Comparison of the preoperative diagnostic accuracy of BIPSS versus MRI for Cushing disease: a single-centre experience

BACKGROUND: Cushing disease (CD) arises due to a pituitary corticotroph adenoma, which is the most common cause of Cushing syndrome (CS). Bilateral inferior petrosal sinus sampling (BIPSS) is a safe method for differentiating CD from ectopic adrenocorticotropic hormone (ACTH)-dependent CS. Enhanced high-resolution magnetic resonance imaging (MRI) can localize tiny pituitary lesions. The aim of this study was to compare the preoperative diagnostic accuracy of BIPSS versus MRI for CD in CS patients. We performed a retrospective study of patients who underwent BIPSS and MRI between 2017 and 2021. Low- and high-dose dexamethasone suppression tests were performed. Blood samples were collected simultaneously from the right and left catheter and femoral vein before and after desmopressin stimulation. MRI images were obtained, and endoscopic endonasal transsphenoidal surgery (EETS) was performed in confirmed CD patients. Dominant sides of ACTH secretion during BIPSS and MRI were compared with surgical findings. RESULTS: Twenty-nine patients underwent BIPSS and MRI. CD was diagnosed in 28 patients, 27 of whom received EETS. Localizations of microadenomas by MRI and BIPSS agreed with the EETS findings in 96% and 93% of the cases, respectively. BIPSS and EETS were successfully performed on all patients. CONCLUSION: BIPSS was the most accurate method (gold standard) for establishing a preoperative diagnosis of pituitary-dependent CD and was more sensitive than MRI in diagnosing microadenoma. High-resolution MRI with enhancement had an advantage over BIPSS in microadenoma lateralization diagnostics. The combined use of MRI and BIPSS could improve the preoperative diagnosis accuracy in ACTH-dependent CS patients.