Dorsal cyst malformations. Part II. Galenic dysgenesis and its embryological considerations.

In the preceding part, galenic dysgenesis was stated to be a diagnostic hallmark of dorsal cyst malformations. Failed formation of the galenic drainage system conducts the diencephalic drainage laterally into the transverse sinuses as in the embryonal stage, and it is frequently associated with arrested descent of the torcular portion or other anomalies of the dural sinuses. Highly malformed structures of the deep cerebral veins and the dural sinuses seen in this malformation are correctly interpreted in comparison with findings of venous injection studies performed in human fetuses. Pathogenesis of this malformation is also discussed on the basis of embryological studies of the dural sinuses and falcotentorial structures.