Unexpected inconsistency of cranial MRI and cranial US measurements: new normative values in the neonatal period

Cranial ultrasonography (US) enables differentiation of normal from abnormal in a reasonable scanning time and without radiation. However, there is not enough data comparing measurements of cranial US and magnetic resonance imaging (MRI) for some intracranial structures in the neonatal period. We aimed to assess the reliability of cranial US compared with brain MRI. We also sought reference values of the pituitary gland and infundibulum, which is important in searching for growth retardation or abnormal growth in this population. Normative measurements of the width of the 4^th, 3^rd and lateral ventricles, length and width of the corpus callosum (CC), biventricular width (BVW), and biparietal diameter (BPD) were prospectively obtained from 95 healthy full-term neonates on both cranial US and brain MRI. Besides the well-known structures, the height of the pituitary gland, thickness of the infundibulum, height and width of the cerebellum were measured on MRI. Comparison of cranial US and brain MRI showed good correlation in the BPD, width of the splenium and genu of CC, anteroposterior length of CC, and width of the 3^rd ventricle (κ=0.88-0.99). Correlation was poor in BVW, width of the corpus of CC, and width of the lateral ventricles (κ=0.28-0.56). New normative values of the height of pituitary gland and thickness of the stalk in the neonatal period are novel findings of this prospective study. In conclusion, cranial US and MRI measurements were not consistent in some brain structures. It is crucial to know the normative values, and to differentiate congenital and developmental brain anomalies in the neonatal period. The new reference values of the pituitary gland and infundibulum were also established in this period.