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 Disclosure Statement • No financial interests to disclose 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 Orbital Anatomy Anatomic subsections: • Preseptal • Postseptal • Extraconal • Intraconal • Ocular Axial CT Axial T1 Orbital Anatomy Anatomic subsections: • Postseptal • Extraconal • Intraconal Coronal CT (mid orbit) Coronal T1 (mid orbit) 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) Expected course of the orbital septum • Acts as boundary to extension of pathology from preseptal to postseptal space Preseptal Cellulitis • Infection within soft tissues anterior to the orbital septum • Typically polymicrobial (e.g. Staphylococcus, Streptococcus, Pneumococcus, Neisseria) Left preseptal inflammation consistent with preseptal cellulitis • Treated with outpatient oral antibiotics, drainage of abscess if present Preseptal Cellulitis Key Imaging Findings • Inflammation/Swelling anterior to expected course of orbital septum Rim enhancing fluid collection in left preseptal space consistent with preseptal abscess • Preseptal abscess – rim enhancing fluid collection in preseptal space 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 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 Acute Dacryocystitis • Infection of the lacrimal sac at the medial canthus, typically secondary to nasolacrimal duct obstruction • Common organisms: Staphylococcus, Streptococcus Dilatation of the left lacrimal sac with rim enhancement consistent with acute dacryocystitis • Treatment with oral antibiotics, warm compresses, possible surgical relief of nasolacrimal duct obstruction 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 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 Cone formed by the four rectus muscles and intermuscular fascia and extraconal space • Infection in postseptal extraconal space are typically extension from adjacent sinus infection 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 Rim enhancing fluid collection along left lamina papyracea with mass effect on left medial rectus, and left ethmoid sinus disease consistent with subperiosteal abscess • More common in pediatric population 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 Left superior extraconal rim enhancing fluid collection with adjacent frontal sinus opacification consistent with subperiosteal abscess • Adjacent sinus opacification Invasive Fungal Sinusitis • Aggressive fungal infection across tissue boundaries with high morbidity/mortality • Associated with immunocompromised states (e.g. uncontrolled diabetes mellitus, absolute neutropenia) Ill-defined intraconal enhancement and nonenhancement of the left ethmoid sinus mucosa consistent with invasive fungal sinusitis • Secondarily affects orbit after extension from paranasal sinuses Invasive Fungal Sinusitis Key Imaging Findings • Ill-defined T2 hyperintensity and enhancement of involved soft tissues • Adjacent paranasal sinus opacification Ill-defined enhancing inflammation in the right retrobulbar soft tissues and nonenhancing necrosis of the right palate compatible with invasive fungal sinusitis • Nonenhancement of the paranasal sinus mucosa necrosis Acute Dacryoadenitis • Inflammation/Infection of the lacrimal gland • Multiple infectious etiologies: viral (most common), bacterial, protozoan/fungal Enlargement and enhancement of the left lacrimal gland consistent with dacryoadenitis • Supportive treatment (warm compresses) with or without antibiotics Acute Dacryoadenitis Key Imaging Findings Rim enhancing fluid collection in left lacrimal gland consistent with abscess, also left paranasal sinus disease, subdural empyema, and preseptal cellulitis • Swelling/Inflammation of the lacrimal gland in superolateral extraconal soft tissues • Diffuse T2 hyperintensity and enhancement 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 crosssectional images Cone formed by the four rectus muscles and intermuscular fascia and intraconal space • Intraconal space infections are typically a result of extension of infection from the extraconal space 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 Preseptal and postseptal enhancement with proptosis and posterior tenting of the left globe consistent with orbital cellulitis • Requires more aggressive antibiotic treatment and surveillance than preseptal cellulitis Orbital Cellulitis Key Imaging Findings • Inflammatory fat stranding, T2 hyperintensity, and enhancement involving the retrobulbar soft tissues Inflammatory stranding within the left retrobulbar (intraconal and extraconal) soft tissues with proptosis and tenting of the left posterior globe consistent with orbital cellulitis • Possible exophthalmos, posterior tenting of the globe at the optic nerve insertion if severe and vision-threatening 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 Orbital Abscess Key Imaging Findings • Defined rim enhancing fluid collection in postseptal soft tissues • Central T2 hyperintensity and restricted diffusion Rim enhancing fluid collection with internal air in preseptal and postseptal soft tissues consistent with orbital abscess • Exophthalmos and mass effect upon adjacent structures (e.g. optic nerve, extraocular muscles) 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 Right superior ophthalmic vein thrombosis and cavernous sinus thrombosis • Treatment with broad-spectrum IV antibiotics, IV heparin (controversial), and IV steroid (controversial) Cavernous Sinus Thrombophlebitis Key Imaging Findings • Non-enhancement of the affected cavernous sinus secondary to indwelling clot • Expansion of affected cavernous sinus Right superior ophthalmic vein thrombosis and bilateral cavernous sinus thrombosis • Enlargement +/- nonenhancement of the superior ophthalmic vein 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 Inflammatory changes in the preseptal and postseptal soft tissues and cavernous sinus thrombosis – herpes zoster ophthalmicus • Treated with IV antiviral therapy (e.g. acyclovir) Herpes Zoster Ophthalmicus Key Imaging Findings • In presented case: • May demonstrate cranial nerve enhancement and thickening – affected additional cranial nerves traversing cavernous sinus Inflammatory changes in the postseptal soft tissues and superior ophthalmic vein thrombosis – herpes zoster ophthalmicus • May demonstrate T2 hyperintensity and enhancement of optic nerve – associated optic neuritis 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 Endophthalmitis/Panophthalmitis FLAIR hyperintensity in the anterior/posterior segments, posterior uveal thickening/enhancement and preseptal/postseptal inflammation 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. 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 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 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 Choroidal detachments with choroidal thickening and enhancement – Cryptococcus chorioretinitis • Endophthalmitis – combination of vitreitis and chorioretinitis Mimics • Many infiltrative, inflammatory, and neoplastic etiologies may have similar imaging appearance to infection Right intraconal and ocular wall enhancement in a patient with idiopathic orbital inflammatory syndrome • Must rely on history, symptoms, and additional imaging findings to separate potential etiologies Mimic: Idiopathic Orbital Inflammatory Syndrome (Orbital Pseudotumor) Ill-defined contrast enhancement expanding and surrounding the left medial rectus muscle consistent with myositic subtype of IOIS • 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 IgG4related disease • Key Imaging – Ill-defined enhancement, T2 isointense to hyperintense (generally less than infection) 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 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 Enhancing, T2 hypointense, and diffusion restricting soft tissue in the extraconal spaces of the bilateral orbits consistent with orbital lymphoma • Key Imaging – Diffusion restriction, homogeneous enhancement, and T2 hypointensity 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 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 Left retrobulbar enhancement, septal perforation, medial maxillary sinus wall • Key Imaging – Ill-defined orbital T2 destruction, and diffuse paranasal sinus hyperintensity and enhancement, inflammation consistent with septal perforation and destructive paranasal sinus disease granulomatosis with polyangiitis Mimic: Vogt-Koyanagi-Harada • Presumed autoimmune disease Syndrome 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 Bilateral posterior uveal thickening and enhancement compatible with VogtKoyanagi-Harada Syndrome • Key Imaging – Bilateral posterior uveal thickening and enhancement, possible retinal detachment, and possible meningeal enhancement 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. References • • • • • • • • • • • • • • • • LeBedis C, Sakai O. Nontraumatic orbital conditions: Diagnosis with CT and MR imaging in the emergent setting. RadioGraphics 2008;28:1741-1753.2. Cunnane ME, Sepahadari AR, Gardiner M, Mafee MR. Head and Neck Imaging. 5Th ed. St. Louis: Mosby; c2011. Chapter 9, Pathology of the Eye and Orbit; p. 591-756. Handler L, Davey I, Hill J, et al. The acute orbit: Differentiation of orbital cellulitis from subperiosteal abscess by computerized tomography. Neuroradiology 1991;33:15-18. Sepahdari A, Aakalu V, Kapur R, et al. MRI of orbital cellulitis and orbital abscess: The role of diffusion-weighted imaging. AJR 2009;193:W244-W250. Aribandi M, McCoy V, Bazan C. Imaging features of invasive and noninvasive fungal sinusitis: A review. RadioGraphics 2007;27:1283-1296. Groppo E, El-Sayed I, Aiken A, et al. Computed tomography and magnetic resonance imaging characteristics of acute invasive fungal sinusitis. Arch Otolaryngol Head Neck Surg. 2011;173:1005-1010. Rumboldt Z, Moses C, Wieczerzynski U, et al. Diffusion-weighted imaging, apparent diffusion coefficients, and fluidattenuation inversion recovery MR imaging in endophthalmitis. AJNR Am J Neuroradiol 2005;26:1869-1872. Crump JR, Elner SG, Elner VM, Kauffman CA. Cryptococcal endophthalmitis: case report and review. Clin Infect Dis 1992;14:1069-73. Wenting SZ, Sanjay S. Role of Magnetic Resonance Imaging in Herpes Zoster Ophthalmicus Ophthalmoplegia. Kapur R, Sepahdari A, Mafee M, et al. MR imaging of orbital inflammatory syndrome, orbital cellulitis, and orbital lymphoid lesions: The role of diffusion-weighted imaging. AJNR Am J Neuroradiol 2009;30:64-70. Yousem D, Atlas S, Grossman R, et al. MR imaging of Tolosa-Hunt syndrome. AJNR Am J Neuroradiol 1989;10:1181-1184. Andrew NH, Sladden N, Kearney DJ, Selva D. An analysis of IgG4-related disease (IgG4-RD) among idiopathic orbital inflammations and benign lymphoid hyperplasia using two consensus-based diagnostic criteria for IgG4-RD. Br J Ophthalmol. 2015 Mar;99(3):376-81. Santiago Y, Fay A. Wegener's granulomatosis of the orbit: A review of clinical features and updates in diagnosis and treatment. Semin Ophthalmol 2011;26:349-355. Provenzale J, Mukherji S, Allen N, et al. Orbital involvement by Wegener's granulomatosis: Imaging findings. AJR 1996;166:929-934. Lohman BD, Gustafson CA, McKinney AM, et al. MR Imaging of Vogt-Koyanagi-Harada syndrome with leptomeningeal enhancement. AJNR Am J Neuroradiol. 2011;32:169-71. Okamoto K, Ito J, Emura I, et al. Focal Orbital Amyloidosis Presenting as Rectus Muscle Enlargement: CT and MR Findings. AJNR Am J Neuroradiol 1998;19:1799-1801.