Frontonasal Dysplasia: A Diagnostic Challenge with Fetal MRI in Twin Pregnancy

Abstract

Callosal agenesis is a complex condition with disruption in the steps such as cellular proliferation, migration, axonal growth, guidance, or glial patterning at the midline. Agenesis of the corpus callosum (AgCC) is associated with diverse midline craniofacial malformations affecting the frontal-cranial and midface skeleton. Diagnosing midline abnormalities prenatally can be challenging, especially in twin pregnancies, due to poor resolution of skull base structures on fetal MRI, basal cephalocele could be mistaken for fluid in the nasopharynx, motion limitation, and fetal positioning. Our case highlights the importance of evaluation for other associated midline anomalies when there is callosal agenesis.

Keywords: agenesis of the corpus callosum; fetal MRI; frontonasal dysplasia; morning glory syndrome.

Figure 1.

Prenatal fetal MR: T2-weighted images in the axial (A), coronal (B), and sagittal (C) planes demonstrate a small focal T2 hyperintense signal (white arrows), which extends from the skull base to the nasopharynx, consistent with the cephalocele. Agenesis of the corpus callosum is also present (B).

Figure 2.

Postnatal MR: sagittal T2 image (A) and sagittal T1 MPRAGE (B) show a large defect consistent with a craniopharyngeal canal, with herniation of the adenohypophysis into the defect, which protrudes into the nasopharynx (blue arrows). Bilateral optic disc anomalies (C, white arrows) and agenesis of the corpus callosum (D) are also present.

Figure 3.

Fundus examination revealed a normal optic disc within a slight staphyloma in the right eye as well as normal macula and vessels. In the left eye, there was a Morning Glory Disc (large and excavated with vessels leaving from the side with the absence of central vasculature) surrounded by pigmentation (black arrow) that extended to the macula. Please see online publication for color images.