ABSTRACT
The primary reason for venous sampling in the head and neck region has been the evaluation of the secretory nature of a possible pituitary microadenoma, most commonly to distinguish between pituitary and other causes of Cushing’s syndrome (CS). Pituitarydependent hypercortisolism accounts for over 70% of cases of CS (1,2). The differentiation between pituitary and ectopic adrenocorticotropin (ACTH) secretion requires the integrated evaluation of biochemical tests and imaging techniques, none of which has a 100% diagnostic accuracy (3). Inferior petrosal sinus (IPS) sampling was devised in an attempt to improve the diagnostic work-up of CS (4,5). The rationale for IPS sampling is that a large proportion of the venous drainage of the pituitary glands is via the IPSs, allowing for analysis of samples uncontaminated from other sources. Therefore, in Cushing’s disease (CD), the concentration of ACTH is expected to be higher in the IPS draining the hemi-hypophysis bearing the tumor than in the contralateral IPS or in the peripheral vessels (4,5).
