Improved diagnostic accuracy of inferior petrosal sinus sampling over imaging for localizing pituitary pathology in patients with Cushing's disease

The majority of patients with Cushing's disease can be cured by transsphenoidal microsurgery; however, precise localization of the pituitary source of ACTH is not always possible by standard imaging techniques. Bilateral venous sampling from the inferior petrosal sinuses (IPSS) is also useful for diagnosing Cushing's disease, but the interpretation of discordant findings between IPSS and imaging remains problematic. We tested the ability of imaging and IPSS to localize an ACTH-secreting pituitary lesion in comparison to definitive histopathological examination of the pituitary in patients with Cushing's disease (n = 37). Bilateral IFS catheterization was technically feasible in 32 patients and provided evidence of lateralization in 31 patients. Histological examination confirmed a corticotropic adenoma in 28 patients and corticotropic hyperplasia in 2 patients; Crooke's hyaline change was found in 7 patients, among whom 1 subsequently was found to have an ectopic sphenoid corticotropic adenoma, and the remainder had suspected microadenomas that were not identified microscopically. Accurate localization of the pituitary lesion was more frequent when based on IPSS results than on imaging studies (70% vs. 49%, P < 0.06). The 2 tests provided directly discrepant results for 8 patients; among these, IPSS was more likely than imaging to agree with final pathology (63% vs. 13%, P < 0.10). Imaging was entirely normal for another 9 patients, in whom IPSS accurately localized the lesion for the majority (89%; 95% confidence interval: 50-99%). We suggest that IPSS is an effective tool for localizing pituitary pathology and planning surgery for patients with Cushing's disease.