Well-circumscribed lobulated sellar mass (originated from the sella turcica as evidenced by upwards displacement of diaphragmatic leaflets, which they themselves constrict onto the mass forming the characteristic snowman configuratioNconfiguration) causes expansion of sella turcica. It has suprasellar extension.The mass demonstrates isointensity on T1W and T2W (relative to grey matter) and homogeneous enhancement post gadolinium.No intralesional hyperintensity on T1W to suggest hemorrhagichaemorrhagic component.Superiorly, it compresses onto the optic chiasm significantly as well as upward displacement floor of third ventricle. Obstruction of bilateral Foramen of Monro results in acute obstructive hydrocephalus with transependymal CSF seepage.Postero-inferiorly, the suprasellar mass exerts onto the midbrain with obliteration of interpeduncular cistern.Laterally, no extension into the bilateral cavernous sinuses without encasement of internal carotid arteries.

Normal pituitary gland and infundibulum are not well visualised.

Annotated images show the importance of diaphragma sella/leaflets to guide radiologists the most likely origins of the sellar/suprasellar mass.If the diaphragmatic leaflets are pushed upwards by the sellar mass, the origin is from the sella turcica. If the diaphragmatic leaflets are pushed downwards by the suprasellar mass, the origin is from the suprasellar region (possible differential diagnoses include meningioma, aneurysm, and craniopharyngioma).The constriction of the soft pituitary macroadenoma by the diaphragmatic leaflets formed the "snowman sign".

Patient went on to have trans-sphenoidal surgery and histopathological examination confirmed pituitary macroadenoma.

This case demonstrates the usefulness of assessing the displacement of diaphragmatic leaflets to formulate the possible differential diagnoses for sellar/suprasellar mass.

The mass effect ontoon adjacent structures such as optic chiasm, third ventricle, Foramenforamen of Monro, and midbrain superiorly should be reported.

Assessment of cavernous sinuses and encasement of cavernous segment of internal carotid arteries is important for pre-operative surgical planning.