Bilateral cavitations of ganglionic eminence: a fetal MR imaging sign of halted brain development

Abstract

Ganglionic eminence is the main transitory proliferative structure of the ventral telencephalon in human fetal brain and it contributes for at least 35% to the population of cortical interneurons; however data on the human GE anomalies are scarce. We report 5 fetal MR imaging observations with bilateral symmetric cavitations in their GE regions resembling an inverted open C shape and separating the GE itself form the deeper parenchyma. Imaging, neuropathology, and follow-up features suggested a malformative origin. All cases had in common characteristics of lissencephaly with agenesis or severe hypoplasia of corpus callosum of probable different genetic basis. From our preliminary observation, it seems that GE cavitations are part of conditions which are also accompanied by severe cerebral structure derangement.

Fig 1.

Prenatal single-shot FSE T2-weighted MR images of the 5 reported cases, each case displayed horizontally in a row. Case number, GA, and sex are reported. White arrows indicate GE region cavitations. In the case 3 row, an inverted open C shape is drawn, showing how cavitation appears on sagittal sections. The corpus callosum is agenetic or severely hypoplastic in all cases. Frontal opercula are shallow and dysmorphic.

Fig 2.

A and B, Sagittal and axial single-shot FSE T2-weighted sections of case 1 (22-week GA), respectively: black rectangle encompasses GE and relative cavitation. C, Thionin-stained paraffin coronal section shows a hemisphere at the level of GE cavitation (asterisk). D, Higher magnification of the black rectangle area in C, illustrating the regular border (epithelium-like structure) of cavitation (arrows). E, Higher magnification of the cortex (dotted rectangle in C): heterotopic cortical plate neurons extending in the marginal zone (arrowheads). Scale bar = 300 μm.

Fig 3.

A–C, Single-shot FSE T2-weighted sections from case 2 (29-week GA) prenatal study shows GE region cavitations (arrows), which tend to be relatively smaller with respect to the brain size in this older fetus. Arrowheads indicate bilateral bands of heterotopias. Gyration appears to be poor. D, Coronal FSE T2-weighted and sagittal (E) spin-echo T1-weighted sections show cavitations now relatively smaller and confirming band heterotopias (arrowheads).

Fig 4.

A and C, Single-shot FSE T2-weighted sections from case 3 (23-week GA) prenatal study, show large symmetric GE region cavitations (arrows). B and D, FSE T2-weighted corresponding MR autopsy sections, which confirm the prenatal findings (arrows): cavitations appear to have regular smooth margin, albeit brain was compressed and deformed during delivery.

Fig 5.

A, Coronal single-shot FSE T2-weighted section from case 4 (22-week GA); brain is shown upside-down to better match the corresponding coronal oblique histologic section in B, Thionin-stained paraffin section with black rectangle encompassing part of GE and related cavitation; C, higher magnification of the black rectangle in B; D, inside part of the cavitation (asterisks in C and D) lined by epithelium-like structure (arrow); E, detail of the developing cortex shows heterotopic cortical plate neurons extending in the marginal zone (arrowheads). Scale bar = 410 μm.