The procedure is usually reserved for patients with consistent ACTH-dependent Cushing's syndrome without a clear cut lesion on pituitary MRI.
[1] The procedure is typically performed in large medical centers by an experienced interventional radiologist, neurologist or neurosurgeon and guided using fluoroscopy.
ACTH levels are measured in the petrosal (central) and peripheral venous plasma before and within 10-12 minutes after administration of CRH.
[2] Measurement of the central-to-peripheral prolactin ratio can assist in verifying the correct placement of the catheters as well as in normalization of ACTH levels.
[5] Some studies have shown that if catheters were appropriately placed, a gradient of ≥1.4 for ACTH concentrations between the two sinuses predicted the side of the tumor with ~70% accuracy.