Ординатура / Офтальмология / Английские материалы / Surgical Atlas of Orbital Diseases_Mallajosyula_2009
.pdf
62 Surgical Atlas of Orbital Diseases
Bony Lesions
Bony lesions include Osteoma (Figures 3.18A to C), fibrous dysplasia (Figure 3.19), Ossifying fibroma (Figures 3.20A and B). Subperiosteal hemorrhage (Figure 3.21) and subperiosteal abscess (Figures 3.22A to C) are other common lesion frontoethmoidal mucoceles (Figures 3.23A and B), Angiofibroma from sinuses (Figures 3.24A and B) are also seen fairly common. Fractures (Figures 3.25A and B, 3.26A and B) are quite frequent.
Figure 3.17: Hyperostosis and erosion of the sphenoid (yellow arrow) in a case of sphenoid ridge meningioma with intracranial component (red arrow), temporal fossa (green arrow) and orbital involvement
(Blue arrow)
A
B |
C |
Figures 3.18A to C: Osteoma of the ethmoid bone involving the entire ethmoid, and leading to optic nerve compression. See the uniformly dense tumor with Hounsfield values similar to bone in both soft tissue windows (A) and bone window (B). The tumor was excised through a modified Lynch incision (C)
Imaging a Case of Proptosis: CT and MRI 63
Figure 3.19: Fibrous dysplasia usually involves flat bones of face and hence orbital involvement is not uncommon. Imaging shows expansion of the bone with thinning of the overlying cortex. A ‘ground-glass’ appearance is common on CT
A |
B |
Figures 3.20A and B: Ossifying fibroma Imaging shows a well circumscribed lesion eroding the bone with a sclerotic margin (yellow arrow) and foci of internal calcification (green arrow).
Figure 3.21: Sub-periosteal hemorrhage: Subperiosteal hemorrhage is less common than subperiosteal abscess. The periorbita can be seen clearly as a thickened membrane (yellow arrow). Note that the sinuses are clear in this film, unlike in subperiosteal abscess (red arrow) where the sinuses are involved (Figure 3.22)
64 Surgical Atlas of Orbital Diseases
A |
B |
C |
Figures 3.22A to C: Sub-periosteal abscess, infection extending from the Fronto-ethmoidal sinuses (red arrow). Note the congestion and edema of the lids and peri-orbital region, chemosis and congestion of the conjunctiva apart from the eccentric proptosis. Periorbita (yellow arrow) could be well made out
A |
B |
Figures 3.23A and B: Fronto-ethmoidal mucocele is a very common cause of eccentric proptosis in which the globe is pushed down and out. You can see a very gross eccentric proptosis of left eye with fullness in the superomedial quadrant. The CT Scan shows a grossly enlarged frontal sinus with mucosal thickness (yellow arrow)
A |
B |
Figures 3.24A and B: Angio fibroma arising from sinuses is not very rare. Note the huge tumor mass. Occupying the entire maxillary sinus, and distorting the orbital cavity. Its extension into the nose and the fullness of left cheek could be made-out. Also note the severe eccentric proptosis and corneal leucoma due to exposure
Imaging a Case of Proptosis: CT and MRI 65
A |
B |
Figures 3.25A and B: Limitation of elevation of right eye with diplopia in upgaze following trauma while at play. Note the subconjunctival hemorrhage. The FDT was positive. Clinical diagnosis of fracture floor of orbit with entrapment of inferior Rectus was made. But the CT scan
(B) of orbit showed fracture roof of the orbit with the displaced fragment impinging on the globe and mechanically restricting its movement (yellow arrow)
A |
B |
Figures 3.26A and B: Fracture floor of orbit can either involve a large area (Red arrow- A) and may show hemorrhage in the sinus or may be very tiny with trap-door mechanism and the typical "tear-drop" sign (yellow arrow- B). The rectus muscle may or may not be entrapped. Entrapment of the rectus with positive FDT and diplopia is one of the important indications for early surgery
Trauma: Trauma leading to orbital fractures (Figures 3.25A and B, 3.26A and B) is fairly common and its incidence is on the raise in view of increase in road traffic accidents and violence in the society. Apart from traumatic optic neuropathy, diplopia is another very important symptom. Persistent diplopia due to entrapment of a rectus muscle and positive FDT is one of the indications for surgery.
Eyeball: After examining the bony orbit, look at the globe and its relation to the lesion. The lesion may be soft and molding along the eyeball like a lymphoma (Figure 3.27) The globe is pushed ahead by the lesion and also can alter its shape depending on its consistency (Figures 3.28A and B). In Severe proptosis, tenting of posterior pole (Figure 3.29) can be noticed.
66 Surgical Atlas of Orbital Diseases
Figure 3.27: Molding: Look at the lesion which is molding along the globe, without altering its curvature (yellow arrow). This is very typical of lesions which are soft like lymphoma. Molding can also be seen in fungal granuloma, adenoid cystic carcinoma of lacrimal gland
A |
B |
Figures 3.28A and B: Firmer lesions indent the globe and can induce refractive errors. Compression of the globe by cystic lesion (Hydatid Cyst figure A yellow Arrow) and compression of the globe by tumor (schwannoma figure B, yellow Arrow). The intraconal lesions cause hyperopic shift in the refraction, by virtue of flattening the globe, while the lesions in the peripheral space cause astigmatism
Figure 3.29: In severe proptosis, tenting of the globe with stretching of the optic nerve can occur. This also can contribute to defective vision. Look at the tenting of the posterior pole of the globe with loss of the normal curvature (yellow arrow)
After examining the contour of the eyeball, (Figures 3.30 to 3.32) look at the intraocular contents. Retinoblastoma and uveal melanoma (Figures 3.33A to D) are the most common intraocular tumors which can spread into the orbit and can cause secondary
Imaging a Case of Proptosis: CT and MRI 67
proptosis. It is a routine practice to get a CT Scan of orbit in retinoblastoma. The tumor can be seen as an intraocular mass lesion with calcification. It can be confined to the globe or can extend into the orbit, optic nerve or brain.
A |
B |
Figures 3.30A and B: Retinoblastoma; The typical amaurotic cat's eye reflex in the left eye( A) The intraocular mass with calcification (yellow arrow–B) is very typical of retinoblastoma. The sclera looks normal
A |
B |
Figures 3.31A and B: This child had a painful proptosis of right eye. Note the gross proptosis with mild congestion, increase in the corneal diameter, and amaurotic cat's eye reflex (A). The CT scan reveals intraocular masses with calcification (yellow arrow-B). in both the globes.
Note the loss of integrity of the sclera with orbital extension (red arrow)
68 Surgical Atlas of Orbital Diseases
A
B |
C |
Figures 3.32A to C: This child presented with recurrent mass after enucleation elsewhere for retinoblastoma. CT scan of the orbit reveals that the entire socket is filled with the mass (B) leading to expansion of the orbital walls (yellow arrow) and a very significant intracranial extension (red arrow-C)
A |
C |
B |
D |
Figures 3.33A to D: Uveal Melanoma is the most common intraocular malignancy in adults and it can extend into the orbits. Note the tumor which could be seen very clearly in external examination(A) and its brown color and the retinal vessels over it in the slit lamp examination
(B). The tumor arising from the choroid is very well visualized in the CT scan in the coronal view (C) and its antero-posterior extent in the sagittal reconstruction (D). Note the absence of calcification. The sclera appears intact
Enlarged extraocular muscle: Enlarged extraocular muscle (EOM) is the most common finding we come across on imaging in proptosis, followed by mass (tumor). This is because of high prevalence of myocysticercosis as cysticercosis is endemic in our area. The important causes of enlarged extraocular muscle include thyroid
Imaging a Case of Proptosis: CT and MRI 69
orbitopathy, (Figures 3.34A and 3.35A and B) myocysticercosis, (Figures 3.36A and B) idiopathic orbital inflammation (Figure 3.34B), rhabdomyosarcoma, lymphoma (Figures 3.39A to D), carotid cavernous fistula (Figures 3.37A and B to 3.38A and B), and metastasis. (Figures 3.40A to D).
A |
B |
Figures 3.34A and B: Thyroid associated orbitopathy (TAO) is the most common cause of enlarged extraocular muscle in most studies (A). Myositis due to idiopathic orbital inflammation (IOI) is also very common (B). Hence it is very important to differentiate these two conditions on imaging. The above pictures are very classical. In TAO, the tendon is spared and in myositis it is also involved. Contrast enhancement and only lateral rectus muscle involvement can occur in IOI but not in TAO. Lacrimal gland and even fat can be involved in IOI, but not in TAO. Most often in TAO, the CT scan of the orbit reveals bilateral enlargement of extraocular muscles
A |
B |
Figures 3.35A and B: In TAO, enlarged extraocular muscle can compress the optic nerve and cause loss of vision. Note the grossly enlarged recti muscles surrounding the optic nerve (red arrow) in the mid coronal sections of left orbit where as the optic nerve on the right side is free from compression. The posterior coronal sections reveal a severe compression of optic nerve on the left orbit. This patient had presented with a vision of 20/200 in left eye. Note that the floor and medial wall if orbit are reaching the posterior most part of the orbit, but not the zygoma.
Hence in orbital decompression aimed to relieve optic nerve compression, I invariably include the medial wall or floor or both. I also excise orbital fat. Lateral wall decompression is more for cosmetic purpose
70 Surgical Atlas of Orbital Diseases
A |
B |
Figures 3.36A and B: Myocysticercosis is a very frequent cause of enlargement of extraocular muscle in endemic areas. It can involve any of the extraocular muscles. The image is very characteristic in that a cystic lesion with a hyper-dense spot within (represents the scolex) is seen in an enlarged EOM. Commonly a single cyst is common. Rarely more than one cyst is encountered. I am yet to see a case where more than one muscle is affected. Intracranial cysticercosis can be rarely associated with orbital cysticercosis. In figure A notice the presence of two cysts in the superior oblique (SO) muscle. Compare the size of this grossly enlarged SO with the normal SO of left eye. Figure B shows the typical cyst with scolex involving the inferior rectus muscle
Another common cause of enlarged EOMs is CarotidCavernous Fistula (CCF). The incidence of it is on the raise due to increase in the incidence of trauma. CCF may be low flow or high flow in nature.
In view of the arteriovenous communication, enlarged EOMs and superior ophthalmic vein are seen in the CT scan
A |
B |
Figures 3.37A and B: CCF low flow fistula. Note the dilated Superior ophthalmic vein of the right eye (yellow arrow) and the EOMs. Note how big the lateral rectus (green arrow) is. Notice also the subtle enlargement of superior and inferior recti
Imaging a Case of Proptosis: CT and MRI 71
A |
B |
Figures 3.38A and B: CCF High-flow fistula: Compare the grossly enlarged superior ophthalmic vein (yellow arrow) and the huge enlargement of the inferior rectus muscle( green arrow) with the previous picture. The high flow CCF usually follows trauma, and clinically characterized by pulsatile proptosis, caput medusae, chemosis, restricted ocular motility, gross retinal venous engorgement and secondary glaucoma
A |
B |
C |
D |
Figures 3.39A to D: Lymphoma: Lymphoma is characterized by a soft tissue lesion which typically molds around the globe (yellow arrow A,B and D). Salmon's patch is the typical presentation (C…green arrow). Some times enlarged EOMS can be seen in some sections of the CT scan
(D…red arrow)