Tumours Of The Orbit

Question 1

What do they need to know for tumours of the orbit?

Answer 1

1. Distribution of pathology
2. Possible diagnosis based on imaging
3. Relationship to normal structures - ON
4. Definition of bony anatomy - ON
5. Definition of bony anatomy

Question 2

When may MR be useful?

Answer 2

Looking for intracranial disease spread - direct or distant peripheral better definition of pathology and relationship to/arising from ON vascular masses

Question 3

What are neoplasms?

Answer 3

Arise from optic nerve sheath complex which consist of nerve, a white matter tract and surrounding sheath which is an extension of dura

Question 4

What are optic nerve sheath complex?

Answer 4

1. Meningioma

2. Glioma

Question 5

What is conal/intraconal?

Answer 5

1. Inside the muscle cone
2. A lot of pathology can straddle different compartments
3. Lymphoma
4. Peripheral nerve sheath tumour
5. Melanoma

Question 6

What are examples of extraconal?

Answer 6

1. Lacrimal
2. Peripheral nerve sheath tumour
3. Rhabdomysarcoma
4. Haemangiopericytoma
5. Metastasis

Question 7

What is ON glioma 1?

Answer 7

1. Tumour arising from the optic nerve
2. Most common one is optic nerve glioma
3. Optic nerve glioma is often seen in children
4. Childhood form is usually a low grade - non aggressive aplastic astrocytoma

Question 8

What is ON glioma 1?

Answer 8

1. 60% of all primary ON tumours
2. 4% of all orbital tumours
3. Peak age 2-8 years
4. Strong association with NF1 - 25%
5. If bilateral then pathgnomic of NF1
6. 2 distinct forms - childhood and adult
7. Childhood form - more common; may follow indolent course - even spontaneous regression
8. Histologically similar time pilocytic astrocytoma

Question 9

What is ON glioma imaging?

Answer 9

1. NF1 May see other intracranial lesions - cerebellum, basal ganglia
2. Spectrum - thickening of ON due to arachnoid hyperplasia through to fusiform or globular mass
3. Cystic change common
4. Optical canal widening
5. MR - T1 is oi tends to brain; T2 hyper intense
6. Variable enhancement - often less than ONSM

Question 10

What is radiological differential of ON glioma?

Answer 10

1. ONS meningioma
2. Schwannoma
3. Lymphoma
4. Metastasis
5. Optic neuritis
6. Infectious/granulonateous neuritis
7. Idiopathic orbital inflammation

Question 11

What is ON sheath meningioma?

Answer 11

1. 10-33% of orbital tumours
2. Meningothelial cells of arachnoid or extension from intracranial lesion
3. Occasionally - ectopic arachnoid cells in muscle cone or orbital wall
4. Clinical triad - progressive visual loss, optic atrophy and opticociliary shing vessels
5. Middle aged females
6. Express female hormone receptors
7. Childhood form more aggressive and associated with NFII
8. Bilateral tumours may/may not be associated with NF

Question 12

What do patient notice subtle changes in their vision with?

Answer 12

1. Menstruation

2. Pregnant

Question 13

What shouldn’t you put patients with meningioma on?

Answer 13

Hormone replacement therapy

Question 14

What can meningioma be associated with?

Answer 14

Neurofibromatosis type 2

Question 15

What are the shape of tumours?

Answer 15

Variable shape

Long and tubular centric

Question 16

What is exposure ceroscopy?

Answer 16

When the globe comes forward you cannot close your eyelids

You can get problems with lubrications of the globe

Question 17

What is meningioma?

Answer 17

Low grade - slow growing

Question 18

What is ON sheath meningioma:imaging?

Answer 18

1. CT - sheath calcification almost pathognomic
2. Variable shape - tubular, fusiform or globoid
3. enhancement avid
4. Encased ON attenuated/ atrophic
5. Pneumosinus dilitans
6. Hyperostosis of anterior clinoid process; optic canal narrow or widened
7. Anterior capping cyst
8. MR - often Isointense to brain on T1 and T2; May be T1 hypointense and T2 hyper intense

Question 19

What is ON sheath meningioma radiological differential?

Answer 19

1. Glioma
2. Cavernous haemangioma
3. Schwannoma
4. Haemangiopericytoma/solitary fibrous tumour
5. Lymphoma
6. Metastases
7. Idiopathic orbital inflammation
8. Optic neuritis
9. Sarcoidosis

Question 20

What is Lymphoma?

Answer 20

Insidious presentation - painless propria is and decreased motility (not greatly impaired due to small amount of collagen)

Age 50-70 years - rare in children

Predilection for lacrimal gland - smooth superotemporal palpable pink mass

Superior/anterior orbit, conjunctiva and eyelids frequently involved

75% unilateral -bilateral older age group

Question 21

What are patterns of involvement for lymphoma ?

Answer 21

1. Anterior preseptal/postseptal and superior involvement
2. Lacrimal gland - orbital + often palpebral components; bony remodelling; bulkier than IOI
3. Retrobulbar involvement; well circumscribed mass or infiltrative replacing fat; moulds around existing orbital structures - no identation of globe regardless of size
4. Extension of lymphomarous lesions e.g. from sinonasal cavity

Question 22

What does lymphoma mass affect?

Answer 22

Inferior rectus

Question 23

What is lymphoma ?

Answer 23

A cellular tumour - it enhances a lot

Question 24

What is lymphoma imaging?

Answer 24

1. 75% homogenous on CT
2. Bone destruction rare
3. Infiltration and thickening of muscles less common than in idiopathic orbital inflammation
4. MR: isointense to muscle on T1; T2 signal variable
   - hyperintense to fat and isointense to brain (IOI isointense to fat on T2)
5. Enhancement less than IOI

Question 25

What is radiological differential?

Answer 25

1. Reactive lymphoid hyperplasia 2. Metastases 3. Inflammatory - idiopathic, sarcoid, Wegner 4. Infection 5. Unusual

Question 26

What is Leukaemia?

Answer 26

1. Orbital involvement - part of systemic disease 2. In children mainly with AML and adults CLL 3. Imaging: intraocular and orbital haemorrhage- low platelet 4. Leukaemic infiltration of uvea, choroid, Regina and ON 5. Infiltration of soft tissues; mass like or diffuse, usually fat 6. AML - granulocytic sarcoma (chloroma) with bone destruction 7. AML in absence of peripheral blood involvement; either lateral wall extending to temporal fossa or medial to anterior cranial fossa - presents at approximately age 7

Question 27

What are lacrimal tumours?

Answer 27

1. Lacrimal lesions - epithelial - mainly neoplastic - 40-50% of lacrimal masses - non epithelial - congenital / inflammatory and some neoplasms (lymphoma) 2. Most common lacrimal tumours - benign mixed pleomorphic Adenoma and adenocystic Carcinoma

Question 28

What is lacrimal tumours: adenocystic carcinoma ?

Answer 28

1. 2nd most common epithelial lacrimal tumour (29%) 2. 4.8% of primary orbital neoplasms 3. Younger age 4th decade 4. Better prognosis in young patients than adults 5. Firm hard mass; rapid growth, Peru neural and vascular invasion 6. Rounded configuration distorting globe and orbitals content 7. Involvement of surrounding bone 8. Calcification more common

Question 29

What is peripheral nerve tumours?

Answer 29

1. PNT - 4% of orbital tumours 2. 2% plexiform neurofibromas, 1% isolated neurofibromas, 1% schwannoma 3. Sensory neves > motor 4. Slowly progressive proptosis & pain; ocular motility preserves 5. Malignant transformation is rare - more common in neurofibromas

Question 30

What is plexiform?

Answer 30

Pathognomonic of NF with orbital involvement

Question 31

What is neurofibromas?

Answer 31

Infancy/childhood - initially eyelid mass localised to lateral 1/3 Adolescences spread to forehead, temple and orbit Diffuse: similar to plexiform, less likely to be associated with NF Circumscribed: slow growing, more common in superior quadrant Presents 3rd-5th decade

Question 32

What is imaging of neurofibromas?

Answer 32

1. Childhood forms associated with orbital enlargement 2. Look for features on NF with plexiform types-sphenoid wing dysplasia, enlarged glove 3. Infiltrative appearance involving soft tissues heterogenous hypointense T1 and hyper intense T2 signal 4. variable enhancement; may be avid as vascular

Question 33

What are schwannomas?

Answer 33

1. Schwannoma clinically indistinguishable from circumscribed neurofibromas 2. Arise from sensory nerves 3. Located near orbital apex 4. Solitary neurofibromas/ schwannomas - well circumscribed oval/ fusiform mass 5. Isointense to muscle and brain on T1 6. Hyperintense on T2 7. Heterogenous enhancement

Question 34

What is solitary fibrous tumour?

Answer 34

1. Rare orbital vascular tumour 2. Arises from Pericytes of Zimmerman, around capillaries and post capillary venues 3. Histology varies from benign to malignant 4. Propensity for late recurrence - several decades 5. Age - infancy to elderly; most in early 40s 6. No gender predilection

Question 35

What is Rhabdomyosarcoma 1?

Answer 35

1. Most common soft tissue childhood malignancy (50% of soft tissue sarcoma) 2. Most common primary orbital childhood tumour - rare 3. Derived from undifferentiated mesenchyme of orbital soft tissue 4. Most present < 16 years; average age at diagnosis 7-8 years 5. May be present at birth 6. Rapid proptosis with globe displacement

Question 36

What is Rhabdomyosarcoma 2?

Answer 36

1. Unilateral and unifocal; anywhere in orbit, though most superior and medial 2. Epicentre mainly extraconal in 60%, intraconal in 40% both 47% 3. Chromosomal translocation between 2 & 13, and abnormality of Chr 11 4. Embryonal is most common type 5. Alveolar type is 2nd most common; older children inferior orbit, more aggressive