looking up fissure stuff as it seemed a HUGE difference between 28w and 33w in fissure size; looks like I was right: the difference between 28 and 29 weeks is a huge difference; curved branches show up at 29 weeks where there’s none at 28.
_Brain structure development of very pre-term infants on serial cranial ultrasound_
“In infants born at GAs of 27 to 28 weeks, the lateral fissure exhibited wide gaps with short branches. Deep inside the cerebral parenchyma, a few shallow sulci appeared perpendicular to the cerebral longitudinal fissure. No obvious cerebral sulcus structures were present in the shallow layer of the cerebral parenchyma. The cingulate gyrus was well developed with few branches in the sulcus. In infants born at a GA of 28 weeks, the parieto-occipital sulcus exhibited short linear echoes in the shallow layer of the parenchyma. In infants born at a GA of 29 weeks, the cingulate sulcus exhibited multiple curved branches that extended into the cerebral parenchyma. The boundary of the cingulate gyrus was essentially formed, and gaps between the lateral fissures narrowed and branched. Numerous cerebral sulci with short line-like echoes appeared next to the longitudinal fissure and the shallow layer of the cerebral parenchyma. The brain development of infants born at a GA of 29 weeks was more mature than that of pre-term infants born at a GA <28 weeks.”
“In infants born at GA of 25 to 28 weeks, the cerebral parenchyma in the cerebellar hemisphere was smooth. However, the boundary between the cortex and medulla was unclear. Few sulci were present in the cortex, and the vermis had a visible but loose texture.
In infants born at a GA of 29 weeks, the cerebellar hemisphere exhibited short, line-like shallow sulci, and the vermis was longer than that in infants born before a GA of 28 weeks.”
In conclusion, cerebral and cerebellar structures develop in very pre-term infants (GA ≤29 weeks), and cerebellar measurements changed as the GA increased. The brain development of infants born at a GA of 29 weeks was significantly more mature than that of pre-term infants born at a GA <28 weeks. This difference indicates an age watershed between the two groups of infants.