Pituitary stalk interruption syndrome with partial ectopic posterior pituitary

A 19-year-old male who had a past of treatment for delayed puberty 4 years ago.

Contrast-enhanced pituitary magnetic resonance imaging was performed. Pre-contrast T1-weighted images revealed the presence of a double bright spot of neurohypophysis seen at the posterior aspect of the sella turcica (orthotopic) and at the infundibulum, next to the upper portion of the pituitary stalk (ectopic) (Figures 1a, 1b and 1c). Post-contrast T1-FAT-SAT images demonstrated a hypoplastic anterior pituitary gland and a thin pituitary stalk (Figures 2a and 2b). FIESTA images showed hypoplasia of the left olfactory bulb (Figure 3). And T1 pre-contrast images displayed focal cortical thickening with aspect of polymicrogyria (Figures 4a, 4b and 4c).

Partial ectopic posterior pituitary is a rare entity in which coexist a bright T1 spot at the posterior sellae and another one usually found in the infundibulum. Often there are no findings of pituitary stalk interruption syndrome associated [1].

Despite not finding those associations in the literature, this case presented with partial ectopic posterior pituitary and all the other findings of pituitary stalk interruption syndrome, which is also a rare entity that consists of three findings: hypoplastic or aplastic anterior lobe, ectopic posterior lobe and thin or interrupted pituitary stalk [2]. It has been attributed to degeneration of hypothalamic nuclei or a migration defect and can lead to various pituitary hormone abnormalities, including growth hormone deficiency [3].

Sometimes, in addition to these findings, there is an absence of septum pellucid and optic nerve hypoplasia, comprising the septo-optic dysplasia spectrum [4]. In some cases, there are also malformations of cortical development associated, such as polymicrogyria, and the absence of olfactory bulbs [3].

The diagnosis of ectopic posterior pituitary is best made at sagittal magnetic resonance imaging and should be distinguished by other entities, such as lipoma or dermoid cyst with fat compounds, by using other sequences like T1 FAT-SAT [1].

A partial ectopic posterior pituitary must be differentiated from simply an ectopic posterior pituitary. To characterise the first one is mandatory that the posterior pituitary is seen at its usual location, a bright T1 spot directly behind the anterior pituitary, and that another bright T1 spot is visualised along the median line, usually in the infundibulum or along the pituitary stalk. On the contrary, the second does not present the posterior pituitary at its usual location, just the T1 bright spot along the median line.

The patient, in this case, underwent hormonal therapy repositioning, which remains the established treatment for this condition [5].

All patient data have been completely anonymised throughout the entire manuscript and related files.