Transcript MRI findings in Kallmann syndrome

MRI findings in
Kallmann
syndrome
H. ZAGHOUANI BEN ALAYA, Z. ACHOUR,
M.BHOURI, M. LIMEME, S. MAJDOUB, H.
AMARA, D. BAKIR, CH. KRAIEM
HN27
INTRODUCTION:
Kallmann syndrome is an inherited disorder
characterized by hypogonadotrophic hypogonadism
and anosmia or hyposmia.
KS is due to abnormal migration of gonado-tropinreleasing hormone (GnRH) as well as olfactory
neurons from olfactory placode to the forebrain and
hypothalamus during fetal life.
Structural olfactory tract abnormalities are well seen
on MRI
PURPOSE:
the aim of this work is to describe the MR
appearance of the olfactory bulbs and tracts in
patients with Kallmann syndrome,
MIETHODS:
High-resolution MR scans were performed in two patients
with Kallmann syndrome.
Coronal T2 weighted contiguous sections were obtained
through the olfactory bulbs and tracti.
RESULTS:
Cases:
A 15-year-old female and 20-year-old male adressed to MRI
for hypogonadotrophic hypogonadism ((Serum LH < 1.5 IU/L,
Serum FSH < 1.5 IU/L, Testosterone <20 ng/dl) and hyposmia.
Coronal T2-weighted MR images through the anterior fossa
shows:
 aplasia of both olfactory bulb
and absence of the left
olfactory sulcus (case1).
 Bilateral aplasia of olfactory bulb with normal olfactory tract
(case2)
No other cranial abnormality found.
CASE 1:
Coronal T2-weighted MR image through the
anterior fossa.
olfactory bulbs are absent and the left olfactory
sulcus is hypoplastic.
CASE 2:
coronal T2 images through the frontal lobes
demonstrate abnormal anatomy with absence of the
olfactory bulbs.
Olfactory sulcus,the gyrus rectus and medial orbital
gyrus are normal.
DISCUSSION:
Kallmann syndrome is an inherited disorder characterized by
hypogonadotrophic hypogonadism and anosmia or hyposmia.
The inheritance may be X-linked, Autosomal recessive or
Autosomal dominant with variable penetrance.
The reported incidence is 1 in 10,000 men and 1 in 50,000
women.
Kallmann syndrome is an anomaly of neuronal
migration.
Cells that differentiate into Gonadotrophin releasing
hormone (GnRH) secreting neurons originate from
within embryonic olfactory epithelium and migrate
along fascicles of vomeronasal and terminalis nerves
into forebrain.
This migration of GnRH neurons is arrested in KS
resulting in GnRH deficiency followed by different
degrees of luteinizing hormone (LH) and follicle
stimulating hormone (FSH) deficiencies.
Abnormal development of olfactory placode also
results in improper development of olfactory bulbs
and sulci.
diagnosis of KS in adults is fairly straightforward,
depending on the co-existence of anosmia with subnormal
levels of gonadal steroids and gonadotrophins.
However the diagnosis may be difficult to establish in
patients of pre-pubertal age who may require genetic
testing and MRI.
In such patients, MRI enables a presumptive diagnosis of
KS to be made by demonstrating characteristic
abnormalities in olfactory sulci and tracttory.
IMAGING
Morphological abnormalities of olfactory apparatus in KS
are best evaluated with MRI.
High resolutions coronal fast spin echo T2W images are the
preferred sequences for morphologic evaluation of the
olfactory system.
Olfactory bulbs are optimally visualized in coronal planes.
it
is
easier
to
appreciate
anatomical anomalies present in Kallmann syndrome
by comparing it to a normal patient.
The normal anatomy of the region consists of the
olfactory bulbs located in the olfactory grooves of
the anterior cranial fossa.
The inferior surface of the frontal lobes usually
consists gyrus rectu separated from the medial orbital
gyrus (M) by the olfactory sulcus (yellow arrow).
o
Olfactory bulb: blue arrows
gyrus rectus: R
the medial orbital gyrus : M
olfactory sulcus : yellow arrow
MRI FINDINGS:

hypoplasia of the olfactory bulbs with olfactory
tracts present,

aplasia of the olfactory bulbs with olfactory tracts
present.

aplasia of both olfactory bulbs and olfactory tracts

It was also described mild to moderate volume
loss in temporal and frontal lobes

Hypoplasia of anterior pituitary may be secondary
to
limited
stimulation
due
hypothalamic GnRH neurons.
to
absence
of
CONCLUSION:
Kallmann’s syndrome is a rare genetic disorder.
High resolutions coronal fast spin echo T2W is the
preferred sequences for morphologic evaluation of
the olfactory system.