Introduction: Objective: Pituitary adenomas are typically soft with occasional cases of firm fibrous tumors. The prevalence of fibrous adenomas is approximately 5-13%. These tumors are defined as difficult to remove by curettage or suction. Their surgical resection can be challenging with usually higher rate of incomplete resection and need for multiple surgeries. Predicting fibrous adenomas by magnetic resonance (MR) imaging is usually difficult and unreliable. We propose a new method based on MR T2 sequence intensity ratios of the tumor with reference to the cerebellar peduncle to predict these cases on preoperative imaging.

Methods: Methods: The MR images of 36 consecutive patients who underwent non-secreting macroadenoma resection were evaluated by a blinded radiologist. Using MR T2-weighted sequence, regions of interest were sampled from the adenoma and the cerebellar peduncle, and the ratio was calculated. Intraoperatively, tumors were graded prospectively for their consistency as soft or fibrous by the operating surgeon.

Results: Results: There were 28 soft and 6 fibrous tumors. Unpaired t test for these ratios was found to be statistically significant (p < 0.0240; 95% CI -0.8229 to -0.06207). Mean values for soft tumors was found to be 1.918 (SEM=0.08212). Mean values for firm tumors was found to be 1.475 (SEM=0.1179). Soft tumors were associated with ratios >1.5 (sensitivity 100%; specificity 66.7%); firm tumors were associated with ratios <1.8 (sensitivity 100%; specificity 42.9%).

Conclusions: Conclusion: Fibrous adenomas are typically diagnosed intraoperatively. However, their resection can be technically challenging. Using T2 intensity ratios of tumor to cerebellar peduncle on routine preoperative MRI will allow identification of these cases on preoperative imaging. The surgeon can then be better prepared for the surgical resection of these cases.

Patient Care: Prediction of consistency of adenomas, namely soft or firm, carries implications for the neurosurgeon. Fibrous adenomas are often difficult to resect. Prediction of firm adenomas allows planning for surgery such as use of extracapsular dissection and availability of surgical adjuncts such as a side-cutting instrument such as NICO myriad in our series (NICO Corporation, Indianapolis, IN). Patient care and safety may be affected as well if fibrous adenomas are able to be predicted and referred to tertiary centers, if needed.

Learning Objectives: 1) Attendees will have the opportunity to learn a new, proposed method of fibrous adenoma prediction 2) Attendees will have the opportunity to discuss benefit and opportunity for surgical planning with knowledge of adenoma consistency

References: 1. Bahuleyan B, Raghuram L, Rajshekhar V, Chacko AG: To assess the ability of MRI to predict consistency of pituitary macroadenomas. Br J Neurosurg 20:324-326, 2006 2. Chakrabortty S, Oi S, Yamaguchi M, Tamaki N, Matsumoto S: Growth hormone-producing pituitary adenomas: MR characteristics and pre- and postoperative evaluation. Neurol Med Chir (Tokyo) 33:81-85, 1993 3. Hagiwara A, Inoue Y, Wakasa K, Haba T, Tashiro T, Miyamoto T: Comparison of growth hormone-producing and non-growth hormone-producing pituitary adenomas: imaging characteristics and pathologic correlation. Radiology 228:533-538, 2003 4. Iuchi T, Saeki N, Tanaka M, Sunami K, Yamaura A: MRI prediction of fibrous pituitary adenomas. Acta Neurochir (Wien) 140:779-786, 1998 5. Mahmoud OM, Tominaga A, Amatya VJ, Ohtaki M, Sugiyama K, Sakoguchi T, et al: Role of PROPELLER diffusion-weighted imaging and apparent diffusion coefficient in the evaluation of pituitary adenomas. Eur J Radiol 80:412-417, 2011 6. Naganuma H, Satoh E, Nukui H: Technical considerations of transsphenoidal removal of fibrous pituitary adenomas and evaluation of collagen content and subtype in the adenomas. Neurol Med Chir (Tokyo) 42:202-212; discussion 213, 2002 7. Pierallini A, Caramia F, Falcone C, Tinelli E, Paonessa A, Ciddio AB, et al: Pituitary macroadenomas: preoperative evaluation of consistency with diffusion-weighted MR imaging--initial experience. Radiology 239:223-231, 2006