Partial ectopic posterior pituitary: A rare imaging entity with literature review.

Abnormal development of the posterior pituitary gland can lead to an ectopic location of the neurohypophysis, commonly seen at the median eminence of the hypothalamus or along the infundibular stalk. A partial ectopic posterior pituitary (PEPP) is a very rare variant of the ectopic posterior pituitary, defined as the presence of a double bright spot of neurohypophysis seen in both orthotopic and ectopic locations. We report a two-year-old male toddler with bilateral optic nerve hypoplasia and severe visual impairment who presented to the endocrine outpatient clinic for hypopituitarism evaluation. Magnetic resonance imaging (MRI) of the brain revealed a hypoplastic pituitary gland and infundibulum with a double bright spot of neurohypophysis in the expected normal location and along the median eminence. Severe hypoplasia of both optic nerves and the optic chiasm was also seen. Septum pellucidum was present with no evidence of other brain malformations. The findings are in the septo-optic dysplasia spectrum associated with hypothalamic-pituitary dysfunction and a very rare entity called PEPP. To our knowledge, only a handful of reported cases of this rare entity exist in the literature.