Resection Control in Trans-sphenoidal Surgery of Pituitary Macroadenoma by Intraoperative High-Field MRI

Introduction: This study was initiated to evaluate the influence of intraoperative MRI on the course of trans-sphenoidal surgery for pituitary macroadenomas with special regard to the extent of resection.

Material and Methods: A 1.5-T Magnetom Sonata (Siemens Medical Solutions, Erlangen, Germany) was used for pre- and intraoperative imaging. T1- and (later in the study) T2- weighted sequences were applied before and during surgical resection. Additional T2-weighted HASTE sequences were used for a 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 intraoperative imaging results. Results of repeated inspections, necessary further resection, and final imaging results were also ducumented.

Results: Intraoperative MRI was used in 112 patients with pituitary macroadenoma. Complete resection was considered to be possible in 89 of these prior to surgery. In 56 of these resection was already complete when the first intraoperative images were obtained. In another 23 patients tumor remnants were detected which then could be removed completely. Thus intraoperative resection control led to an increase in the rate of complete tumor resection from 63% to 88%.

There were some cases (n = 4) in which initial intraoperative MRI showed suspect intrasellar findings but a repeated inspection revealed no further tumor but rather some blood clot. Operative technique had to be adapted (especially with regard to hemostasis) in order to achieve MR images of sufficient quality. A reliable evaluation of suprasellar tumor resection was possible in all cases; the parasellar part and compression or invasion of the cavernous sinus could be evaluated in the majority of cases. There is a correlation of the dimensions of the tumor, notably its suprasellar extension, and the benefit of intraoperative MRI. Patients with large intra- and suprasellar lesions benefit most from intraoperative imaging.

Conclusions: Intraoperative high-field MRI used during trans-sphenoidal surgery of pituitary adenomas can increase the rate of complete resection, in particular for lesions with a large suprasellar extension.