Introduction

In the twenty-first century neonatal neuroimaging will be classified as either “structural,” that is, based on anatomic or morphologic data, or “functional,” in which images will be generated based upon physiologic or metabolic data. Currently the major structural imaging modalities are ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI). These are commonly used to screen for anatomic abnormalities associated with neonatal intracranial hemorrhage (ICH) and ischemia associated with hypoxic-ischemic injury (HII). While US, CT, and MRI are technologically mature, few studies address the issue of which imaging protocols are most appropriate for the diagnosis of neonatal ICH and ischemia. US, the most commonly employed imaging modality in neonates, is less sensitive and less specific for the detection of intracranial ischemia and hemorrhage compared with CT or MRI. It is unclear, however, if the greater expense and logistical difficulties in obtaining CT and MRI examinations in critically ill neonates are justified. Furthermore, the lack of white-matter myelinization and patterns of ischemic and hemorrhagic lesions are markedly different in premature infants as compared to term which complicates the interpretation of CT or MRI examinations. The predictive value and clinical utility of US, CT, or MRI in neonates with HII have also been the subject of a number of longitudinal studies. However, it is difficult from any of these investigations to distill out a uniform set of imaging protocols for the screening and management of neonates with HII and, more importantly, individual prognostication.