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MR-appearance of the pituitary gland before and after resection of pituitary macroadenomas
Abstract:
Pituitary macroadenomas can cause severe compression and displacement of the pituitary gland. This study was undertaken to determine the value of contrast administration for the detection of the pituitary gland in patients with pituitary macroadenomas, to evaluate the preoperative location and configuration of the pituitary gland and to describe its postoperative changes after tumour resection. Preoperative and postoperative MR imaging examinations of 30 patients with histologically proven pituitary macroadenomas were retrospectively evaluated. The examinations were performed on a 1.5 T unit, by obtaining T1-weighted sagittal and coronal images after administration of gadopentetate dimeglumine. On preoperative MR images, contrast administration increased the detectability of the anterior lobe from 30% to 80%. Depending on the size and extension of the adenoma, the pituitary gland was displaced to the suprasellar space (53%) and/or deformed to a club-shaped (27%) or sickle-shaped (47%) configuration. In six patients, the sickle-shaped pituitary gland was interposed between the cavernous sinus and the adenoma ('rim-sign'), which was seen only on gadopentetate dimeglumine-enhanced images. In these cases, there was no infiltration of the cavernous sinus at surgery. Postoperatively, descent of the pituitary gland was found in 63%, and reexpansion in 54%. We conclude that contrast administration improves the detectability of the pituitary gland on preoperative MR images, and that the displacement and deformation of the pituitary gland depend on the size, location and extension of the adenoma. Preoperatively, demonstration of the pituitary gland interposed between the cavernous sinus and the adenoma ('rim-sign') is a very useful sign for exclusion of cavernous sinus infiltration, best seen on contrast-enhanced coronal MR images. The normal postoperative changes of the pituitary gland after tumour resection include repositioning and re-expansion.