Empty sella is characterized by CSF herniation into the sella turcica with compression or flattening of the pituitary gland. It may be primary (due to incomplete diaphragma sellae allowing arachnoid herniation) or secondary (after surgery, infarction, apoplexy, or irradiation). Frequently incidental, but may correlate with idiopathic intracranial hypertension or endocrine dysfunction.

MRI (Gold standard):

Sellar morphology: Enlarged sella (>12 mm vertical height or >16 mm transverse diameter).

CSF signal intensity: T1 hypointense, T2 hyperintense, matching subarachnoid CSF.

Pituitary thickness: Thinned gland (<2 mm for complete empty sella; 2–4 mm for partial).

Infundibulum sign: Pituitary stalk traverses midline and remains central, confirming continuity (distinguishes from cystic lesion).

Chiasmal position: May be inferiorly displaced in large or long-standing cases.

Associated findings: Partially distended optic nerve sheaths, flattening of posterior sclera, and transverse sinus stenosis (in idiopathic intracranial hypertension).

Classification:

Partial Empty Sella: ≤50% of sellar space filled with CSF, pituitary >2 mm thick.

Complete Empty Sella: >50% of sellar space filled with CSF, pituitary <2 mm thick.

CT:

Enlarged sella with CSF attenuation (~0–10 HU).

Thin rim of enhancing pituitary along the floor.

Bony remodeling without cortical destruction.

Plain Radiography (rarely used):

Enlarged, rounded sella with thinned dorsum sellae — nonspecific.