Orbital Lesions Part 1
Part 1 of my review of the orbit for radiology board exams. After all episodes on the orbit are posted, check out the free downloadable study guide by clicking here.
Show Notes/Study Guide:
What cranial nerves pass through the superior orbital fissure?
Cranial nerves 3, 4, V1 (ophthalmic) branch of the trigeminal nerve, and 6 pass through the superior orbital fissure. Superior orbital fissure syndrome is dysfunction of these nerves that occurs due to something like trauma, tumor, or inflammation interrupting the function of these cranial nerves.
What cranial nerves pass through the inferior orbital fissure?
This is somewhat of a trick question as there is only one: the V2 (maxillary) branch of the trigeminal nerve. To be more specific, the maxillary branch of the trigeminal nerve gives off the zygomatic nerve, infra-orbital nerve, and orbital branches of the pterygopalatine ganglion that pass through the inferior orbital fissure.
What types of Le Fort fractures involve the orbit?
Le Fort Types 2 and 3 involve the orbit.
Le Fort Type 1: Palate dislocation with transverse fracture involving the lower nasal septum, pterygoid plates and maxillary sinuses.
Le Fort Type 2: Maxillofacial dislocation with oblique fracture involving the inferior orbital rim/orbital floor, nasal bridge and zygomaticomaxillary suture.
Le Fort Type 3: Craniofacial dislocation with fracture through lateral and medial orbital walls, nasofrontal suture, and zygomatic arch.
Note that all Le Fort fractures classically involve the pterygoid plate so if there is no pterygoid plate fracture, there is no Le Fort fracture.
What is a coloboma?
A coloboma is focal discontinuity of the orbital globe (usually posterior aspect of the globe) resulting from failure of the choroid fissure to close. If bilateral colobomas are present need to think of CHARGE syndrome where the C in CHARGE is for Coloboma, H=heart defects, A=atresia choanal, R=retardation developmental, G=genital hypoplasia, E=ear abnormalities. “Starts with eyes and ends with ears”.
What entity presents with painful inflammation of the extraocular muscles, involving the myotendinous insertions, most commonly of the lateral rectus muscle?
Orbital pseudotumor which results from idiopathic inflammation of the extraocular muscles. Unlike Grave’s the myotendinous insertions are involved. Steroid treatment leads to improvement.
If findings of orbital pseudotumor are present and also involve the cavernous sinus, what is this disease entity called?
Tolosa Hunt syndrome. This is a painful ophthalmoplegia that involves the orbital apex and adjacent cavernous sinus. Steroid treatment leads to improvement.
What is the most common benign congenital mass of the orbit?
A dermoid of the orbit is the most common benign congenital orbital mass. These typically involve the superolateral aspect of the orbit and contain internal fat density.
What is the most common malignant orbital mass in a child?
Metastatic retinoblastoma to the orbit. Remember with retinoblastoma that there is a problem with the chromosome 13 retinoblastoma suppressor gene that is also associated with osteosarcoma. This means there is an association with facial osteosarcoma following radiation therapy for orbital retinoblastoma. About 1/3 will have bilateral retinoblastomas of the orbit. If you see calcification in the globe of a child this is classic for orbital retinoblastoma.
What is so called trilateral retinoblastoma?
Retinoblastoma involving both orbits as well as the pineal gland.
What is so called quadrilateral retinoblastoma?
Retinoblastoma involving both orbits as well as the pineal gland and suprasellar region.
What is the most common intra-ocular metastatic lesion in an adult?
Metastatic melanoma which often appears as an enhancing soft tissue mass in the posterior globe.
What are some key differences between an orbital lymphangioma and an orbital venous varix?
Orbital lymphangioma: Contains malformed veins and lymphatics together. Does not increase in size with Valsalva. Can show fluid-fluid levels, multiloculated cystic components, and trans-spatial involvement throughout orbit.
Orbital venous varix: Contains veins with weakened walls and lack of functional valves, therefore distends (sometimes massively) with Valsalva. Look for provided history of proptosis or diplopia upon straining or positional changes. May look normal on imaging without Valsalva and very abnormal upon Valsalva so provocative maneuvers can be key for imaging diagnosis with ultrasound, CT or MRI. A top cause of spontaneous orbital hemorrhage. Can also have painful thrombosis.
What orbital mass is associated with chlamydia psittaci (bird fever)?
Orbital lymphoma which classically is associated with the lacrimal gland and conjunctiva (aka ocular adnexa). Look for a homogeneously enhancing mass with restricted diffusion on MRI.
What is the most common vascular orbital lesion in adults?
Orbital cavernous venous malformation aka cavernous hemangioma. These have weak arterial supply and therefore often show slow initial and delayed, incomplete enhancement. On imaging look for a well-circumscribed lesion that has slow and incomplete internal enhancement with delayed washout, most commonly located in the lateral intraconal compartment, sparing the orbital apex.
True or False: Post-septal orbital infections usually originate from the face.
False. Post-septal orbital infections usually originate from the paranasal sinuses. Pre-septal orbital infections usually originate from the facial tissues.
Note that an orbital subperiosteal abscess often results from ethmoid sinusitis.
What is dacrocystitis?
Dacrocystitis is inflammation of the lacrimal sac. On imaging, look for a rim-enhancing lesion in the lacrimal fossa. Dacrocystitis-induced dilation of the lacrimal sac can cause obstruction and predisposes to staph and strep infections.
