Periventricular leukomalacia (PVL) refers to injury and necrosis of the white matter of the brain in a particular distribution near the lateral ventricles. There are two pathologic types of PVL. Focal, and often cystic, necrotic lesions occur most commonly around the foramina of Munro and near the trigone of the lateral ventricles. These cysts can be seen on ultrasound if they are at least 2-3 mm in size. The top image at the right shows these cysts quite well.
The other type of PVL is a diffuse white matter injury (DWMI) which often does not become cystic. For this reason, ultrasound may not demonstrate this lesion. While pathologically, DWMI is less severe than focal cystic PVL, it is usually more widespread. MRI studies indicate that it may actually be more common than cystic PVL. This lesion can be seen in the bottom image at the right.
PVL of either type can occur in a patient with IVH, either as a separate lesion or as a secondary hemorrhage into an area of PVL. This latter occurs more commonly into an area of cystic PVL. Ultrasound may not distinguish between an intraparenchymal bleed (a primary IVH) and hemorrhage into a focal area of PVL, although histologically the 2 lesions would look different.