Pituitary stalk thickening on MRI: when is the best time to re‐scan and how long should we continue re‐scanning for?

Magnetic resonance imaging (MRI) has proved to be an essential tool in the assessment of pituitary stalk lesions including lymphocytic infundibulo-hypophysitis, Langerhans cell histiocytosis (LCH), germ cell tumours, nongerminomatous germ cell tumours, pituicytomas and other tumours, metastases from lymphoma or breast cancer, Wegener's hypophysitis, neurosarcoidosis and inflammatory infiltrations by infectious diseases. The diagnosis of lesions determining pituitary stalk thickness is challenging, and the identification of the underlying condition may require a long-term follow-up. Thus, clinicians should readily recognize that, when the diagnosis of central diabetes insipidus has been established, specific MRI sequences should be used in the assessment of the hypothalamic-pituitary region, and whole-brain evaluation is recommended. For clinical practice, a timely diagnosis is advisable to avoid central nervous system damage, pituitary defects and the risk of dissemination of germ cell tumours or organ involvement by LCH. Proper aetiological diagnosis can be achieved via a series of steps that start with careful observation of several neuroimaging predictors and endocrine dysfunction and then progress to more sophisticated and advanced imaging techniques.