Christian Mitter MD, Presenter: Nothing to Disclose

Daniela Prayer MD, Abstract Co-Author: Nothing to Disclose

Peter Christian Brugger MD, PhD, Abstract Co-Author: Nothing to Disclose

Gregor Kasprian MD, Abstract Co-Author: Nothing to Disclose

The ganglionic eminence (GE) is a transient structure of the developing fetal brain located adjacent to the lateral ventricle, and contains the proliferative zone for developing GABAergic basal ganglia projection neurons and cortical interneurons. Due to its highly anisotropic organisation the GE can be visualized and investigated by diffusion tensor imaging. We used in utero DTI-based tractography to identify the normal 3D imaging patterns of this structure in the developing fetal brain during the second trimester in vivo.

Preselected non-motion degraded in utero DTI examinations of 13 unsedated fetuses (21 – 27 gestational weeks, GW) without gross cerebral malformations were included. Orthogonal axial diffusion tensor sequences (16 directions, reconstructed voxel size 0.94mmx0.94mmx3mm, b-values of 0s/mm2 and 700s/mm2) were performed using a 1.5T superconducting MR unit. Color coded FA maps were geometrically coregistered with multiplanar T2-weighted MR sequences. The GE was anatomically defined using a multiple ROI approach and visualized using a FACT algorithm.

Three-dimensional visualization of anisotropic diffusion within the GE by in utero tractography resulted in multiple “pseudofiber” tracts with a C-shaped course along the wall of the lateral ventricle. Pseudofibers showed an anterior-posterior orientation along the body of the lateral ventricle and a superior-inferior orientation in front of the trigone. Coregistered T2w sequences confirmed the location to be within the strongly hypointense cell rich proliferative layers of the GE. Overall, in utero tractography of the GE was successful in 10/13 subjects in both hemispheres and in 3/13 subjects in only the right hemisphere.

This study demonstrates the potential of DTI-based in utero tractography to visualize the three-dimensional anisotropic organization of the GE in the developing fetal brain in vivo as early as 21 GW. Anisotropic diffusion within the GE may be related to tangential migration of developing neurons in this region. In utero tractography of GE pseudofibers may be useful for a more detailed assessment of this transient fetal structure in both normal development and fetal brain pathologies.

Due to its important role in the production of GABAergic neurons, a more detailed assessment of the GE in utero may be useful in a range of neurodevelopmental disorders, including epilepsy.

Mitter, C, Prayer, D, Brugger, P, Kasprian, G, In Utero Tractography of Ganglionic Eminence Pseudofibers.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014376.html