Orbital Lesions

Anatomic Considerations

The first thing you do when you see a lesion in the orbit, is to decide whether it is an ocular lesion or a non-ocular lesion, i.e. is it involving the globe or involving the structures outside the globe.If it is a non-ocular lesion, the next question is whether the lesion is located within the intraconal space, i.e. within the space bounded by the cone formed by the extraocular muscles, or whether it is located within the conal or extraconal space?Once you have decided where the lesion is located, consider the differential diagnostic possibilities .

Ocular space

The eye has the following well defined anatomic spaces:
Anterior chamber

When we move from anterior to posterior the first area is the anterior chamber. It is bounded by the cornea anteriorly and the lens and iris posteriorly.
Specific pathologies within the anterior chamber are:
Rupture of the globe
Hemorrhage: also known as anterior hyphema
Cataract
Keratitis: inflammation of the cornea
Periorbital cellulitis
Posterior chamber

This is a very small area posterior to the iris, which we cannot discern on imaging. Specific pathologies in this area are: glaucoma, uveitis and ciliary melanoma.

Vitreous body

The larger area posterior to the lens is the vitreous body.
Specific pathologies within the vitreous body are:
Rupture
Hemorrhage
CMV infection: especially in HIV
Persistent Hyperplastic Primary Vitreous (PHPV): primary vitreous failed to develop into secondary clear vitreous leading to blurred vision
Reinflation procedures for detachments leading to different densities within the vitreous body

The vitreous body is surrounded by the membranes of the retina, the choroid and the sclera.
Retina pathology:
Retinoblastoma: a common tumor in children
Hemangioblastoma: most common retinal tumor in the adult and associated with von Hippel Lindau disease
Detachment: most common retinal lesion mostly seen in diabetic retinopathy
Choroid pathology:
Melanoma: choroid contains the melanin cells
Metastases: choroid is the most vascular structure in the eye
Detachment: usually post-traumatic
Sclera pathology:
Infection: either due to sinusitis or viral
Pseudotumor
Detachment

The intraconal space is marked by arrows and is located within the muscle cone It contains the optic nerve, vessels and cranial nerves III, IV and VI.
Intraconal spaceThe ocular muscles within the orbit form a muscle-cone.These ocular muscles are connected via the annulus of Zin, which is a fibrous connective tissue sheet and together they form the conal space.It separates the intraconal from the extraconal space.Intra-orbital pathology which is non-ocular is either in the intraconal, conal or extraconal space.
Intraconal space pathology:
Venous vascular malformation
Capillary hemangioma
Optic nerve lesions
Optic neuritis
MS
Devic's syndrome
Neuritis due to infection (e.g.herpes zoster)
Autoimmune (e.g.Lupus)
Drugs (e.g.chloramphenicol, ethambutol)
Optic nerve glioma
Optic nerve meningioma
Pseudotumor
Venous dilatation
Carotid Cavernous Fistula
Varices
Schwannoma of 3rd, 4th and 6th cranial nerve
Conal space

The conal space is formed by the ocular muscles and an envelope of fascia.
Conal space pathology:
Thyroid eye disease; usually enlargement of the inferior and medial rectus
Pseudotumor: idiopathic orbital inflammation
Adjacent inflammation: sinusitis
Uncommon causes of enlargement of the extra-ocular muscles are glycogen storage disease and lymphoma.

Extraconal space

The extraconal space is the area outside the muscle cone.
Extraconal space pathology:
Abscess due to sinusitis
Schwannoma of the V1 and V2 branches of the trigeminal nerve
Bone lesions:
Fibrous dysplasia of the sphenoid wing
Metastases
Multiple myeloma
Diseases of the orbital appendages

Orbital appendages

The lacrimal gland is located superolaterally in the orbit.Diseases of the lacrimal gland can be divided into granulomatous, glandular and developmental (see Table).
Secretions go medially across the globe and are collected in the punctum and then go into the lacrimal sac.From the lacrimal sac secretions travel inferiorly to the nasal lacrimal duct, which drains under the inferior terminate into the nose.In children congenital obstructions of the valves in the lacrimal duct can lead to cystic areas medially in the orbit also known as dacryocystoceles.In adults obstruction is more often due to strictures from ethmoid sinusitis or stones blocking the nasolacrimal duct.This will result in epiphera or increased tearing.Drainage can be improved with balloon dilatation.

A)Ocular Pathology:

1)Calcification:

-In adult:

.Tendinous insertion of the ocular muscles.

.Optic nerve druzen(optic nerve head calcification).

-In childrencalcification means retino-blastoma untill proven otherwise even,if it is bilateral.

image of an adolescent with bilateral retinoblastoma.

2)Retinoblastoma:

-Tumors affecting children in the

first year of life

.Retinoblastoma:most common.

.Wilms tumor.

.Neuroblastoma.

.Leukaemia.

.Teratoma.

a 13 month old female with bilateral lesions as a result of bilateral retinoblastomaRetinoblastoma with calcification

3)Leukocoria

Usually, when a light shines through the iris, the retina appears red to the observer. In leukocoria (white pupil) the retina abnormally appears white. Retinablastoma is usually detected through leukocoria as it occurs in two third of patients with retinoblastoma. These children are usually too young to present with visual complaints. There are many causes of leukocoria as listed in the table on the right.

Causes of leukoria

.Retinoblastoma(most common)

.PHPV(second most common)

4)Melanoma
On the right images of an adult with an ocular mass.The most common intraocular lesion in an adult is melanoma (as in this case). Number two is metastases and others like hemangioma, leiomyoma and osteoma are uncommon.

Intraocular masses:

.Melanoma:is the most intraocular

mass in adult

.Then,metastases.

.Others like hemangioma,leiomyoma

and osteoma.

5)Persistent hyperplastic primary vitrous (PHPV)

This is persistent hyperplastic primary vitrous (PHPV). There is a persistent hyaloid canal when the hyaloid artery does not integrate. On the images we see a persistent canal that goes from the optic nerve to the lens. There is also retinal detachment (occurs in 30-55%) and notice the microphtalmia.

6)Coats' disease
Coats' disease is a rare eye disorder of unknown cause, leading to full or partial blindness, characterized by abnormal development of blood vessels behind the retina.

7)Globe rupture

On the down images of a patient who presented in the ER with post-traumatic orbital swelling.This patient has globe rupture and specifically rupture of the anterior chamber.As radiologists we are used to looking at the vitreous body if we think of globe rupture, but that is not enough.Notice that the depth of the anterior chamber is decreased.There is increased density anteriorly as a result of hyphema (blood in the anterior chamber).Also notice that the lens on the right side is blurred and slightly less dense.This is called a traumatic cataract.Maybe you would have expected the lens to be more dense, but that is usually not the case.

On the down CT images of a patient who had a left eye trauma.Study the images for 5 findings and then continue reading.
The findings are :
The anterior chamber is shallow compared to the right side indicating globe rupture.
The density in the anterior chamber is higher indicating hyphema.
The density of the lens is lower, so this patient has a traumatic cataract.
There is an area of high density in the vitreous body indicating hemorrhage.
The globe is flat on the posterior side so there is vitreous rupture as well.
Globe rupture is seen most commonly at the anterior chamber. 8)Retinal and choroidal detachment

Blood can be located in the following locations:
Anterior chamber: anterior hyphema
Posterior chamber: posterior hyphema (too small to see)
Vitreous: vitreous hemorrhage
Choroidal detachment
Retinal detachment
Retinal detachment can be distinguished from choroidal detachment, because the retinal epithelium ends at the ora serrata (down figure).Evidently a retinal detachment will not go beneath this point.Retinal detachment with haemorrhage is seen mostly in adults with diabetes mellitus and hypertension.

a CT(down image and left one) of a choroidal detachment going beyond ten and two o'clock (with the lens at twlve o'clock) and evidently more anteriorly to the ora serrata.It looks as if the detachment ends at the optic nerve but, if you look carefully, the choroidal detachment actually crosses the optic nerve.On the right image a T1WI of a retinal detachment.It ends at the optic nerve and at the ora serrata. an image(down image) of another case of choroidal detachment.9) Coloboma
Coloboma is a congenital malformation in which part of the eye does not form due to failure of fusion of an embryonic structure called the intraocular fissure.

Coloboma can be part of the CHARGE syndrome:
Coloboma
Heart anomalies
choanal Atresia
Retardation of growth and development
Genital and Ear anomalies.
Coloboma can also be part of the COACH syndrome:
Cerebellar vermis hypoplasia,
Oligophrenia (MR)
congenital Ataxia
Coloboma
Hepatic fibrosis.

Bilateral colobomas Colobomas

The patient on the above had a coloboma and also agenesis of the corpus callosum with an associated midline lipoma.

B)Intraconal pathology

1-Devic's syndrome

Devic's syndrome is also known neuromyelitis optica.Let's first look at the images and then discuss it in more detail.On the down image there is a normal optic nerve on the right side.Notice that the optic nerve is white matter tract.It has the same signal intensity as the white matter in the brain.On the contralateral side there is high signal intensity in the optic nerve.This is therefore extra-ocular intraconal disease and we will be thinking of neoplastic versus demyelinating diseases.Continue with the next image.

On the down a FLAIR image with fat-sat.Notice the abnormal signal intensity and the fact that the optic nerve is not enlarged, which argues against the possibility of a tumor.






Images of the cervical spinal cord show a long segment of non-space occupying disease.Based on these images the differential diagnosis is MS and Devic's syndrome (also caled neuromyelitis optica).Since MS is far more common, this would be the most likely diagnosis, but this happened to be Devic's syndrome.
Some consider Devic's syndrome as a form of MS, but Devic's syndrome differs from MS:
The patients are very ill, as Devic's is more acute and more fulminant.
Usually there is a combination of one-sided blindness and paraparalysis due to the long segment of transverse myelitis (in MS it is usually one- or two-segment).
Devic's is usually monophasic.
Usually no brain plaques.

2-MS
On the down images of a different patient, who also has optic neuritis. There is high signal in the optic nerve and in the brain there are multiple lesions as a result of MS. These lesions did not occur at the same time, so there is dissemination in time and in place, which is specific for MS.
50% of patients with optic neuritis eventually develop MS. The other 50% have isolated optic neuritis (see differential diagnosis above).
80% of patients with MS develop optic neuritis at some point in time.
D.D.of high signal optic nerve:

.Devics syndrome

.Multiple sclerosis

3-Meningioma:(see down image)

The optic nerves are normal, but there is abnormal mass-like enhancement of the optic nerve sheath on the left. So this is probably a neoplasm and of the neoplasms meningioma is by far the most common optic nerve sheath tumor.

4-Abnormal enhancement of the optic nerve sheath

This will give the tram track sign

D.D. of diseases giving that sign

(see the table on the right)

5-Optic nerve glioma
First look at the images on the down. Which side is abnormal and what is the most likely diagnosis?
There is sphenoid wing hypoplasia on the right and on the left the optic nerve near the chiasma is enlarged (visible on the MR). So the diagnosis is neurofibromatosis type I with sphenoid wing hypoplasia and an optic pathway glioma.


The term optic nerve glioma is a misnomer. Actually the tumor can present anywhere along the optic tract from the occipital region to the chiasm and the optic nerve. The term glioma is also rather non-specific. These tumors are juvenile pilocytic astrocytomas WHO type 1, which is the most benign form of astrocytoma. They make up 4% of all orbital tumors. More than 50% of patients who have an optic nerve glioma have NF1, but in NF1 only about 10% have optic nerve glioma. They are less commonly cystic in NF than in non-NF. The mean age at diagnosis is 4-5 years and only 20% of these patients have visual symptoms, because the glioma does not affect the optic nerve early and because these small children do not complain of vision problems.
On the left another case with a more typical example of optic nerve glioma also in a patient with NF1.

The criteria for the diagnosis of NF1 are met in an individual if 2 or more of the following signs are found:
Six or more café au lait macules
Two or more neurofibromas of any type or 1 plexiform neurofibroma
Multiple freckles in the axillary or inguinal region
Bone dysplasias
Optic glioma
Two or more iris hamartomas (Lisch nodules)
A first-degree relative with NF1

Optic glioma in NF1

LEFT: multiple iris hamartomas (Lisch nodules) RIGHT: axillary freckling (small brown spots) and café au lait spots


C) Conal Pathology

1-Thyroid Eye Disease:

The great danger of thyroid eye disease is compressive optic neuropathy either due to direct compression by the muscles or ischemic by compression of the vessels. The key feature to look for is the orbital apex. If you do not see any fat around the orbital apex, there is a great chance of compression. These patients are treated with decompression through an endoscopic procedure in which the medial wall of the orbit i.e. the lamina papyracea is crushed.

The key distinction between pseudotumor and thyroid eye disease is the fact that in pseudotumor not only the muscles, but also the tendons are involved. These patients feel pain when they are moving their eyes as the tendons get irritated. On the image on the far left notice the tapering of the swollen muscle at the point of the tendinous insertion in a patient with thyroid eye disease. Next to it the images of the patient with pseudotumor. Notice that the swelling includes to the tendinus insertion.

Thyroid eye disease

Pseudo tumor:

Pseudotumor is idiopathic inflammation of the orbit. It can affect every part of the orbit: muscles, tendons, fat, optic nerve, nerve sheet, lacrimal gland etc.

Pseudotumor of the orbit Thyroid eye disease versus pseudotumor






D)Extraconal pathology

1-Periorbital abscess
The image below is of a nonenhanced CT-images of a patient with a evident periosteal or periorbital abscess. The teaching point to make is the following:

Do not wait for peripheral enhancement to call it an abscess!

In every other location you wait for nice rim enhancement to call it an abscess and if not you say it is a phlegmone. The treatment is the treatment of the sinusitis.

Periorbital abscess

The other teaching point to make is the following:In children be very careful about extension outside the sinuses!Any change outside the sinus should be called an abscess. In children the periorbita is far more fenestrated and disease will easily spread. So be aggressive in calling small abnormalities an abscess.
Periorbital abscess can lead to venous thrombosis of the superior and inferior ophtalmic vein. In certain fungal sinusitis (e.g.aspergillosis) you can even get cavernous sinus thrombosis and cavernous-carotid fistula


2-Orbital and periorbital cellulitis
the down images of a patient who presented in the ER with a 'red hot eye' and proptosis. Now the difference between orbital and periorbital cellulitis is an important one and is based on an anatomic structure, which is called the orbital septum. If a patient comes in the ER with a red hot eye and the inflammation includes the orbital septum and everything superficial to it, the diagnosis is periorbital cellulitis and the patient is treated with oral antibiotics on an outpatient basis. In the case on the left however the structures posterior to the septum are also involved. This patient has an orbital cellulitis and will have to stay in the hospital to receive antibiotics intravenously.

Orbital cellulitis





3-Sphenoid wing lesions
On the down a CT image of a patient with proptosis due to a sphenoid wing lesion.There are four sphenoid wing lesions that can cause proptosis:
Sphenoid wing dysplasia
Fibrous dysplasia
Paget's disease
Meningioma with hyperostosis of the sphenoid wing

Fibrous dysplasia of the sphenoid wing