MRI Findings at Term-Corrected Age and Neurodevelopmental Outcomes in a Large Cohort of Very Preterm Infants

Abstract

Background and purpose: Brain MR imaging at term-equivalent age is a useful tool to define brain injury in preterm infants. We report pragmatic clinical radiological assessment of images from a large unselected cohort of preterm infants imaged at term and document the spectrum and frequency of acquired brain lesions and their relation to outcomes at 20 months.

Materials and methods: Infants born at <33 weeks' gestation were recruited from South and North West London neonatal units and imaged in a single center at 3T at term-equivalent age. At 20 months' corrected age, they were invited for neurodevelopmental assessment. The frequency of acquired brain lesions and the sensitivity, specificity, and negative and positive predictive values for motor, cognitive, and language outcomes were calculated, and corpus callosal thinning and ventricular dilation were qualitatively assessed.

Results: Five hundred four infants underwent 3T MR imaging at term-equivalent age; 477 attended for assessment. Seventy-six percent of infants had acquired lesions, which included periventricular leukomalacia, hemorrhagic parenchymal infarction, germinal matrix-intraventricular hemorrhage, punctate white matter lesions, cerebellar hemorrhage, and subependymal cysts. All infants with periventricular leukomalacia, and 60% of those with hemorrhagic parenchymal infarction had abnormal motor outcomes. Routine 3T MR imaging of the brain at term-equivalent age in an unselected preterm population that demonstrates no focal lesion is 45% sensitive and 61% specific for normal neurodevelopment at 20 months and 17% sensitive and 94% specific for a normal motor outcome.

Conclusions: Acquired brain lesions are common in preterm infants routinely imaged at term-equivalent age, but not all predict an adverse neurodevelopmental outcome.

Fig 1.

Typical MR imaging brain appearances of term-born and preterm infants, at TEA. Axial T1-(A) and T2- (B) and sagittal T1 (C)-weighted images of a term-born infant (40 weeks’ gestational age) imaged at 44 weeks PMA. Note the high-T1/low-T2 signal within the PLIC from the myelin (arrows, A and B); the complex cortical folding; small, symmetric ventricles; and the typical appearance of a normal corpus callosum (arrowheads, C). By comparison, D–F are comparable images obtained from an infant born at 25 + 2 weeks’ gestational age and imaged at 42 + 4 weeks’ PMA. This infant had no acquired focal lesions however, note the scaphocephaly, reduced cortical folding, globally thinned corpus callosum (arrowheads, F), mildly dilated ventricles, and diffuse high-T2/low-T1 signal in the white matter compared with the term infant. There is grossly normal myelination in the PLIC (arrows, D and E).

Fig 2.

HPI. T2-weighted MR images through the mid (A) and low (B) basal ganglia level in an infant born at 29 weeks and imaged at 44 + 6 weeks. There is right-sided HPI with formation of a porencephalic cyst lined with low signal intensity consistent with previous hemorrhage (arrow, A), a paucity of low T2 signal myelin in the right PLIC compared with the left (arrowheads, A), and ipsilateral basal ganglia and thalamic atrophy (arrowheads, B). This infant had a motor impairment at 20 months.

Fig 3.

PVL. T2-weighted images in the axial plane at the level of the basal ganglia (A) and the corona radiata (B) of an infant born at 29 + 5 weeks’ and imaged at 39 + 1 weeks’ PMA. There are cysts in the periventricular white matter bilaterally (arrows, A and B) accompanied by an absence of high-T1/low-T2 signal in the PLIC, denoting an absence of myelin (arrowheads, A). More commonly, cysts are not seen at term age. T2- (C) and T1-weighted (D) images in the axial plane at the level of the basal ganglia and PLIC in an infant born at 29 + 3 weeks’ and imaged at 40 + 2 weeks’ PMA show mild angulation and dilation of the posterior horns of the lateral ventricles and high-T1/low-T2 signal in the periventricular white matter (arrows, C and D), secondary to white matter volume loss (note that the sulci approximate the ventricular surface), similarly accompanied by a lack of myelin in the PLIC (arrowheads, C and D), features that are typical of noncystic PVL.

Fig 4.

Germinal matrix. T1- (A) and T2-weighted images (B) of an infant born at 24 + 2 weeks and imaged at 26 + 7 weeks, demonstrating normal appearance of the germinal matrix for this gestation, here seen as a thin rim of low-T2/high-T1 signal in the subependymal region (arrows, A and B). Germinal matrix hemorrhage is a complication of prematurity and is distinguished from normal matrix remnants by its shape and size. C, An infant born at 26 + 6 weeks and imaged at 42 + 3 weeks. D, An infant born at 28 weeks and imaged at 44 + 5 weeks. The germinal matrix hemorrhage is recognized here as a thin, irregular focus of T2 low signal isolated to the subependyma, which may be unilateral (arrows, C and D).