MR findings in patients with idiopathic panhypopituitarism

High-resolution MR imaging was performed in seven patients with pituitary dwarfism and panhypopituitarism. In five cases MR-findings included absence of the infundibulum and of the normal intrasellar posterior pituitary bright spot, and the presence of a small nodule at the median eminence. The absence of diabetes insipidus in these patients and the signal characteristics of the nodule at the median eminence suggest that the latter may represent a functioning ectopic posterior pituitary lobe. This complex of findings was only observed in patients with complications in the perinatal period (breech delivery) and appears to be the end result of an ischemic or traumatic injury of the infundibular stem. The infundibular defect would explain both the permanent hormone deficiency of the anterior pituitary gland through a disruption of the hypothalamic-hypophyseal portal system and the absence of diabetes insipidus through an ectopic regeneration of the neurohypophysis at the median eminence.