Corpus callosum development.

Corpus callosum embryology can be divided into three parts: during "commissuration", a cellular mass develops between two telencephalic vesicles. The primitive lamina terminalis corresponds to the closing point of the anterior neuropore. Its dorsal part grows and forms the lamina reuniens (6-8 intra uterine weeks, IUW). From ventral to dorsal, this lamina reuniens gives rise to the area praecommissuralis (origin of the anterior commissure), to the primordium hippocampi (10 I.U.W., fornix), and to the massa commissuralis (10 S.I.U., corpus callosum). Fibers arising from the developing hemispheres run through this primitive corpus callosum. The growth of the corpus callosum follows the expansion of the hemispheres, in a rostro-caudal and then dorso-ventral circular movement. The last part of the corpus callosum to form is the rostrum. Maturation occurs postnatally, and corresponds to axomal elimination, and myelination, progressively changing the callosal connection pattern of the newborn and infant into the adult pattern.