection of white matter injury in very preterm infants?

Abstract

Introduction: Cranial ultrasound (cUS) may not be reliable for detection of diffuse white matter (WM) injury. Our aim was to assess in very preterm infants the reliability of a classification system for WM injury on sequential cUS throughout the neonatal period, using magnetic resonance imaging (MRI) as reference standard.

Methods: In 110 very preterm infants (gestational age <32 weeks), serial cUS during admission (median 8, range 4-22) and again around term equivalent age (TEA) and a single MRI around TEA were performed. cUS during admission were assessed for presence of WM changes, and contemporaneous cUS and MRI around TEA additionally for abnormality of lateral ventricles. Sequential cUS (from birth up to TEA) and MRI were classified as normal/mildly abnormal, moderately abnormal, or severely abnormal, based on a combination of findings of the WM and lateral ventricles. Predictive values of the cUS classification were calculated.

Results: Sequential cUS were classified as normal/mildly abnormal, moderately abnormal, and severely abnormal in, respectively, 22%, 65%, and 13% of infants and MRI in, respectively, 30%, 52%, and 18%. The positive predictive value of the cUS classification for the MRI classification was high for severely abnormal WM (0.79) but lower for normal/mildly abnormal (0.67) and moderately abnormal (0.64) WM.

Conclusion: Sequential cUS during the neonatal period detects severely abnormal WM in very preterm infants but is less reliable for mildly and moderately abnormal WM. MRI around TEA seems needed to reliably detect WM injury in very preterm infants.

Fig. 1

a Coronal (left) and parasagittal (right) cUS of preterm infant (GA 27.9 weeks), scanned at PMA 31.1 weeks, showing normal echogenicity of periventricular WM (WM score of serial cUS during admission: normal/mildly abnormal). b Coronal (left) and parasagittal (right) cUS of preterm infant (GA 28.0 weeks), scanned at PMA 32.3 weeks, showing homogeneous PVE in parieto-occipital WM on the left and inhomogeneous PVE in parieto-occipital WM on the right (arrows); (WM score of serial cUS during admission: normal/mildly abnormal)

Fig. 2

a Coronal cUS of preterm infant (GA 28.0 weeks), scanned at PMA 42.0 weeks, showing moderately dilated lateral ventricles (TEA-cUS WM score: moderately abnormal). b. Coronal cUS of preterm infant (GA 30.3 weeks), scanned at PMA 41.9 weeks, showing severe lateral ventricular dilatation (TEA-cUS WM score: severely abnormal). Poor image quality is due to small size of fontanel

Fig. 3

Transverse T₁- (left) and T₂-weighted (right) MRI at high-ventricular level of preterm infant (GA 26.9 weeks), scanned at PMA 42.7 weeks, showing bilateral, multiple PWML (arrows) in a linear distribution parallel to the LV. Also showing dilated, irregularly shaped lateral ventricles and widening of extracerebral spaces (TEA-MRI WM score: moderately abnormal)

Fig. 4

Transverse T₂-weighted MRI at midventricular level of preterm infant (GA 30.6 weeks), scanned at PMA 42.3 weeks, showing homogeneous SI increase (DEHSI) in periventricular and subcortical WM (TEA-MRI WM score: normal/mildly abnormal)

Fig. 5

a Transverse T₁- (left) and T₂-weighted (right) MRI at midventricular level of preterm infant (GA 27.1 weeks), scanned at PMA 42.1 weeks, showing normal signal in WM. Also showing normal size and shape of lateral ventricles (TEA-MRI WM score: normal/mildly abnormal). b Transverse T₂-weighted MRI at midventricular level of preterm infant (GA 27.9 weeks), scanned at PMA 43.1 weeks, showing moderately dilated and abnormally square-shaped lateral ventricles (TEA-MRI WM score: moderately abnormal). c Transverse T₂-weighted MRI at midventricular level of preterm infant (GA 31.6 weeks), scanned at PMA 43.4 weeks, showing severely dilated and abnormally shaped lateral ventricles due to volume loss of the WM (TEA-MRI WM score: severely abnormal)

Fig. 6

Flow diagram showing the number of infants eligible for the study, the number of infants included and not included in the study, and the final number of infants with sequential cUS and MRI between 40- and 44-week PMA (n, number of infants)

Fig. 7

Coronal (left) and parasagittal (right) cUS of preterm infant (GA 26.9 weeks), scanned at PMA 29.1 weeks, showing only mild, homogeneous PVE bilaterally in the parietal WM; the cUS of this infant performed around TEA (PMA 42.7 weeks) showed normal WM and mildly abnormal size and shape of lateral ventricles (sequential cUS WM score: normal/mildly abnormal). However, the MRI of the same infant (see Fig. 3) showed bilateral, multiple PWML and dilated, irregularly shaped lateral ventricles (TEA-MRI WM score: moderately abnormal)