[Corticotroph microadenomas of the pituitary stalk. Diagnostic and therapeutic difficulties]

Thirteen percent of the pituitary adenomas in our series have been corticotroph adenomas. Most have been microadenomas located in the adenohypophysis, more often laterally than posteromedially. In a few rare cases, the corticotroph cells of the pars tuberalis gave rise to an adenoma. Only 16 cases of pituitary stalk adenomas have been published to date. We report here three new cases among a series of 150 patients who underwent surgery for corticotroph adenomas (2% incidence as in the literature). There was no difference in the clinical or biological presentation of intrasellar and pituitary stalk adenomas. This location must be systematically searched on the MRI, but a negative exploration cannot excluded the diagnosis of pituitary stalk adenoma like in intrasellar ones. Two anatomical entities seems to be separated. Some stalk adenomas developed preferentially in the supradiaphragmatic space (one in our series) and are accessible for selective resection. Others develop within the pituitary stalk itself and sometimes in the pars distalis (two patients in our series) which requires section of the pituitary stalk with hypophysectomy if the lower limit is not clearly seen during surgery. The subfrontal or pterional access is the approach of choice for suprasellar tumors. These approaches remain controversial for pituitary stalk adenomas because of the poor visibility of the pituitary stalk and the floor of the third ventricle. The transnasosphenoidal approach with extension to the sphenoidal planum and opening of the optochiasmatic cisterna appears to be the best alternative for surgical removal of these adenomas.