T1 pre-gad T1 post-gad T1 post-gad with fat sat

Diagnosis: Ectopic posterior pituitary (presumed)

Ectopic posterior pituitary or neurohypophysis is an unusual congenital anomaly of the pituitary and is often associated with hypoplastic or absent pituitary gland. On imaging the lesion appears as a retro-chiasmal mass which is bright on T1 due to normal increased T1 signal associated with the posterior pituitary gland and may demonstrate some degree of enhancement. Fat saturation fails to decrease the signal associated with the posterior pituitary. Patients often present with growth failure and panhypopituitarism.

The general diagnosis of suprasellar lesions with increased T1 signal pre-gad includes craniopharyngioma, Rathke cleft cyst, hemorrhage, dermoid & lipoma, and ectopic posterior pituitary. Interruption of transport of hormones from the hypothalamus due to such entities as trauma, sarcoidosis or Langerhans cell histiocytosis may also produce a focus of increased T1 signal in the suprasellar region which may mimic these other entities. In this case the differential is limited due to the fact that the lesion is stable over time, mildly enhances and does not contain fat. In addition, the presence of a hypoplastic or absent sella suggests the diagnosis of an ectopic posterior pituitary gland. Related Cases

Kelly WM, Kucharczyk W, Kucharczyk J, et al. Posterior pituitary ectopia: an MR feature of pituitary dwarfism. AJNR, May-Jun 1988; 9(3):p453-60.

Kuroiwa T, Okabe Y, Hasuo K, et al. MR imaging of pituitary dwarfism. AJNR, Jan- Feb 1991; 2(1):p161-4.

el Gammal T, Brooks BS, Hoffman WH. MR imaging of the ectopic bright signal of posterior pituitary regeneration. AJNR Mar-Apr 1989; 10(2):p323-8.

Abrahams JJ, Tefelner E, Boulware SD. Idiopathic growth hormone deficiency: MR findings in 35 patients. AJNR Jan-Feb 1991; 12(1): p155-60.

Histiocytosis Craniopharyngioma Dermoid