Ruxandra-Iulia Milos MD, Presenter: Nothing to Disclose

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

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

Christian Mitter, Abstract Co-Author: Nothing to Disclose

Daniela Prayer, Abstract Co-Author: Nothing to Disclose

The periventricular crossroads were described histological as transient regions of the fetal brain with an abundant hydrophilic extracellular matrix where major fiber systems intersect. Aim of this study was to characterize the parietal crossroads situated lateral to the exit of the posterior limb of the internal capsule (PLIC) on in vivo fetal MR- images.

In vivo MRIs of 280 fetal brains between the 18th and 39th gestational week (GW) (median GW27) were analysed. Studies were performed on a 1.5T superconducting unit using ultrafast T2-weighted, T1-weighted, diffusion-weighted sequences and diffusion tensor imaging (DTI) in 3 orthogonal section-planes. Fetuses were divided in two groups: one with normal (n=135), and the second with pathological brain development (n=145).

In normal brains, we observed triangular shaped areas with the basis of the triangle in the continuity of the PLIC, adjacent to the posterior ganglionic eminence, and the tip oriented in the direction of the subplate. They appeared hyperintense to the subplate on T2- (Figure), and iso- or hypointense on T1- and diffusion-weighted images. Using DTI we found that these areas are located at the merging point of PLIC, external capsule, and fronto-occipital association fibers. The triangular crossroads were best detected at GW24 and became isointense with the adjacent structures by GW30. In different pathologies, such as malformations (n=21), acquired brain lesions (n=7), or intrauterine growth restriction (n=2) they were larger as in normals, and/or had increased T2- weighted signal intensity, and/or persisted after GW30.

The transient MR-features of the triangular crossroads may be explained by the high water content of the abundant extracellular matrix, which gradually diminishes with ongoing cellular maturation. Their increased signal-intensity/size or persistence after GW30 probably reflects oxidative stress or impairment of fiber development in these regions. Normal triangles should not be misdiagnosed as ischemic lesions. Thus, the persistence of the triangular crossroads after GW30 and/or their increased intensity/size seems to be an unspecific indicator of the presence of cerebral pathology.

Normal signal of triangular crossroads should not be interpreted as ischemic lesions. Their persistence after GW30 and/or increased intensity/size may indicate the presence of fetal brain pathology.

Milos, R, Kasprian, G, Brugger, P, Mitter, C, Prayer, D, Periventricular Triangles: Persistent Crossroads in the Pathological Fetal Brain.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11011832.html