INTRAOPERATIVE ULTRASOUND-DIRECTED RESECTION OF PITUITARY-TUMORS

Microadenomas of the pituitary vary in size, particularly those relate d to Gushing's disease. They are often not visualized on preoperative magnetic resonance (MR) imaging and may be difficult to find during su rgical exploration of the pituitary. To enhance intraoperative localiz ation of pituitary adenomas, we assessed the feasibility of using ultr asound to detect and localize pituitary tumors. Intraoperative ultraso und (IS) in the axial and sagital planes was performed with an Intrasc an system using a 12-MHz mechanically oscillating, end-firing transduc er. Interpretation of the scans was performed by two individuals, who were usually blinded to the results of preoperative MR imaging or petr osal sinus sampling. Twenty-eight patients were examined. Eighteen of these patients had microadenomas (1.5-7 mm), all with Cushing's diseas e; nine had macroadenomas (10-20 mm), three of which were adrenocortic otropic hormone-secreting, three growth hormone-secreting, two thyroid -stimulating hormone-secreting, and one nonfunctioning; and one patien t had an intrasellar craniopharyngioma. Normal sellar and parasellar s tructures, such as intrapituitary cysts, the intracavernous carotid ar teries, and the diaphragma sella were easily visualized. Twenty-three of the 28 tumors, including 13 of the 18 microadenomas, were detected on IS (82% sensitivity). Tumors were seen as hyperechoic masses in 19 patients, mixed echogenicity in three, and isoechoic in one. In most m acroadenomas IS allowed visualization of the interface between the tum or and the normal pituitary gland. These results indicate the potentia l of IS to aid the intraoperative localization and definition of pitui tary tumors.