MRI findings in Kallmann syndrome

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MRI findings in Kallmann syndrome

• H. ZAGHOUANI BEN ALAYA, Z. ACHOUR, M.BHOURI,  M.
  LIMEME, S. MAJDOUB, H. AMARA, D. BAKIR, CH. KRAIEM

HN27
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INTRODUCTION

• Kallmann syndrome is an inherited disorder
  characterized by hypogonadotrophic hypogonadism
  and anosmia or hyposmia.
• KS is due to abnormal migration of
  gonado-tropin-releasing 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

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PURPOSE

• the aim of this work is to describe the MR
  appearance of the olfactory bulbs and tracts in
  patients with Kallmann syndrome,

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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.

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RESULTS
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Cases

• A 15-year-old female and 20-year-old male
  adressed to MRI for hypogonadotrophic
  hypogonadism ((Serum LH lt 1.5 IU/L, Serum FSH lt
  1.5 IU/L, Testosterone lt20 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.

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CASE 1
Coronal T2-weighted MR image through the
anterior fossa. olfactory bulbs are absent and
the left olfactory sulcus is hypoplastic.
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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. 
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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.

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• 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.

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• 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.

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• 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.

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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.

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• it is easier to appreciate anatomical anomalie
  s 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).

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o
Olfactory bulb blue arrows gyrus rectus R the
medial orbital gyrus M olfactory sulcus
yellow arrow
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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

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• 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 to absence of
  hypothalamic GnRH neurons.

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CONCLUSION

• Kallmanns syndrome is a rare genetic disorder.
• High resolutions coronal fast spin echo T2W is
  the preferred sequences for morphologic
  evaluation of the olfactory system.