Bilateral Inferior Petrosal Sinus Sampling in Corticotropin-Dependent Cushing's Syndrome: A Single Center Experience from Western India

OBJECTIVE: Efficacy of bilateral inferior petrosal sinus sampling (BIPSS) in corticotropin-dependent Cushing's syndrome (CS) for localization and lateralization of excess adrenocorticotropic hormone (ACTH) source, as compared to high-dose dexamethasone suppression test (HDDST) and magnetic resonance imaging (MRI) pituitary, respectively. METHODOLOGY: Thirteen patients with clinically and biochemically confirmed CS underwent HDDST, MRI pituitary, and BIPSS by an experienced team of intervention neurologist, neurosurgeon, and endocrinologist using percutaneous femoral vein approach. RESULTS: Of 13 patients (11 adults and two children) who underwent BIPSS, raised central to peripheral ACTH ratio was achieved in 12 cases, remaining one case being ectopic ACTH secretion (EAS). However, inter IPS gradient >1.4 was achieved in 11 (91.6%) of 12 Cushing's disease (CD) cases before vasopressin stimulation; and in 9 (75%) of 12 CD cases after vasopressin stimulation (P-value 0.583). HDDST suppression of more than 50% was present in only ten cases with CD, falsely negating CD in two cases (16.6%), sensitivity 83.3% and specificity 100%. MRI sella demonstrated pituitary microadenoma in 12 cases and macroadenoma in one case. Lateralization by BIPSS and MRI was concordant in 7 (58.3%) out of 12 cases with CD, with rate of remission after transsphenoidal surgery being higher in patients with concordant lateralization by BIPSS and MRI. CONCLUSIONS: BIPSS is an important investigation to distinguish CD and EAS. BIPSS was superior to HDDST for confirming the source of excess ACTH. Our findings favor the use of BIPSS for localization and pituitary MRI for lateralization of microadenoma.