2. Diffusion Tensor Tractography for Central Nervous System Anomalies
−Analysis of fiber tracts forming Probst bundle in complete callosal agenesis−

Hidetsuna Utsunomiya
Department of Radiology, Fukuoka University Faculty of Medicine

Abstract
　　Callosal agenesis occurs as a result of the failure of association fibers to decussate to the contralateral hemisphere via the callosal precursor, due to a lack of induction by the massa commissuralis. When the development of association fibers from the cortical plate is normal, those which do not pass through the callosal precursor grow caudally along the medial surface of the ipsilateral cerebral hemisphere and form Probst bundles. This article describes the arrangement and development of fiber tracts forming Probst bundles in patients with complete callosal agenesis, using a novel technique of diffusion tensor tractography（DTT）, which can show the orientation of white matter fibers in vivo. The arrangement of neuronal fibers that form Probst bundle, which are altered hemispheric connection fibers in an acallosal brain, may support the idea that the growth of the corpus callosum is primarily antero-posterior, with the genu forming first, then the trunk and splenium, and lastly the rostrum.

Keywords： Callosal agenesis, Diffusion tensor tractography (DTT), Probst bundle