Key features of cerebral lamination and sulcation at 22 weeks gestation.
The Sylvian fissure is deeper and more squared, but temporal lobes have not yet begun to cover the operculum. Calcarine, parieto-occipital and hippocampal fissures are nor visible.
Normal lamination. Note the normal five-layered laminar pattern with alternating T2 dark and bright bands, seen in fetuses from 20 to 30 weeks gestation. From inner to outer, the layers are:
1. ventricular zone (arrowhead)
2. periventricular fibre-rich zone (dotted arrow)
3. intermediate zone (curved arrow)
4. sub-plate (long thin arrow)
5. cortex (short thick arrow)
Note the normal appearance of ganglionic eminences.