Skull II (Orbit)

Question 1

Anterior view of the orbit demonstrating

Answer 1

EOM
Superior orbital fissure
The content of the intraconal space

Question 2

Lateral view of orbit demostrating

Answer 2

Oculomotor nerve (CN III) with its inferior and superior divisions

Question 3

Imaging modalities of orbit

Answer 3

CT
MRI

Question 4

Indication of imaging and why?

Answer 4

Patients with exophthalmos:
To distinguish bt masses arising with in the orbit, or outside it and thyroid eye disease

Question 5

Ct scan of the orbit can show:

Answer 5

• Retro orbital fat
• medial and lateral rectus M
• Lens
• optic nerve

Question 6

Radiolographic features of retinoblastoma:

Answer 6

NB : infant with hx of leukocoria:
• Intraocular mass
• calcifications are common (90%)
• slight T1 hyperintensity and Low T2 signal
• Some degree of contrast enhancement
• Associated with other malignancies most common (osteosarcoma)

Question 7

The most common cause of diffuse optic nerve enlargement

Answer 7

Optic nerve glioma (especially in childhood)

Question 8

Modality of choice for optic nerve glioma

Answer 8

MRI

Question 9

Radiolographic features of optic nerve glioma

Answer 9

Fusiform enlargement of optic nerve
Contrast enhancement variable
Calcifications are rare

NB: coronal MRI can also show the optic nerve enlargement (so don’t be confused and focus on the arrows )

Question 10

Benign tumor in optic nerve
4th decade (80% female)
Have NF

Answer 10

Optic nerve meningioma
Arising from the arachnoid cap cells of the optic nerve sheath

Question 11

Radiolographic features of optic nerve meningioma

Answer 11

Mass surrounding the ON
Calcification is common
Intense contrast enhancement “tram track sign”

Question 12

Common causes of orbital infection

Answer 12

Spread from infected sinus (post-septal or orbital cellulitis)

trauma, dental disease (pre-septal or peri-orbital cellulitis)

Question 13

Signs or complications of post-septal infection:

Answer 13

• Sub periosteal infiltrate or abscess
• Stranding of retro-bulbar fat
• Lateral displacement of enlarged medial rectus muscle
• proptosis

Question 14

Sub-periosteal abscess usually presenting as

Answer 14

Fluid collection b/w the lateral rectus and the lamina papyracea

Question 15

Thyroid orbitopathy affection on the EOM

Answer 15

•Enlargement of EOM with sparing of the tendons
• Mucopolysaccharide deposition may result in relative low attentuation centers of the muscle involved
• muscular involvement follows the temporal pattern (IMSLO)

Question 16

Radiolographic features of thyroid orbitopathy:

Answer 16

NB : hx of bilateral painless proptosis

• Exophthalmos
• muscle involvement (enlarged with spared of tendon insertion)
• often bilateral asymmetrical

Question 17

Features of Orbital pseudotumor

Answer 17

• Infiltrating, intraconal, reto-orbital, non-granulomatous mass
• usually unilateral
• involvement of EOM with tendons
• painfull proptosis
• many of orbital structures may involved
• intense enhancement on T1+C
• low T1 signal
• patchily high T2 signal

Question 18

Blow-out fracture imaging is best to perform by:

Answer 18

Coronal CT reconstructions

Question 19

Blow out fracture on Coronal CT

Answer 19

• fracture of the orbital floor
• Crescentic soft tissue mass in the roof of the antrum, this should not be confused with mucosla thickening (hx of trauma)

Question 20

May find air-fluid level in the maxillary antrum in case of blow-out fracture

Answer 20

Tear drop