The transfrontal view: a new approach to the visualization of the fetal midline cerebral structures.

The objective of this study was to assess the feasibility of using the frontal suture as an acoustic window to visualize sonographically the midline cerebral structures (transfrontal view) in midtrimester fetuses. The study design was prospective and observational. In 124 healthy fetuses and in 2 fetuses with agenesis of the corpus callosum at 19 to 24 weeks' gestation, an attempt was made to obtain a transfrontal view by using transabdominal sonography. The transfrontal view was successfully and rapidly obtained in 110 (89%) of the healthy fetuses; it always provided detailed visualization of the entire corpus callosum, cavum septi pellucidii, third ventricle, brain stem, fourth ventricle, vermis cerebelli, and cisterna magna. The anatomic information was comparable with that obtained from a median sagittal scan obtained through the anterior fontanelle. In both fetuses with agenesis of the corpus callosum, the transfrontal view provided clear evidence of the anomaly. The transfrontal view is feasible in midtrimester fetuses and allows rapid demonstration of the cerebral midline structures and the corpus callosum in particular. It may be helpful in the diagnosis or exclusion of cerebral anomalies, and at least in some cases, it may obviate the need for a transvaginal examination. The transfrontal view may also be used to standardize the scanning plane for the evaluation of the fetal facial profile.