Brain Development and Perinatal Vulnerability to Cerebral Damage
The recent exponential rise in detailed magnetic resonance (MR) imaging studies has emphasized the concept of gestationally determined regional vulnerability in the brain. The site and nature of the injury is determined by a combination of the characteristics of the insult, the specific tissue and cell vulnerability, and the gestational age. Acute perinatal hypoxic ischemic events, previously considered characteristic for the term newborn presenting with hypoxic-ischemic encephalopathy, may occur at earlier points in gestation. White matter lesions, which are considered the hallmark of injury to the preterm brain, may also occur in a small percentage of term neonates. The regional tissue vulnerability at a given gestational age will be determined by the local metabolic requirements in combination with specific cell characteristics, such as the expression of different glutamatergic receptor subtypes and endogenous antioxidant mechanisms. In addition, neonatal neurons are programmed for cell death to allow for essential pruning and optimal connectivity, but this characteristic increases the vulnerability of such cells to injury. The nature of the insult is also important in dictating lesion site. In this chapter we will discuss the vulnerability of tissue and cell types in relation to gestational age and examine how these relate to patterns of injury seen on brain MR imaging and the clinical history and presentation of the infant.
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