Masticator space abcess

Radiological Assessment of Typical
and Atypical Orbital Infections: A
Space-based Approach
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
• 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
• Preseptal
• Postseptal
• Extraconal
• Intraconal
• Ocular
Axial CT
Axial T1
Orbital Anatomy
• Postseptal
• Extraconal
• Intraconal
Coronal CT (mid orbit)
Coronal T1 (mid orbit)
Preseptal Space
• Preseptal and postseptal
spaces separated by orbital
• 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,
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
Rim enhancing
fluid collection in
left preseptal
space consistent
with preseptal
• Preseptal abscess –
rim enhancing fluid
collection in preseptal
Acute Bacterial Conjunctivitis
• Infection of the conjunctiva –
inner layer of the eyelid &
outer layer of the anterior
• Common organisms –
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
• Typically unilateral
• No drainable fluid
Left conjunctival rim
enhancing fluid collection
with air and preseptal soft
tissue swelling – bacterial
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:
Dilatation of the left lacrimal sac with rim
enhancement consistent with acute
• 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
• 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
Left superior extraconal rim enhancing
fluid collection with adjacent frontal
sinus opacification consistent with
subperiosteal abscess
• Adjacent sinus
Invasive Fungal Sinusitis
• Aggressive fungal infection
across tissue boundaries
with high morbidity/mortality
• Associated with
states (e.g. uncontrolled
diabetes mellitus, absolute
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
Ill-defined enhancing inflammation in
the right retrobulbar soft tissues and
nonenhancing necrosis of the right
palate compatible with invasive fungal
• Nonenhancement of the
paranasal sinus mucosa necrosis
Acute Dacryoadenitis
• Inflammation/Infection
of the lacrimal gland
• Multiple infectious
etiologies: viral (most
common), bacterial,
Enlargement and enhancement of the
left lacrimal gland consistent with
• Supportive treatment
(warm compresses)
with or without
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
• Diffuse T2
hyperintensity and
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
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
• 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
Orbital Cellulitis
Key Imaging Findings
• Inflammatory fat
stranding, T2
hyperintensity, and
enhancement involving
the retrobulbar soft
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
Orbital Abscess
• Complication of orbital
• 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
• Central T2 hyperintensity
and restricted diffusion
Rim enhancing fluid collection with
internal air in preseptal and postseptal
soft tissues consistent with orbital
• 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
• May affect both eyes if clot extends
to involve contralateral cavernous
Right superior ophthalmic vein
thrombosis and cavernous sinus
• Treatment with broad-spectrum IV
antibiotics, IV heparin
(controversial), and IV steroid
Cavernous Sinus Thrombophlebitis
Key Imaging Findings
• Non-enhancement of the
affected cavernous sinus
secondary to indwelling
• 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
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,
• Imaging typically performed for
posterior segment pathology,
since anterior segment pathology
can be easily clinically assessed
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
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.
Typically polymicrobial and caused by
a variety of bacteria or fungi.
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
• 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
• Must rely on history,
symptoms, and additional
imaging findings to
separate potential
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
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
Enhancement at left orbital apex extending
into the left cavernous sinus – Tolosa-Hunt
Mimic: Orbital Lymphoma
• Non-Hodgkin lymphoma affecting
the orbital soft tissues
• Approximately 50% malignant
orbital tumors
• Adnexal Orbital MALT-lymphoma
associated with Chlamydia psittaci
• Diagnosed by biopsy
• Treated with chemotherapy and
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
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
Mimic: Granulomatosis with
Formerly known as Wegener
Autoimmune vasculitis of small to
medium-side vessels which primarily
affects the respiratory tract and
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
resulting in attack of melanocytes
in skin, uvea, meninges, and inner
• Results in bilateral panuveitis and
retinal detachments
• Four phases: prodromal, uveitic,
convalescent, and chronic
• 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
• 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
• 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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