Utility of Early Postoperative High-Resolution Volumetric Magnetic Resonance Imaging After Transsphenoidal Pituitary Tumor Surgery

OBJECTIVE: Controversy exists over the utility of early postoperative magnetic resonance imaging (MRI) after transsphenoidal pituitary surgery for macroadenomas. We investigate whether valuable information can be derived from current greater resolution scans. METHODS: Volumetric MRI scans were obtained in the early (<10 days) and late (>30 days) postoperative periods in a series of patients undergoing transsphenoidal pituitary surgery. The volume of the residual tumor, resection cavity, and corresponding visual field tests were recorded at each time point. Statistical analyses of changes in tumor volume and cavity size were calculated using the late MRI as the gold standard. RESULTS: A total of 40 patients met the inclusion criteria. Preoperative tumor volume averaged 8.8 cm(3). Early postoperative assessment of average residual tumor volume (1.18 cm(3)) was quite accurate and did not differ statistically from late postoperative volume (1.23 cm(3), P = 0.64), indicating the utility of early scans to measure residual tumor. Early scans were 100% sensitive and 91% specific for predicting >= 98% resection (P < 0.001, Fisher exact test). The average percent decrease in cavity volume from preoperative MRI (tumor volume) to early postoperative imaging was 45% with decreases in all but 3 patients. There was no correlation between the size of the early cavity and the visual outcome. CONCLUSIONS: Early, high-resolution volumetric MRI is valuable in determining the presence or absence of residual tumor. Cavity volume almost always decreases after surgery, and a lack of decrease should alert the surgeon to possible persistent compression of the optic apparatus that may warrant reoperation.