Magnetic resonance imaging of the brain at term equivalent age in extremely premature neonates: to scan or not to scan?

Abstract

In the last decade, the role of magnetic resonance imaging (MRI) in neonatal care for prematurely born infants has rapidly expanded and evolved. Recent investigations addressed many of the practical issues pertaining to image acquisition and interpretation, enabling high-quality MR images to be obtained without sedating medications in preterm infants at any institution. Expanded application has demonstrated that MRI provides superior ability to assess cerebral development and identify and define cerebral injury in comparison to other imaging modalities. Term equivalent MRI results have been shown to correlate with neurodevelopmental outcomes, providing improved predictive ability over other neuroimaging, clinical or physical examination measures. Regular utilisation of MRI in this population is fundamental to gaining the knowledge and expertise necessary for rational, accurate application. Ongoing experiences will continue to shape the nature and type of information available to clinicians and families using MRI, further refining its role as a routine element of neonatal care.

Figure 1. Procedures for preparing infant for non-sedated MRI scan

Procedures for preparing infants prior to placement in the MRI scanner includes A) snuggly wrapping the infant prior to placement in the vacuum bag; B) securing the infant in the stabilizing vacuum bag; C) placing the stabilized infant in the MR-compatible isolette for movement into the scanner.

Figure 2. Development of cortical folding in the premature human brain

Representative A) 3-dimensional surfaces and B) axial T2-weighted images illustrating regionally-specific cortical folding occurring in the premature brain secondary to sulcation and gyration throughout early development. Provided are images obtained from a single preterm infant from MRI scans performed at 28, 31, 34, and 38 weeks post-mentrual age. Note the marked increase in brain size and folding complexity between each set of images.

Figure 3. Myelination of the posterior limb of the internal capsule

Representative axial A) T1- and B) T2-weighted MR images from a very preterm infant at term equivalent age demonstrating myelination evident in the the posterior limb of the internal capsule bilaterally. Note myelinated white matter appears hyperintense on T1-weighted images and hypointense on T2-weighted images (arrows).

Figure 4. Classification of periventricular leukomalacia and cerebellar hemorrhage

Coronal T1- and T2-weighted MR images demonstrating representative examples of periventricular leukomalacia (PVL, upper panel) and cerebellar hemorrhage (CBH, lower panel) of progressive severity. A) Grade 1 and B) Grade 2 PVL defined by punctate lesions; C) Grade 3 PVL defined by high signal along the wall of lateral ventricles; D) Grade 4 PVL defined by cysts in the periventricular white matter. CBH was also classified into 4 grades including: E) Grade 1 CBH defined by unilateral punctate lesions ≤3 mm in size; F) Grade 2 CBH defined by bilateral punctate lesions; G) Grade 3 CBH defined by a unilateral lesion >3 mm in size; H) Grade 4 CBH defined by extensive lesions bilaterally.