Imaging of the pituitary gland in cushing's disease

ABSTRACT

To evaluate the sensitivity of computed tomography [CT] and magnetic resonance imaging [MRI] of the pituitary gland in detecting pituitary adenomas in patients with Cushing's disease. Twenty-five patients aged 8-55 years [average age 30 years], clinically and biochemically diagnosed as having Cushing's disease, were evaluated with a contrast-enhanced CT scan and MRI of the pituitary gland. Contrast-enhanced CT scans of direct 2-mm-thick coronal sections were performed. Pre- and post-enhanced MRI of the pituitary gland was performed on a 1.5-tesla superconducting magnet, taking 2-mm-thick sections in the sagittal and coronal planes. MRI revealed adenomas in 16 patients [12 microadenomas and 4 macroadenomas]. Twelve [75%] adenomas were delineated more clearly on post-gadolinium MRI scans. Nine [56%] adenomas were better delineated on coronal images. Out of 16 adenomas identified on the MRI, only 5 were seen on the CT scan. All patients underwent trans-sphenoid surgery and the MRI findings were confirmed. Contrast-enhanced MRI is the preferred modality for the detection of ACTH-secreting adenomas, which are difficult to visualize on CT scans due to their small size. A focal hypointense lesion is the commonest finding on T1-weighted images and, if identified on coronal sections, is the most sensitive diagnostic criterion. However, a negative MRI does not exclude the presence of a microadenoma