Intraoperative high-field magnetic resonance imaging in transsphenoidal surgery of hormonally inactive pituitary macroadenomas

OBJECTIVE: The aim of the study was to evaluate the effect of intraoperative, high-field (1.5 T) magnetic resonance imaging (MRI) on the results of transsphenoidal surgery of hormonally inactive pituitary macroadenomas. METHODS: One hundred six patients (tumor size, 29.9 +/- 10.1 mm; minimum, 11.3 mm; maximum, 57.2 mm) with hormonally inactive pituitary macroadenoma were investigated by intraoperative high-field MRI during transsphenoidal surgery. If intraoperative imaging depicted an accessible tumor remnant, resection was continued. RESULTS: Among the 85 patients in whom complete tumor removal was intended preoperatively, intraoperative imaging revealed definite tumor remnants or suspicious findings in 36 (42%) patients. Imaging led to an extended resection in 29 (34%) patients of this group. Among them, resection could be completed in 21. This increased the rate of complete tumor removal from 58% (49 out of 85) to 82% (70 out of 85). In the group of patients with intended partial removal (n = 21), resection was extended in 38% (eight out of 21) because of intraoperative imaging. Comparison with scanning 3 months after surgery did not reveal any false-negative findings of intraoperative MRI; in six cases, intraoperative MRI was suspicious for some minor remnant that could not be reproduced in the postoperative control. CONCLUSION: The extent of resection in transsphenoidal surgery can be reliably assessed using intraoperative high-field MRI. In addition to the suprasellar compartment, intra- and parasellar structures are also visualized in great detail. Intraoperative imaging acts as an immediate intraoperative quality control, allowing one to not only increase the extent of resection, but to also increase the percentage of complete removals.