The majority of venous effluent from each side of the pituitary gland drains into the ipsilateral inferior petrosal sinus.
Threshold criteria for pituitary source is defined as an inferior petrosal sinus to peripheral (IPS:P) basal ratio of 2:1 or greater without CRH or an IPS:P ratio 3:1 or greater after the administration of CRH (3,6,12).
Fortunately, performing angiography before the BIPSS prevented an incorrect interpretation of the results because of the hypoplasic right petrosal sinus.
The presence of a unilateral hypoplastic or plexiform inferior petrosal sinus may result in false-negative results regarding the central-to-peripheral ACTH gradient, and it also leads to misleading values in side-to-side gradients.
A critical analysis of the value of simultaneous inferior petrosal sinus sampling in Cushing's disease and the occult ectopic adrenocorticotropin syndrome.
Adrenocorticotropic hormone-dependent Cushing's syndrome: sensitivity and specificity of inferior petrosal sinus sampling.