1. Look at Me Now! A Case Based Review of Common Emergent Orbital Pathologies
Asha Bhatt, MD, PGY 5
Parul Patel, MD, Attending Radiologist
Rochester Radiology Associates
ASNR 2016
eEdE-123
Control#:1947

2. No Disclosures

3. Purpose
Review normal orbital anatomy using both computed tomography (CT) and magnetic resonance (MR).
Case based review of common emergent pathologies of the orbits and globes divided into two major categories:
Trauma
Globe
Fractures
Hemorrhage
Infection

4. Anatomy
The orbital septum, typically not visualized, is a membranous structure which extends from the orbital rim to the eyelids and serves as the anterior boundary of the orbit.
The globe is subdivided into anterior and posterior segments by the lens.
The extra-ocular muscles within the orbit form a “muscle-cone” to create three spaces
Conal space or cone: Comprised of the extra ocular muscles and fascia
Extraconal space: Comprised of fat and lacrimal gland (arrow)
Intraconal space: Comprised of fat, cranial nerve II, superior ophthalmic vein, ophthalmic artery

5. Anatomy
Coronal noncontrast CT demonstrates extraconal air (yellow arrow) within the right orbit above the level of the superior rectus muscle.
Axial CT, on lung windows, the orbital septum (red arrows) is easily delineated between the intraorbital (extra-conal) air anterior to the globe and periorbital soft tissue emphysema.

6. Anatomy Levator Palpebrae Superioris Superior Rectus
Superior Ophthalmic Vein
Superior
Oblique
Muscle
Medial Rectus
Inferior Rectus Muscle
Lateral Rectus
Levator Palpebrae Superioris
Inferior
Ophthalmic Vein
Globe

7. Anatomy Posterior Segment Lens Aqueous Fluid Superior Rectus
Vitreous Fluid
Anterior
Segment
Posterior Segment
Optic Nerve
Inferior Rectus
Muscle
Superior Rectus
Aqueous Fluid

8. MR Signal Characteristics of Major Orbital Structures
Aqueous fluid, Vitreous fluid and CSF
Hypointense
Hyperintense
Lens
Hyperintense to vitreous
Hypointense to vitreous
Scelera, choroid and retina
Intermediate signal
Extraocular muscles
- Intermediate signal
- Enhance with contrast
Optic nerve
- Isointense to cerebral white matter
- Normal optic nerve does not enhance with contrast
Isointense to cerebral white matter
Orbital fat
Intermediate
Lacrimal gland
Intermediate signal similar to grey matter T2 T1

9. CT versus MRI in the Evaluation of Orbital Pathologies
Superior in delineation of calcifications within lesions/masses
Superior to evaluate bony erosions, and orbital fractures
Modality of choice for evaluation of metallic foreign bodies
MRI
Exquisite contrast resolution makes MR superior to CT in the evaluation of soft tissues structures
Signal abnormalities in the optic nerves, muscles and other soft tissues allows the radiologist to pick up pathology on MRI that would be occult on CT

10. Globe Trauma Diagnosis Features CT MRI Retinal detachment
- Accumulation of blood or fluid in the sub- retinal space between two layers of retina
- Configuration of collection is typically crescent or “V” shaped with apex at the optic disc
“V” shaped hyperdense abnormality in the globe
T1 “V” shaped hyperintense and T2 “V” shaped isointense (to normal vitreous body) abnormality in the globe
Choroidal detachment
- Accumulation of blood or fluid in between choroid and sclera
- Configuration of abnormality is lentiform shaped along the medial and lateral walls of globe
Lenitform shaped hyperdense abnormality in the globe
Leniform shaped T1 hyperintense and T2 isointense (to normal vitreous body) abnormality in the globe
Lens Dislocation
- Subluxation or dislocation of the lens from its normal position secondary to dysfunction or disruption of zonular fibers
Lens displaced from its normal location and typically seen in the posterior chamber
Globe Rupture
- Disruption of the outer membranes of the globe by blunt or penetrating trauma
Globe deformity or wall irregularity, destruction or dislocation of the lens, intraocular hemorrhage, intraocular foreign body, shallow AC, and intraocular gas
-Not the study of choice to initially evaluate globe rupture due to possible metallic foreign bodies (contraindication), time constraints, not widely accessible, and poor definition of osseous structures
Foreign Body (FB)
- Associated with orbital fractures and globe injury
- Unlike metallic foreign bodies, organic foreign bodies like wood are porous and provide a good medium for microbial agents which can result in cellulitis and abscess
CT demonstrates most foreign bodies
CT is safe for the evaluation for metallic foreign bodies
- Metallic foreign bodies however result in beam-hardening artifact limiting evaluation of the globe and adjacent structures at times
- May fail to detect organic foreign bodies like wood
- T1 post contrast demonstrates enhancement of inflammatory tissue around organic foreign bodies
- STIR demonstrates increased signal due to inflammatory response around an organic foreign bodies
- Gradient Echo (GRE) demonstrates susceptibility artifact

11. Lens Dislocation- Native Lens
There is a thin high density curvilinear object in the posterior chamber corresponding to a dislocated right lens (red arrows).
Note the normal position of the left lens (yellow arrow).

12. Lens Dislocation- Prosthetic Lens
There is a thin high density curvilinear object in the posterior chamber of the right globe corresponding to a dislocated prosthetic right lens (red arrows). Note the normal position of the left prosthetic lens (yellow arrow).

13. Globe Rupture
There is irregularity of the left globe, with loss of the normal spherical shape compatible with contained rupture. The lens is absent (red oval) and there is free communication between the anterior and posterior segments (yellow arrow). There is a curvilinear hyperdensity at the posterior aspect of the globe which may represent blood products and/or the dislocated lens (blue arrow).

14. Globe Rupture
There is abnormal morphology (yellow arrow) and appearance of the left globe. There is high density material replacing the normal hypodense fluid in the posterior chamber (red arrow) along with significant left periorbital soft tissue edema.
Ophthalmology Exam- Total hyphema (blood within the anterior chamber), and a hypotenous, shallow appearing anterior chamber
Patient underwent surgical repair for globe rupture.

15. Traumatic Iritis
There is a small amount of hyperdense material located inferior to the left ocular lens (red arrow). This was felt to represent a small amount of vitreous hemorrhage given the history of left eye pain after assault.
Ophthalmology evaluation demonstrated traumatic iritis (inflammation of the uvea, iris, or both).

16. Foreign Body
There is an 2.4 cm metallic foreign body within the anterior aspect of the left orbit (red arrow). There is hyperdense material within the posterior aspect of the left globe suggestive of hemorrhage (yellow arrow).

17. Vitreous Hemorrhage
There is an elliptical peripherally based hyperdensity at the posterior aspect of the right globe (red arrow). Differential diagnosis includes hemorrhage, retinal detachment or neoplasm.
Ophthalmology Exam- Likely vitreous hemorrhage but unable to rule out retinal detachment.

18. Full Thickness Scleral Laceration
The right globe has an irregular contour (yellow arrow) with increased soft tissue density circumferentially about the central aspect of the globe (red arrow). Initial report suggested possible contained globe rupture given the history of fall and subsequent pain, redness, and blurriness in the right eye.
Surgical evaluation demonstrated no rupture, but a circumferential full thickness scleral laceration.

19. Retinal Detachment T2
There are V-shaped thin T2 hypointense lines arising from the optic disc and extending anteriorly towards the ciliary bodies in the left globe. Findings are consistent with retinal detachment (yellow arrow).

20. Trauma: Fractures Diagnosis Features CT MRI Blow out fracture
- Due to an increase in intra-orbital pressure which forces the intra-orbital fat inferiorly through the roof of the maxillary sinus.
- Entrapment is a clinical, not radiographic diagnosis
- Simple or comminuted fracture of orbital floor/medial wall
- May have herniation of orbital contents such as fat and extraocular muscles
- May have associated injury to the orbital soft tissues such as globe rupture or retrobulbar hematoma
- Not the study of choice to evaluate orbital fractures

21. Superior Wall Fracture
There is a fracture of the superior wall of the right orbit (red arrow) extending into the extra-conal fat. Linear fracture fragment is located immediately adjacent to the superior aspect of the right orbit (yellow arrow).

22. Inferior Orbital Wall Fracture
There is a comminuted displaced fracture of the right inferior orbital wall with herniation of intraorbital fat into the maxillary sinus (red arrows). There is no herniation of extraocular muscles. The inferior rectus muscle is in its normal location (red oval). There is extratraconal air (purple arrow), as well as right periorbital soft tissue emphysema and edema (yellow arrow). There is high density layering fluid within the right maxillary sinus, consistent with hemosinus (blue arrow).

23. Medial Orbital Wall Fracture
There is a medially displaced right medial orbital wall (lamina papyracea) fracture with medial herniation of intraorbital fat (red arrow) and the medial rectus muscle. The medial rectus muscle is slightly thickened and medially displaced (yellow arrow). There are multiple tiny foci of intraconal and extraconal air (purple arrow). Clinical correlation for entrapment should be considered.

24. Medial Orbital Wall Fracture
There is a fracture of the medial wall (lamina papyracea) of the left orbit with medial herniation of the intraorbital fat and medial rectus muscle into the left ethmoid air cells (blue arrow) The left medial rectus muscle is enlarged and shows mild hyperdensity, likely related to hemorrhage and edema (red arrow). Clinical correlation for entrapment should be considered. There is high density material/stranding within the intra-conal fat (yellow arrow) suggestive of hemorrhage.

25. Fractures Continued
There are left lamina papyracea and inferior orbital wall fractures with inferior herniation of extraconal fat (blue arrow). Additionally, there is medial bowing of the medial rectus muscle suggesting muscle entrapment (red arrow). Clinical correlation for entrapment should be considered. There is associated traumatic hemosinus (yellow arrow).

26. Acute-Orbital Blowout Fracture
STIR T1
T1 FS +C
There is a right orbital blowout fracture involving the floor of the orbit with herniation of intraorbital fat (yellow arrow) into the right maxillary sinus with elongation of the right inferior rectus muscle (red arrow) that extends across the fracture. There is complex fluid within the right maxillary sinus, likely hemorrhagic (blue arrow). There is mild edema and corresponding enhancement surrounding the right optic nerve sheath, likely related to posttraumatic edema (purple arrows). The left globe is within normal limits. Left extra ocular muscles show normal size and configuration with normal homogeneous enhancement on the postcontrast images. Left optic nerve shows normal signal characteristics.

27. Chronic Orbital Floor Fracture
Coronal T2
There is deformity of the left orbital floor with herniation of orbital fat (red arrow). Note the lack of edema and blood products in this case, as findings are related to a remote prior injury. There is mild polypoid mucosal thickening identified within both maxillary sinuses (blue arrows).

28. Chronic Orbital Floor Fracture
T1 FS +C T2
There is a left orbital floor fracture with herniation of the orbital fat into the left maxillary sinus (red arrow). The inferior rectus muscle is slightly inferior in location when compared to the right side, however, without evidence for entrapment (yellow arrow).

29. Trauma: Miscellaneous
Diagnosis
Features CT
MRI
Carotid-Cavernous fistula
- May be traumatic (direct, high flow) or atraumatic/spontaneous (indirect, low flow)
- Clinical symptoms: bruit, pulsating exophthalmos, orbital edema/erythema, decreased vision, glaucoma, headache
- Dilated superior ophthalmic vein (SOV) and ipsilateral cavernous sinus (CS)
- Increased enhancement of EOMs and small orbital vessels
- T1-Dilated SOV and CS with asymmetric enhancement
May see tortuous collaterals with cerebral drainage
T2-Flow void in enlarged SOV & cavernous sinus
Retrobulbar hemorrhage
- Due to rupture of infraorbital artery/branches following trauma or surgery
- Irregular soft tissue mass involving posterior globe surface and distal portion of the intraorbital portion of optic nerve

30. Carotid-Cavernous Fistula
The right extraocular muscles are enlarged with assoicated proptosis and edema in and around the right orbit. There is asymmetric enlargement of the right superior ophthalmic vein (yellow arrows) and the right cavernous sinus. There is abnormal enhancement within the right cavernous sinus (red arrow) in the arterial phase. Findings are consistent with a right carotid-cavernous fistula.

31. Hemorrhage
Axial unenhanced CT images of the brain at the level of the orbits demonstrate extraconal (red arrow) and intraconal (yellow arrows) hemorrhage within the left orbit with moderate left proptosis. There is no evidence of a lens dislocation. There is a fracture of left lamina papyracea with medial herniation of intraorbital contents (blue arrow).

32. Soft Tissue Hematoma
There is a large right periorbital soft tissue hematoma (red arrow). The globes are intact. There is no intraconal hemorrhage.

33. Infection Disease Location Complications CT T1 T2
Pre-septal Orbital Cellulitis
Disease limited to periorbital soft tissues, anterior to orbital septum
Post-septal cellulitis
Infiltration of periorbital fat
- Hypointense infiltration of normal fat
- Diffuse heterogeneous enhancement
Heterogeneous hyperintensity
Post-septal Orbital Cellulitis
Disease involving the structures posterior to the orbital septum:
- Intraconal
- Extraconal
- Periosteum
Abscess, empyema, cerebritis, subdural or epidural effusions
Infiltration of periorbital and intraorbital fat
- Hypointense infiltration of normal intraorbital fat

34. Pre-Septal Orbital Cellulitis
There is mild to moderate right periorbital soft tissue thickening with associated inflammatory stranding (yellow arrows). There is no post-septal involvement. The intraconal fat is normal in appearance. Note the thin curvilinear hyperdensity along the anterior surface of the right globe (red arrow), from fluorescein used during slit lamp exam prior to CT.

35. Post-Septal Orbital Cellulitis
There is mild to moderate left periorbital soft tissue swelling and edema with mild left proptosis (blue arrow). There are associated pre-septal inflammatory changes along the inferior aspect of the orbit. There is a subcentimeter subperiosteal rim enhancing focus along the medial orbital wall, compatible with a small subperiosteal abscess (yellow arrow).

36. Post-Septal Orbital Cellulitis
Same case as prior slide. Note the infiltrative changes in the left intraconal fat (yellow arrow) in this patient with left orbital post-septal cellulitis. Note the normal appearance of the intraconal fat on the right (red arrows).

37. Orbital Cellulits with Hyphema
There is an elliptical fluid collection adjacent to the left orbit with a punctate focus of gas, which may represent an abscess or effusion (red arrows). There is also a soft tissue density focus within the anterior chamber of the left globe (yellow arrow), and thickening of the sclera.
Occular exam demontrated 100% hyphema (blood within the anterior chamber)
Pathology demonstrated retinal neovasuclarization with diffuse vitrous hemorrage and hyphema.

38. Conclusion
CT and MRI are commonly used in the evaluation of the orbits and globes.
CT is optimal to evaluate bony structures and foreign bodies whereas MRI has superior contrast resolution in the evaluation of soft tissue structures.
CT is the typically the imaging modality of choice in the evaluation of acute orbital pathologies such as trauma and infection
Familiarity with normal orbital anatomy and common acute orbital pathologies is imperative for the radiologist who interprets such exams.

39. References
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