The Poorly Known Posterior Lobe

The posterior lobe of the pituitary gland is poorly shown on sagittal T1WIs where it is frequently confused with a fatty dorsum sellae or an incidental T1W hyperintense Rathke cleft cyst. The best MR sequence for the demonstration of vasopressin storage is the axial T1W Fatsat sequence. T1 intensity of the posterior lobe varies with plasmatic osmolality. It is reduced in the elderly, in last pregnancy, in diabetes mellitus, or with hemodialysis. The “bright spot” designating the T1W hyperintense posterior lobe is absent with central diabetes insipidus.