MR Imaging of the Preterm Brain: safer better faster stronger

Abstract

Human brain development and maturation consist of complex processes that span from the first trimester of pregnancy to adult life. These processes include: 1) neuronal proliferation, characterized by generation of neurons in the dorsal subventricular zone and ventral germinative epithelium of the ganglionic eminence; 2) migration, where neurons move from these zones to specific sites where they will reside for life; 3) organization, in which neurons differentiate to subplate neurons, align, orientate and connect through their axons and dendrites. Glial cells differentiate into astrocytes, oligodendrocytes and microglia, and 4) myelination, where oligodendrocytes produce myelin that will be deposited around axons. Preterm infants are born in this critical period, in which the brain is particularly vulnerable to exogenous and endogenous events. Perinatal hypoxia-ischemia, hyperoxia, infection and hypocarbia can result in fluctuations in cerebral blood flow, inflammation, increased excitotoxicity and oxidative stress, all of which can affect normal brain ontogenesis and cause irreversible injury. In general, the two most commonly recognized variants of preterm brain injury are: periventricular white matter (WM) injury and hemorrhage in the germinal matrix and lateral ventricle. These injury patterns will be discussed separately in the following sections.