Download Ectopic posterior pituitary gland

NR38
H. ZAGHOUANI BEN ALAYA, N. MALLAT, Z. ACHOUR,
S. MAJDOUB, H. AMARA, D. BAKIR, CH. KRAIEM
Imaging department, Farhat Hached Hospital, Sousse, Tunisia


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)

(a)
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).
(b)
Fig.1 (c,d) : Gadoliniumenhanced
coronal
and
midsagittal T1-weighted MR
imaging :The pituitary stalk is
not visible (b). The ectopic
posterior pituitary gland is
visible (a,b)
(c)
(d)

(a)
Case 2 : 10 year old child, short stature with diabetes
insipidus
(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).
(c)
Fig.2 (c) : midsagittal T2
T1-weighted MR imaging :
ectopia of cerebellar tonsils
(
) with V4 in place :
Arnold Chiari I malformation

Case 3 : 12 year old child, short stature with Growth
Hormone deficiency
(a)
(b)
(c)
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).

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) (
).



The SITP was first described in 1987 by
Fujisawa et al
It is a syndrome defined by morphological
abnormalities revealed by MRI:



a thin or interrupted pituitary stalk
a hypoplastic anterior pituitary
an ectopic or absent posterior pituitary

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.

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