Why a dedicated protocol

The pituitary sits in the sella, bordered by the optic chiasm above and the cavernous sinuses (with the carotids and cranial nerves) laterally. A focused protocol uses thin coronal and sagittal slices and dynamic contrast — rapid post-gadolinium imaging, because a microadenoma enhances more slowly than normal gland and is best seen as a transient relative filling defect.

Micro- vs macroadenoma

• Microadenoma (<10 mm): often functioning (e.g. prolactinoma, Cushing’s, acromegaly) — correlate with endocrine bloods.
• Macroadenoma (≥10 mm): assessed for chiasm compression (bitemporal hemianopia) and cavernous sinus invasion; may present with mass effect or hypopituitarism.

Don’t miss

Pituitary apoplexy — acute haemorrhage/infarction of a tumour with sudden headache, visual loss and endocrine collapse — is a neurosurgical/endocrine emergency. Other sellar lesions include Rathke cleft cyst, craniopharyngioma and meningioma. Imaging is always read with the hormonal picture.

Reference: Bonneville JF et al. Magnetic resonance imaging of pituitary adenomas. Endocr Rev / MRI pituitary imaging reviews.