Diagnostic Imaging of Perinatal CNS Lesion Sequelae

Periventricular leukomalacia (PVL)

Periventricular leukomalacia is a classic variant of brain injury in newborns, characterized by necrosis of the white matter immediately adjacent to the lateral ventricles. Axial MRI slices are traditionally used for optimal visualization of these changes.

The main imaging signs of PVL include:

• Change in tissue volume: a pronounced deficit of periventricular white matter is visualized, indicating massive cell death.
• Ventricle deformation: the walls of the lateral ventricles lose their normal smoothness. Due to the loss of adjacent white matter, they acquire a characteristic uneven, so-called «scalloped» contour.
• Focal MR signal changes: gliotic changes form in the areas of prior necrosis. On tomograms, this manifests as areas with altered signal intensity in the periventricular regions.

Atrophic changes in the brain parenchyma

Periventricular leukomalacia very rarely occurs in isolation. Most often, it is accompanied by or naturally leads to a secondary loss of brain tissue volume. On MRI scans, this process is recorded as various variants of cerebral atrophy.

Two main patterns of volume loss are distinguished:

1. Corticosubcortical atrophy. This variant is characterized by diffuse changes. The scans clearly show widening of the subarachnoid spaces, as well as significant deepening of the cerebral hemispheric sulci. Such a picture is direct evidence of a massive decrease in volume of both the cortex itself and the underlying white matter.
2. Local (regional) atrophy. In contrast to the diffuse process, there is a selective decrease in brain tissue volume here. Typical examples are changes in the temporal and temporoparietal regions, where pronounced widening of the corresponding sulci and fissures is visualized.

Alterations in adjacent anatomical structures

The marked brain tissue deficit resulting from necrosis and subsequent atrophy inevitably leads to secondary deformation of adjacent anatomical structures of the brain.

• Ventriculomegaly. There is a marked widening of the entire ventricular system. It is important to understand that in this context, ventriculomegaly is exclusively of a replacement nature (hydrocephalus ex vacuo develops). Cerebrospinal fluid passively fills the excess space formed due to progressive cortical and white matter atrophy.
• Corpus callosum hypoplasia. Sagittal slices are optimal for assessing this sign, visualizing a sharp thinning of the corpus callosum structure. This phenomenon is a direct consequence of PVL and cortical atrophy: there is massive death of commissural nerve fibers that normally run from the cortex to the opposite hemisphere and form the bulk of the corpus callosum.

Class and exam questions

What else to study on this topic

• MRI signal characteristics of gliotic changes at the site of prior necrosis
• Differential imaging diagnostics of regional and diffuse corticosubcortical atrophy
• Evaluation of corpus callosum hypoplasia on sagittal MRI slices
• Visualization of local atrophy in the temporal and temporoparietal regions
• Morphological differences between replacement ventriculomegaly and hypertensive hydrocephalus

Other topics in «Chapter 2. Neonatology»

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