FIBROUS DYSPLASIA: IMAGING CHARACTERISTICS

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FIBROUS DYSPLASIA IMAGING CHARACTERISTICS
H. ZAGHOUANI BEN ALAYA, A.BEN ABDALLAH,S.
YAHYAOUI, S. MAJDOUB,T. RZIGUA, L. BEN
CHRIFA,H. AMARA, D. BEKIR, CH. KRAIEM Imaging
department, Farhat Hached Hospital, Sousse,
Tunisia
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INTRODUCTION

• Fibrous Dysplasia (FD) of bone is a rare
  non-inheritable congenital disease.
• It is characterized by a focal proliferation of
  fibrous tissue in the bone marrow leading to
  osteolytic lesions deformities and fractures.
• FD can be presented in a monostotic or
  polyostotic form.
• The complications are represented mainly by bone
  deformities and nerve compression

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Introduction

• The imaging appearance is often characteristic
  and allows in combination with the clinic
  findings the diagnosis
• Authors attempted to highlight the interest of
  imaging in the diagnosis of FD.
• The literature is reviewed to delineate
  radiologic features of monostotic and polyostotic
  fibrous dysplasia.

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PATIENTS AND METHODS

• Retrospective study of 7 cases.
• FD was monostotic in 4 cases and polystotic in 3
  cases
• It involves proximal femurs in 1 case, ribs in 2
  cases
• 4 reported cases were craniofacial form and the
  involved bones were maxilla (n 1), sphenoid (n
  1), temporal (n 1), and frontal bone (n 2)
• Only 2 cases showed involvement of spine.

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CASE N1

• A 19-year-old boy presented to his doctor because
  of shoulder pain of 1 years duration.

b
(a) Well-defined lytic lesions of the humerus and
both bones of the forearm, which at times appear
multilocular and expansile with thinnes but
unruptured cortical (b) CT showed in the
medullary cavity replacement of cancellous bone
with a homogeneous hyperdense beach responsible
for thinning of the cortical
a
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Case n 1
MR coronal images The lesions has low signal
intensity on T1-weighted MR image (a ), high
weighted intensity on T2 (b) T1-weighted MR
image with fat saturation and after
administration of gadolinium (c ) show that there
is mild to moderate heterogeneous enhancement of
lesion.
Polyostotic FD
a
b
c
The same patient has cervical MRI for cervical
pain that shows a lesion of the vertebral
hemibody of D1 which has low intensity signal on
T1 without cortical lysis or soft tissue
abnormality on sagittal T1-weighted MR image
(d). T1-weighted MR image with fat saturation
and after administration of gadolinium (e ) show
that there is an intense enhancement of lesion.
e
d
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CASE N2

• A 24-year-old man who presents with a meningeal
  syndrome. A cerebro-medullar MRI was indicated

Monostotic FD of spine
c
Sagittal T2-weighted MR image (a ) shows a low
signal lesion of the vertebral body of D1 with
an intense and homogene enhancement of the
lesion on T1-weighted MR image (b ). CT scan
reveals increased bone density of D1 (c ).
a
b
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CASE N3
A 27-years-old woman , consultsfor diplopia
lasting for 6 months. the clinical examination
found left convergent squint and paralysis of the
V and VI cranial nerves.
a
b
c
Coronal MR images show a lesion interesting the
left greater wing of sphenoid. This lesion has
an intermediaire signal on T1 (a) , a low signal
on T2 (b) and present an intense enhancement on
contrast-enhanced T1-weighted MR image with
fat-saturation (c ).
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Case n 3
Base of the skull (sphenoid) FD
Axial and coronal CT scan show fibrous dysplasia
involving body, the left greater wing of
sphenoid bone (blue arrows). Note expanded left
pterygoid process (arrowhead) and inflammatory
changes in left sphenoid sinus ().
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CASE N4
A 35-year old woman who consulted for left
frontal and orbital swelling
Cranio-facial FD
c
a
b
Axial T1-weighted MR (a ) and coronal
T2-weighted MR (b) images reveal expansile
lesion, with low signal intensity involving
rleft frontal and parietal bones Axial
T1-weighted MR image with fat saturation and
after administration of gadolinium (c ) show that
there is mild to moderate heterogeneous
enhancement of lesion.
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CASEN5
A 12-years old boy who presented a ptosis of the
left upper eyelid
Cranio-facial FD
a
b
c
Axial CT scan (a) show thickening and increased
fronto-orbital left bone density. Coronal MR
images show a lesion interesting left roof of
orbit. This lesion has a low signal intensity on
T1 (c) and T2 (b) . T1-weighted MR image after
administration of gadolinium (d ) show that
there is intense and heterogeneous enhancement of
the lesion.
d
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DISCUSSION

• Fibrous dysplasia (FD) is a congenital and
  noninherited benign bone disease
• FD has been regarded as a developmental skeletal
  disorder characterized by replacement of normal
  bone with benign cellular fibrous connective
  tissue.
• It affects both sexes with a slight female
  predominance and is diagnosed between 5 and 30
  years on average

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Discussion

• It affects both sexes with a slight female
  predominance and is diagnosed between 5 and 30
  years on average
• The lesions grow with the child, stabilize after
  puberty and appear exceptionally in adulthood
• FD can affect one bone (monostotic form) or
  multiple bones (polyostotic form), and the latter
  may form part of the McCune-Albright syndrome
  (MAS) or Mazabraud syndrome

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Monostotic Fibrous Dysplasia

• The monostotic form of FD comprises approximately
  80 of all cases
• It is seen in patients between 10 and 70years
  old.
• The most common sites of involvement include the
  rib, femur, tibia, mandible, skull, and humerus
• Solitary involvement of other bones is unusual
• FD of the spine is rare. It most commonly
  involves the body and adjacent pedicle without
  particular predilection for a part of the spinal
  column

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Monostotic Fibrous Dysplasia

• The skull and facial bones are the affected sites
  in 1025
• All bones of the skull and the face may be
  affected
• It concerns mainly the ethmoid (72), sphenoid
  (43), the frontal bone (33), maxilla (24) and
  less frequently the temporal, parietal, occipital
  or mandible bone.

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Monostotic Fibrous Dysplasia

• Uncomplicated monostotic lesions are generally
  asymptomatic and usually do not cause significant
  deformity.
• As a rule, monostotic fibrous dysplasia does not
  convert to the polyostotic form
• lesions do not increase in size over time, and
  the disease becomes inactive at puberty

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Polyostotic Fibrous Dysplasia

• The polyostotic form of FD may involve many or
  few bones, most commonly the skull and facial
  bones, pelvis, spine, and shoulder.
• Polyostotic fibrous dysplasia is often
  unilateral, and may be bilateral, always
  asymmetric
• It tends to involve larger segments of bone and
  is frequently associated with fractures and
  severe deformities.

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Polyostotic Fibrous Dysplasia

• Involvement of the skull may cause cranial nerve
  dysfunction with visual and hearing impairment
• Although the manifestations of polyostotic
  fibrous dysplasia may be severe, it does not
  spread or proliferate and generally becomes
  quiescent at puberty, but existing deformities
  may progress

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Syndromes Associated with Fibrous Dysplasia

• 1-McCune-Albright syndrome is an
  endocrinopathy occurring mainly in girls,
  consisting of the triad of precocious puberty,
  polyostotic FD, and characteristic cutaneous
  pigmentation referred to as café au lait spots
• 2-Mazabraud syndrome is the rare combination
  of fibrous dysplasia and soft-tissue myxomas

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Imaging findings radiograh and CT

• Classically, fibrous dysplasia lesions are
  intramedullary, expansile, and well defined
  lesion with thick sclerotic borders
• Although endosteal scalloping may be present, a
  smooth cortical contour is always maintained
• Lesions show varying degrees of hazy density with
  a ground-glass quality, although some may appear
  almost completely radiolucent or sclerotic

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• Three types of lesions are distinguished
  depending on the degree of hazy density
• The ground-glass pattern
• The homogeneously dense pattern increased
  bone density compared with adjacent normal bone
• The cystic variety At times, a
  mubtilocubar, cystic lesion with well-defined
  margins can be seen
• Occasionally, calcified cartilaginous and osseous
  foci may be present within the lesion

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MRI findings

• The MRI characteristics of FD are variable
• Typically showing signal intensity that is
  intermediate to low on T1- weighted images
• Intermediate to high signal on T2-weighted images
• These high signal intensities on T2- weighted
  images correspond to nonmineralized areas and
  regions of cystic change
• Fibrous dysplasia reveals varying degrees of
  enhancement after gadolinium infusion.

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MRI findings

• The fibrous tissues in FD are well vascularized
  and often show numerous small vessels in the
  center and large peripheral sinusoids. These
  histologic features explain why fibrous dysplasia
  enhances intensely after the injection of
  contrast material

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Complications of Fibrous Dysplasia

• 1-Pathologic fracture
• These fractures generally heal normally, but
  additional fractures may subsequently occur at
  the same site
• 2-Malignant degeneration of FD
• Complicates less than 1 of all cases
• Radiographic findings include cortical
  destruction and associated soft-tissue masses
• The most common malignancies include
  osteosarcoma, fibrosarcoma, and malignant fibrous
  histiocytoma.

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CONCLUSION

• Fibrous dysplasia is a common benign bone disease
  existing in monostotic and polyostotic forms
• Complications, and associations of fibrous
  dysplasia is important to ensure the accurate
  diagnosis and appropriate management of this
  disease
• The imaging features of fibrous dysplasia are
  characteristic, although not specific, and depend
  on the underlying histopathology of a given
  lesion.