Pre- and Postoperative Magnetic Resonance Imaging Comparative Studies of Pituitary Tissues Following Transsphenoidal Resection of Pituitary Macroadenomas

Background: Magnetic resonance imaging (MRI) has become the most important radiological procedure for diagnosing and following pituitary tumors. But previous MRI studies on pituitary adenomas are mainly focused on the posterior pituitary. Few research has been done on residual normal pituitary tissue before and after transsphenoidal surgery. This retrospective cohort study investigates the pre- and postoperative magnetic resonance imaging characteristics of normal pituitary tissues regarding transsphenoidal resection of pituitary macroadenomas. Methods: Pre- and postoperative magnetic resonance imaging scanning of 112 consecutive pituitary macroadenoma patients who underwent tumor resection via transsphenoidal approach was performed, and their medical records were studied. Results: On preoperative MRI, 66 cases of pituitary stalks were identifiable, 9 of them were roughly in the middle, and 57 cases showed left or right deviation, with the angle between pituitary stalks and the sagittal plane was 5.32 degrees-64.05 degrees (average 21.65 degrees). Among the 57 patients with preoperative pituitary stalk deviation, 55 of the pituitary stalk deviations improved in 1 week after surgery, and 30 cases were almost in the middle in 4-6 months after operation, with the other cases get better in varying degrees. The diameter of pituitary stalk was 1.08-3.89 mm (mean 2.36 mm) in pre-operation, and 1.29-3.43 mm (mean 2.30 mm) in 4-6 months after operation. The length of pituitary stalk was 1.41-11.74 mm (mean 6.12 mm) preoperatively, 3.61-11.63 mm (mean 6.93 mm) early postoperatively, and 5.37-17.57 mm (mean 8.83 mm) in 4-6 months after operation. Pituitary stalk was thickened or compressed on preoperative MR images, and gradually recovered to normal during postoperative period. It tended to be in the middle position and its length increased gradually until 4-6 months after operation. On preoperative MRI, 69 out of 112 patients showed residual pituitary tissues (RPT)(+) on enhanced MRI. RPT were likely located above the adenomas in somatotroph adenoma patients. Morphological restitution of postoperative normal pituitary tissues was better in lateral displacement than in superior or superolateral patterns on preoperative magnetic resonance imaging. Postoperative normal pituitary tissues usually subsided directly in superior displacement pattern on preoperative MRI, while were likely to be confined in the lateral side in lateral and superolateral displacement patients. Postoperative morphologic remodeling grade of RPT was positively correlated with the maximum diameter of pituitary adenoma (p = 0.000), but not with age. Conclusions:The larger the tumor diameter, the worse the pituitary morphological recovery after tumor resection. Relative locations of normal pituitary and adenoma tissues may be related to adenoma type and may affect postoperative reconstruction of residual normal pituitary tissues. These findings enable surgeons to distinguish pituitary tissue from residual or recurring tumor tissue on postoperative magnetic resonance imaging.