Latent prolactinoma on MRI-selective venous sampling and trans-sphenoidal microsurgical treatment

Bilateral and simultaneous selective venous sampling from the cavernous sinus, inferior petrosal sinus, jugular vein and peripheral vein was performed in 13 patients with hyperprolactinemia in whom dynamic magnetic resonance imaging failed to reveal pituitary adenoma. The prolactin level in peripheral veins of the patients on admission ranged from 35 to 141 ng ml(-1), with a mean value of 69 ng ml(-1). All patients showed disturbance of menstruation or galactorrhea. The indication for surgery in the present study was extremely rare; the patients each wanted to become pregnant and had an intolerance of dopamine agonists. Trans-sphenoidal surgery was performed based on the results of selective venous sampling. The postoperative levels of prolactin were normalized in nine of the patients and normal pituitary function was preserved after surgery. The present study revealed a correspondence of laterality of the peak prolactin level with the main tumor location in patients with latent prolactinoma. However, the tumor/nontumor ratio did not necessarily coincide with the pattern of tumor location, and tumor location was accurately predicted in only 70% of the cases. Selective venous sampling directly from central veins is useful for diagnosis of microprolactinoma.