The role of inferior petrosal sinus sampling in the diagnostic localization of Cushing's disease
USHING'S syndrome is a clinical condition that results after long-standing exposure to elevated levels of glucocorticoids. 33 One of the main diagnostic challenges is identifying the underlying cause of hypercortisolism. In approximately 80% of cases, the cause is an ACTH-dependent process; in approximately 20% of cases the hypercortisolism is related to primary adrenal causes (that is, ACTH independent). 2 Of the cases in which the cause is ACTH-dependent, most (approximately 70% of all cases)
... y 70% of all cases) are due to a pituitary adenoma (CD); in the remaining cases, the hypercortisolism is secondary to ectopic ACTH secretion, as summarized in Table 1 . 33, 36 For patients with CD, surgical removal of the pituitary adenoma is the treatment of choice. Thus, localization of the source of ACTH secretion is critical in guiding timely treatment decisions. A number of noninvasive biochemical tests are available Neurosurg. Focus / Cushing's syndrome can present a complex problem of differential diagnosis. Of cases in which hypercortisolemia results from an adrenocorticotropic hormone (ACTH)-dependent process, approximately 80% are due to a pituitary adenoma (Cushing's disease [CD]), 10% are due to adrenal lesions, and the remaining 10% are secondary to ectopic ACTH secretion. For patients with CD, surgical removal of the pituitary adenoma is the treatment of choice. Thus, localization of the source of ACTH secretion is critical in guiding timely treatment decisions. Inferior petrosal sinus sampling (IPSS) is considered to be the gold standard for confirming the origin of ACTH secretion in patients with Cushing's syndrome. The authors present an overview of IPSS-both the technique and its interpretation-as well as a summary of recent studies. A number of other techniques are discussed including sampling from the cavernous sinus, the jugular vein, and multiple sites to aid the diagnosis and lateralization of ACTH-producing pituitary adenomas. Management is best undertaken by a comprehensive multidisciplinary team taking into account the results of all the biochemical and imaging studies available, to provide the best advice in patient treatment decisions. (DOI: 10.3171/FOC-07/09/E2) KEY WORDS • Cushing's disease • Cushing's syndrome • diagnosis • inferior petrosal sinus sampling C 1 Abbreviations used in this paper: ACTH = adrenocorticotropic hormone; CD = Cushing's disease; CRH = corticotropin-releasing hormone; EAS = ectopic ACTH secretion; IPSS = inferior petrosal sinus sampling; MR = magnetic resonance. * GHRH = growth hormone-releasing hormone; 5-HIAA = 5-hydroxyindoleacetic acid.