White Matter Dissection of the Fetal Brain

Abstract

Neuroplasticity is a complex process of structural and functional reorganization of brain tissue. In the fetal period, neuroplasticity plays an important role in the emergence and development of white matter tracts. Here, we aimed to study the architecture of normal fetal brains by way of Klingler's dissection. Ten normal brains were collected from in utero deceased fetuses aged between 13 and 35 gestational weeks (GW). During this period, we observed modifications in volume, shape, and sulci configuration. Our findings indicate that the major white matter tracts follow four waves of development. The first wave (13 GW) involves the corpus callosum, the fornix, the anterior commissure, and the uncinate fasciculus. In the second one (14 GW), the superior and inferior longitudinal fasciculi and the cingulum could be identified. The third wave (17 GW) concerns the internal capsule and in the fourth wave (20 GW) all the major tracts, including the inferioroccipital fasciculus, were depicted. Our results suggest an earlier development of the white matter tracts than estimated by DTI tractography studies. Correlating anatomical dissection with tractography data is of great interest for further research in the field of fetal brain mapping.

Subdivision of Superior Longitudinal Fasciculus in Human Neonatal Brain

“…Their results showed that the periinsular portion of SLF, corresponding to our SLF III segment and AF, can be identi ed by dissection at 14 weeks. Then the newer bers always emerge in more super cial positions with the gestational age increasing and formed a more super cial component of SLF (Horgos et al 2020), corresponding to our SLF II segment. The sequence of development in periinsular area from ventral to the dorsal direction supported our quantitative analysis results, that is, ventral SLF III is more mature than dorsal SLF II in human neonatal period.…”

Cadaveric White Matter Dissection Study of the Telencephalic Flexure: Surgical Implications

“…These rotational movements of the hippocampal rudiment occur due to gradients induced by genetic expression, the fact that is key in some malformations ( 8 ). The formation of the forebrain fissures is also impacted by the development of the ventricles, which behaves as an external mechanical force rather than an internal force ( 8 , 10 , 11 ).…”

“…Moreover, and although the horizontal segment is widely similar in humans and monkeys, the vertical segment is missed in the latter. The frontotemporal connections are the first ones to be identified during the embryogenesis (around the 17 gw), while the parietal branches appear a few weeks later during the development (20 gw) ( 11 ). SLF II and III posterior extensions to the angular and supramarginal gyri show a slight inferolateral curve, probably given by the inferior parietal lobe ventrolateral movement during the CNS development.…”

“…Regarding the frontal connections, most of the studies reveal that monkeys' IFOF lacks the posterior projections to the occipital lobe ending at the temporal lobe level (22). Regarding the human brain's embryological development, the IFOF is one of the latest fascicles to develop, not appearing clearly identifiable till 20 gw (11). This longitudinally oriented tract is located ventral to the telencephalic bending, so it looks like not being too much affected by the flexure.…”

New Molecular Players in the Development of Callosal Projections

“…The formation of the CC begins with the projection of pioneer fibers from the cingulate and rostrolateral cortices [ 25 , 26 , 27 ] at around the 12th week of gestation (GW) in humans, followed by formation of the genu [ 20 , 28 ]. The fusion of these different parts of the CC completes at around GW14, and the CC expands as the brain increases in size [ 29 , 30 ]. Though each region grows at different rates, the overall volume of the CC increases rapidly in early development (GW19–21), and continues to grow at a slower rate until it reaches a plateau at around GW33 [ 29 , 31 , 32 ].…”