1. Radiological Assessment of Typical and Atypical Orbital Infections: A Space-based Approach
eEdE-108
Blair A Winegar, M.D.
H. Christian Davidson, M.D.
Edward P Quigley, III, M.D. Ph.D.
University of Utah Neuroradiology

2. Disclosure Statement
No financial interests to disclose

3. Purpose
Illustrate the imaging features of typical and atypical orbital infections
Elucidate critical imaging findings which affect clinical management
Discuss disease entities which may mimic the imaging appearance of orbital infection

4. Anatomic subsections:
Orbital Anatomy
Anatomic subsections:
Preseptal
Postseptal
Extraconal
Intraconal
Ocular
Axial CT
Axial T1

5. Anatomic subsections:
Orbital Anatomy
Anatomic subsections:
Postseptal
Extraconal
Intraconal
Coronal CT (mid orbit)
Coronal T1 (mid orbit)

6. Preseptal Space
Preseptal and postseptal spaces separated by orbital septum
Orbital septum is a sheet of fibrous tissue which is continuous with the periosteum of the orbital rim and fuses with the levator aponeurosis (upper lid) and tarsus (lower lid)
Acts as boundary to extension of pathology from preseptal to postseptal space
Expected course of the orbital septum

7. Preseptal Cellulitis
Infection within soft tissues anterior to the orbital septum
Typically polymicrobial (e.g. Staphylococcus, Streptococcus, Pneumococcus, Neisseria)
Treated with outpatient oral antibiotics, drainage of abscess if present
Left preseptal inflammation consistent with preseptal cellulitis

8. Preseptal Cellulitis Key Imaging Findings
Inflammation/Swelling anterior to expected course of orbital septum
Preseptal abscess – rim enhancing fluid collection in preseptal space
Rim enhancing fluid collection in left preseptal space consistent with preseptal abscess

9. Acute Bacterial Conjunctivitis
Infection of the conjunctiva – inner layer of the eyelid & outer layer of the anterior eyeball
Common organisms – Staphylococcus, Streptococcus, Haemophilus
Typically initially unilateral (in contrast to viral conjunctivitis, which is typically bilateral)
Right conjunctival enhancement and T2 hyperintensity consistent with conjunctivitis

10. Acute Bacterial Conjunctivitis
Key Imaging Findings
Inflammation/Swelling limited to the conjunctiva
Typically unilateral
No drainable fluid collection
Left conjunctival rim enhancing fluid collection with air and preseptal soft tissue swelling – bacterial conjunctivitis
Clinical image of same patient demonstrating conjunctival inflammation and pus

11. Acute Dacryocystitis
Infection of the lacrimal sac at the medial canthus, typically secondary to nasolacrimal duct obstruction
Common organisms: Staphylococcus, Streptococcus
Treatment with oral antibiotics, warm compresses, possible surgical relief of nasolacrimal duct obstruction
Dilatation of the left lacrimal sac with rim enhancement consistent with acute dacryocystitis

12. Acute Dacryocystitis Key Imaging Findings
Dilatation of the lacrimal sac at the medial canthus
Rim enhancement of the lacrimal sac
Surrounding inflammatory change +/- abscess in the preseptal soft tissues
Right rim enhancing fluid collection at site of lacrimal sac and associated preseptal soft tissue swelling consistent with acute dacryocystitis

13. Postseptal – Extraconal Space
Postseptal space is posterior to the orbital septum
Extraconal space is peripheral to the cone formed by the four rectus muscles and enveloping sheet of fascial tissue between these muscles
Infection in postseptal extraconal space are typically extension from adjacent sinus infection
Cone formed by the four rectus muscles and intermuscular fascia and extraconal space

14. Subperiosteal Abscess
Abscess confined between orbital osseous wall and periosteum
Secondary to sinus infection, therefore, seen most commonly along the medial or superior orbital walls
More common in pediatric population
Rim enhancing fluid collection along left lamina papyracea with mass effect on left medial rectus, and left ethmoid sinus disease consistent with subperiosteal abscess

15. Subperiosteal Abscess
Key Imaging Findings
Rim enhancing fluid collection typically along the medial or superior orbital walls
Internal T2 hyperintensity and restricted diffusion on MRI
Adjacent sinus opacification
Left superior extraconal rim enhancing fluid collection with adjacent frontal sinus opacification consistent with subperiosteal abscess

16. Invasive Fungal Sinusitis
Aggressive fungal infection across tissue boundaries with high morbidity/mortality
Associated with immunocompromised states (e.g. uncontrolled diabetes mellitus, absolute neutropenia)
Secondarily affects orbit after extension from paranasal sinuses
Ill-defined intraconal enhancement and nonenhancement of the left ethmoid sinus mucosa consistent with invasive fungal sinusitis

17. Invasive Fungal Sinusitis
Key Imaging Findings
Ill-defined T2 hyperintensity and enhancement of involved soft tissues
Adjacent paranasal sinus opacification
Nonenhancement of the paranasal sinus mucosa - necrosis
Ill-defined enhancing inflammation in the right retrobulbar soft tissues and nonenhancing necrosis of the right palate compatible with invasive fungal sinusitis

18. Acute Dacryoadenitis Inflammation/Infection of the lacrimal gland
Multiple infectious etiologies: viral (most common), bacterial, protozoan/fungal
Supportive treatment (warm compresses) with or without antibiotics
Enlargement and enhancement of the left lacrimal gland consistent with dacryoadenitis

19. Acute Dacryoadenitis Key Imaging Findings
Swelling/Inflammation of the lacrimal gland in superolateral extraconal soft tissues
Diffuse T2 hyperintensity and enhancement
Rim enhancing fluid collection in left lacrimal gland consistent with abscess, also left paranasal sinus disease, subdural empyema, and preseptal cellulitis

20. Postseptal – Intraconal Space
Postseptal space is posterior to the orbital septum
Intraconal space is central to the cone formed by the four rectus muscles and enveloping sheet of fascial tissue between these muscles
Intermuscular fascia is thicker anteriorly – seen on cross- sectional images
Intraconal space infections are typically a result of extension of infection from the extraconal space
Cone formed by the four rectus muscles and intermuscular fascia and intraconal space

21. Orbital Cellulitis
Infection of the orbital soft tissues posterior to the orbital septum (intraconal or extraconal)
Typically an extension of paranasal sinus disease, but may be from extension of preseptal cellulitis, trauma/foreign body, or hematogenous
Potential for series complications: vision loss, orbital abscess, cavernous sinus thrombophlebitis, intracranial abscess
Requires more aggressive antibiotic treatment and surveillance than preseptal cellulitis
Preseptal and postseptal enhancement with proptosis and posterior tenting of the left globe consistent with orbital cellulitis

22. Orbital Cellulitis Key Imaging Findings
Inflammatory fat stranding, T2 hyperintensity, and enhancement involving the retrobulbar soft tissues
Possible exophthalmos, posterior tenting of the globe at the optic nerve insertion if severe and vision-threatening
Inflammatory stranding within the left retrobulbar (intraconal and extraconal) soft tissues with proptosis and tenting of the left posterior globe consistent with orbital cellulitis

23. Orbital Abscess Complication of orbital cellulitis
Requires surgical drainage in addition to antibiotics
Typically present with more severe symptoms than uncomplicated orbital cellulitis: proptosis, ophthalmoplegia, increased pain with eye movements
Right preseptal and postseptal rim enhancing fluid collection consistent with orbital abscess

24. Orbital Abscess Key Imaging Findings
Defined rim enhancing fluid collection in postseptal soft tissues
Central T2 hyperintensity and restricted diffusion
Exophthalmos and mass effect upon adjacent structures (e.g. optic nerve, extraocular muscles)
Rim enhancing fluid collection with internal air in preseptal and postseptal soft tissues consistent with orbital abscess

25. Cavernous Sinus Thrombophlebitis
Life-threatening complication caused by clot formation in the cavernous sinus
Symptoms/signs include: periorbital edema, pain, proptosis, cranial nerve palsies (e.g. ptosis, ophthalmoplegia, dysesthesia to face)
May affect both eyes if clot extends to involve contralateral cavernous sinus
Treatment with broad-spectrum IV antibiotics, IV heparin (controversial), and IV steroid (controversial)
Right superior ophthalmic vein thrombosis and cavernous sinus thrombosis

26. Cavernous Sinus Thrombophlebitis
Key Imaging Findings
Non-enhancement of the affected cavernous sinus secondary to indwelling clot
Expansion of affected cavernous sinus
Enlargement +/- non- enhancement of the superior ophthalmic vein
Right superior ophthalmic vein thrombosis and bilateral cavernous sinus thrombosis

27. Herpes Zoster Ophthalmicus
Reactivation of the herpes zoster virus affecting the soft tissues supplied by cranial nerve V1
Typically confined to facial skin supplied by CN V1
However, severe infection may affect globe, retrobulbar soft tissues, optic nerve, or cavernous sinus
Treated with IV antiviral therapy (e.g. acyclovir)
Inflammatory changes in the preseptal and postseptal soft tissues and cavernous sinus thrombosis – herpes zoster ophthalmicus

28. Herpes Zoster Ophthalmicus
Key Imaging Findings
In presented case:
May demonstrate cranial nerve enhancement and thickening – affected additional cranial nerves traversing cavernous sinus
May demonstrate T2 hyperintensity and enhancement of optic nerve – associated optic neuritis
Inflammatory changes in the postseptal soft tissues and superior ophthalmic vein thrombosis – herpes zoster ophthalmicus

29. Ocular Space
The globe can be separated into anterior and posterior segments
Anterior segment – structures anterior to and including the lens, ciliary body, and suspensory ligaments (includes anterior and posterior chambers)
Posterior segment – structures posterior to the lens, ciliary body, and suspensory ligaments (includes vitreous body and posterior layers of the globe)
Posterior ocular wall (inner to outer) – retina, choroid, sclera, episclera
Imaging typically performed for posterior segment pathology, since anterior segment pathology can be easily clinically assessed

30. Endophthalmitis/Panophthalmitis
Endophthalmitis is inflammation involving the ocular cavities and adjacent structures
Panophthalmitis is inflammation involving the entirety of the ocular structures
Typically a result of ocular surgery (e.g. cataract surgery), penetrating traumatic injury, or retained intraocular foreign body
Less commonly a result of hematogenous spread (i.e. metastatic endophthalmitis) in immunocompromised patients (e.g. diabetics)
Typically polymicrobial and caused by a variety of bacteria or fungi.
FLAIR hyperintensity in the anterior/posterior segments, posterior uveal thickening/enhancement and preseptal/postseptal inflammation - panophthalmitis

31. Endophthalmitis/Panophthalmitis
Key Imaging Findings
Increased FLAIR hyperintensity within the vitreous body
Thickening and increase enhancement of the posterior ocular walls
Possible extension of T2 hyperintensity and enhancement to adjacent retrobulbar soft tissues
Intraocular abscesses suggested by internal restricted diffusion
Nodules of restricted diffusion along the inner surface of posterior chamber wall – subchoroidal abscesses

32. Intraocular Cryptococcus Infection
Cryptococcus neoformans is a ubiquitous encapsulated yeast found in soil
Can cause rare intraocular infection in immunocompromised state (e.g. AIDS)
May result in endophthalmitis, chorioretinitis, or vitreitis
Treatment with oral, IV, or intravitreal antifungals
Choroidal detachments with mildly hyperintense T1 and isointense T2 signal with respect to vitreous – Cryptococcus chorioretinitis

33. Intraocular Cryptococcus Infection
Key Imaging Findings
Imaging finding dependent on structures affected
Chorioretinitis – enhancement and thickening of the posterior uvea, potential retinal or choroidal detachments
Vitreitis – FLAIR hyperintensity within the vitreous
Endophthalmitis – combination of vitreitis and chorioretinitis
Choroidal detachments with choroidal thickening and enhancement – Cryptococcus chorioretinitis

34. Mimics
Many infiltrative, inflammatory, and neoplastic etiologies may have similar imaging appearance to infection
Must rely on history, symptoms, and additional imaging findings to separate potential etiologies
Right intraconal and ocular wall enhancement in a patient with idiopathic orbital inflammatory syndrome

35. Mimic: Idiopathic Orbital Inflammatory Syndrome (Orbital Pseudotumor)
Benign, non-granulomatous inflammatory process of yet unknown etiology which may affect many sites of the orbital soft tissues
Diagnosis of exclusion
Painful (in contrast to orbital lymphoma which is painless)
Many cases now linked to IgG4- related disease
Key Imaging – Ill-defined enhancement, T2 isointense to hyperintense (generally less than infection)
Ill-defined contrast enhancement expanding and surrounding the left medial rectus muscle consistent with myositic subtype of IOIS

36. Mimic: Idiopathic Orbital Inflammatory Syndrome (Orbital Pseudotumor)
Categorized by area affected by inflammation: myositic, lacrimal, anterior, diffuse, or apical
If inflammation affects the cavernous sinus, given name Tolosa-Hunt Syndrome
Enhancement at left orbital apex extending into the left cavernous sinus – Tolosa-Hunt Syndrome

37. Mimic: Orbital Lymphoma
Non-Hodgkin lymphoma affecting the orbital soft tissues
Approximately 50% malignant orbital tumors
Adnexal Orbital MALT-lymphoma associated with Chlamydia psittaci infection
Diagnosed by biopsy
Treated with chemotherapy and radiation
Key Imaging – Diffusion restriction, homogeneous enhancement, and T2 hypointensity
Enhancing, T2 hypointense, and diffusion restricting soft tissue in the extraconal spaces of the bilateral orbits consistent with orbital lymphoma

38. Mimic: Orbital Amyloidosis
Amyloidosis is a heterogeneous group of diseases characterized by deposition of amorphous proteinaceous material
There are systemic (multiorgan) and localized (single organ) forms of amyloidosis
Localized orbital amyloidosis is rare and requires biopsy for definitive diagnosis and exclusion of systemic forms of the disease
Key Imaging – T2 hypointensity and diffuse enhancement
Ill-defined enhancing, T2 hypointense lesion in left medial extraconal soft tissues with linear enhancement involving CN III – orbital amyloidosis

39. Mimic: Granulomatosis with Polyangiitis
Formerly known as Wegener granulomatosis
Autoimmune vasculitis of small to medium-side vessels which primarily affects the respiratory tract and kidneys
Orbital involvement is one of the most frequently involved sites outside the respiratory tract and kidney, and may be a result of localized disease involvement or extension of adjacent upper respiratory inflammation
Key Imaging – Ill-defined orbital T2 hyperintensity and enhancement, septal perforation and destructive paranasal sinus disease
Left retrobulbar enhancement, septal perforation, medial maxillary sinus wall destruction, and diffuse paranasal sinus inflammation consistent with granulomatosis with polyangiitis

40. Mimic: Vogt-Koyanagi-Harada Syndrome
Presumed autoimmune disease resulting in attack of melanocytes in skin, uvea, meninges, and inner ear
Results in bilateral panuveitis and retinal detachments
Four phases: prodromal, uveitic, convalescent, and chronic recurrent
Treated with aggressive immunomodulatory therapy
Key Imaging – Bilateral posterior uveal thickening and enhancement, possible retinal detachment, and possible meningeal enhancement
Bilateral posterior uveal thickening and enhancement compatible with Vogt-Koyanagi-Harada Syndrome

41. Summary
Orbital imaging evaluation is common in the setting of suspected orbital infection as it can reliably detect pathology, quantify severity of disease, and assess for potential complications which would alter clinical management.
Knowledge of orbital anatomy and cross-sectional imaging findings of orbital infections is paramount in directing appropriate clinical care.
Many inflammatory, infiltrative, and neoplastic processes may mimic orbital infection.

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