Diagnostic Imaging of Orbital Lesions

Head & Neck

Orbit

Mohamed Zaitoun

Assistant Lecturer-Diagnostic Radiology Department , Zagazig University Hospitals

EgyptFINR (Fellowship of Interventional

Neuroradiology)[email protected]

Knowing as much as possible about your enemy precedes successful battle

and learning about the disease process precedes successful management

Orbit1-Anatomy of the Orbit2-Orbital Mass Lesions3-Orbital Trauma

1-Anatomy of the Orbit :-The orbit is a pyramidal space that is formed by seven

bones-The globe lies in the anterior orbit; the globe and its

contents are contained by three layers :1-The sclera and cornea form the fibrous outermost

layer2-The vascular uveal tract, including the ciliary body

anteriorly and the choroid posteriorly, forms the middle layer

3-The retina forms the innermost sensory layer

Photomicrograph (original magnification, × 80; hematoxylineosin stain) shows the three layers of the globe

-The lens is connected to the sclera by radially oriented zonular fibers

-The lens divides the globe into an anterior segment, which contains the aqueous humor, and the posterior segment, which contains the more viscous vitreous humor

-The iris further subdivides the anterior segment into the anterior chamber and the posterior chamber

-Posterior to the globe, the six extraocular muscles and their intermuscular fascial membranes form an intraorbital conical structure

-Veins and lymphatics lie within the orbital fat of the muscle cone-Centrally, the optic nerve sheath passes from the posterior globe

to the brain-The optic nerve sheath is an extension of the dura mater and

contains the ophthalmic artery, the optic nerve, and small veins

Unenhanced axial CT scan of a healthy 32-year-old man. AC = anterior chamber, L = lens, ON= optic nerve, PS = posterior segment (vitreous humor)

-Orbital Structures :1-Globe (lens , anterior chamber , posterior

chamber , vitreous , sclerouveal coat)2-Intraconal , extraconal fat

3-Optic nerve and sheath4-Ophthalmic artery and vein

5-Rectus muscles

Normal orbital anatomy, axial CT image (left) with color overlays shows the orbit divided into intraocular and extraocular spaces by the muscle cone and their relationships to the globe, coronal CT images (right) with color overlays show the configuration of the extraocular muscles, vascular structures, and lacrimal gland

Orbital Spaces: -Intraconal space:

space inside the rectus muscle pyramid

-Extraconal space: space outside the rectus muscle pyramid

-Preseptal space-Postseptal space

-Lacrimal fossa

The intraconal space is located within the muscle cone It contains the optic nerve , vessels and cranial nerves III , IV and VI

Extraconal space

Orbital Septum :-Represents condensed orbital rim periosteum-Attaches to outer margins of bony orbit and

deep tissues of lids- Separates all the structures in the orbit from

soft tissues in the face (preseptal versus postseptal)

2-Orbital Mass Lesionsa) Within or involving the globeb) Within the muscle cone (Intraconal)c) Arising from the muscle cone (conal)d) Outside the muscle cone (Extrconal)e) Arising from the orbital wall

a) Within or involving the Globe :1-Retinoblastoma2-Melanoma3-Detachment and Choroidal Effusion

1-Retinoblastoma :a) Incidenceb) Typesc) Clinical Pictured) Radiographic Featurese) Differential Diagnosis

a) Incidence :-The most important ocular tumor of childhood-20-40% of patients have bilateral tumors and this is most

often the AD type-5-10% of patients have a family history of

retinoblastoma -Children with the hereditary form are at risk of

developing second non-ocular malignancies either within or out of the radiation field , osteosarcoma is the commonest tumor

b) Types :-Four types have been recognized :1-Those that are non-inheritable2-Those that are inherited as an AD trait 3-Those that are associated with a partial

deletion of chromosome 134-Bilateral retinoblastoma and pineal tumor

(trilateral retinoblastoma)

Trilateral retinoblastoma

c) Clinical Picture :-Most children present with leukokoria or white pupillary reflex

d) Radiographic Features :1-CT :-Intraocular high density (calcification , hemorrhage)

mass-Over 90% of tumors show calcification on CT which may

be small , large , single or multiple-Diffuse infiltrating tumors are less likely to show

calcification-Intraocular calcification in children under 3 years of age

is highly suggestive of retinoblastoma

-In absence of calcification in retinoblastoma , suspect other mass lesions :

1-Persistent Hyperplastic Primary Vitreous (PHPV) :

-Congenital persistence of remnants of hyaloid vessels

-Small globe with a shadow of retrolental mass-Unilateral

PFV in a 3-year-old boy, (a) Axial CT image shows uniform high attenuation of the vitreous. (b) Axial T2 shows the hyaloid canal (arrow), a characteristic finding of PFV. (c) T1+C shows enhancement of the retrolental primary vitreous (arrow)

PHVV with microphthalmia

2-Coat’s Disease :-Rare-Not a congenital lesion-Age : 6-8 years , more in males-No retrolental mass-Unilateral retinal telangiectasia >> massive subretinal

exudate >> Retinal Detachment3-Retinopathy of Prematurity (Retrolental

Fibropalsia):-Bilateral-History of prematurity & oxygen therapy

Coat’s disease, (a, b) Axial unenhanced (a) and contrast-enhanced (b) CT images of the right orbit show an intraocular high-attenuation lesion, no calcification or enhancement is seen

Coat’s disease, (a, b) Axial unenhanced (a) and contrast-enhanced fat-saturated (b) T1 show the intraocular lesion, which is homogeneous with intermediate signal intensity, no enhancement is seen after administration of contrast material

-The non-calcified component of the tumor is moderately dense on CT , enhances poorly or not at all and may be difficult to differentiate from the associated retinal detachment and subretinal effusion

-The presence of enhancement excludes subretinal exudate and haemorrhage while marked enhancement suggests persistent hyperplastic primary vitreous (PHPV)

2-MRI :*T1 : The tumor is slightly/moderately

hyperintense*T2 : Moderately low intensity *T1+C : The tumor enhances

e) Differential Diagnosis :1-Persistent Hyperplastic Primary Vitrous2-Coat’s Disease3-Retinopathy of prematurity4-Toxocariasis (close contact with dogs)5-Chronic Retinal Detachment6-Retinal Astrocytoma (T.S.) 7-Retinal Dysplasia

-N.B. : Differential Diagnosis of Intraorbital Calcification :a) Retina :1-Drusen 1% population at optic disc (benign)2-Retinoblastoma3-Retinocytoma4-Tuberous sclerosis (TS): "giant drusen", astrocytic

hamartomas5-Epiretinal membranes6-Retrolental fibroplasia (retinopathy of prematurity),

rare calcification 7-Coats disease

Drusen Retinoblastoma

Retinal astrocytic hamartoma in a patient with tuberous sclerosis, axial unenhanced CT image shows a high-attenuation focal intraocular mass (arrowhead) in the right globe

b) Retinochoroidal :-Chorioretinitis : most commonly

following Toxoplasmosis

c) Choroidal :1-Choroidal osteoma : more common in patients

with tuberous sclerosis2-Choroidal angioma : occasionally calcify

Chorioretinitis Choroidal osteoma

d) Sclerochoroidal :1-Metastatic calcification :-Abnormal calcium and phosphate metabolisma) Hyperparathyroidismb) Pseudohypoparathyroidismc) Renal tubular acidosis2-Dystrophic calcification :-Abnormal tissues become calcified, despite normal

calcium and phosphate metabolism-Seen occasionally in elderly caucasians, most

frequently men3-Phthisis bulbi :-Is the end result of major injury to the eye (trauma,

infection) with a shrunken calcified 'lump' remaining4-Scleral calcific plaques (senile)

Phthisis bulbi Senile scleral calcific plaque

2-Melanoma :a) Incidenceb) Radiographic Featuresc) Prognosis

a) Incidence :-Most common (75%) ocular malignancy in

adults-Arises from pigmented choroidal layer , retinal

detachment is common

Diagram illustrates how a melanotic lesion causes retinal detachment, as melanoma breaks through the choroid, it separates the retina from the choroid

b) Radiographic Features :1-CT :-Thickening or irregularity of choroid (localized, polypoid,

or flat)-Exophytic , biconvex mass lesion related to choroid-Usually unilateral, posterior location-Retinal detachment, common-Contrast enhancement2-MRI :-T1 hyperintense , T2 hypointense

Unenhanced, axial CT image of the right orbit showing a choroidal melanoma

Choroidal melanoma discovered at fundoscopy in a 55-year-old woman, axial CT+C shows a subtle enhancing nodule at the level of the optic disk (arrow)

(a) T1 shows that the mass (*) is mildly hyperintense, (b) T2 shows that the tumor (*) is hypointense, (c) T1+C shows that the tumor (*) enhances moderately, these findings are compatible with a typical malignant melanoma of the choroid

Choroidal melanoma (a) T1 shows a rounded hyperintense mass (arrow) in the right posterior globe, (b) T2 , the lesion appears hypointense

c) Prognosis :-Poor prognostic indicators : 1-Large tumor size2-Heavy pigmentation3-Infiltration of the angles , optic nerve , sclera

and ciliary body

3-Detachment and Choroidal Effusion :-May mimic melanoma-Retinal detachment with hemorrhage is seen

mostly in adults with diabetes mellitus and hypertension

-In young infants it can be seen as part of a shaken baby syndrome

-In choroidal detachment recent intraocular surgery is the most common association followed by trauma

**N.B. : Other globe lesions1-Drusen2-Globe-shape Abnormalities3-Leukokoria

1-Drusen :-Focal calcification in hyaline bodies in the optic

nerve head-Usually bilateral and asymptomatic-Blurred disk margins may be mistaken for

papilledema

2-Globe-shape Abnormalities :a) Coloboma :-Focal outpouching involving retina, choroid, iris-Caused by deficient closure of fetal optic fissure-Located in region of optic disc-Associated with :Morning glory anomalyMicrophthalmos with cyst

-Coloboma can be part of the CHARGE syndrome :ColobomaHeart anomaliesChoanal AtresiaRetardation of growth and developmentGenital and Ear anomalies

-Coloboma can also be part of the COACH syndrome:Cerebellar vermis hypoplasiaOligophrenia (MR)Congenital AtaxiaColobomaHepatic fibrosis

b) Staphyloma :-Acquired defect of globe wall with protrusion of choroid or

sclera-As opposed to coloboma, staphyloma defect is located off-

center

c) Axial Myopia :-AP elongation but no protrusion

d) Buphthalmos :-Congenital glaucoma; anterior ocular chamber drainage

problem

Staphyloma

3-Leukokoria :-Leukokoria refers to a white pupil-Clinical, not a radiologic finding-Underlying causes : 1-Retinoblastoma2-PHPV3-Congenital cataract4-Toxocariasis5-Other :-Sclerosing endophthalmitis-Coats' disease-Retrolental fibroplasia-Trauma-Chronic retinal detachment

b) Within the Muscle Cone (Intraconal) :1-Optic nerve Glioma 2-Optic nerve Meningioma 3-Hemangioma (mostly cavernous) and Orbital

varices4-Inflammatory Orbital Pseudotumor5-Lymphoma and Metastases6-Hematoma7-Neurofibroma

The intraconal space is located within the muscle cone It contains the optic nerve , vessels and cranial nerves III , IV and VI

1-Optic nerve Glioma :a) Incidenceb) Clinical Picturec) Radiographic Featuresd) Differential Diagnosis

a) Incidence :-Most common cause of diffuse optic nerve

enlargement especially in childhood ( 1st decade of life )

-In neurofibromatosis (NF1) the disease may be bilateral

b) Clinical Picture :-Visual loss and painless with preservation of eye

movements because the lesion is intraconal

c) Radiographic Features :1-CT :-The optic nerve is variably enlarged and the mass may

either be fusiform or exophytic in appearance , additionally the nerve may be elongated with kinking or buckling

-Enlargement of optical canal ; >1 mm difference between left and right is abnormal

-Lower CT density than meningioma-Contrast enhancement variable-Calcifications rare (but common in meningioma)

2-MRI :*T1 : Enlargement, often iso to hypointense

compared to the contralateral side *T2 : Hyperintense centrally , low signal at the

periphery representing the dura*T1+C : Enhancement is variable

-Tumor extension best detected by MRI: chiasm → optic tracts → lateral geniculate body →

optic radiation

Optic nerve glioma in a 6-year-old girl with proptosis. (a) Axial short inversion time inversion-recovery MR image shows an expansile mass that involves the right optic nerve, the hyperintense rim at the tumor periphery (arrowheads) reflects leptomeningeal infiltration. (b) Axial T1+C fat-suppressed image shows minimal enhancement in the mass (arrow), the nerve itself cannot be separated from the tumor

Bilateral optic nerve gliomas in a 25-year-old man with NF-1., axial T1 shows the tortuous and kinked appearance of the bilateral optic nerves (arrows)

Coronal T1 reveals circumscribed enlargement of the optic nerve with an isointense signal

T1 reveals bilateral , fusiform enlargement of the optic nerves (arrows) in a 14-year-old patient with neurofibromatosis type 1 , consistent with bilateral optic nerve gliomas

T1 in a 46-year-old man demonstrates enlargement of both optic tracts (arrowheads) and the optic chiasm (arrow)

T2 reveals hyperintense signaling of the mass that is contained within the dura of the optic nerve

T2 demonstrates bilateral optic nerve gliomas in the setting of NF1

FLAIR , the fusiform image of the optic nerve tumor is seen , also here evident are several enhancing lesions in the midbrain and cerebellum, consistent with the classic hamartomatous CNS neurofibromas of NF1

T2 in a 46-year-old man demonstrates a mass in the lateral geniculate nucleus of the thalamus resulting from contiguous extension of the patient's known optic nerve glioma

T1+C shows enhancement of the fusiform , kinked shaped optic nerve tumor

T1+C with fat saturation reveals diffuse intense enhancement of the intraorbital mass , the lesion is confined to the orbit

T1+C with fat saturation in a 6-year-old girl demonstrates enhancement of the intracranial optic nerve (arrow) which is slightly expanded

d) Differential Diagnosis :-From optic nerve meningioma1-Age :-Glioma , 50 % < 5 years-Meningioma , middle aged women2-Laterality :-Glioma , +/- bilateral -Meningioma , unilateral3-Hyperostosis :-In meningioma

4-Optic canal :-Widened in 90 % in glioma and in 10 % in meningioma5-Calcification :-Glioma : rare without prior radiotherapy-Meningioma : Calcification6-Contrast :-Glioma : variable contrast with mottled lucencies due

to mucinous degeneration-Meningioma : diffuse homogenous enhancement

2-Optic nerve sheath Meningioma :a) Incidenceb) Clinical Featuresc) Radiographic Featuresd) Differential Diagnosis

a) Incidence :-Optic nerve sheath meningiomas arise from

arachnoid rests in meninges covering the optic nerve

-Age: 4th decade (80% female) ; younger patients typically have NF

-These lesions are almost always unilateral with the exception of NF2 patients which may be unlucky enough to have bilateral tumours

b) Clinical Features :1-Visual loss (95 % of cases)2-Proptosis

c) Radiographic Features :1-CT :a) Mass b) Enhancementc) Others

a) Mass :-Tubular , 60%-Fusiform , surrounding the optic nerve , 25%-Eccentric , 15%-Calcification (common)

Calcification

b) Enhancement :-Intense contrast enhancement-Linear bands of enhancement (nerve within tumor)

: tram track sign (enhancing mass around the optic nerve , the optic nerve itself is not enlarged and is nonenhancing ; mass, such as a arising from the optic nerve sheath

c) Others :Sphenoid bone and / or optical canal hyperostosis

Optic nerve sheath meningioma incidentally found in a 50-year-old woman, axial CT+C shows the tram-track configuration of an enhancing tumor (arrows) surrounding the optic nerve, the mass extends to the orbital apex, the optic nerve itself can be separated from the tumor

Optic nerve tram-track sign, T1+C (A) shows an enhancing mass (thick small arrows) around the left optic nerve , the optic nerve (thin long arrow) itself is not enlarged and is nonenhancing, this is suggestive of a mass ; meningioma arising from the optic nerve sheath, T2 in a different patient (B) shows fusiform enlargement of the left optic nerve itself (arrows) , in a case of optic nerve glioma

CT + C

Tram track sign

*MRI :-T1 : Isointense to somewhat hypointense

compared to the optic nerve-T2 - Isointense to somewhat hyperintense

compared to the optic nerve-T1+C : Homogeneous enhancementd) Differential Diagnosis :-See before

Optic nerve sheath meningioma in a 62-year-old patient who presented with blurry vision of the right eye, axial T1+C fat-suppressed shows an avidly enhancing tumor along both sides of the right optic nerve, the intraoptic and intracanalicular portions of the optic nerve are involved (arrows), as well as the prechiasmatic portion of the intracranial optic nerve (arrowhead). * = normal left intracranial optic nerve

-N.B. Differential Diagnosis of Orbital Hyperostosis :1-Meningioma2-Sclerotic metastases3-FD4-Paget’s Disease5-Osteopetrosis6-Chronic Osteomyelitis7-Lacrimal Gland Tumor8-LCH9-Postradiotherapy

-N.B. Optic Neuritisa) Causesb) Clinical Picturec) Radiographic Findings

a) Causes :1-Multiple sclerosis (most common cause;

occurs in 80% of MS patients)Devic's syndrome: optic neuritis (bilateral) with

transverse myelitis (MS or ADEM may be the cause)

2-Ischemia3-Vasculitis

b) Clinical Picture :1-Visual loss2-Pain on eye movement3-Afferent papillary defects

c) Radiographic Findings :-Fat-suppressed T2 or post gadolinium with fat

suppression best for diagnosis-T2 : Typically findings are most easily identified in the

retrobulbar intra-orbital segment of the optic nerve, which appears swollen, with high T2 signal, high T2 signal persists and may be permanent; chronically the nerve will appear atrophied rather than swollen

-Enhancement of the optic nerve

T2-weighted fat-saturated coronal image shows high signal in the left optic nerve, consistent with optic neuritis

T1+C fat suppression shows edema and enhancement of the optic nerve (arrow)

3-Hemangioma (usually cavernous) and Orbital varices :

Cavernous Hemangioma (adults): a) Incidenceb) Radiographic Features

a) Incidence: -True capsule , benign

-Common benign tumor of the intraconal space most commonly in the lateral aspect

-Large , dilated venous channels with fibrous capsule

b) Radiographic Features: 1-CT:

-Well circumscribed , somewhat hypoattenuating compared to muscle , which gradually fills in following administration of contrast

Cavernous malformation in a 46-year-old man with right-sided headache, sagittal unenhanced CT image demonstrates a round, well-circumscribed intraconal mass that causes superior displacement of the optic nerve (*)

Cavernous malformation in a 39-year-old woman with painless progressive proptosis, CT+C shows an enhancing intraconal mass (dot) immediately adjacent to the lateral rectus muscle (black arrows), the mass is causing medial deviation of the optic nerve (white arrow)

2-MRI :*T1 :Isointense If areas of thrombosis are present, then hyperintense regions

may be visible *T2 :HyperintenseMay have low intensity septationPseudocapsule is of low intensity*T1+C :Low gradual irregular enhancement with delayed wash out

Large cavernous malformation in a 43-year-old woman with painless proptosis of the right eye. (a) T1 shows a well-circumscribed, hypointense intraconal lesion causing orbital expansion (arrows), (b) T1+C fat-suppressed MR image, obtained immediately after the intravenous administration of a gadolinium-based contrast material, shows inhomogeneous enhancement predominantly in the center of the lesion (dot). (c) T1+C fat-suppressed MR image, obtained 1 hour later, shows the characteristic complete enhancement of the lesion

`

T1 + C

N.B. :Capillary Hemangioma (children ; strawberry nevus) : no capsule

a) Incidence: -Represents 10% of all pediatric orbital tumors

( Most common orbital tumor in infancy)-Infiltrates conal and extraconal spaces

-Grows for <1 year and then typically involutes-90% are associated with cutaneous angioma

-Can be part of the PHACE-syndrome: Posterior fossa malformations, Hemangiomas, Arterial anomalies, Cardiac malformation and Eye abnormalities such as coloboma, glaucoma

b) Radiographic Features:1-CT :-The CT appearance is that of a strongly enhancing

lobulated mass , the enhancement is typically homogeneous

-On imaging alone , it is difficult to differentiate these lesions from other vascular lesions of the orbit thus relying on patients age and clinical appearance

Capillary hemangioma in a 4-month-old boy with proptosis of the left eye, inferior displacement of the globe, and a bluish discoloration under the skin, CT+C depicts an intensely enhancing, irregularly marginated lesion with intraconal (dots) and extraconal (arrows) components

2-MRI :*T1 : Hypointense*T2 : Iso- to hyperintense on with multiple

serpiginous flow voids*T1+C : Enhancement is homogenous with

gadolinium with marked enhancement of intra-tumoral vessels

-Its lobulated appearance with thin septa is characteristic

Typical capillary hemangioma in a 41/2-month-old girl with proptosis of the right eye and cutaneous hemangioma. (a) T1 demonstrates an extraconal, lobulated, irregularly marginated lesion with hypointense signal and small serpentine flow voids (arrow), (b) T2 fat-suppressed image shows the same lesion with slight signal hyperintensity, characteristic fine internal septa, and flow voids (arrow), (c) T1+C fat-suppressed image demonstrates homogeneous intense enhancement of the lesion and provides improved delineation of the flow voids (arrow)

Orbital Varices :a) Incidenceb) Radiographic Features

a) Incidence :-Varices are the most common cause of spontaneous

orbital hemorrhage, however, these lesions are uncommon overall

-They typically manifest in the 2nd or 3rd decade of life, and they affect males and females equally

-The lesions result from a presumably congenital weakness in the postcapillary venous wall, a condition that leads to the proliferation of venous elements and massive dilatation of the valveless orbital veins

-Most varices have a large communication with the venous system and distend during maneuvers that increase venous pressure

-Patients with orbital varices usually manifest stress proptosis, which is characterized by a dramatic protrusion of the eye

Conjunctival orbital varix in a 56-year-old man whose right eyelid bulges when straining, (a) Photograph obtained with the patient at rest shows a relatively normal appearance of the upper eyelid, (b) Photograph obtained during the Valsalva maneuver shows abnormal fullness of the upper eyelid, which appears bluish. (c) Photograph obtained with the upper eyelid elevated shows the varix

b) Radiographic Features :1-CT :-Axial CT images obtained with the patient in the supine position

usually show a normal appearance or only mild enlargement of the involved veins

-A maneuver that increases venous pressure (scanning in the prone position, jugular vein compression with a tourniquet, or the Valsalva maneuver) is required to demonstrate lesion dispensability

-Varices may be smooth contoured, clublike, triangular, or segmentally dilated, or they may appear as a tangled mass of vessels

2-MRI :*T1 : Varices have hypo- to hyperintense*T2 : Hyperintense*T1+C : Usually enhance intensely after the administration of

contrast material

Bilateral orbital varices in a 27-year-old woman with a sensation of eye pressure when stooping to pick up her child. (a) CT+C obtained with the patient at rest shows enhanced and slightly elongated soft-tissue lesions (arrows). (b) CTC+C obtained during the Valsalva maneuver shows the marked distention typical of orbital varices (arrows)

Orbital varix in a 33-year-old woman with proptosis when straining. (a) T1 obtained with the patient supine shows a well-circumscribed, triangular, homogeneous, hypointense, retrobulbar lesion (dot), (b, c) T1+C fat-suppressed images obtained with the patient supine (b) and prone (c) show homogeneous intense enhancement of the lesion in b and enlargement and distention of the lesion in c, features that help confirm the diagnosis of an inferior ophthalmic venous varix

4-Inflammatory Orbital Pseudotumor :-An enhancing soft tissue mass which may involve the muscle

cone or optic nerve (See later)

5-Lymphoma and Metastases :-See later

6-Hematoma :-Most are intraconal

7-Neurofibroma :-Rare

c) Arising from the Muscle Cone :1-Inflammatory Orbital Pseudotumor2-Dysthyroid Ophthalmopathy 3-Rhabdomyosarcoma

1-Inflammatory Orbital Pseudotumor :a) Definitionb) Clinical Findingsc) Causesd) Radiographic Findingse) Differential Diagnosis

a) Definition :-Inflammation of orbital soft tissues of unknown

origin

b) Clinical Findings :-Painful proptosis-Unilateral-Steroid responsive

c) Causes :-Idiopathic-Systemic disease: sarcoid , endocrine-Unrecognized focal infections , foreign bodies

d) Radiographic Findings :-Infiltrating intraconal or extraconal inflammation presenting

as ill-defined infiltrations or less commonly as a mass-Typical features : 1-Unilateral2-Unlike thyroid ophthalmopathy , pesudotumors involve

tendons of muscles (because it is inflammatory disease)3-Muscle enlargement-Stranding of orbital fat (inflammation)-Enlarged lacrimal gland-May involve orbital apex including superior orbital fissure

(Tolosa-Hunt syndrome)-MRI : *T1 : affected region typically iso to hypointense

*T2 : affected region typically hypointense

e) Differential Diagnosis :Pseudotumor Thyroid

ophthalmopathyInvolvement Unilateral , 85% Bilateral , 85%

Tendon Involved Normal

Muscle Enlargement Enlargement: I > M > S > L

Fat Inflammation Increased amount of fat

Lacrimal gland Enlarged

Steroids Good response Minimal response

2-Dysthyroid Ophthalmopathy :a) Definitionb) Clinical Featuresc) Gradesd) Radiographic Features

a) Definition :-Orbital pathology (deposition of glycoproteins

and mucopolysaccharides in the orbit) caused by long-acting thyroid-stimulating factor (LATS) in Graves' disease

b) Clinical Features :-Painless proptosis , patients may be euthyroid ,

hypothyroid or hyperthyroid

c) Grades :-Grade 1: Lid retraction , stare, lid lag (spasm of upper lid

due to thyrotoxicosis)-Grade 2: Soft tissue involvement-Grade 3: Proptosis as determined by exophthalmometer

measurement-Grade 4: Extraocular muscle involvement ; affects muscles

at midpoint-Grade 5: Corneal involvement-Grade 6: Optic nerve involvement: vision loss

d) Radiographic Features :1-Exophthalmos2-Muscle involvement :-Mnemonic for involvement: “I'M SLow”: Inferior (most common)

MedialSuperiorLateral

-Enlargement is maximal in the middle of the muscle and tapers toward the end (infiltrative, not inflammatory disease)

-Spares tendon insertions-Often bilateral, symmetrical3-Other :-Optic nerve thickening-Expansion of orbital fat

3-Rhabdomyosarcoma :a) Incidence b) Clinical Featuresc) Radiographic Featuresd) Spread

a) Incidence :-Most common malignant orbital tumor in

childhood-Mean age: 7 years

b) Clinical Features :-Rapid onset of proptosis , usually with lateral

deviation of the eye , as anteromedial or superomedial points of origin are most common

-Vision is preserved

c) Radiographic Features :-Large , aggressive soft tissue mass (intraconal or extraconal)-Metastases to lung and cervical nodes1-CT :-Are typically homogeneous soft tissue masses isodense to

normal muscle , the mass may extend into the eyelid or through bone into the paranasal sinuses (especially the ethmoid sinus) and superiorly into the anterior cranial fossa

-Following contrast administration, enhancement is usually present

-18-year-old male presenting with right sided proptosis and history of choroid plexus papilloma and seizures-Axial CT soft tissue window shows a soft tissue mass centered in the right ethmoid sinus with bony destruction and invasion into the right orbit and left ethmoid sinus

-Coronal CT image using bone windows clearly demonstrates the osseous destruction and invasion of the right medial orbital wall , bilateral ethmoid sinuses , right frontal sinus , both nasal cavities , turbinates , and nasal septum

-MRI :*T1-Low to intermediate intensity , iso intense to

adjacent muscle*T2-Usually hyperintense*T1+C-Shows considerable enhancement

T1+C with fat saturation better demonstrate the enhancing soft tissue mass and its extension , the mass invades the medial orbit , displacing the right medial rectus laterally (black arrow) and causes proptosis (star) , on coronal , the mass is again seen invading the adjacent sinuses and obstructing the nasal passage ; however , unlike CT , abnormal enhancement is seen of the frontal dura (white arrows) , the dural thickening and enhancement are compatible with direct tumor invasion

d) Spread :-The tumor is closely related to the paranasal sinuses and

though extension out of the orbit anteriorly and medially is not uncommon , most tumors lie preseptally or extraconally and extension backwards into the brain is not common

-It is important to differentiate between a primary orbital location and a parameningeal location (defined as a tumor close enough to the meninges to permit intracranial spread of tumor) because therapy differs

d) Outside the Muscle Cone (Extrconal) :1-Orbital Cellulitis and Abscess 2-Lymphoma and Metastases3-Dermoid and Teratoma 4-Lymphangioma, Lymphohaemangioma 5-Spread from lacrimal gland tumors

Extraconal space

1-Orbital Cellulitis and Abscess :a) Etiologyb) Radiographic Features

a) Etiology :-The orbital septum represents a barrier to

infectious spread from anterior to posterior structures

-Common causes of orbital infection include spread from infected sinus and trauma

b) Radiographic Features :-Periorbital cellulitis: soft tissue swelling-Postseptal infection (true orbital cellulitis) :*Subperiosteal infiltrate*Stranding of retrobulbar fat*Lateral displacement of enlarged medial rectus m.*Proptosis

Preseptal Cellulitis : CT+C of the orbit shows soft tissue thickening of the right preseptal region (between arrows) , the retro-orbital fat is normal (arrowheads)

Periorbital Abscess

Opacification of left paranasal sinuses and left subperiosteal orbital abscesses of the orbital roof

Orbital Cellulitis

Orbital abscess

-Axial image from a CT scan of the orbits performed with contrast demonstrates sinusitis of the left ethmoid sinus and both sphenoid sinuses-There is left sided prespetal cellulitis anterior to the left orbit-Furthermore , there is a left sided subperiosteal abscess between the medial wall of the left orbit and the left medial rectus muscle

2-Lymphoma and Metastases :-Lymphoma :a) Incidenceb) Clinical Featuresc) Radiographic Findings

a) Incidence :-Orbital lymphomas account for only 2% of all

lymphomas but constitute 5-15% of all extranodal lymphomas and approximately 50% of all primary orbital malignancies in adults

-Typically patients are between 50 and 70 years of age

b) Clinical Features :-Clinical presentation is variable as any part of the orbit can be

involved , in 25% of patients the conjunctiva is involved in which case patients demonstrate a (salmon red patch) of swollen conjunctiva

-The majority of patients who do not have conjunctival involvement (75% of cases) presentation is due to an orbital mass usually in the superior lateral quadrant in proximity to the lacrimal gland :

1-Palpable mass2-Exophthalmos3-Ptosis4-Diplopia and abnormal ocular movement-Generally the mass is painless , however a subset of patients

demonstrate inflammatory-like changes with pain , erythema and swelling, direct infiltration of the globe and / or optic nerve is rare and vision is usually preserved

c) Radiographic Findings :-Soft tissue mass either involving the conjunctiva or

elsewhere in the orbit , frequently in the upper outer quadrant , closely associated with the lacrimal gland

-Although the extraocular muscles may be surrounded or displaced by the mass , they can usually be identified as not being the origin of the tumor, helpful in distinguishing lymphomas from other orbital masses

-Invasion of the globe or optic nerve is rare

a This graph represents the lymphoma distribution at the diagnosis, the superior (SUP) and lateral (LAT) quadrant is the most common, medial (MED) and inferior (INF) quadrants are less affected. b Coronal reconstruction of contrast CT shows bilateral orbital lymphoma: two homogeneous masses are circled in both superior and lateral quadrants

-CT :*On non-contrast CT , the mass is usually

homogeneous in density either isodense or slightly hyperdense when compared to the extraocular muscles

-Following administration of contrast , only mild to moderate enhancement is seen similar again to the extraocular muscles and lacrimal gland

CT+C obtained in two different patients show typical pattern of orbital involvement by lymphoma. a There is superior and lateral rectus muscle as well as lacrimal gland involvement in a coronal reconstruction of CT, it is highlighted the predominant superior lateral quadrant involved. b CT after contrast shows a slight enhancement lesion within the eyelid (red arrows)

-MRI :Similar to intracranial lymphoma , the densely cellular

nature of these tumors with high nucleus-to-cytoplasm ratio results in relatively specific appearances :

*T1 : Iso to hypointense to muscle*T2 : Iso to hyperintense to muscle*T1+C: Homogeneous enhancement*DWI : Increased signal intensity, i.e. restricted diffusion*ADC : Reduced values, i.e. restricted diffusion

-Metastases :*Children: Ewing's tumor , neuroblastoma &

leukemia*Adults: -Breast , lung , renal cell & prostate carcinoma-Direct extension of SCC from paranasal sinus

Orbital soft tissue mass leading to bone erosion and intracranial invasion

Breast cancer metastasis in a 56-year-old woman who presented with eye pain, axial T1+C fat-suppressed shows thickening of the left lateral rectus muscle (arrows), with involvement of the tendinous insertion, biopsy results revealed breast cancer, which was undiagnosed at presentation

Metastatic scirrhous breast cancer in a 43-year-old woman with bilateral paradoxical enophthalmos. (a) Axial T1 shows abnormally hypointense and heterogeneous bilateral retrobulbar fat (arrows), (b) Axial T1+C fat-suppressed shows patchy enhancement of the retrobulbar fat (arrows), the left medial rectus is also thickened because of metastatic involvement (arrowhead)

Melanoma metastatic to the extraocular muscle in a 37-year-old man who presented with decreased vision, Axial T1 shows a mass of the inferior rectus muscle that appears isointense (arrow), reflecting its amelanotic nature

3-Dermoid and Teratoma :a) Incidenceb) Radiographic Features

a) Incidence :-Common orbital tumor in childhood-Age: 1st decade

b) Radiographic Features :-Low CT attenuation and T1 hyperintensity (fat) are

diagnostic-Contiguous bone scalloping or sclerosis is common-May contain debris (inhomogeneous MRI signal)

CT Ruptured Orbital dermoid cyst

4-Lymphangioma & Lymphohaemangioma :a) Incidence b) Clinical Picturec) Radiographic Features

a) Incidence :-2% of orbital childhood tumors-Known as venous lymphatic malformation -Age: 1st decade-Associated with other lymphangiomas in head

and neck-Lymphangiomas of the orbit do not involute

spontaneously

b) Clinical Picture :-Although venous lymphatic malformations may

enlarge slowly, producing progressive proptosis, restriction of eye movements, or vertical globe displacement, many manifest abruptly because of hemorrhage

-Hemorrhages within these malformations often occur after minor trauma or infection and occasionally develop spontaneously

Marked right proptosis and superior displacement of the globe, also note enlarged right orbit compared with left orbit

c) Radiographic Features :1-CT :-Variable CT appearance because of different

histologic components (lymphangitic channels , vascular stroma)

-Multiloculated-Rim enhancement

2-MRI :-MR imaging is the modality of choice for the evaluation of

lymphatic malformations because it best depicts the various components

-The signal intensity of the lesions depends on the type of fluid within the cystic components, whether hemorrhage has occurred, and the age of the hemorrhage

-T1 best depict lymphatic or proteinaceous fluid, and T1-weighted fat-suppressed images are best for detecting blood or blood products

-T2 fat-suppressed images provide improved visibility of components that contain nonhemorrhagic fluid

-T1+C : The use of contrast material does not typically provide significant additional information, but an absence of enhancement is indicative of a lymphatic component

-Fluid-fluid levels produced by hemorrhages of various ages within multiple cysts are almost pathognomonic

Venous lymphatic malformation in an 11-year-old boy with progressive proptosis of the right eye and lateral displacement of the globe. (a) Axial unenhanced CT shows multiple fluid-fluid levels (arrows) within a lobulated, predominantly extraconal lesion, features typical of a lymphatic malformation with an intralesional hemorrhage. (b) Axial T2 fat-suppressed MR image shows multiple fluid-fluid levels within the lesion, which has both intra- and extraconal components

Lymphatic malformation (lymphangioma), axial T2 shows a hyperintense, trans-spatial mass involving the intra- and extra-conal compartments. Hypointense septations (black arrows) are typical of this lesion. Layering blood products (white arrows) are variably present, and indicate recent intralesional bleeding

5-Spread from Lacrimal Gland Tumors :a) Lymphoidb) Epithelial tumors

a) Lymphoid , 50% :-Benign reactive lymphoid hyperplasia-Lymphomab) Epithelial tumors , 50% :-Benign mixed (pleomorphic) tumor (75% of

epithelial tumors)-Adenoid cystic carcinoma-Mucoepidermoid carcinoma- Malignant mixed tumor

Lymphoma

Pleomorphic adenoma T1

e) Arising from the Orbital Wall :1-Metastases and Lymphoma 2-Langerhans Cell Histiocytosis 3-Invasion by ethmoidal or maxillary antral

tumors 4-Ethmoidal Mucocoele

5-Spread of Ethmoidal or Antral infection

Langerhans cell histiocytosis :-Occurs in children with peak incidence at age 1

and 4-Osteolytic mass like lesion located in the

superolateral orbit in pediatric patients with varibale degree of proptosis and inflammatory signs

-The diagnosis should be confirmed by histopathology and this will show the presence of langerhans cells

Coronal CT scan showing an osteolytic right superolateral orbit lesion

**N.B. : Erdeheim-Chester Disease :-Lipid granulomatosis with retroorbital

deposition, xanthelasma of eyelids, skeletal manifestations (medullary sclerosis, cortical thickening), and cardiopulmonary manifestations due to cholesterol emboli

-Rare

**N.B. Ocular Manifestations of Phakomatosis:a) NF1 :1-Lisch nodules2-Sphenoid bone dysplasia3-Choroidal hamartoma4-Optic glioma5-Plexiform neurofibromab) NF2 :1-Meningioma2-Schwannoma

c) Sturge-Weber :1-Choroidal angioma2-Buphthalmos3-Glaucomad) Tuberous sclerosis :-Retinal astrocytic hamartomae) Von Hippel-Lindau (VHL) :-Retinal angioma

3-Orbital Trauma1-Anterior Chamber Injuries2-Injuries to the Lens3-Open-Globe Injuries4-Ocular Detachments5-Intraorbital Foreign Bodies6-Carotid Cavernous Fistula7-Optic Nerve Injuries

Unenhanced axial CT scan of a healthy 32-year-old man. AC = anterior chamber, L = lens, ON= optic nerve, PS = posterior segment (vitreous humor)

1-Anterior Chamber Injuries :-Posttraumatic bleeding into the anterior chamber, or

traumatic hyphema, is caused by the disruption of blood vessels in the iris or ciliary body

-The blood extravasates into the anterior chamber, where a blood-fluid level is usually readily appreciated at clinical examination

-CT images may show increased attenuation in the anterior chamber, but the primary role of imaging is to evaluate for other related injuries, corneal lacerations are usually associated with a penetrating trauma

Photograph shows posttraumatic hyphema in a 25-year-old man

-After a laceration, the iris may prolapse into the anterior chamber, thereby closing the defect

-On CT images, the key finding is decreased volume of the anterior chamber, which appears as a diminished anterior-posterior dimension compared to that of the normal globe

-Anterior subluxation of the lens is an important mimic of corneal laceration, to accurately diagnose a corneal laceration, the radiologist needs to not only assess the volume of the anterior chamber, but to also determine the position of the lens

Corneal laceration in a 22-year-old man, unenhanced axial CT scan shows decreased volume of the anterior chamber, a finding that confirms the diagnosis

2-Injuries to the Lens :-Blunt trauma to the eye results in deformation of the

globe and typically displaces the cornea and anterior sclera posteriorly

-Deformation of the globe causes the zonular attachments that hold the lens in position to stretch and potentially tear; tearing of the zonular attachments may be either partial or complete

-After a complete disruption, the lens may dislocate posteriorly or, less commonly, anteriorly

-Posterior dislocations are more common, in part because the iris impedes anterior subluxation of the lens

-After complete posterior subluxation, the lens usually lies within the dependent portion of the vitreous humor

-If there is only partial disruption of the zonular fibers, the intact fibers retain one margin of the lens in its normal position just behind the iris while the remainder of the lens is angled posteriorly and projects into the vitreous humor

-Trauma is the most common cause of lens dislocation; it accounts for more than half of all cases

-An important pitfall for the radiologist to avoid is that of the spontaneous dislocated lens, nontraumatic lens dislocation may be associated with systemic connective tissue disorders, such as Marfan syndrome, Ehlers-Danlos syndrome, and homocystinuria

-If the dislocation is bilateral, the radiologist should suspect an underlying systemic condition

Unenhanced axial CT scan of a 29-year-old man shows complete subluxation of the lens

Unenhanced axial CT scan of a 49-year-old woman shows a partially dislocated lens

3-Open-Globe Injuries :A ruptured globe or an open-globe injury must

be assessed in any patient who has suffered orbital trauma, because open-globe injuries are a major cause of blindness

-In blunt traumas, ruptures are most common at the insertions of the intraocular muscles where the sclera is thinnest

-If intraocular contents are visualized at clinical examination, a diagnosis of a ruptured globe can be obvious, otherwise, CT scanning is the test of choice

-Blow-out fractures can occur through one or more of the walls of the orbit :

1-Inferior (floor), most common, orbital fat prolapses into the maxillary sinus and may be joined by prolapse of the inferior rectus muscle

2-Medial wall (lamina papyracea) , 2nd most common, occurring through the lamina papyracea, orbital fat and the medial rectus muscle may prolapse into the ethmoid air cells

3-Superior (roof)4-Lateral wall

Inferior

Medial

-CT findings suggestive of an open-globe injury include a change in globe contour, an obvious loss of volume, the “flat tire” sign, scleral discontinuity, intraocular air, and intraocular foreign bodies

-Posterior movement of the lens enlarges or deepens the anterior chamber, a deep anterior chamber has been described as a clinical finding in patients with a ruptured globe and can also be a useful clue on CT image

-There are several nontraumatic causes for an altered globe contour that may mimic an open-globe injury, including congenital deformities at the optic nerve head (eg, coloboma) and acquired contour deformities, which may involve any portion of the globe (eg, staphyloma), a posttraumatic orbital hematoma may deform the globe, mimicking an open-globe injury

75-year-old man with right globe rupture, axial unenhanced CT scan shows eyelid hematoma (thick straight arrow), lens dislocation (arrowhead), vitreous hemorrhage (thin straight arrow), and irregular scleral wall (curved arrow)

80-year-old man with left eyeball rupture. Axial unenhanced CT scan shows gas (short arrow) and metallic foreign body (long arrow) in ruptured globe

34-year-old man with left eyeball rupture, axial unenhanced CT scan shows shallow anterior chamber depth (ACD) of left globe (single arrow), ACD is evaluated at level of equator of globe from posterior surface of cornea to anterior surface of lens (parallel lines) and is measured along line perpendicular to long axis of lens (double arrows)

Ruptured globe in a 43-year-old man. Unenhanced axial CT scan shows the flat tire sign, which indicates an open-globe injury

Ruptured globe in a 35-year-old man. Unenhanced axial CT scan shows extrusion of the lens

Open-globe injury in a 20-year-old man who presented with orbital trauma that may or may not have been an open-globe injury, unenhanced axial CT scan shows increased depth of the anterior chamber, which helps confirm the diagnosis of an open-globe injury

Congenital coloboma in a 53-year-old man who presented with decreased visual acuity, unenhanced axial CT scan shows a deformity at the left optic nerve head

Globe deformity in a 58-year-old man with facial fractures. (a) Unenhanced axial CT scan shows deformity of the globe, but it is unclear if there is an open-globe injury, after the facial fractures were internally fixed and the soft-tissue swelling decreased, the globe appeared normal, (b) Unenhanced axial CT scan shows no open-globe injury, a finding that suggests that the globe deformity was secondary to posttraumatic hematoma and soft-tissue swelling, which subsequently resolved

4-Ocular Detachments :-The three layers of the globe can separate,

thereby creating potential spaces between the layers

-The retina is the inner, sensory layer of the globe

-The retina is very firmly attached along its anterior margin, called the ora serrata, and posteriorly at the optic disc

-The remainder of its surface is only loosely attached to the choroid

-Retinal detachment occurs when the retina is separated from the choroid

- Common causes of retinal detachment include both inflammatory and neoplastic etiologies

-Retinal detachment may also occur secondary to trauma, particularly if there is a break in the retina, which can allow vitreous fluid to pass into the subretinal space

-Collections of subretinal fluid assume a characteristic V-shaped configuration, with the apex at the optic disk and the extremities at the ora serrata

Photograph of a gross pathologic specimen (hematoxylineosin stain) shows a retinal detachment, note the characteristic V-shaped configuration caused by tethering of the retina near the optic nerve head (arrow), ON = optic nerve

Axial CT shows hemorrhagic subretinal fluid in another patient with retinal detachment (arrow)

-The choroid is part of the middle layer of the globe-It extends from the optic nerve head to the ora serrata

and is tethered to the sclera by arteries and veins, which supply this vascular layer

-Choroidal detachments are caused by an accumulation of fluid in the potential suprachoroidal space that lies between the choroid and the sclera

-Ocular hypotony is the underlying cause of choroidal detachment; hypotony may be the result of an inflammatory disease, accidental perforation, or surgery, decreased ocular pressure results in decreased pressure in the suprachoroidal space, transudate may accumulate in the suprachoroidal space, resulting in a serous choroidal detachment

Unenhanced axial (a) and coronal (b) CT images of a 40-year-old woman show a right serous choroidal detachment secondary to ocular hypotony

-If there is associated tearing of blood vessels, a hemorrhagic choroidal detachment may occur

-Suprachoroidal fluid collections usually assume a biconvex or lentiform configuration that extends from the level of the vortex veins to the ora serrata

-Posttraumatic bleeding can also occur within the vitreous humor, or it may occur in the layer between the vitreous and the retina

Unenhanced axial CT scan of an 84-year-old woman shows a posttraumatic, hemorrhagic choroidal detachment

Unenhanced CT scan of an 81-year-old woman receiving anticoagulation therapy, who presented after a trauma, shows an extensive vitreous hemorrhage

5-Intraorbital Foreign Bodies :-The detection and localization of intraorbital foreign

bodies is an important task for the radiologist-CT is sensitive and is usually the first imaging test

performed-MR imaging may be of value, particularly for detecting

nonmetallic foreign bodies, however, a metallic foreign body must be definitively ruled out before MR imaging is performed, failure to detect a metallic foreign body before performing MR imaging may result in blindness

-Fortunately, CT is a very sensitive imaging modality that can demonstrate metal fragments less than 1 mm in size

-CT is most sensitive in detection of glass objects-Unlike metallic and glass foreign bodies, wooden

foreign bodies usually appear hypoattenuating on CT images; because of their low attenuation, they can be mistaken for air, the radiologist should suspect a wood or organic foreign body if the low-attenuation collection seen on CT images displays a geometric margin

-MR imaging may demonstrate wooden foreign bodies in cases where CT results have been either negative or equivocal, T2 or T1+C performed with fat suppression can demonstrate an intraorbital foreign body by enhancing the inflammatory response seen surrounding that foreign body

-Penetrating injury from a tree branch in a 7-year-old boy, the branch was removed, and unenhanced CT was performed to evaluate for any remaining foreign bodies

(a) CT scan shows only a low-attenuation defect; no definite foreign body is seen, three days later, the eye became infected, and contrast-enhanced CT was performed

(b) CT scan shows soft-tissue swelling and abnormal enhancement consistent with the infection, but no definite foreign body is seen

(c, d) Coronal unenhanced T2 inversion recovery (c) and coronal T1+C fat-saturated MR (d) show the infection surrounding a low-signal-intensity foreign body, the MR images were obtained on the same date as the CT images, during surgery, a small piece of wood was removed

6-Carotid Cavernous Fistula :-The presence of posttraumatic diplopia

associated with proptosis and chemosis suggests a diagnosis of carotid cavernous fistula, objective pulsatile tinnitus may also be present

-A tear in the cavernous internal carotid artery allows arterial blood to enter the cavernous sinus, thereby increasing the sinus pressure and reversing the flow in the venous tributaries

-On unenhanced CT scans of the orbit, a dilated superior ophthalmic vein is usually seen

-Isolated dilatation of the superior ophthalmic vein is a potential diagnostic pitfall; this finding has been reported in multiple other conditions, including cavernous sinus thrombosis, venous varix, Graves disease, and as a normal venous variant

-The diagnosis of carotid cavernous fistula can be confirmed with CT angiography, or more definitively with conventional angiography

Carotid cavernous fistula in a 16-year-old boy who presented with exophthalmos and objective pulsatile tinnitus after trauma, (a) Axial CTA shows dilatation of the periorbital veins and the left superior ophthalmic vein and a dilated left cavernous sinus, (b) Sagittal CTA shows an apparent communication between the cavernous segment of the ICA and the cavernous sinus (arrow), (c) Lateral view from left internal carotid angiography shows the carotid cavernous fistula

7-Optic Nerve Injuries :-Optic nerve injuries can result from either direct or

indirect trauma-Rarely, a blunt orbital injury may fracture the optic

canal and lacerate the optic nerve-More commonly, a definitive fracture is not found, in

these cases, the optic nerve or its vascular supply is torn, thrombosed, or compressed

-In patients with a rapid posttraumatic decrease in visual acuity, high-resolution CT of the orbital apex should be performed to evaluate for possible fracture and to guide surgical intervention, if there are no contraindications to MR imaging, T2 prolongation may be visualized as increased signal intensity in the injured optic nerve

Optic nerve injury in a 33-year-old man who presented with multiple facial fractures and decreasing vision in his right eye, axial unenhanced CT scan shows a right orbital apex fracture with a bone fragment impinging on the optic nerve

Diagnostic Imaging of Orbital Lesions

Health & Medicine

Transcript of Diagnostic Imaging of Orbital Lesions