Visualization of fetal lips and palate using a surface‐rendered oropalatal (SROP) view in fetuses with normal palate or orofacial cleft lip with or without cleft palate

In the presence of an orofacial cleft detected at routine midtrimester antenatal screening, precise characterization of the malformation is necessary, as this will affect the medical work-up and help in informing the parents1. The best method with which to analyze the palate is still under debate. Evaluation is usually based on multiplanar or tomographic reconstructions obtained with three-dimensional (3D) ultrasonography. Analysis of the posterior palate is impeded by artifacts due to acoustic shadowing by the anterior bony structures of the maxilla2. Various specific views have been advocated to overcome this difficulty, such as the 'reverse face' view, the intraoral 'en face' view, the 'flipped face' view, 'angled insonation', the 'axial underside' view and the 'oblique face' view (reviewed by To3). However, none has received general agreement. Our group has shown that the use of all three traditional orthogonal planes is necessary to examine thoroughly the different landmarks, in order to differentiate the involvement of the lip, alveolus and posterior hard palate. Lip analysis necessitates visualization of the coronal planes, and, in the case of bilateral clefts, the midsagittal plane. The palate (alveolus, maxilla, secondary palate) is best analyzed using coronal and axial planes4, 5. However, 3D multiplanar reconstructions are impeded by certain drawbacks: to convey the information necessitates multiple scans; they focus on the bony defect of the palate; and they are difficult to interpret, in particular by lay people, in contrast with the more readily understood surface-rendered views6. To overcome these flaws, we have developed a surface-rendered representation, corresponding to the submental intraoral photograph of the neonatal palate that is used by orofacial surgeons to visualize clefts7, 8 : the surface-rendered oropalatal (SROP) sonographic view. The SROP sonographic view is oriented in an oblique direction, transoral and directed upwards, from cephalad to caudal. Image reconstruction utilizes the surface rendering mode, which combines representation of the surface itself and that of the subjacent muscles and bony structures. The virtual lighting (in HDlive mode (GE Medical Systems, Zipf, Austria)) is focused on the frontal view of the palate. This view allows simultaneous visualization of the lips, the alveolar ridge and the secondary palate, thus synthesizing the essential information that must be communicated to the orofacial team about the bony and soft tissue defects, and helping the parents to understand the malformation. In the case of a normal palate, the SROP view visualizes, from front to back, the following structures (Figure 1): the cutaneous and mucous structures that cover the perioral muscle, the maxilla and the palatal processes. The posterior border of the horizontal plates of the palate bone is imaged at the level of the pterygoid processes. The integrity of the palate at this level constitutes a reliable landmark for excluding a cleft of the bony palate. The velum is also apparent. In the case of unilateral cleft lip with or without cleft palate (CL ± P), the SROP view visualizes, from front to back, the following anatomical landmarks relevant for description of the defect (Figure 2): the nostril rim, allowing description of its deformation and splaying; the thickness of the soft tissues of the internal and external banks of the separated lip; and the size, form and position of both the larger and lesser fragments that constitute the bony lining of the alveolopalatal cleft. Similarly, in the presence of a bilateral CL ± P, the following structures relevant to describe the defect are imaged, from front to back (Figure 3): the protruding premaxillary prolabium, with the possibility of characterizing the degree of its protrusion, and the width and length of both its bony and its soft tissue components; the lips on both sides of the premaxillary prolabium; and the bony parts of the alveolopalatal cleft (thickness and spacing of the banks). Thus, the SROP view is a comprehensive ultrasonographic view of the fetal perioral region. It allows visualization, in a single view, of the lips, the alveolar ridge and the hard palate, condensing the basic information on a cleft as proposed by Mulliken and Benacerraf: side, type and extent7. As the SROP view originates from the same acquired volumes as do the three standard orthogonal planes, it provides the same basic information about the anatomical defects as does traditional 3D multiplanar reconstruction. However it has several advantages. First, thanks to the combination of the surface rendering mode with virtual lighting, it allows visualization of the surface itself and that of the subjacent muscles and bony structures. Adding an analysis of the soft tissues enables more precise prediction of the severity of the defect to be corrected, providing the surgeon with information that can help him to predict with more precision both the technical difficulties that he will encounter and the expected final result. Accurate nasal and lip reconstruction is essential to the final esthetic result9. Second, it combines in a single view the essential information that needs to be communicated to various members of the orofacial team. Finally, it provides the parents with a representation of the defect affecting their child, facilitating their understanding of the malformation and of the information provided by the orofacial team regarding the nature of the defect and the sequence of therapeutic steps required.