ORBITA CT & MR BY OPHSO.NET SOURCE http://www.radiologyassistant.nl/en/489ca7c544b19#p489ca7c564ebc
In adults the most common intraorbital calcifications occur at the tendinous insertion of the ocular muscles. Other common calcifications are at the optic nerve head within the eye, also called 'optic disc drusen'. These are usually asymptomatic, but when the ophtomologist inspects the eye, there is the impression of papilledema, i.e. pseudo-papilledema. In children calcifications in the globe means retinoblastoma until proven otherwise even if it is bilateral.
On the left an image of an adolescent with bilateral retinoblastoma.
On the left 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.
PERSISTENT HYPERPLASTIC PRIMARY VITROUS
On the left another cause of leukocoria. 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.
PHPV is the second most common cause of leukocoria. These patients also develop glaucoma and cataract.
On the left 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.
On the far left a CT 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. That would be very unusual for a retinal detachment, but is sometimes seen in choroidal detachment.
On the left an image of another case of choroidal detachment.
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. Often there is microphtalmia and the eye protrudes inferiorly. In 10% there are other CNS anomalies.
On the left images of a patient with bilateral colobomas.
On the left images of a patient with a small coloboma at the entrance of the optic nerve.
OPTIC NERVE GLIOMA
First look at the images on the left. 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.
OPTIC NERVE 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.
THYROID EYE DISEASE
Take a look at the images on the left, describe them and come up with a differential diagnosis and again disregard the title of this paragraph.
The diagnosis is thyroid eye disease and the differential diagnosis is pseudotumor of the orbit. In a moment we will discuss how to differentiate these two diseases. In the past the term Grave's ophtalmopathy was used. This however suggested that the patient is hyperthyroid. Nowadays we know that patients that are treated for Graves disease can be euthyroid or even hypothyroid and still develop thyroid eye disease and therefore nowadays we use the term 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.
Take a look at the images on the left. This is a case of pseudotumor. 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.
On the left 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.
ORBITAL AND PERIORBITAL CELLULITIS
On the left 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.
VENOUS VASCULAR MALFORMATION
On the left an image of a venous vascular malformation. There is a lesion in the intraconal compartment with a phlebolith. Most are unilocular, but this one is multilocular.
On the left images of a patient with an orbital varix, who had noticed that during straining there was a propulsion of the left eye . The upper image is during rest and the lower image is during valsalva at the moment of sneezing. During valsalva the varix shows extreme dilation (red arrow). Notice that during valsalva also on the normal side the superior ophthalmic vein dilates (blue arrow).