2. LocationLocation
A lesion in the orbit?
Decide whether it is an ocular lesion OR
a non-ocular lesion, i.e. is it involving the globe
or involving the structures outside the globe.
If it is a non-ocular lesion, see the lesion is
involving which space.
7. Conal space
The ocular muscles within the orbit form a
muscle-cone.
These are connected via the annulus of Zin,
which is a fibrous connective tissue sheet.
The muscles and fascia together form the conal
space.
18. Conal space pathology:
Thyroid eye disease
Pseudotumor
Enlargement of the extra-ocular muscles by
glycogen storage disease
Lymphoma
Rhabdomyosarcoma
19. Extraconal space pathology:
Abscess due to sinusitis
Schwannoma of the trigeminal nerve
Dermoid
Bone lesions, Fibrous dysplasia of the sphenoid wing
Metastases
Diseases of the orbital appendages
20. ORBITAL LYMPHOMA
Presents in middle age with painless orbital
swelling progressing to proptosis.
Orbital lymphoma is of the B-cell variety
(NHL); Hodgkins disease of the orbit is rare.
21. Site of involvement
Any structure in the orbit may be affected.
The lacrimal gland is involved most frequently,
then the conal/intraconal compartment.
Superior rectus is the commonest extra-ocular
muscle involved.
23. Can produce diffuse infiltration leading to
destruction of the normal anatomical
architecture.
Molds to the contour of the orbit without bone
destruction, unless it is very aggressive.
24. Enhanced axial CT image
demonstrates extension of
right orbital apex mass to the
right cavernous sinus (arrow)
via superior orbital fissure.
with proptosis. Enlargement
and abnormal enhancement
of right medial and lateral
rectus muscles could
represent
infiltration by tumour, but are
more likely due to venous
congestion from
cavernous sinus obstruction.
25.
26. On MRI
lymphoma tends to be hypointense on T1, is
usually hyperintense on T2, and enhances.
Bilateral orbital masses suggest the diagnosis of
lymphoma.
27. T1-weighted MR image (A)
demonstrates proptosis
of right globe due to a large
intermediate signal intensity
lesion that involves the
lacrimal fossa and the right
lateral rectus muscle,with
extension posteriorly in the
extraconal compartment.
Postcontrast(B)
demonstrates homogeneous
enhancement.
28. (A) Axial T2, (B) axial T1, (C)
axial T1 MRI with
gadolinium, (D) coronal
T1 with gadolinium and fat
suppression.
A diffusely infiltrating mass in
the superior right orbit
,isointense to brain on T2-
& slightly hypointense on
T1sequence. The mass
extends outside the orbit
to involve the temporal
fossa. Following
gadolinium, there is
homogeneous signal
enhancement of the mass.
On coronal imaging, there
is thick meningeal
enhancement indicating
intracranial spread of
lymphoma.
30. presents with rapidly progressive
exophthalmos.
Originates from extra-ocular muscles,
nasopharynx, or paranasal sinuses.
Usually present in the superomedial orbit and
may produce bone destruction.
31. On CT,
A bulky aggressive-looking mass.
isodense or slightly hyperdense.
shows uniform enhancement.
32. Contrast-enhanced axial CT image through orbits demonstrates right
proptosis due to large, lobular, intraorbital mass.
Image at lower level demonstrates invasion of right maxillary sinus as well
as extension through lateral orbital wall,consistent with the aggressive
nature of this tumour.
33. (A) Axial and (B) coronal CT images with contrast medium.
There is a large mass in the superior right orbit which is difficult
to separate from the extra-ocular muscles. There is deformity of
the posterior wall of the globe and marked proptosis. The mass
shows uniform contrast enhancement.
34. On MRI
they are of intermediate signal intensity on both
T1 and T2 sequences.
There is bone destruction in 40 per cent of
cases and frequent distortion of the globe.
35. ORBITAL METASTASIS
6% of orbital tumours.
Most retrobulbar metastases are extraconal in
location,
subsequently encroach on the intraconal
compartment as they increase in size.
36. when large,produce infiltrating poorly
marginated masses.
originate mostly from the greater wing of the
sphenoid, resulting in bone destruction.
37. In children, the primary lesions are most
commonly Ewing's sarcoma and neuroblastoma.
In Ewing's sarcoma, proptosis is usually
unilateral with sudden onset & accompanying
hemorrhage.
38. The presentation in neuroblastoma is similar;
however, it is bilateral in 50% of cases.
Other pediatric malignancies that metastasize
to the orbit are testicular tumors and
leukemias.
39. In adults, the primary tumor is usually breast or
lung carcinoma.
Tumor metastasizes more frequently to eye
than the orbit (8:1 ratio).
The orbital metastases may be the initial
manifestation of the lung, GI, thyroid, or renal
Ca.
40. In adults, an infiltrative retrobulbar mass and
enophthalmos is characteristic of scirrhous
carcinoma of the breast.
41. RADIOLOGIC FINDINGS
Metastases often are diffusely infiltrating and
have indistinct margins. Less frequently, they are
well circumscribed.
On CT, these lesions are isodense or
hyperdense, and enhance.
42. Metastatic prostate carcinoma. Axial CT image (A) through
orbits demonstrates small lytic lesion of left lateral orbital wall in a patient
with prostate carcinoma. Soft-tissue windows (B) demonstrate contiguous
extension of soft tissue into lateral extraconal compartment with
medial displacement of the lateral rectus muscle.
44. On MRI,
the signal intensity is low on T1-weighted
images and high on T2-weighted images.
These lesions enhance with contrast.
45. Ocular metastasis from systemic lymphoma. (A) Axial T2, (B) axial T1,
(C) axial T1 MRI with IV gadolinium and fat suppression. There is thickening of
the wall of the globe with soft tissue and enhancement extending into the
vitreous and retrobulbar space.
46. Coronal T1-weighted, fat-saturated MRI shows infiltration of the retrobulbar fat on right
and infiltration of the superior orbit on left. B,C, Axial T1-and T2 MRI show swelling and
infiltration by metastasis of the left orbit and eyelid.
47. DERMOID CYSTS
usually occur in children and make up 4% to 6%
of orbital tumors.
Painless mass, free from the skin, with variable
ocular displacement.
48. Mostly located near the lacrimal fossa or nasal
bone.
Grow slowly, remodeling adjacent bones or
sutures.
50. On CT
appear as well defined low attenuating (fat
density) lobulated masses. Calcifications may be
present in the wall. Enhancement is uncommon.
The central cavity may appear heterogeneous
as a result of keratin and other cystic debris.
51. This is a coronal CT scan demonstrating a dumbbell dermoid that straddles
the right lateral orbital wall. A bony channel in the lateral orbital wall connects
the two lobes. Note that the deep lobe displaces many of the lateral
intraorbital structures.
52. This coronal CT image without contrast demonstrates a lateral dermoid cyst
with the characteristic hyperdense cyst wall and hypodense cyst cavity.
53.
54. On MRI
T1 -> typically hyperintense
droplets in the subarachnoid space may be
visible if rupture has occurred
T1 C+ (Gd) -> typically do not enhance
T2 - variable signal ranging from hypo to hyper
intense.
divided into four main compartments,
Intraconal space
Extraconal space
Optic nerve/sheath complex
Globe.
Although small, the orbits are a complex anatomical space. Determining which compartment/s pathology arises from, is important in reducing the differential diagnoses.
Normal anatomy. Coronal CT reformat
Normal anatomy - Coronal T1W MR
The orbital spaces are important when considering different pathologies:
globe
subdivided into anterior and posterior chambers by the lens
optic nerve-sheath complex
optic nerve
ophthalmic artery
central retinal artery and vein
surrounding sheath of meninges as an extension of the cerebral meninges
conal space
extraocular muscles
interconnecting fascia
intraconal space
orbital fat
ophthalmic artery
superior ophthalmic vein
cranial nerves II, III, IV, V1, VI
axial CT section through the orbit (Blue - intra conal space, Red - Globe)
extraconal space
fat
lacrimal gland and sac
portion of the superior ophthalmic vein
Orbital lymphoma comprises 55% of orbital malignancies. Unilateral and bilateral presentations can occur within any orbital compartment, although the lacrimal gland, (found within the extraconal compartment) is the most common. The CT appearance is of a hyperdense, enhancing mass which may have a spectrum of appearances from well defined to diffusely infiltrative. On MRI there is low to intermediate signal on T2 weighted images.
Bilateral lymphoma - Coronal CT reformat
extraconal tumour
Rhabdomyosarcoma is a highly malignant, extraconal tumour of childhood, often with rapidly progressing proptosis. The most common age of development is between 5 and 10 years. The CT presentation is of a well-defined but irregular, muscle-like density mass in the extraconal space, although intraconal extension is possible. The MRI appearance is of a hyperintense T2 mass, hypointense T1 (relative to muscle) with marked uniform enhancement
Angular dermoid
intracranial dermoids have more variable signal characteristics
