3D and 4D sonography and magnetic resonance in the assessment of normal and abnormal CNS development: alternative or complementary.

Advanced transvaginal neurosonography has revealed normal and abnormal intracranial morphology. Transvaginal three-dimensional (3D) sonography demonstrates bony structure, multiplanar analysis of inside detailed morphology, tomographic ultrasound imaging in any cutting sections, 3D sonoangiography and volume calculation of ventricles and/or intracranial lesions. Longitudinal assessment of normal and abnormal central nervous system (CNS) development is done by serial scanning. However, the transvaginal high-frequency approach has several limitations due to lack of penetration and cranial bone ossification with advanced gestational age. Magnetic resonance neuroimaging enabled observation of the whole intracranial cavity, brainstem and cortical gyral/sulcal development. On the other hand, neuro-sonography has advantages in detecting intracranial calcification, vascular abnormalities, intratumoral vascularity and bone dysplasia. Moreover, 3D ultrasound demonstrates extra CNS abnormalities, strongly associated with CNS abnormalities. Any less-invasive modalities can be used for a CNS anomaly screening scan and ultrasound is no doubt the first choice. Once CNS abnormality is suspected, it is suggested to use the different technologies according to what is looked for in each abnormal CNS case. Of course, MR and 3D ultrasound imaging should be complementary as well as alternative.