Cavernous sinus sampling is highly accurate in distinguishing Cushing's disease from the ectopic adrenocorticotropin syndrome and in predicting intrapituitary tumor location

Inferior petrosal sinus sampling (IPSS) is used to distinguish pituitary Gu shing's disease from occult cases of the ectopic ACTH syndrome, but is limi ted in that it requires the use of ovine CRH (oCRH) and is not highly accur ate at predicting the intrapituitary location of tumors. This study was des igned to determine whether cavernous sinus sampling (CSS) is as safe and ac curate as IPSS, whether CSS can eliminate the need for oCRH stimulation, an d whether CSS can accurately predict the intrapituitary location of tumors. Ninety-three consecutive patients with ACTH-dependent Cushing's syndrome we re prospectively studied with bilateral, simultaneous CSS before and after oCRH stimulation. Prediction of a pituitary or ectopic ACTH source was base d on cavernous/peripheral plasma ACTH ratios. Intrapituitary tumor location was predicted based on lateralization (side to side) ACTH ratios. These pr edictions were compared to surgical outcome in the 70 patients who had surg ically proven pituitary (n = 65) or ectopic (n = 5) disease. CSS distinguished pituitary Gushing's disease from the ectopic ACTH syndrom e in 93% of patients with proven tumors before oCRH administration and in 1 00% of patients with proven tumors after oCRH. It was as safe and efficacio us as published IPSS results. CSS accurately predicted the intrapituitary l ateralization of the tumor in 83% of all patients and 89% of those patients with good catheter position and symmetric venous flow. CSS is as safe and accurate as IPSS for distinguishing patients with pituit ary Gushing's disease from those with the ectopic ACTH syndrome. In additio n, CSS appears to be superior to IPSS for predicting intrapituitary tumor l ateralization.