Specific Imaging Findings

CT is incapable of showing this abnormality and thus MR is the imaging method of choice. The pituitary stalk may be absent, truncated or very thin. The adenohypophysis (anterior pituitary lobe) is generally small but may be absent. The ectopic posterior pituitary lobe (EPPL) is bright on T1-weighted images and may be located anywhere along the expected stalk or in the hypothalamus at the stalk insertion. The EPPL is generally small, 1–3 mm in diameter and does not suppress with fat saturation techniques nor does it change significantly in size and signal intensity after administration of contrast. The intrasellar posterior lobe is absent in all cases. MRI is also the best modality to show the associated brain anomalies.

Pertinent Clinical Information

EPPL is more common in males and may be associated with midline defects (holoprosencephaly, septo-optic dysplasia, Joubert syndrome, midline facial dysraphisms, cleft palate and lip, central megaincisor, Dandy-Walker type malformations, and abnormalities of the olfactory nerves – Kallmann syndrome). This condition occurs in 1 : 5000–20 000 live births. It has been associated with difficult deliveries, and shearing of the stalk during head manipulation may account for it. Children are generally of short stature and delayed physical maturation. Hormones produced by the anterior pituitary gland are of low levels or absent, while those produced by the ectopic posterior lobe are normal or of near-normal levels. Treatment is geared towards replacement of hormones and other associated anomalies.