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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 |
| Asymmetric mass | − | + |
| Stalk thickening | + | − |
| Homogenous enhancement with contrast | + | − |
| Suprasellar extension | + | + |
| Stalk displacement | − | + |
| Loss of posterior pituitary gland hyperintensity | + (except medication-related hypophysitis) | − |
+, More common; −, less common; MRI, magnetic resonance imaging.
