Clinical MR Neuroimaging: Physiological MR imaging of normal development and developmental delay

Introduction Imaging is a crucial tool in the evaluation of neonates and infants with neurological abnormalities: the encephalopathic neonate, the epileptic child, and the developmentally delayed infant.[1–5] Transfontanelle sonography was the non-invasive imaging tool to be used to evaluate the neonate and was extremely successful, providing a new window for the evaluation of the pathological processes in the preterm and term neonate. Ultrasound was valuable in the assessment of intracranial hemorrhage in premature neonates,[6] but less successful in the assessment of non-hemorrhagic parenchymal injury in both term and preterm infants,[3,7–9] and of little use after closure of the fontanelles. Therefore, computed tomography (CT) and anatomical magnetic resonance imaging (MRI) have been investigated as imaging tools for neurological disease in infants. There has been some success with MRI in this regard,[8,10–13] and it has been shown to be clearly superior to sonography and CT in the assessment of developmental delay caused by structural and metabolic disorders.[14,15] Many children with neurodevelopmental disorders, however, have normal anatomical imaging. The ability to assess physiological and biochemical parameters through the use of MR, in particular diffusion tensor imaging (DTI) and proton spectroscopy (MRS), has considerably broadened the potential use of MR in the assessment of neurologically impaired neonates and infants. This chapter discusses the normal developmental processes of the brain as assessed by these new techniques and then discusses the early application of these techniques in the evaluation of neurologically impaired and developmentally delayed neonates. Technical aspects of neonatal/infant MRI Transportation, sedation, and technical aspects Obviously, no technique is useful if the patient cannot be transported to the MR suite and imaged safely, and high-quality images obtained. Transportation and sedation of neonates for MR is critical for obtaining high-quality images safely but is beyond the scope of this chapter. It is discussed in all major pediatric imaging textbooks and readers should become completely familiar with techniques for sedation and monitoring during routine neonatal and infant MRI before using the techniques discussed in this chapter. Although MR can sometimes be performed in premature infants without sedation, it is nearly impossible to obtain high-quality imaging data in term neonates and infants without sedation.