Infundibulum sign (pituitary)
Citation, DOI & article data
In the former, although the sella is enlarged, there is no mass as such and the pituitary infundibulum traverses the enlarged sella to its floor where residual pituitary tissue is present. This represents a positive infundibulum sign.
When a cystic mass is present then the infundibulum is displaced away from the mass. This represents a negative sign.