MR Imaging Diagnosis of Diencephalic-Mesencephalic Junction Dysplasia in Fetuses with Developmental Ventriculomegaly

Abstract

Diencephalic-mesencephalic junction dysplasia is a rare malformation characterized by a poorly defined junction between the diencephalon and the mesencephalon, associated with a characteristic butterfly-like contour of the midbrain (butterfly sign). This condition may be variably associated with other brain malformations, including callosal abnormalities and supratentorial ventricular dilation, and is a potential cause of developmental hydrocephalus. Here, we have reported 13 fetuses with second-trimester obstructive ventriculomegaly and MR features of diencephalic-mesencephalic junction dysplasia, correlating the fetal imaging with available pathology and/or postnatal data. The butterfly sign can be clearly detected on axial images on fetal MR imaging, thus allowing for the prenatal diagnosis of diencephalic-mesencephalic junction dysplasia, with possible implications for the surgical management of hydrocephalus and parental counseling.

Fig 1.

DMJ dysplasia in a 28-week-old fetus (case #9). A, Axial T2-weighted image reveals fusion of the hypothalamus and midbrain (asterisk), enlargement of the dorsoventral axis of the midbrain, and a ventral midbrain cleft (arrow) resulting in a butterfly-like appearance. B, Sagittal T2-weighted image demonstrates partial callosal agenesis (black arrow) associated with hypoplasia of the pons (empty arrow) and vermis and mild kinking of the cervicomedullary junction (white arrowhead). Note that the cerebral aqueduct is not visible. The interthalamic adhesion is enlarged and ventrally located (black arrowhead). C, Coronal T2-weighted image shows fusion between the midbrain and thalami (asterisks) as well as moderate supratentorial ventriculomegaly.

Fig 2.

Prenatal and postnatal MR findings of DMJ dysplasia in a 23-week-old fetus (case #7). A, Axial T2-weighted image reveals abnormal contour of the midbrain with a deep ventral cleft (arrow), resulting in a butterfly-like appearance. B, Sagittal T2-weighted image demonstrates marked hypoplasia of the pons (thick arrow) and vermis, aqueductal stenosis, and mild kinking of the cervicomedullary junction (thin arrow). The interthalamic adhesion is enlarged and ventrally located (arrowhead). C, Coronal T2-weighted image shows fusion between the midbrain and thalami (thick arrow) and complete callosal agenesis. Corresponding axial (D), sagittal (E) and coronal (F) T2-weighted images obtained on day 5 after birth confirm the prenatal findings, including the DMJ dysplasia (arrow, D) and brain stem anomalies, and reveal severe supratentorial hydrocephalus.

Fig 3.

Prenatal and postnatal MR findings with DTI in a 31-week-old fetus with DMJ dysplasia (case #13). A, Axial T2-weighted image shows the typical “butterfly” appearance of the DMJ. B, Axial T2-weighted image obtained at age 7 days confirms the abnormal contour of the midbrain. C, Sagittal T2-weighted driven equilibrium pulse image demonstrates complete callosal agenesis, marked hypoplasia of the pons (white empty arrow) and vermis (black empty arrow), elongated midbrain, and kinked cervicomedullary junction (arrowhead). Coronal (D) and oblique axial (E) T2-weighted images fused with motor tractography reveal no tracking of the corticospinal tracts below the level of the midbrain (thick arrows). Color version available on-line.