Transsphenoidal Resection of Sellar Tumors Using High-Field Intraoperative Magnetic Resonance Imaging

Abstract

There has been increasing experience in the utilization of intraoperative magnetic resonance imaging (iMRI) for intracranial surgery. Despite this trend, only a few U.S centers have examined the use of this technology for transsphenoidal resection of tumors of the sella. We present the largest series in North America examining the role of iMRI for pituitary adenoma resection. We retrospectively reviewed our institutional experience of 59-patients who underwent transsphenoidal procedures for sellar and suprasellar tumors with iMRI guidance. Of these, 52 patients had a histological diagnosis of pituitary adenoma. The technical results of this subgroup were examined. A 1.5-T iMRI was integrated with the BrainLAB (Feldkirchen, Germany) neuronavigation system. The majority (94%) of tumors in our series were macroadenomas. Seventeen percent of tumors were confined to the sella, 49% had suprasellar extensions without involvement of the cavernous sinus, 34% had frank cavernous sinus invasion. All patients underwent at least one iMRI, and 19% required one or more additional sets of intraoperative imaging. In 58% of patients, iMRI led to the surgeon attempting more resection. A gross total resection was obtained in 67% of the patients with planned total resections. There was one case of permanent postoperative diabetes insipidus and no other instances of new hormone replacement. In summary, iMRI was most useful for tumors of the sella with and without suprasellar extension where the information from the iMRI extended the complete resection rate from 40 to 72% and 55 to 88%, respectively. As one would expect, it did not substantially increase the rate of resection of tumors with cavernous sinus invasion. Overall, iMRI was particularly useful in guiding resection safely, aiding in clinical decision making, and allowing identification and preservation of the pituitary stalk and normal pituitary gland. Limitations of the iMRI include a need for additional personnel and training as well as additional operative time, which diminishes over time as personnel learn to optimize workflow efficiency. Additional costs are mitigated in part by using the iMRI as an immediate postoperative scan. Other data emerging from our experience suggest that preservation of normal gland and

Use of High-Field Intraoperative Magnetic Resonance Imaging During Endoscopic Transsphenoidal Surgery for Functioning Pituitary Microadenomas and Small Adenomas Located in the Intrasellar Region

“…Tumor invasion of the CS is correlated with poor endocrine outcome after surgery. 6,9,13,22,30) Complete tumor removal was not achieved in either of our two patients who had tiny tumor remnants in the CS on the final iMR images, and the presence of tumor remnants in the CS was significantly associated with failure to achieve long-term endocrine remission. These findings suggest that high-field iMR imaging can reliably detect the presence of tiny tumor remnants in the CS.…”

“…2,11,24,29,31,33) Detection and visualization of tumor remnants by iMR imaging contributes to an increased rate of complete tumor removal, and prevents unnecessary exploration and injury around normal tissues. 30) iMR imaging can be classified as low (0.12-0.2 tesla), medium (0.5 tesla), or high (À1.5 tesla) field according to the strength of the magnetic field used. In transsphenoidal surgery for nonfunctioning macroadenomas, low-field iMR imaging revealed residual tumor and resulted in further resection in 17 of 55 cases, and the rate of complete tumor removal increased from 58% to 84%.…”

“…10,24,30) This may be advantageous in the treatment of patients with functioning microadenomas or small pituitary adenomas located in the intrasellar region. Although functioning microadenomas or small adenomas have high endocrine remission rates after transsphenoidal surgery, not all patients achieve endocrine remission.…”

“…6,9,13,22,30) However, postoperative changes make it difficult to interpret postoperative MR imaging in the intrasellar and CS region, 35) and it is therefore difficult to judge whether or not remnant tumors are present. Our third hypothesis is that long-term endocrine status will be associated with the presence or absence of tumor remnants in the CS on the iMR imaging at the end of transsphenoidal surgery.…”

“…As a result, the use of iMR imaging increases the rate of complete tumor removal and thus prevents further unnecessary exploration. 2,10,11,24,[29][30][31]33) High-field (1.5 tesla) iMR imaging offers superior image quality to low-field (0.12-0.2 tesla) iMR imaging, and can de-…”