Inferior petrosal (IPSS) vs. cavernous sinus sampling (CSS) in Cushing's syndrome (CS)

IPSS was developed to facilitate the evaluation of ACTH-dependent CS. We compared CSS to IPSS to determine if CSS can eliminate the need for ovine corticotrophin releasing hormone (oCRH) stimulation and provide better information about the lateralization of pituitary adenomas. Simultaneous bilateral CSS and IPSS before and after oCRH were performed on 46 consecutive patients with ACTH-dependent CS with no complications. In follow-up, 31 patients had a surgically proven pituitary source of ACTH and one an ectopic source and form the group for statistical analysis. Test Sensitivity Specificity Positive/Negative predictive Accuracy (Sens) (Spec) (PPV) values (NPV) (ACC) CSS pre-oCRH 90% 100% 100% 25% 91% post-oCRH 100% 100% 100% 100% 100% IPSS pre-oCRH 52% 100% 100% 6% 50% post-oCRH 77% 100% 100% 13% 77% CSS was also compared to published IPSS results and was superior to IPSS for predicting lateralization of pituitary tumors (PPV 81%, ACC 78% for CSS compared to PPV 71%, ACC 70% for IPSS). In summary, CSS is technically feasible and safe. It is highly accurate in the differential diagnosis of CS, however oCRH stimulation is still required. In this series, IPSS was not accurate, probably for technical reasons. CSS also provides improved accuracy in predicting pituitary tumor lateralization.