Localization of pituitary adenomas by using intraoperative ultrasound in patients with Cushing's disease and no demonstrable pituitary tumor on magnetic resonance imaging

Object. Pituitary surgery has been reported to produce remission of Gushing 's disease with preservation of pituitary function in only 60 to 70% of pat ients. The inability to identify an adenoma accounts for most failed sellar explorations. Most negative surgical explorations occur in patients in who m magnetic resonance (MR) imaging of the pituitary demonstrates normal find ings, which happens in at least 35 to 45% of patients with Gushing's diseas e. Methods. To examine the usefulness of intraoperative ultrasonography (IOUS) for identifying an adenoma in patients with no demonstrable tumor (negativ e findings) on pituitary MR imaging, we prospectively assessed the results of IOUS in 68 patients with a negative (59 patients) or equivocal (nine pat ients) MR image from a consecutive series of 107 patients with Gushing's di sease (64%). We compared surgical findings and outcomes in these 68 patient s with a group of 68 patients with Gushing's disease and negative findings on MR imaging in whom IOUS was not available. Intraoperative ultrasonography localized a tumor in 47 (69%) of 68 patients with negative findings on MR imaging. Surprisingly, the size of the adenom as that were detected with IOUS compared with the size of those not detecte d did not differ (6.8 +/- 3.4 mm compared with 6.1 +/- 2.8 mm [mean +/- sta ndard deviation], respectively [p = 0.5]). In four patients, no adenoma was found at surgery or in the pathological specimen ("true negative"). In eig ht patients, nine abnormalities detected by IOUS that were suspected adenom as were negative on exploration ("false positive"). Thus, IOUS has a sensit ivity of 73% and a positive predictive value of 84% for detecting pituitary adenomas in patients with Cushing's disease and negative findings on MR im aging. Compared with the 68 patients who did not undergo IOUS, remission af ter surgery was improved (61 patients [90%] compared with 57 patients [84%] ), the number of tumors found on exploration was increased (61 tumors compa red with 51 tumors; p = 0.02), and the number of hemihypophysectomies was d ecreased (five compared with 15; p = 0.02) with IOUS. When the groups were compared after excluding patients with prior pituitary surgery, tumors were found in 91% versus 72% (p = 0.008), and remission occurred in 95% versus 87% of patients, respectively, in the groups that had or did not have IOUS. Conclusions. The IOUS is a sensitive imaging modality when used in patients with Gushing's disease in whom findings on pituitary MR imaging are negati ve. The improved ability to detect and localize these tumors by using IOUS positively affects surgical outcome.