- Seen in adults (peak age 30–60 years; accounts for 10–15% of all intracranial neoplasms and is the most common sellar/suprasellar mass in adults), presenting with bitemporal hemianopia (from superior compression of the optic chiasm), hypopituitarism, hyperprolactinaemia ('stalk effect' or prolactinoma), or acute thunderclap headache with ophthalmoplegia (pituitary apoplexy).
- Caused by a benign clonal proliferation of anterior pituitary (adenohypophyseal) cells measuring ≥ 10 mm in diameter (microadenomas measure < 10 mm), classified clinically as functioning (prolactin, GH, ACTH) or non-functioning gonadotroph macroadenomas.
Imaging Findings
- MRI Pituitary / Sella Protocol (Thin-Slice Coronal & Sagittal T1/T2 + Dynamic Contrast - Gold Standard):
- –'Snowman' / 'Figure-of-8' Configuration: Intrasellar mass that expands the sella turcica and extends superiorly into the suprasellar cistern with a characteristic waist-like indentation at the diaphragma sellae; normal anterior pituitary gland is compressed or inseparable from the mass.
- –T1WI & T2WI Signal: Typically isointense to cerebral cortex on both T1WI and T2WI; large tumours often contain focal T2-bright cystic degeneration or T1-bright subacute hemorrhage.
- –T1 C+ (Contrast): Moderate, heterogeneous enhancement (enhancing slightly more slowly and less intensely than normal residual pituitary tissue); displaces and elevates the optic chiasm (producing T2 hyperintensity within the chiasm when chronically compressed).
- –Cavernous Sinus Invasion (Knosp Grading): Assessed on coronal MRI relative to the intracavernous internal carotid artery (ICA); Knosp Grade 3–4 (>50% or complete encasement of the intracavernous ICA without narrowing its lumen) indicates true cavernous sinus invasion.
- –DWI / ADC: Uncomplicated macroadenomas show intermediate diffusivity without marked restriction; acute pituitary apoplexy demonstrates marked diffusion restriction within the infarcted/hemorrhagic adenoma early on.
- –**SWI / T2* GRE: Demonstrates prominent blooming artifact and fluid-fluid levels in hemorrhagic pituitary apoplexy**, whereas intratumoral calcification is rare (<1–2%, unlike craniopharyngioma).
- CT & Plain Skull Radiograph (X-Ray) Findings:
- –CT Head: Enlarged, remodelled sella turcica with thinning or depression of the sellar floor into the sphenoid sinus; absence of coarse calcification helps distinguish macroadenoma from craniopharyngioma.
- –Lateral Skull X-Ray: Classic ballooning enlargement of the sella turcica, thinning/erosion of the dorsum sellae, and a 'double-floor' sign from asymmetric downward depression of the sellar floor.
Differential Diagnosis
| Differential Diagnosis | Key Distinguishing Features |
|---|---|
Craniopharyngioma | Bimodal age (children 5–15 years and adults 50–70 years); predominantly suprasellar with a normal-sized sella and separate normal pituitary gland; coarse calcification (90%), T1-bright 'machine-oil' cysts, and vivid nodular enhancement. |
Tuberculum Sellae / Diaphragma Sellae Meningioma | Broad dural attachment with a prominent dural tail, avid homogeneous enhancement, hyperostosis of the planum sphenoidale/tuberculum sellae, and often narrows the encased cavernous ICA lumen. |
Rathke Cleft Cyst | Well-defined midline non-enhancing intrasellar/suprasellar cyst located between the anterior and posterior pituitary lobes; frequently contains a pathognomonic T1-bright, T2-dark intracystic mucinous nodule without solid enhancement. |
Giant Cavernous / Supraclinoid ICA Aneurysm | Demonstrates a patent lumen with prominent T2 flow void, pulsatile phase-encoding artifact, concentric mural thrombus, and direct continuity with the ICA on CTA/MRA. |
Important Points to Remember
- Mandatory Serum Prolactin Before Surgery: Always measure serum prolactin (with serial dilutions to avoid the 'high-dose hook effect'); macroprolactinomas respond dramatically to first-line medical therapy with dopamine agonists (cabergoline), whereas non-functioning macroadenomas with optic chiasm compression require endoscopic transsphenoidal resection.
- Pituitary Apoplexy Emergency: Acute hemorrhage/infarction into a macroadenoma causing sudden headache, visual loss, and CN III/IV/VI palsy requires immediate IV hydrocortisone replacement (to prevent fatal adrenal crisis) and urgent neurosurgical/ophthalmological review.