Predicting Pituitary Adenomas Consistency with Preoperative Magnetic Resonance Elastography

Background: Pituitary adenomas account for 15% of all primary intracranial neoplasms, which makes them the third most common primary intracranial tumor. Pituitary adenomas are usually soft but up to 15% have a firm consistency. Tumor consistency is a common characteristic associated with surgical outcome and extent of tumor resection, as well as time spent in the operative theater. Knowledge of consistency preoperatively may improve preoperative counseling of the risks to the patient. Multiple studies have tried to predict pituitary tumor consistency with conventional MR imaging techniques. Magnetic resonance elastography (MRE) is a noninvasive, dynamic imaging technique that characterizes the viscoelastic properties of tissue. The purpose of this study is to evaluate the efficacy of preoperative MRE and MRI in 40 patients undergoing surgical treatment for pituitary adenomas to determine tumor consistency. This is an update of our previously published experience.

Methods: With institutional review board approval and written informed consent, 40 patients with pituitary adenomas were prospectively evaluated with MRI and MRE before surgery from September 2013 to July 2019. Tumors were classified into three groups: soft consistency (easily removable through aspiration), intermediate consistency (parts easily removed with suction but other portions difficult to remove with suction requiring mechanical techniques such a sharp dissection), and firm consistency (not removable through aspiration and requiring piecemeal resection). MRE classifications were determined prospectively by radiologists unaware of the surgical findings. A Chi-squared test was performed to compare surgical grading and MRE classification. p-Values < 0.05 were considered significant.

Results: Forty patients (22 males; median age at surgery: 53 years; range: 22–74) with pituitary adenomas were prospectively imaged with MRI and MRE prior to resection. Thirty-nine patients underwent endoscopic endonasal approach (EEA) and only one patient had a frontotemporal craniotomy. Thirty-four patients had a nonfunctional adenoma (85%), five patients had a GH-secreting adenoma (12.5%), and one patient had an ACTH-secreting adenoma (2.5%). The mean tumor size in maximal diameter was 3.6 cm (range: 2–6 cm). By intraoperative findings, two tumors had a firm consistency (5%), six had an intermediate consistency (15%), and 32 were soft tumors (80%). MRE measurements and intraoperative findings correlated in 35 (87.5%) of 40 patients. One patient had an MRE predicting a soft tumor and the intraoperative finding was a firm tumor.

Conclusion: In our study, MRE predicted soft tumors well, but only one of the two firm tumors was correctly identified. Further study is needed and development of this technology, particularly in patients with firm tumors, is necessary to determine the usefulness of MRE for pituitary tumor surgery.

No conflict of interest has been declared by the author(s).