H. ZAGHOUANI BEN ALAYA, N. MALLAT, Z. ACHOUR, S. MAJDOUB, H. AMARA, D. BAKIR, CH. KRAIEM Imaging department, Farhat Hached Hospital, Sousse, Tunisia

NR38

Advances in magnetic resonance imaging (MRI) of the hypothalamic pituitary region may actually explain a number of hormonal disturbances associated with an abnormality of the pituitary stalk 

The syndrome of interruption of the pituitary stalk (SIPS) is a rare cause of anterior pituitary deficiencies

It is defined by morphological abnormalities revealed by MRI:

Interruption or significant thinning of the pituitary stalk

a hypoplastic anterior pituitary an ectopic or lacking posterior pituitary 

The aim of this work is to illustrate the contribution of MRI in this syndrome through five observations.

        

Retrospective study of 5 patients

Over a period of 5 years from 2006 to 2011 collected from department of medical imaging

The age varies from 09 to 23 years : 4 children aged between 09 and 12 years old and an adult of 23 years

Sex : 3 males and 2 females

The reason for consultation and exploration :

Short stature with anterior pituitary deficit (n=5) Primary amenorrhea (n=1) Diabetes insipidus (n=1)

A pituitary MRI was performed in all patients :

MRI 1.5 Tesla GE Thin Sagittal and coronal (3mm) Fast spin echo

T2 and T1 before and after gadolinium injection

MRI showed an abnormality of the pituitary stalk in all cases : Interruption of the pituitary stalk : complete

transection (n=4)  and incomplete with a filiform pituitary stalk (n=1)

Ectopic posterior pituitary gland appeared as an area of high signal intensity in the midline at the median eminence (n=4)

Hypoplasia of the anterior pituitary (n=5) Absence of the posterior pituitary gland

associated with Arnold Chiari I malformation (n=1)

Case 1 : 9 year old child, panhypopituitarism

Fig.1 (a,b) : coronal unenhanced T1-weighted MR imaging : ectopic posterior pituitary gland ( ) seen as an area of high signal intensity in the midline at the median eminence (a). the pituitary stalk is not visible ( ) (b).

Fig.1 (a,b) : coronal unenhanced T1-weighted MR imaging : ectopic posterior pituitary gland ( ) seen as an area of high signal intensity in the midline at the median eminence (a). the pituitary stalk is not visible ( ) (b).

Fig.1 (c,d) : Gadolinium-enhanced coronal and midsagittal T1-weighted MR imaging :The pituitary stalk is not visible (b). The ectopic posterior pituitary gland is visible (a,b)

Fig.1 (c,d) : Gadolinium-enhanced coronal and midsagittal T1-weighted MR imaging :The pituitary stalk is not visible (b). The ectopic posterior pituitary gland is visible (a,b)

(a) (b)

(c) (d)

Case 2 : 10 year old child, short stature with diabetes insipidus

Fig.2 (a,b) : midsagittal unenhanced and contrast material– enhanced T1-weighted MR imaging : small anterior pituitary gland( ), absence of the habitual pituitary posterior lobe hyperintense signal within the sella turcica cavity and also within the median eminence (a). the pituitary stalk is also not visible even after administration of Gadolinium ( ) (b).

Fig.2 (a,b) : midsagittal unenhanced and contrast material– enhanced T1-weighted MR imaging : small anterior pituitary gland( ), absence of the habitual pituitary posterior lobe hyperintense signal within the sella turcica cavity and also within the median eminence (a). the pituitary stalk is also not visible even after administration of Gadolinium ( ) (b).

Fig.2 (c) : midsagittal T2 T1-weighted MR imaging : ectopia of cerebellar tonsils ( ) with V4 in place : Arnold Chiari I malformation

Fig.2 (c) : midsagittal T2 T1-weighted MR imaging : ectopia of cerebellar tonsils ( ) with V4 in place : Arnold Chiari I malformation

(a) (b)

(c)

Case 3 : 12 year old child, short stature with Growth Hormone deficiency 

Fig.3 (a,b,c) : sagittal and coronal unenhanced T1-weighted MR imaging : small anterior pituitary gland( ) (a), presence of the ectopic posterior pituitary ("bright spot“) at the median eminence level ( ) (b,c). the pituitary stalk is not visible ( ) (b).

Fig.3 (a,b,c) : sagittal and coronal unenhanced T1-weighted MR imaging : small anterior pituitary gland( ) (a), presence of the ectopic posterior pituitary ("bright spot“) at the median eminence level ( ) (b,c). the pituitary stalk is not visible ( ) (b).

(a) (b)

(c)

Case 4 : 23 year old patient, primary amenorrhea with gonadotropin deficiency 

Fig.4 : midsagittal unenhanced T1-weighted MR imaging : ectopic posterior pituitary in hypersignal ( ), small anterior pituitary gland, pituitary stalk interruption in its incomplete form (thin pituitary stalk) ( ).

Fig.4 : midsagittal unenhanced T1-weighted MR imaging : ectopic posterior pituitary in hypersignal ( ), small anterior pituitary gland, pituitary stalk interruption in its incomplete form (thin pituitary stalk) ( ).

The etiology of pituitary stalk interruption is not completely understood. Two theories have been proposed : Traumatic theory: facing a high proportion of history

of fetal distress, breech presentation and of head trauma in patients with a SIPS

Malformative theory: The SITP is frequently associated with abnormalities of

the midline Facial dysmorphism may be associated There is as familial forms

The genetic theory remains the most creditable versus the traumatic theory

SIPS is often revealed in the neonatal period and childhood. His revelation in adults is exceptional

This syndrome is clinically discussed in presence of hypopituitarism: Isolated most often a Growth hormone deficiency Multiple with a normal posterior pituitary function

Classically, there is an isolated GH deficiency if the pituitary stalk is thin and a panhypopituitarism if the pituitary stalk interruption is complete

Isolated GH deficiency can progress to panhypopituitarism and requires biological monitoring for life

The diagnostic strategy of growth retardation currently leaves an important place to imaging and particularly to cerebral MRI thanks to: its high contrast resolution its character multiplanar the absence of bone artifacts  of the base (limit of

CT)

MRI offers a morphological study of the hypothalamic-pituitary region and search for  associated brain abnormalities  of the midline

The browsing protocol: Sagittal and coronal thin (2-3 mm) Centered on the hypothalamic-pituitary FSE T1-weighted sequence FSE T2-weighted sequence Injection of contrast material paramagnetic

The whole brain must be explored to eliminate the associated malformations

1. Anomaly of the posterior pituitary:

It appears in spontaneous hypersignal on T1-weighted  and enhances after gadolinium injection

It is ectopic and it is localized whether at the infundibulum (50%) or at the pituitary stalk or sometimes even in the hypothalamus

This ectopic hyperintensity can be

located anywhere along the pituitary stalk

2. Anomaly of the pituitary stalk: Complete form: not visualized pituitary

stalk whatever the sequence Incomplete form: with a filiform pituitary

stalk or visible only after gadolinium injection

This classification has a prognostic value, since in the complete forms the hormonal deficiency is most often multiple

3. Anomaly of the anterior pituitary:

The anterior lobe is often hypoplastic (height less than -2SD compared to normal values according to age)

But even when it is of normal size, the dynamic sequence may reveal, among patients with GH deficiency, delayed contrast enhancement of the anterior pituitary

4. Malformations of the midline:

Arnold Chiari malformation type I Basipharyngial Canal  Total or partial agenesis of the corpus

callosum Agenesis or hypoplasia of the septum and

the optic chiasma (septo-optic dysplasia) Dandy-Walker malformation

If MRI is normal in the context of growth hormone deficiency :  

It has a prognostic impact because the deficit is often incomplete or even transitional

  Some studies have shown the  higher

frequency of genetic abnormalities in the group of patients with GH deficiency and normal MRI, which allows to select patients for genetic studies

The SIPS is a rare congenital malformation, responsible for most cases of growth hormone isolated deficiency but also for multiple anterior pituitary deficits. 

MRI is currently the most performed imaging means for the diagnosis of this malformation and the prognostic approach : Morphological study of the hypothalamic-pituitary Establish clinical and radiological correlations Detect associated brain malformations.

Van der Linden A S A and Van Es Hendrik W. Case 112: Pituitary Stalk Transection Syndrome with Ectopic Posterior Pituitary Gland. Radiology 2007;243:594–597.

Vijayanand P, Mahadevan S, Shivbalan So et al. Pituitary Stalk Interruption syndrome (PSIS). Indian Journal of Pediatrics 2007;74:874-5.

L.Tabelsi, M.Mnif, N.Rekik et al. Anomalies de la tige pituitaire à l’IRM : aspects étiologiques à propos de 11 cas. Ann. Endocrinol. 2006; 67, 6 : 604-612.

G.Zuccoli, F.Nicoli, G.Tognini, F.Ferrozzi. Pituitary stalk interruption syndrome : magnetic resonance findings. URL: http://www.eurorad.org/case.php?id=1591

Lippincott Williams & Wilkins. Pituitary stalk lesions. Curr Opin Endocrinol Diabetes Obes 15:339–345.

C Barbeau, B Jouret, D Gallegos et al. Syndrome d'interruption de la tige pituitaire. Arch Pédiatr 1998 ; 5 : 274-9. Elsevier, Paris.

N. Hammami, C. Drissi, M. Salah, A. Kerkeni, R. Sebai, L. Belghith, S. Nagi, M. Ben Hamouda. S Syndrome d'interruption de la tige pituitaire : à propos de cinq observations. Service de neuroradiologie - Institut national de neurologie de Tunis. JFR 2010.