Intraventricular hemorrhage (IVH) and periventricular leukomalacia (PVL) are the leading causes of CNS disability in the premature infant. I will discuss them together, not only because of their significance in long-term outcome, but also because highlighting their similarities and differences may make them easier to understand.
The origin of the bleeding in IVH is the germinal matrix (GM). This highly vascular area is the site of neuronal proliferation and migration, the main neurodevelopmental processes of the premature infant. In other words, it is in the GM that new neurons are being formed and from the GM that they migrate to the part of the CNS for which they are destined. Just as importantly, the GM is a source of glial cells which are important in the organization of the developing brain and its eventual myelinization. The GM is primarily located near the head of the caudate nucleus at the level of the foramina of Munro - see the picture above which also shows bilateral GM hemorrhage - although it extends subependymally into the temporal and occipital horns as well. As gestation progresses, the GM gradually involutes and is essentially gone by 36 weeks.
As we will see later, bleeding that starts in the GM can spread to the ventricles and even to the parenchyma of the brain. There are many terms used in the literature for this topic, including germinal matrix hemorrhage (GMH), subependymal hemorrhage (SEH), intraventricular hemorrhage (IVH) and intraparenchymal echodensity (IPE). I will use the term IVH here to refer to this entire subject, understanding that this will include babies with only a GMH as well as those with an IVH.