Intraoperative MRI during transsphenoidal surgery of pituitary macroadenomas

Objective: To report our experiences with MRI during transsphenoidal surgery for pituitary macroadenomas with specific regards to the extent of resection and the relevance for the further management of these patients.

Methods: A 1.5 T Magnetom Sonata (Siemens, Germany) was used for pre- and intraoperative imaging. Initially T1-, later in the study, T2- weighted sequences were applied before and during surgical resection. T2- weighted HASTE sequences were used for fast image acquisition and first assessment. The surgeons' estimate of the extent of tumor removal was documented and compared with the actual extent as evidenced by first iop imaging results. Results of repeated inspections, necessary further resection, and final imaging results were also documented.

Results: Intraoperative MRI (iopMRI) was used in 129 patients with pituitary macroadenoma, 106 suffering from hormonally inactive adenomas and 23 suffering from GH secreting adenomas. Complete resection was considered to be possible in 85 cases of hormonally inactive adenomas and in 18 cases of GH secreting adenomas. IopMRI led to further tumor removal in 34 cases. The rate of complete tumor removal could thus be improved from 57% to 82% of the patients with hormonally inactive adenomas (n=85). The rate of remission in acromegalic patients (n=18) could be improved from 33.3% to 44.4%, using the criteria of an international consensus conference (Giustina et al., J Clin Endocrinol Metab. 2000;85:526–9). Comparing the intraoperative results with MR images obtained after 3 months we could show, that there were no false negative results of iopMRI. We evaluated early postoperative MRI in 48 patients. In 64% the results were comparable to iopMRI regarding the assesment of intra- and suprasellar space. In 17% the intrasellar space could not be assessed properly and in 19% an assessment of intra- and suprasellar space was not possible.

Conclusions: IopMRI used during transsphenoidal surgery of pituitary adenomas can increase the rate of complete resection, particularly in lesions with a large suprasellar extension.