Ectopic neurohypophysis

Harvey B Sarnat MD FRCPC MS (Dr. Sarnat of the University of Calgary has no relevant financial relationships to disclose.)
Xing-Chang Wei MD (Dr. Wei of the University of Calgary and Alberta Children's Hospital has no relevant financial relationships to disclose.)
Laura Flores-Sarnat MD (Dr. Flores-Sarnat of Alberta Children's Hospital has no relevant financial relationships to disclose.)
Originally released March 20, 2012; last updated November 19, 2016; expires November 19, 2019

This article includes discussion of ectopic neurohypophysis, ectopic posterior lobe of pituitary, pituitary stalk interruption syndrome, pituitary stalk transection syndrome, and pituitary stalk interruption syndrome. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

The authors review the neuroimaging features of ectopic neurohypophysis and make clinical, genetic, and pathological correlations. This “incidental finding” in MRI may be associated with cerebral defects, including periventricular nodular heterotopia, holoprosencephaly, septo-optic-pituitary dysplasia, infundibular aplasia, perisylvian syndrome, and other brain anomalies. Associated telencephalic malformations may be epileptogenic. Panhypopituitarism or isolated growth hormone deficiency are frequent; diabetes insipidus is rare. The etiology is genetic.

Key points

 

• Ectopic neurohypophysis is a posterior pituitary displaced distally in the infundibulum (pituitary stalk).

 

• Diagnosis is usually made by magnetic resonance imaging showing a bright T1-weighted image, best seen in the sagittal plane.

 

• Ectopic neurohypophysis may be an isolated, incidental finding, but is associated with several cerebral malformations, including periventricular nodular heterotopia, perisylvian syndrome, holoprosencephaly, and septo-optic pituitary dysplasia.

 

• Clinical expression is endocrinological, associated most frequently with growth hormone deficiency (of adenohypophysial origin) or panhypopituitarism rather than diabetes insipidus.

 

• In some cases renal anomalies may be associated.

 

• The origin is developmental during early fetal life, thus a genetically-determined congenital anomaly.

 

• Multiple genetic mutations or deletions and, rarely, chromosomopathies are identified in association with ectopic neurohypophysis, so this entity should be regarded as a syndrome.

Historical note and terminology

The first recorded description of ectopic neurohypophysis was a neuropathological study in 1927 by Priesel (Priesel 1927). The entity was then essentially forgotten for many decades and rediscovered in the era of MRI by Fujisawa and colleagues in a 1987 paper (Fujisawa et al 1987). An ectopic or ventrally displaced posterior pituitary gland was then reconfirmed on MRI by numerous subsequent authors (Kaufman et al 1988; Kelly et al 1988; Abrahams et al 1991; Maghni et al 1991; Argyropoulou et al 1992; Brodsky and Glasier 1993; Triulzi et al 1994; Pinto et al 1997; Hamilton et al 1998; Kornreich et al 1998; Chen et al 1999; Mitchell et al 2002; York 2002; Yekeler et al 2004; Tajima et al 2007; van der Linden and van Es 2007; Iorgi et al 2012; Mahomed and Motshudi 2013). It is most readily recognized by the intense unenhanced T1-weighted signal of the neurohypophysis normally seen in MRI at the median eminence in the floor of the 3rd ventricle, but which also can disclose an ectopic location.

Image: Neurohypophysis (normal)
Image: Ectopic neurohypophysis in infant
Image: Ectopic neurohypophysis in neonate
The increased T1 signal is attributed to neurosecretory vesicles, more specifically an enhanced relaxation of water protons adjacent to these vesicles (Brant-Zawadzki et al 2001; York 2002). The T1 signal is enhanced by gadolinium.

More than 90% of publications on the topic are found in the radiology literature, with additional publications in genetics and endocrinology journals, but almost none are found in the neurologic literature. Yet neurologists continue to receive imaging reports of their patients with this diagnosis and have few articles in their journals to understand the nature and significance of this finding.

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