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13  Optic Nerve Meningioma

• Frequently familial and associated with infratentorial hemangioblastomas, angiomatosis retinae, and abdominal visceral cysts.14

• Usually in patients with von Hippel-Lindau

(VHL) syndrome.15

7. Erdheim-Chester Disease (ECD)

• Also known as polyostotic sclerosing histiocytosis.

• Systemic granulomatosis.

• Non-Langerhans cell histiocytosis.

• Predominately affects adults, with a mean

age of onset of 53 years.

• Infiltration of lipid-laden macrophages,

multinucleated giant cells, lymphocytes, and

histiocytes into the bone marrow.

• Generalized sclerosis of the long bones.

• Exopthalmos in some patients.

• Usually bilateral, symmetrical, and painless.

• In most cases occurs several years before

final diagnosis.

• Recurrent pericardial effusion.

• Radiologic osteosclerosis and histology are

key observations.

• May identify adrenal enlargement.

• High mortality rate, with a 3-year survival

rate of approximately 50%.1


• Main differential diagnosis is ONG.

• 90% of ONMs originate outside the orbit.

Fast Facts

• The second most common optic nerve


• 80% of cases occur in women.3

• Develop during the third to fifth decades.3

• Comprise 5% of primary orbital tumors.3

• 10% of ON lesions.

• 1% to 2% of all meningiomas.2

• 2% of orbital tumors.

• ,100 ONMs diagnosed in the United

States annually.

• ,10,000 meningiomas diagnosed in the

United States annually.


• 9% of patients with an ONM have NF2.

• Comprise one third of tumors of the optic

nerve or nerve sheath.3

• 95% are unilateral, 5% are bilateral.2

• Bilateral ONMs are associated with NF1

and NF2.12

• 0% tumor-related mortality.2


1. Gupta A, Kelly B, McGuigan JE: Erdheim-Chester

disease with prominent pericardial involvement: clinical, radiologic, and histologic findings, Am J Med Sci

324(2):96–100, 2002.

2. Dutton JJ: Optic nerve sheath meningiomas, Surv

Ophthalmol 37(3):167–183, 1992.

3. Runge VM: Review of neuroradiology, Philadelphia,

1996, WB Saunders, p 52.

4. Weissleder R, Rieumont, MJ, Wittenberg J: Primer of

Diagnostic Imaging, ed 2, St Louis, 1997, Mosby.

5. Turbin RE, Thompson CR, Kennerdell JS, et al: A

long-term visual outcome comparison in patients with

optic nerve sheath meningioma managed with observation, surgery, radiotherapy, or surgery and radiotherapy, Ophthalmology 109(5):890–899, discussion 899–900,


6. Saeed P, Rootman J, Nugent RA, et al: Optic nerve

sheath meningiomas, Ophthalmology 110(10):

2019–2030, 2003.

7. Narayan S, Cornblath WT, Sandler HM, et al:

Preliminary visual outcomes after three-dimensional

conformal radiation therapy for optic nerve sheath

meningioma, Int J Radiat Oncol Biol Phys 56(2):

537–543, 2003.

8. Mafee MF, Inoue Y, Mafee RF: Ocular and orbital

imaging, Neuroimaging Clin N Am 6(2):291–318, 1996.

9. Wright JE, Call NB, Liaricos S: Primary optic nerve

meningioma, Br J Ophthalmol 64(8):553–558, 1980.

10. Hotta H, Uede T, Morimoto S, et al: Optic nerve

hemangioblastoma, case report [Japanese], Neurol Med

Chir (Tokyo) 29(10):948–952, 1989.

11. Kerr DJ, Scheithaurer BW, Miller GM, et al: Hemangioblastoma of the optic nerve: case report,

Neurosurgery 36(3):573–580, 1995.

12. Lindegaard J, Heegaard S, Prause JU: Histopathologically verified non-vascular optic nerve lesions in

Denmark 1940-99, Acta Ophthalmol Scand 80(1):32–37,


13. Grossman RI, Yousem DM: Neuroradiology: The Requisites, St Louis, 1994, Mosby, pp 293–294.

14. Landert M, Baumert BG, Bosch MM, et al: The visual

impact of fractionated stereotactic conformal radiotherapy on seven eyes with optic nerve sheath meningiomas, J Neuroophthalmol 25(2):86–91, 2005.

15. Ortiz O, Schochet SS, Kotzan JM, et al: Radiologicpathologic correlation: meningioma of the optic nerve

sheath, AJNR Am J Neuroradiol 17(5):901–906, 1996.


PART II  Benign Tumors





FIGURE 13-1  ​n ​A, B, T1 axial MRI show tubular enlargement of the ONs from the globe through the orbital apices.

C, T1 axial MRI image with Gd using fat saturation accentuates homogeneous enhancement of involved optic

nerve sheaths. While this case is beyond the typical “tram track” appearance, the enhancement is clearly around

the ON with relative sparing of the ON itself. D, Coronal T2 of the OD (right eye) demonstrates dilation of the

subarachnoid space around the tumor.



FIGURE 13-2  ​n ​Canine orbital meningioma, pathology. A, Gross photograph of a canine globe with

orbital meningioma. B, Subgross photomicrograph of canine orbital meningioma. (From Dubie zig

RR: Diseases of the orbit. In Dubielzig RR, Ketring K, McLellan GJ, et al, editors: Veterinary Ocular

Pathology: A Comparative Review, Philadelphia, 2010, Saunders, pp 115-141.)

13  Optic Nerve Meningioma

FIGURE 13-3  ​n ​Optic nerve sheath meningioma (ONSM).

Papilledema. (From Litre CF, Colin P, Rousseaux P, et al:

Optic nerve sheath meningiomas, Neurochirurgie 56(2-3):

132-136, 2010.)



Posterior Orbital Dermoids


• Definition: Dermoids originate from

totipotential germ cells. Present at

birth, these differentiate abnormally,

developing characteristics of mature

dermal cells.

• Synonym: Orbital dermoids, retrobulbar

orbital dermoids, or deep dermoids.

• Classic clue: Well-circumscribed

encapsulated mass with low Hounsfield

numbers, filled with high T1 signal


• Displacement of globe and ocular

muscles may impair ocular motility.

• Compression of the optic nerve (ON) may

result in visual impairment.

• Dermoids may rupture inciting an

inflammatory reaction.

• Posterior retrobulbar orbital dermoids

are rare and much less frequent than the

anterior variety, a key difference which is

well documented in the literature.

Magnetic Resonance Imaging


• The preferred imaging procedure is magnetic resonance imaging (MRI) with Gd

and fat saturation.

• Better at defining disease extent.

• Allows sequential follow-up of patient without increasing cumulative radiation dose.

• Fat saturation imaging is helpful in evaluating subtle lesions.

• MRI is the best method of revealing the

thick low signal dermis-like wall covering

the mass.

• May see chemical shift artifact on T2 at the

fat–fluid interface.

• Shows up as a bright band on one side

and a dark band on the other side of a

fat–soft tissue interface.

• In Figure 14-1, B, the bright line is more

conspicuous than the dark line.

• T1-weighted images are typically hyperintense (due to cholesterol components).

• T1 Gd typically exhibits a thin enhancing


• T2 signal varies from hypo to hyperintense.2


Computed Tomography Features

• Computed tomography (CT) is less preferred but may be the first imaging study


• Radiation to the orbit is undesirable.

• No calcification of fluid-fluid levels are


• Occasionally calcifications may be present,

which are better demonstrated by CT.

• Occasionally teeth, hair tufts, and fat-fluid

levels may be apparent.

• Only approximately 35% show typical fat

density on CT.

• Approximately 40% appear cystic on CT.1

• Extraconal mass with adjacent bone thinning or notching should raise the possibility

of dermoids, especially if rim calcification is





• Patients with posterior orbital dermoids

may present with prominent proptosis and

globe displacement.

• Dermoids may become symptomatic in

adulthood and exhibit considerable growth

over a single year.

• Some suggest these lesions may be dormant

for many years with episodic growth.

• Most orbital dermoids are clinically apparent anterior orbital dermoids, which are not

usually a problem in diagnosis or treatment.

• Neurologic findings:

• ON compression may affect visual acuity,

color vision, brightness perception, and

pupillary reaction.3

14  Posterior Orbital Dermoids

• May produce diplopia by physical restriction of globe movement or compression

of cranial nerves III, IV, or VI.3

Natural History

• Morbidity usually cosmetic.

• Occasionally may result in visual loss, diplopia or orbital inflammation.

• No sex or racial predilection.4

• Dermoids are most often noted in young


• May appear or grow at any age.


• Dermoids occur as a developmental anomaly with embryonic ectoderm trapped within

the closing neural tube between the fifth

and sixth gestational weeks.

• Dermoids occur in a spectrum between

epidermoid cysts and teratomas.

• Epidermoid cysts contain only desquamated squamous epithelium.

• Teratomas contain tissue from all three

embryonic layers.2


• Superficial dermoid cysts are easily removed with few complications.

• Deep dermoids should be removed after

careful planning to prevent long term


• Total removal is mandatory to prevent

recurrence or fistula.6

• Minimally invasive percutaneous drainage

and ablation appears promising for large

orbital dermoids as an alternative to extensive surgery.7

• Requires collaboration of ophthalmologist and interventional radiologist.8



• A dermoid cyst is a cystic teratoma containing developmentally mature solid tissues including skin, hair follicles and sweat glands.

• Covered by a thick dermis-like wall.

• Commonly contained components include:

hair, blood, fat, bone, nails, teeth, eyes,

cartilage, sebum, and thyroid tissue.

• Grows slowly with mature tissue and is

usually benign.


• Rarely, a malignant dermoid:

• In an adult develops into squamous cell

carcinoma (SCC).

• In a child may develop into an endodermal sinus tumor.

Gross Pathology

• Commonly contain considerable cholesterol.

• External layer may be very thin.

• Lined by epithelial cells, which are stratified and produce keratin.

• Contain blood vessels, fat, collagen, sebaceous glands, and hair follicles.

• Internal fluid varies from tan, oily “motor

oil” to yellow or white “cottage cheese” or

a relatively solid mass.

• Commonly inflamed and may contain free


Microscopic Pathology

• Cyst wall lined by keratinizing squamous


• Hallmark is the presence of cell wall pilosebaceous structures.


1. Orbital Cavernous Hemangioma

• A posterior orbital dermoid (POD) may be

remarkably similar to a retrobulbar intraconal cavernous hemangioma, except:

• Dermoids have a high T1 signal, while

cavernous hemangioma is isointense on


• Orbital dermoids have a capsule that typically exhibits a thin enhancing rim.1

• Cavernous hemangiomas have a dark hemosiderin rim with “blooming” artifact

on MRI.

• Orbital cavernous hemangioma exhibits

avid T1 Gd heterogeneous enhancement

with a “mulberry” pattern.

• The chemical shift artifact may be seen in

both dermoids and hemangioma.

2. Orbital Lipoma

• Orbital lipomas are extremely rare accounting for less than 1% of orbital tumors.

• May be difficult to differentiate orbital

lipoma from orbital dermoid.10,11

• True primary orbital lipomas are as uncommon as lipomas elsewhere are common.11


PART II  Benign Tumors

• Heterogeneous low density masses on CT

with attenuation values similar to fat.

• May contain slender, subtle septa.

• High T1 similar to orbital fat. Low T1

signal with fat suppression.

• T2 signal in orbital lipomas may be indistinguishable from collection of orbital


• Enhancement pattern varies with histology

(e.g., angiolipomas, etc.).11

• Both dermoids and orbital lipomas are


3. Ruptured Dermoids

• May mimic orbital cellulitis, metastatic

carcinoma, and rhabdomyosarcoma in



Fast Facts

•Approximately 50% of head and neck

dermoids are in or adjacent to the


• Comprise 2% of orbital tumors.12

• Make up 46% of consecutive orbital biopsies in patients aged under 18 years.13,14

• 10% of head and neck dermoids are


• More than 90% of deep dermoids are


• Only approximately 35% show typical fat

density on CT.15

• Approximately 40% appear cystic on CT.1




1. Nugent RA, Lapointe JS, Rootman J, et al: Orbital dermoids: features on CT, Radiology 165(2):475–478, 1987.

2. Weerakkody Y, Dawes DL, et al: Intracranial dermoid cyst

(website), 9 October 2013. http://radiopaedia.org/articles/

intracranial-dermoid-cyst-1. Accessed 29 December 2013.

3. Cooper T, Hampton, R: Orbital dermoid: treatment

& management, Orbital Dermoid, emedicine.medscape.

com/article/1212740. Publication updated 29 May

2012. Accessed 29 December 2013.

4. Chawda SJ, Moseley IF: Computed tomography of

orbital dermoids: a 20-year review, Clin Radiol

54(12):821–825, 1999.

5. Moin M, Din IU, Nazeer A: Ocular and periocular

dermoid cysts: a clinico-pathological study. E:/Biomedica/Biomedica/Vol.s1, Jul.-Dec. 2005/Bio-14 (A)

p 113-116. Accessed 29 December 2013.

6. Sherman RP, Rootman J, Lapointe JS: Orbital dermoids:

clinical presentation and management, Br J Opththalmol

68(9):642–652, 1984.

7. Golden RP, Shields WE 2nd, Cahill KV, et al: Percutaneous drainage and ablation of orbital dermoid cysts,

J AAPOS 11(5):438–442, 2007.

8. Cavazza S, Laffi GL, Lodi L, et al: Orbital dermoid cyst

of childhood: clinical pathologic findings, classification

and management, Int Ophthalmol 31(2):93–97, 2011.

9. Shields JA, Kaden IH, Eagle RC Jr, et al: Orbital

dermoid cysts: clinicopathologic correlations, classification, and management. The 1997 Josephine E. Schueler

Lecture, Ophthal Plast Reconstr Surg 13(4):265–276, 1997.

10. Shah NB, Chang WY, White VA, et al: Orbital lipoma:

2 cases and review of literature, Ophthal Plast Reconstr

Surg 23(3):202–205, 2007.

11. Garrity JA, Henderson JW, Cameron JD: Henderson’s

Orbital Tumors, Philadelphia, 2007, Lippincott,

Williams & Wilkins, p 132.

12. Shields JA, Shields CL, Scartozzi R: Survey of 1264

patients with orbital tumors and simulating lesions: the

2002 Montgomery Lecture, part 1, Ophthalmology

111(5):997–1008, 2004.

13. Shields JA, Bakewell B, Augsburger JJ, et al: Classification and incidence of space-occupying lesions of the

orbit. A survey of 645 biopsies, Arch Ophthalmol

102(11):1606–1611, 1984.

14. Shields JA, Bakewell B, Augsburger JJ, et al: Space-

occupying orbital masses in children. A review of 250

consecutive biopsies, Ophthalmology 93(3):379–384, 1986.

15. Nugent RA, Lapointe JS, Rootman J, et al: Orbital dermoids: features on CT, Radiology 165(2):475–478, 1987.


FIGURE 14-1  ​n  A, Axial T1 MRI images showing a retrobulbar intraconal mass on the left with prominent hyperintensity relative to the vitreous humor. Exopthalmos is evident with a mass displacing the ON and the extraocular

muscles. B, Axial T2 image shows heterogeneous hyperintensity, which is less bright than the vitreous humor.

Obvious exopthalmos is evident OS. All images demonstrate the presence of a peripheral low signal capsule. A

bright band is visible near the mid portion of the mass from a chemical shift artifact. C, Sagittal T1 image shows

cephalic deviation of the ON over a well-circumscribed hyperintense mass.


Orbital Lipoma


• Definition: Orbital lipomas (OL) are very

rare tumors that are usually benign,

accounting for less than 1% of orbital


• Classic clue: The patient presents with a

well-circumscribed homogeneous orbital

mass with low attenuation approximating

orbital fat, having no calcifications or

fluid-fluid level suggestive of a dermoid or


• True primary OLs are as uncommon as

extraorbital lipomas are common.1

• While usually having a benign course, an

OL has been reported to cause blindness

in a patient with an intracanalicular



Computed Tomography Features

• Computed tomography (CT) is the less

preferred imaging option but may be the

first study performed, particularly if the

lesion is an incidental finding.

• Orbital radiation is undesirable.

• Lesions show characteristic low attenuation

masses with values of Hounsfield units

similar to normal fat.

• Lesions are usually conspicuous unless they

are adjacent to normal intraorbital fat.

• May demonstrate delicate spiderlike thin

internal septations.

• No raised calcium or fluid-fluid levels are


Magnetic Resonance Imaging


• Preferred imaging procedure with Gd and

fat sat.

• Better at defining disease extent.

• Allows sequential follow-up without increasing patient’s cumulative radiation dose.

• OL has high magnetic resonance imaging

(MRI) T1 signal similar to orbital fat. Low

T1 MRI signal with fatsuppression.

• T2 signal in OL may be inseparable from

adjacent orbital hemorrhage.1

• Usually nonenhancing with Gd but may

have heterogeneity and enhancement if

other tissue elements are present.



• Usually present as painless, slowly enlarging

orbital mass probably producing proptosis.

• May or may not cause diplopia.

• Progressive, painless unilateral blindness

from optic atrophy reported in an exceptionally infrequent intracanalicular lipoma.2


• OLs comprise less than 1% of orbital tumors.

• Reported incidence varies from 0% to 9%

of orbital tumors based on histopathology

reporting criteria.

• Some feel the incidence is closer to 0%

when strict criteria are followed.3

• For the purposes of this book chapter, these

authors accept OLs as composing less than

1% of orbital tumors.


• Surgical resection is usually curative.

• There has been one reported case of blindness from ON compression by an intracanalicular lipoma.2

• Vascularity may be problematic for the surgeon if the capsule is opened at orbitotomy.1


Gross Pathology

• Well circumscribed, yellowish white or




PART II  Benign Tumors

• Less yellow than normal fat.

• Less lobulated in orbit than in extraorbital


• Slight encapsulation.4

Microscopic Pathology

• Contains mature adipocytes somewhat

larger than those found in ordinary fat.1,5

• In OL, the flimsy intraseptal vascular

network may be less apparent than in extraorbital lipomas.1,5

• COTs are usually multilocular with multiple fat-fluid levels.

• COTs have a conspicuous collection of

cystic and solid components.

• Displacement of the globe and the extraorbital muscles may impair ocular motility.

• Compression of the ON may result in

visual impairment.

• Rupture may provoke a severe inflammatory reaction.


Fast Facts


1. Orbital Dermoids (OD)

• ODs are usually unilocular with single fatfluid level.

• ODs have a mildly heterogeneous internal


• ODs have a capsule and typically exhibit a

thin enhancing rim.

• Chemical shift artifacts may be seen in

lipoma, OD and in teratoma.

2. Congenital Orbital Teratoma (COT)

• COTs are characteristically massive causing

severe proptosis with facial and eyelid

deformity, often enlarging the orbit 2 to

3 times.6

• COTs are encapsulated tumors with components resembling more than one germ layer.

• Although the tissues may be normal themselves, they may be quite different from

surrounding structures.

• A COT may contain a variety of tissues

such as hair, teeth, and bone.7,8



• Lipomas comprise less than 1% of orbital



1. Garrity JA, Henderson JW, Cameron JD: Henderson’s

Orbital Tumors, ed 4, Philadelphia, 2007, Lippincott

Williams & Wilkins, pp 132–135.

2. Sabates NR, Farris BK, Stratemeier PH: Intracanalicular

lipoma, J Clin Neuroophthalmol 10(2):88–91, 1990.

3. Rootman J: Diseases of the Orbit: A Multidisciplinary

Approach, ed 2, Philadelphia, 2003, Lippincott Williams

& Wilkins, p 270.

4. Shah NB, Chang WY, White VA, et al: Orbital lipoma:

2 cases and review of literature, Ophthal Plast Reconstr

Surg 23(3):202–205, 2007.

5. Goldblum JR, Weiss SW, editors: Enzinger and Weiss’s

Soft Tissue Tumors: Expert Consult, ed 2, St Louis, 1988,

Mosby Elsevier.

6. Kapoor V, Flom L, Fitz CR: Oropharyngeal fetus in

fetu, Pediatr Radiol 34(6):488–491, 2004.

7. Chi JG, Lee YS, Park YS, et al: Fetus-in-fetu: report of

a case, Am J Clin Pathol 82(1):115–119, 1984.

8. Sergi C, Ehemann V, Beedgen B, et al: Huge fetal sacrococcygeal teratoma with a completely formed eye and

intratumoral DNA ploidy heterogeneity, Pediatr Dev Pat

2(1):50–57, 1999.


FIGURE 15-1  ​n  ​A, Axial nonenhanced CT through level of globes reveals the presence of a low attenuation mass

anterior to the left globe. Attenuation is similar to that of subcutaneous and intraorbital fat. B, Coronal CT shows

a low attenuation mass extending just above the globe anterior to the frontal bone. C, Coned axial CT through

the level of the frontal sinus demonstrates a well-circumscribed, probably encapsulated, low attenuation mass

with homogeneous internal density and no calcifications.


Orbital Schwannoma


• Definition: Usually found in middleaged adults, orbital schwannomas (OS)

are well-defined, encapsulated, slowly

growing benign tumors arising from

peripheral nerve Schwann cells, and

comprise 1% to 2% of orbital tumors.1-3

• Classic clue: Middle-aged patient

presenting with optic neuropathy,

proptosis, or diplopia with a wellcircumscribed retrobulbar intraorbital mass

separate from the optic nerve (ON) which

on dynamic magnetic resonance imaging

(MRI) shows enhancement progressing

from the lesion’s periphery to its center.

• OSs are rarely seen in children.

• Because of their occasional occurrence

and scarce unique signs, the preoperative

diagnosis of OS is somewhat difficult.3


General Imaging Features

• Well-circumscribed, encapsulated mass.

• The specific shape of an OS is probably not

helpful in an individual case. OSs may

occur in several shapes (in decreasing

frequency): cone, dumbbell, oval, round,

polylobular, fusiform, sausage, and irregular shapes.3

• Orbital locations included superior, medial

superior, orbital apex, lateral, lateral inferior, and medial, but not lateral superior in

one series of 62 cases.3

Magnetic Resonance Imaging


• The MRI appearance of OSs varies with


• This probably varies with the mix of

Antoni-A and Antoni-B cells.

• T1 is generally described as low (and is

relatively nonspecific showing isointensity

with small patches of hypointensity).3,10-14

• T2 is generally described as high.3,10-14

• T1 Gd enhancement patterns correlate

with T2 patterns.

• T1 Gd enhancement can cause three

general patterns:

• Heterogeneous enhancement in approximately half of cases.6,15

• Homogeneous enhancement in approximately one-quarter of cases.6,12-14

• Ring enhancement pattern in approximately one-quarter of cases.

• Ring enhancement may occur as a ring

around the periphery of the tumor or

as smaller rings inside the tumor (see

Figure 16-1, E and F).

• On dynamic MRI some investigators

reported “progressive” enhancement of an

OS, which begins peripherally and progresses to the center.16

• Other investigators reported no “progressive” enhancement pattern in OS.1

• The difference between these two studies

may be related to technique, as the imaging of the reported cases of progressive

enhancement is quite convincing. When

present this “progressive” enhancement

can be very dramatic.16

• OS may undergo central necrosis and be

confused with a cystic orbital tumor.5

Computed Tomography Features

• Most OSs show mild enhancement on contrasted CT (see Figure 16-1, D).4

• Enlargement of the superior orbital fissure

or invasion of the cavernous sinus may be


• See General Imaging Features earlier.



• Primarily a disease of adults, showing noninvasive insidious onset and slow growth.



PART II  Benign Tumors

• Presentation ranges from optic neuropathy,

proptosis, diplopia, anterior orbital mass

and sinusitis.4


• OS generally occurs as an isolated tumor.

• In 2% to 18% of cases it is associated with

neurofibromatosis (NF).5

Treatment and Prognosis

• Total excision is indicated as the definitive

therapy to prevent recurrence, and to avoid

the rare possibility of malignant transformation.4,5

• Late recurrence with malignant transformation generally occurs primarily in the

presence of NF in an incompletely excised

benign OS.5

• Long-term follow-up is suggested.


• OS is typically a benign, encapsulated, noninvasive tumor.4

• OS is a rare orbital or periorbital tumor

with variable anatomic and histologic


• Half of OSs are located in the superior or

medial superior orbit. Most arise from the

supratrochlear or supraorbital branch of

the trigeminal nerve.3,6

• Other involved nerves include the superior

division of III, VI, infraorbital, and superior

divisions of the ophthalmic nerves.4

• Histology is variable but includes Antoni

type A and B patterns, tumor capsule,

perivascular lymphocytic cuffing, thick hyalinized vessel walls, Schwann cells with

Verocay bodies, loose collagenous stroma,

and nuclear pleomorphism.4


Orbital Cavernous Hemangioma

(OCH; also known as Ocular

Cavernous Hemangioma)

• Conventional MRI imaging can usually distinguish between the top pathologic orbital

masses but does less well in distinguishing

between OCH and OS.

• Some feel that OCH can be differentiated

from OS by the MRI contrast enhancement

spreading pattern on dynamic MRI.16

• On dynamic MRI some investigators report

that OCH enhancement starts centrally

and progresses to the periphery. Enhancement of OS begins peripherally and progresses to the center.16

• Other investigators report a “progressive”

pattern of enhancement in OCH and no

progressive enhancement pattern in OS.1

• While differentiation between OCH and

OS is not critical, it may be beneficial

to avoid biopsy, surgery, or radiation


• If you are not lucky enough to have dynamic MRI images, you can also look for

the following:

• OCH T1 isointense, T2 hyperintense.

• OCH shows avid enhancement with

T1 1 Gd showing a “mulberry” pattern.

Not a feature of OS.

• OCH exhibits a “blooming” artifact,

which is not a feature of OS.

• OCH has a characteristic low signal

pseudocapsule on T2, which is not a

feature of OS.

• OCH resembles cavernous malformations of the brain and spinal cord, which

are not a feature of OS.

• See Chapter 11: Orbital Cavernous Hemangioma.

Optic Nerve Glioma (ONG)

• ONG shows fusiform “sausage-shaped” enlargement of the ON.

• ONG may enlarge the optic canal.

• ONG has a classic imaging appearance:

• Tubular/fusiform enhancing ON mass

kinking/buckling the ON. Not a feature

of OS.

• In ONG T1 is isointense to hypointense.

• ONG has variable T2, typically hyperintense.

• ONG has a low peripheral signal that

corresponds to the dura.

• ONG T1 1 Gd shows variable enhancement.

• The ON cannot be identified as discrete

from an ONG. An OS often shows a

normal but deviated or compressed ON,

which is displaced by the OS.

• See Chapter 12: Optic Nerve Glioma.

Optic Nerve Meningioma (ONM)

• In ONM a high attenuation mass surrounds

the ON. OS may involve any other intraorbital nerve and the ON may be displaced,

stretched or compressed but is usually intact.

16  Orbital Schwannoma

• ONM typically shows “tram tracking” from

calcification or tumor enhancement. OSs

do not exhibit “tram tracking.”

• ONM can cause optic canal enlargement

or erosion and/or hyperostosis of the sphenoid bone. These are not features of OS.

• In ONM, the cerebrospinal fluid (CSF) in

the dilated subarachnoid space causes characteristic perioptic cysts, best demonstrated

on T2-weighted image (or inversion recovery). These are not a feature of OS.

• See Chapter 13: Optic Nerve Meningioma.

Orbital Lymphoma

• Orbital Lymphoma has homogeneous CT

attenuation. OS has heterogeneous CT


• Orbital lymphoma shows the lowest

restricted diffusion of orbital tumors with

the “black hole ADC sign.” Restricted diffusion is not a feature of OS.

• OS can show characteristic “progressive”

dynamic enhancement from the periphery.

Progressive dynamic contrast enhancement

is not a feature of orbital lymphoma.

• Orbital lymphoma is the most common

orbital malignancy encountered by adults.4

OS is a rare orbital or periorbital tumor.

• Orbital lymphoma is unencapsulated with

indistinct margins sparing little in its path

(“Sherman sign”). OS is encapsulated with

sharp margins and comes in many common

shapes: Cone, oval, dumbbell, round, fusiform, and sausage, among others.

• Orbital lymphoma can cause infiltration of

retrobulbar fat with “dirty fat” appearance

on CT. This is not a feature of OS.

• Orbital lymphoma may be bilateral with

systemic disease. This is not a feature

of OS.

• Orbital lymphoma may cause bony destruction. This is not a feature of OS.

Tumefactive Orbital Pseudotumor

• Idiopathic orbital inflammatory disease.

• It is the most frequent cause of an intraorbital mass in adults.


• It is the underlying cause of unilateral exopthalmos in 25% of patients.

• Between 5% and 15% of cases of orbital

pseudotumor occur in children.

• It may cause sudden onset of unilateral

painful proptosis in an otherwise healthy


• It may cause abnormal enhancement of

retrobulbar fat. This is not a feature of OS.

• May exhibit dramatic rapid and lasting

steroid response.17

Extraocular Orbital Metastasis


• Metastasis to the orbit may be intraocular

(uveal metastasis) or extraocular.

• Extraocular metastasis could be confused

with OS.

• EOOM is uncommon accounting for

between 2% and 11% of orbital neoplasms

and is significantly less common than uveal

metastasis by a factor of 8 to 1.18,19,20

• EOOM is more frequently seen in the

superior lateral extraconal quadrant. This

location is infrequent in OS, and was not

seen at all in one study of 62 cases.3

• EOOM has a variable imaging appearance

but usually shows a soft tissue extraconal


• Morphology varies from well-defined oval

to infiltrating lesions.21 This group of

well-defined oval lesions could be confused with OS.

• EOOMs usually enhance and finding other

foci of metastasis is frequently helpful in

making a diagnosis.

• Uveal metastases are bilateral in approximately 25% of cases.5

• EOOMs are usually unilateral (except for



Fast Facts

• OS comprises 1% to 2% of all orbital


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