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Big Trouble in a Little Space: Orbital Apex Pathology
Sara R. Nace, M.D., Tabassum A. Kennedy, M.D., Lindell R. Gentry, M.D.
University of Wisconsin-Madison Department of Radiology
INFECTION
EDUCATIONAL OBJECTIVE
Orbital Cellulitis
Exhibit the anatomy of the orbital apex, and illustrate key
CT and MRI imaging findings of some common pathologic
processes manifesting in this region.
20 year old male presents with recent
mononucleosis, sinus pain, periorbital
soft tissue swelling, and two days of
right eye pain (A-F). Axial and coronal
enhanced CT scans reveal preseptal
soft tissue cellulitis, right proptosis,
and subtle postseptal cellulitis. Acute
ethmoid sinusitis is seen bilaterally on
the bone windows. A subperiosteal
abscess (red arrow) is present along
the right orbital roof. Inflammatory
changes involve the superior rectus
and superior oblique muscles as well
as the lacrimal gland. The abscess is
noted to extend into the orbital apex
(yellow arrow). Intracranial extension
is suspected on the CT scans due to
the presence of small focal gas (blue
arrows) collections and adjacent fluid
within the subdural/epidural space.
(G-H) Axial and coronal contrast
enhanced MRI of the orbits and brain
confirm a subperiosteal abscess
along the orbital roof (green arrow)
with associated intracranial extension
of disease. There are bifrontal
subdural empyema (orange arrows)
as well as diffuse leptomeningeal and
pachymeningeal thickening and
enhancement (white arrows).
INTRODUCTION
The unique, complex anatomy of the orbital apex results in
a high concentration of important neurovascular structures
in a small, confined space. As a result, cranial nerve
palsies, vision loss, and a relative afferent pupil defect can
result from a wide range of infectious, inflammatory,
neoplastic, and vascular processes. The orbital apex is an
important route of communication between the intracranial
cavity and the orbit. Infectious and neoplastic diseases
frequently spread along the complex pathways at the
orbital apex. Familiarity with disease-related CT and MRI
imaging findings is crucial to facilitate accurate, timely
diagnoses, and to avoid disease morbidity as well as
potential life-threatening complications.
DISCUSSION
The normal orbit arguably contains some of the most
complex anatomy of the human body. The bony orbit is
essentially a pyramid with four walls: a roof, lateral wall,
floor, and medial wall. The apex of the orbital pyramid is
situated at the posteromedial aspect and contains a high
concentration of important neurovascular structures, which
accounts for an orbital apex syndrome in the setting of
pathology. The syndrome is manifested as multiple cranial
nerve palsies, specifically of cranial nerves III, IV, and VI,
along with sensory loss in the V1 distribution, accompanied
by loss of vision and a relative afferent pupil defect.
Findings can result from a wide variety of pathology, even
in the absence of significant inflammatory signs or mass
effect.
Pathologies manifesting in this area includes infectious,
inflammatory, neoplastic, and vascular etiologies. Orbital
infections account for approximately 60% of primary orbital
disease processes, and include orbital cellulitis, orbital
abscess, and acute invasive fungal sinusitis. Inflammatory
processes such as idiopathic orbital inflammatory disease
(aka: pseudotumor), granulomatosis with polyangiitis (aka:
Wegener’s), thyroid orbitopathy (Graves), and sarcoidosis
can also affect the apex. Neoplasms such as lymphoma
and leukemia can also be present in this region, as can
optic nerve sheath tumors, sphenoid wing meningioma and
metastatic disease. Lastly, vascular processes such as
cavernous-carotid fistula and arteriovenous malformations
can result in orbital apex involvement.
The orbital apex provides the route of communication
between the intracranial cavity and the orbit via the
superior orbital fissure and the optic canal. These conduits
may transmit tumor, infection, or inflammation between the
two compartments. Given the potential for significant
resultant morbidity and mortality, imaging is crucial to
provide accurate, timely differential considerations, and to
detect potential associated complications. CT examinations
are rapid, cost effective, and provide superior bone detail in
this region, while MRI lends high contrast resolution and
the ability to characterize specific tissue without ionizing
radiation.
B.
A.
Preseptal
 Limited to the soft
tissues anterior to
the orbital septum
 Contiguous spread
of an infection of the
face, teeth or ocular
adnexa
 Treatment: oral
antibiotic therapy
D.
C.
E.
F.
Acute Invasive Fungal Sinusitis
 THE PERIORBITA
* Is the fibrous layer of periosteum which lines the entire orbit. Anteriorly it also contributes to the orbital
septum. The septum helps to prevent the spread of preseptal infections into the postseptal spaces.
* At the optic canal & superior / inferior orbital fissures, the periorbita fuses with the dura, providing a
continuous fibrous connection between the potential subperiosteal and epidural spaces. This
continuity accounts for extradural and subdural empyema, meningitis and parenchymal abscess.
 VENOUS STRUCTURES
* The superior ophthalmic vein (SOV) drains via the lateral aspect of the superior orbital fissure into the
cavernous sinus. This vein provides a route for spread of infection from the face and orbit posteriorly
into the cavernous sinus.
B.
Cavernous- Carotid
Fistula
Axial T2 (A) and T1+C (B)
show findings of
congestive orbitopathy of
the left eye in this patient
with new HA, blurred
vision, and left eye pain.
D.
C.
Proptosis of the left globe,
intra-conal fat stranding
with enhancement, and
EOM enlargement (red
arrows) crowd the orbital
apex. Coronal T1 +C
images (C, D) reveal
F.
E.
compromise of the optic nerve
in the orbital apex (blue arrow)
due to enlarge-ment of the
EOMs and the SOV (C).
Outward bulging of the
cavernous sinus (CS) (yellow
arrow) (D) and adjacent flow
voids suggest a dural fistula.
3D TOF MRA (E) and lateral
view ECA angiogram (F) reveal a left dural CCF. There is supply of the CCF by
accessory middle meningeal artery branches. Note the early filling of the left CS
(orange arrow) with anterior drainage via a dilated left SOV (green arrows) into the
facial vein.
Differential Diagnosis
 In the acute setting, findings may mimic thyroid orbitopathy, idiopathic orbital
inflammatory disease, or even infection with SOV thrombosis.
A.
 Early: Imaging may appear similar to IOID (pseudotumor), GWP
(Wegener’s), sarcoidosis, lymphoproliferative d/o, rhinosinusitis.
 Clinical symptoms, demographics will drive suspicion for infection.
D.
E.
F.
H.
I.
NEOPLASM
C.
E.
E.
D.
C.
 Edema/ Cellulitis
* CT: Fat reticulation, enhancement of phlegmon, +/- muscle enlargement, bony erosion
 Intraorbital phlegmon
* MRI: Isointense T1, bright T2 collection with rim enhancement and restricted diffusion
 Subperiosteal Fluid/ Abscess
 Acute Invasive Fungal Sinusitis
* CT: Dense sinus secretions, foci of Ca++ and gas, +/- bony destruction
* MRI: Variable T1 signal due to edema/fungus. Can mimic normal sinuses (low T1 & T2)
Differential Diagnosis
B.
B.
Imaging Features of Infection
ORBIT ANATOMY
A. The osseous orbit is composed of seven articulating
bones, including the maxillary (M), lacrimal (L), ethmoid
(E), lesser and greater wings of the sphenoid (LWS,
GWS), frontal (F), zygomatic (Z), and palatine (*).
B. The optic canal (blue) is housed in the LWS, and contains the optic nerve and ophthalmic artery. The superior fissure
(SOF) (red) lies between the GWS and LWS.
C. The SOF contents are divided into intraconal and extraconal components by the annulus of Zinn (blue), a tight fibrous
ring from which the four rectus muscles arise (in red). The intraconal, medial SOF contains CN VI, the superior and
inferior divisions of CN III, and the nasociliary nerve (branch of V1). The extraconal, lateral portion contains the
superior ophthalmic vein (SOV), CN IV, and two additional branches of V1: the frontal and lacrimal nerves. The SOF
provides communication between the orbit and middle cranial fossa via the cavernous sinus. (SR = Superior
Rectus, LR = Lateral Rectus, IR= Inferior Rectus, MR= Medial Rectus).
D, E. The posterior part of the inferior orbital fissure (IOF) (dark blue) lies in the infralateral aspect of the orbital apex,
through which the maxillary nerve (V2) enters the orbit, having traversed the pterygopalatine fossa from the foramen
rotundum (light blue). Additional structures crossing the IOF include the infraorbital branch of the maxillary artery, the
inferior ophthalmic vein, and autonomic branches of the pterygopalatine fossa. All connections represent possible
routes of spread for tumor and infection.
A.
B.
B.
D.
E.
C.
Orbital Lymphoma
A diffuse, infiltrative T1 (A) and
T2 (C) hypointense, enhancing
(B) mass is present within the
right pre and postseptal orbital
soft tissues on axial MRI in this
36 y.o. man with 1 week history
G.
F.
of acute on chronic painless
right eye swelling. Both intra and
extraconal involvement extends
to involve the orbital apex (red
arrows) and results in proptosis.
Diffusion restriction (red circles)
(D) indicates a highly cellular process. Asymmetric fullness on the axial T1 +C image
(B) reveals right cavernous sinus involvement (white arrow). Despite the significant
extent of disease, no globe deformity is identified. Coronal (F) and axial (G) T1+C
images demonstrate thickening and enhancement of the bilateral V2 (yellow arrows)
and vidian (orange arrows) nerves, as well as the bilateral pterygopalatine fossae (blue
arrows) and retromaxillary fat (G).
Differential Diagnosis
 Based on imaging alone, it may be impossible to distinguish lymphoma from
IOID, Graves orbitopathy, primary orbital tumors, or even cellulitis.
INFLAMMATORY / GRANULOMATOUS DISEASE
A.
B.
C.
D.
E.
F.
1. Aribandi M, McCoy VA, Bazan C 3rd. Imaging features of invasive and noninvasive
University of Wisconsin-Madison
Email: [email protected]
www.radiology.wisc.edu
 Most lethal form of fungal sinusitis, 50-80% mortality
 Rapidly progressing infection seen in 2 distinct populations
- Immunocompromised (severe neutropenia)
** 80% Aspergillus species
- Poorly controlled diabetes (diabetic ketoacidosis)
** 80% Zygomycetes species (Rhizopus, Mucor, Rhizomucor)
VASCULAR DISEASE
REFERENCES
fungal sinusitis: a review. RadioGraphics 2007; 27(5):1283–1296.
2. Aviv RI, Miszkiel K. Orbital imaging: Part 2. Intraorbital pathology. Clinical Radiology
(2005) 60, 288–307
3. Capps EF, Kinsella JJ, Gupta M, et al. Emergency imaging assessment of acute,
nontraumatic conditions of the head and neck. RadioGraphics. 2011; 31(1):316.
4. Jain R, Sawhney S, Koul RL, Chand P. Tolosa-Hunt syndrome: MRI appearances.
Journal of Medical Imaging and Radiation Oncology (2008) 52, 447–451
5. Lakshamana DN, Newman B, Spottswood SS, et. al. Inflammatory Pseudotumor.
RadioGraphics 2003; 23:719–729
6. Rene C. Update on orbital anatomy. Eye (2006) 20, 1119–1129
7. Smoker WRK, Gentry LR, Yee NK, et. al. Vascular lesions of the orbit: More than meets
the eye. RadioGraphics 2008; 28:185–204
8. Som PM, Curtin HD, eds. Head and neck imaging. St. Louis, Mo.: Mosby Elsevier,
2011:674-724, 869-871
9. Vohra ST, Escott EJ, Stevens D, Branstetter BF. Categorization and characterization of
lesions of the orbital apex. Neuroradiology (2011) 53:89–107
10. Waitzman AA, Birt BD. Fungal sinusitis. J Otolaryngol 1994; 23(4):244–249
Non-Invasive
4. Non-Invasive
5. Fungal mycetoma
Invasive fungal sinusitis is defined by the presence of fungal
hyphae within the submucosa, bone or vessels of the paranasal
sinuses.
H.
SUMMARY
Complete radiologic evaluation of orbital apex pathology
requires an understanding of the complex anatomy of this
region, broad categories of pathology which can manifest,
and potential routes of disease spread that can lead to lifethreatening complications.
Postseptal Cellulitis
 Typically results from extension of sinus
infection
 Complications
- Superior opthalmic vein thrombosis
- Cavernous sinus thrombosis
- Loss of vision
- Meningitis/intracranial extension
 Treatment: IV antibiotics; surgical
drainage may be necessary
Invasive
1. Acute invasive
2. Chronic Invasive
3. Chronic granulomatous invasive
Anatomical Routes of Spread
A.
56 y.o. female on chronic immunosuppression with 2 months of HA and
progressive decline in left visual acuity.
Axial fat-sat T1 +C (A, C, E) and 3D
FIESTA (B, D) images reveal fullness in
the left orbital apex (white arrow) with
edema and enlargement of the optic
nerve resulting in trapping of CSF within
the optic sheath (B). There is evidence of
perineuritis (blue arrows) along the optic
nerve sheath (A). Orbital myositis causes
left EOM enlargement (C). A surgically
proven rim enhancing abscess (yellow
arrows) is seen inferior to the optic nerve
in the orbital apex. Note the presence of
restricted diffusion (F) and lack of central
enhancement in the abscess.
Inflammation of foramen rotundum (red
arrow), the cavernous sinus (orange
arrow), and the trigeminal cistern within
in Meckel’s cave (green arrows) are seen
on coronal T1+C MRI (G). The left orbital
inflammation is
G.
noted to be adjacent
to rather minimal left
ethmoid and
sphenoid fungal
sinusitis.
5 Subtypes of Fungal Sinusitis
F.
G.
Invasive Fungal Sinusitis
Preseptal vs Postseptal Cellulitis
A.
G.
H.
I.
Idiopathic Orbital Inflammatory Disease (Pseudotumor) (IOID), Atypical fibrotic subtype.
Axial (A, B) and coronal (C) CT in a 67 y.o. F with vision loss demonstrates a soft tissue mass causing widening of
the superior orbital fissure (SOF) (red arrows). Axial T1 (D) and T2 (E) MRI images reveals that the hypointense
lesion (yellow arrows) also compress the optic nerve along the inferior aspect of the orbital apex. It extends through
the SOF to involve the right cavernous sinus (white arrows) and sella turcica (blue arrow). Avid homogeneous
enhancement is present on T1 + C (F). Heterogeneous bone marrow is seen in the clivus and sphenoid bone (G,
H). Coronal (H) and axial (I) T1+C delineate abnormally enhancing soft tissue in the right sella, cavernous sinus,
and trigeminal cistern with extension along V3 through the foramen ovale (orange arrow) into the masticator space.
IOID Differential Diagnosis
 Multispatial, infiltrative mass + bony involvement = primary tumor, metastasis, lymphoma, atypical
meningioma, sarcoid, or GWP. IOID is a diagnosis of exclusion!
 Biopsy: Lymphocytic infiltrate with dense fibrotic tissue. Findings resolved at 2 year follow-up (After
steroid tx)
Granulomatosis with Polyangiitis (GWP)
(Wegener’s Granulomatosis)
 Multisystem disease with triad
 Necrotizing granulomas in the upper and lower
respiratory tract
 Necrotizing vasculitis of the lungs
 Glomerulonephritis
 Often fatal if untreated
 Ocular involvement in 18-50% of cases, spread from paranasal
sinuses
 Symptoms include pain, vision loss and ophthalmoplegia
 Treatment- steroid and chemotherapy
 Dx: biopsy an high titer serum C-ANCA
Idiopathic Orbital Inflammatory Disease (IOID)
“Orbital Pseudotumor”
 Benign inflammatory process of unknown etiology composed of
lymphocytic infiltrates
 May involve any part of the orbit
 Symptoms: acute onset orbital pain, proptosis, diplopia, restricted
mobility and decreased visual acuity,
 25% bilateral
 Dramatic response to steroids; however, 25% of cases recur
Imaging Features of IOID & GWP (CT or MRI)
 Both: Poorly marginated, enhancing mass
 IOID
 Classified into 6 types based on location:
Anterior, Myositic, Diffuse, Apical, Perineuritic, Lacrimal
 Tolosa Hunt = cavernous sinus involvement
 GWP
 Polypoid sinonasal mucosal disease, +/- septal and nonseptal
osseous destruction, periantral infiltrating disease
 *CT: Demineralization along perforating arteries (vasculitis)
 *MR: +/- Meningeal thickening, enhancement
A.
B.
C.
Granulomatosis with
Polyangiitis
D.
E.
F.
G.
H.
I.
Axial multisequence MR imaging in
a 57 y.o. F with nasal deformity
and infraorbital nerve numbness
demonstrates an infiltrative low T1
(A) and intermediate PD (B) signal
intensity lesion in the right orbital
apex (red arrows) that is avidly
enhancing on T1+C (C). Abnormal
enhancing soft tissue fills the
bilateral pterygopalatine fossa and
retro-maxillary fat (white arrows)
(D). Extensive bilateral
pachymeningeal enhancement is
evident (blue arrows) on axial
T1+C (E). Coronal T1+C reveals
extensive enhancement involving
the orbital apex, SOF and optic
canal, bilaterally (orange arrows).
Also involved are the maxillary and
vidian nerves (F, G). Axial (H) and
coronal (I) CT images 3.5 years
prior to MRI exam show bilateral
soft tissue masses in the
pterygopalatine fossa as well as
left cribriform plate erosion.
GWP Differential Diagnosis
 Chronic rhinosinusitis, invasive fungal sinusitis, sarcoidosis, nasal cocaine necrosis, lymphoma