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

Abstract

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.

Prenatal diagnosis and outcome of partial agenesis and hypoplasia of the corpus callosum

“…The corpus callosum may be imaged antenatally by targeted multiplanar sonography from the midtrimester 8,9 . Focusing the ultrasound beam on the sagittal suture of the fetal head, the entire length of the corpus callosum may be displayed as a sonolucent band demarcated superiorly and inferiorly by two echogenic lines (Figure 1).…”

“…At two-dimensional (2D) ultrasound in the axial view of the fetal head, suspicious findings are absent cavum septi pellucidi and teardrop configuration of the lateral ventricles with possible ventriculomegaly. Antenatal diagnosis is based upon the non-visualization of the corpus callosum at transfontanellar ultrasound in either the sagittal or the coronal plane 8,9 . More subtle findings, such as hypoplasia and partial agenesis of the corpus callosum, may also be recognized antenatally 7,10 -12 .…”

Avaliação do comprimento e área do corpo caloso fetal por meio da ultrassonografia tridimensional

“…Os autores observaram que o comprimento do CC pela técnica transfrontal foi fortemente correlacionado com aquele obtido pelas técnicas multiplanar (r= 0,8) e volume contrast image c-plane (VCI-C) (r = 0,9); contudo, não determinaram valores de referência para este parâmetro 12 . Deve-se referir que a visão transfrontal do CC fetal já havia sido anteriormente descrita por meio da US2D 25 ; entretanto, a aquisição por meio da US3D é vantajosa, pois permite correções no modo multiplanar de forma a se obter o plano exato de medida do CC, independentemente de o feto não estar na posição ideal para sua obtenção.…”

Feasibility and Reproducibility of Transvaginal, Transabdominal, and 3D Volume Reconstruction Sonography for Measurement of the Corpus Callosum at Different Gestational Ages

“…In our study the success rate of 91% obtained by the transvaginal approach was possible by using slight multiplanar manipulations in some (24%) of the 3D transvaginal volumes. The success rate of direct mid-sagittal view acquisition by transabdominal sonography has been reported as 77 [7] , 87 [8] , 88.3 [19] and 89% [5] . Overall, our results were worse (52%), particularly when the fetus was in a cephalic presentation and at late gestation (20%).…”

“…Therefore, a careful (re-)assessment of the fetal brain, including mid-sagittal views, is also crucial in late gestation. Mid-sagittal planes can be obtained by 2D transvaginal or transabdominal sonography, by aligning the transducer with the fontanelles and cranial sutures [5][6][7][8][9] . These 'acoustic windows' will only close during childhood and so are very helpful throughout pregnancy.…”