A 72-year-old female with history of hypertension, chronic kidney disease stage IV, and worsening headaches over the last few weeks is brought to the ICU for airway watch after falling in her bathroom and suffering multiple rib fractures and mild respiratory distress. CT head without contrast demonstrates no signs of acute cranial bleed but notes “an enlarged pituitary with concern for sellar mass.”
What is the best imaging procedure to further investigate?
A. Computed tomographyCorrect Answer: B
Magnetic resonance imaging (MRI) is the diagnostic modality of choice for most sellar masses. Compared to CT, MRI provides greater soft-tissue contrast, which allows clear visualization of pituitary morphology and neighboring structures, including the optic chiasm, optic nerves, cavernous sinuses, and carotid arteries. The one exception is that calcifications in a craniopharyngioma or meningioma are seen better by CT scan. Regardless, the initial study of a suspected sellar mass should be a MRI scan.
Gadolinium is used as an intravenous contrast agent to enhance and improve the quality of MRI imaging. Normal pituitary tissue takes up gadolinium more than surrounding tissue and will exhibit a higher intensity signal. Micro- and macroadenomas, craniopharyngiomas, and meningiomas take up gadolinium to a less degree than normal pituitary tissue but more than surrounding tissue; this characteristic can help identify a sellar mass. Gadolinium should not be used in patients with moderate to advanced renal failure (eGFR <30 mL/min), as it has been associated with nephrogenic systemic fibrosis. Patients should be well informed of the risks associated with gadolinium administration if its use is warranted.
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