What imaging is helpful in evaluating pituitary stalk lesions?
Ideally, high-resolution, thin-cut, gadolinium-enhanced, pituitary-dedicated magnetic resonance imaging (MRI) should be performed to best characterize the pituitary/stalk lesions and their proximity to adjacent structures. On MRI, the normal posterior pituitary gland is hyperintense/‘bright spot’ on T1-weighted, non–contrast-enhanced images, because of the neurosecretory granules. The presence of a posterior pituitary hyperintense signal makes central DI unlikely (< 5%), although ≈ 10% to 15% of normal subjects will not demonstrate a posterior gland ‘bright spot’, so a negative finding does not exclude the diagnosis.
With regard to potential extrapituitary/stalk MRI image findings, neurosarcoidosis may also demonstrate periventricular lesions and leptomeningeal enhancement. Similarly, TB infection may demonstrate meningeal enhancement, intracranial abscesses, and paranasal sinus involvement. Germinomas may uniquely present with a concomitant pituitary stalk/gland lesion and a pineal gland tumor.
MRI Characteristics of Hypophysitis versus Pituitary Macroadenomas.
|MRI RADIOGRAPHIC FEATURES||HYPOPHYSITIS||MACROADENOMA|
|Homogenous enhancement with contrast||+||−|
|Loss of posterior pituitary gland hyperintensity||+ (except medication-related hypophysitis)||−|
+, More common; −, less common; MRI, magnetic resonance imaging.