Ординатура / Офтальмология / Английские материалы / Oculoplasty and Reconstructive Surgery Made Easy_Garg,Touky, Nasralla_2009
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Histopathological examination of the biopsied tissue confirms the diagnosis.
Orbital Fracture
Signs and symptoms: The patient has a history of trauma, and subsequent pain and diplopia. The eye is enophthalmic, with restriction of ocular movement in the vertical and occasionally the horizontal gaze.
Computed tomography: The blow-out fractures of the floor and medial wall of the orbit are best visualized with bone window settings. The medial wall fracture is best seen in the coronal and axial views, while the floor fracture is best seen in the coronal or re-formatted sagittal views. A discontinuity is seen in the orbital wall. The fractured fragment may be dislocated completely into the paranasal sinus, or may be rotated like a trap-door, hinged at one edge. The orbital soft tissues—fat, septa, or muscle may be entrapped in the fracture (Figures
3A and B).
Differential diagnosis: The orbital fracture should be clinically differentiated from mechanical limitation of movement due to tissue edema, and from traumation extraocular muscle paresis.
Investigation: Preoperative forced duction testing can confirm entrapment of extraocular muscle and soft tissues in the fracture.
Treatment: A small, asymptomatic orbital fracture may be treated conservatively. Surgical repair is required for a large fracture, or one causing diplopia by restriction of ocular motility (Figure 3C).
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Figures 3A to C: (A) Clinical photograph of right orbital floor fracture, with right enophthalmos and restricted elevation of the right eye. (B) Coronal view of the CT scan orbit, showing trap-door deformity in the orbital floor, with soft tissue prolapsing into the maxillary sinus. The lateral edge of the inferior rectus muscle is trapped in the fracture. (C) Clinical photograph after surgical repair of the floor fracture, showing improved ocular elevation
EXTRAOCULAR MUSCLES
Thyroid Eye Disease
Signs and symptoms: Patients of thyroid orbitopathy present with unilateral or bilateral proptosis. There may limitation of ocular movement, eyelid changes such as lid retraction and lagophthalmos, corneal exposure and signs of optic nerve compression.
Computed tomography: On CT scan, thyroid eye disease is commonly bilateral, the eyes are proptosed. The optic nerves appear straightened. Pre-septal soft tissue edema may be seen. There is bilateral fusiform enlargement of the extra-ocular
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muscles, with smooth borders and sparing of the tendons. Multiple sections should be studied to detect posterior enlargement which may be compressing the optic nerve. Occasionally the orbital involvement may be asymmetrical, but some evidence of thyroid-related changes can be seen in the eye with milder disease also (Figures 4A to C).
Differential diagnosis: Thyroid eye disease is to be differentiated from orbital inflammatory myositis, where there is a diffuse enlargement of one or more muscles; the enlargement conforms to the shape of the globe, and the tendinous insertion is involved. An inflammatory process may show contrast enhancement of the muscle.
Figures 4A to C: Axial view of CT scan in thyroid orbitopathy, showing bilateral proptosis, straightening of the optic nerve, and enlargement of the extraocular muscles without tendon involvement. (B) Axial view of the same in a more inferior section. The enlarged inferior rectus may be mistaken for a space-occupying lesion. (C) Coronal view of the same, depicting enlargement of all extraocular muscles
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Arteriovenous fistulas may also show enlargement of multiple extraocular muscles, proptosis, and some contrast enhancement. The dilated superior ophthalmic vein is a differentiating feature.
Cavernous sinus thrombosis would cause bilateral enlargement of multiple extraocular muscles. The superior ophthalmic vein would be enlarged. The cavernous sinus would enhance with contrast, and demonstrate enlargement, and loss of the concavity of the lateral border as seen on an axial section.
Investigations: Ultrasound B scan of the orbit may confirm enlarged size of the extra-ocular muscles.
Systemic evaluation for thyroid abnormalities should be performed. Thyroid function tests for T3, T4, TSH, and antithyroid antibodies may confirm the diagnosis in a previously undetected patient. However, in about 10% of the cases, Graves’ orbitopathy may present in a euthyroid patient.
Myositis
Orbital myositis is a non-specific inflammatory condition of the extraocular muscles, though it may be associated with underlying immune disease.
Signs and symptoms: The patient presents with periorbital pain, which increases on ocular movement, and orbital inflammatory signs such as periocular and lid edema, and conjunctival chemosis. The episodes may be recurrent, and involve different muscles in the recurring episodes.
Investigation
Computed tomography: The CT scan shows enlargement of one or more extraocular muscles, commonly unilateral. The
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muscle borders are irregular, and the diffuse inflammatory shadow extends to the tendon and the orbital fat (Figures 5A to C).
Differential count of leucocytes may help to rule out eosinophilia, which is associated with trichinellosis causing myositis.
Differential diagnosis: In thyroid orbitopathy, the involvement of the muscles is bilateral, and in multiple extraocular muscles. There is a fusiform dilatation of the muscle, but the tendon is usually spared. The commonly affected muscles are the inferior, superior and medial recti.
Figures 5A to C: (A) Clinical photograph of patient with right orbital myositis involving the superior rectus and levator palpebrae superioris.
The patient presented with right ptosis and limitation of elevation. (B)
The coronal section of the CT scan shows isolated enlargement of the right superior rectus. (C) Axial section showing the the thickened superior rectus, with irregular outline depicting an inflammatory process. The thickening extends anteriorly to the tendon
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In an intracranial arteriovenous fistula, all muscles will be enlarged. The superior ophthalmic vein will also be dilated, seen on axial as well as coronal views.
Other infiltrative disease, including lymphoma may cause enlargement of extraocular muscles.
Treatment: Depending on the severity and extent of the disease, myositis may be treated with systemic nonsteroidal antiinflammatory drugs, low dose steroids, or high dose steroids. Recurrent disease may need intravenous pulses of steroids.
Orbital Cysticercosis
Introduction: Orbital cysticercosis occurs in the extraocular muscles and may migrate anteriorly and subconjunctivally. Depending on the exact location, the clinical presentation is varied. The inflammatory signs may be moderate or severe.
Signs and symptoms: The patient may present with axial or non-axial proptosis; pain, diminished vision, limitation of ocular motility and ptosis.
Investigation: Orbital imaging is the mainstay of diagnosis in orbital myocysticercosis.
Computed tomography orbit will show a wellcircumscribed lesion within an extraocular muscle. The muscle may be thickened and have surrounding soft tissue shadows of inflammation. The cyst shows low internal density, with a high density internal spot representing the scolex (Figures 6A and B).
Magnetic resonance imaging will depict a well circumscribed cystic lesion within an extraocular muscle, which is hypo-intense on T1 sequences, and hyper-intense on T2-weighted sequences, with an internal hypo-intense spot representing the scolex (Figure 7A).
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Figures 6A and B: (A) Axial CT scan of orbital myocysticercosis showing cystic lesion with low internal density, with a high density internal spot representing the scolex, surrounded by inflammatory soft tissue shadow.
(B) The coronal section confirms the location in the inferior rectus muscle
Figures 7A and B: (A) T1 –weighted MRI of orbital myocysticercosis, showing hyper-intense lesion with surrounding inflammatory changes and internal hypo-intense spot of the calcified scolex. (B) USG B-scan of orbital myocysticercosis shows an echo-lucent cystic structure in an extraocular muscle, with the internal scolex showing high echo-reflectivity
Ultrasound B scan of the orbit will show a low-echo reflective cystic structure in relation to an extraocular muscle. The cyst will show internal high-echo reflective area of the scolex. Te adjacent muscle will also demonstrate thickening. Sometimes only the cyst is visualized, without the scolex.
(Figure 7B).
For a patient on medical management, requesting serial ultrasound B scans is a good way of monitoring improvement. The scolex disappears, and the cyst gradually grows smaller in size and finally collapses.
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Differential diagnosis: The appearance of myocysticercosis is very characteristic. If only the cyst is seen, the differentiation is from other cystic lesions.
Treatment: Medical management comprises the use of oral anthelminthic, albendazole, and steroid. Surgical excision of the cyst is rarely required.
EXTRACONAL LESIONS OF THE ORBIT
Dermoid Cyst
A dermoid cyst is the commonest cystic space-occupying lesion of the orbit. The dermoid cyst may be superficial, as external and internal angular dermoids, or deep dermoid cysts.
Signs and symptoms: Superficial dermoid cysts present early in life with gradually enlarging periorbital cystic lesion. Deep dermoid cysts present later in life, with progressive proptosis. If the dermoid cyst is bilobular, and is dumbbell shaped, and has a component in the temporal fossa, the patient may present with intermittent proptosis.
Ultrasound B scan: The dermoid cyst has a smooth wellcircumscribed shape. There may be erosion of the adjacent bone. The internal reflectivity of the dermoid cyst is variable.
Computed tomography orbit will show a smooth rounded lesion, with or without fossa formation of the adjacent bone. The internal consistency of the cyst is heterogeneous, due to the variable nature of the contents. Occasional deep dermoid cysts are dumb-bell shaped, with components in both the orbit and the temporal fossa, and erosion of the lateral wall of the orbit (Figures 8 and 9).
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Figure 8: Axial CT scan of superficial dermoid cyst, showing well-defined lesion with low internal density, with a shallow fossa formation in the adjacent bone
Figures 9A and B: (A) Coronal CT scan of deep dermoid cyst, showing well circumscribed extraconal lesion, with low internal density, with extension to the temporal fossa through a defect in the lateral orbital wall. (B) Axial CT scan of the same, showing the deep dermoid with a dumb-bell shaped extension into the temporal fossa
Differential diagnosis: The clinical and imaging features are characteristic of dermoid cysts. A cyst with inflammation needs to be distinguished from other orbital inflammatory disorders.
Treatment: The progressively enlarging dermoid cyst is excised surgically.
Sphenoid Wing Meningioma
Sphenoid ridge meningiomas are intracranial tumors, but affect the orbit secondarily to have significant orbital and visual effects. They comprise 18-20% of all intracranial meningiomas, and are commoner in women.
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Signs and symptoms: The more medially arising tumors compress the optic nerve and structures in the superior orbital fissure, and present more often with visual loss and limitation of ocular motility. The visual loss is slowly progressive, and may be bilateral. Defects in color perception are early indicators.
The tumors arising from the lateral part of the greater wing of sphenoid bone tend to enlarge before they are symptomatic. They cause progressive proptosis and fullness of the temporalis fossa (Figure 10A).
Computed tomography: The tumor is well defined, and shows intracranial, intraorbital and temporalis fossa components, the orbital component extending at the apex and along the posterolateral wall of the orbit. The bones may show lysis (Figure 10B ) or hyperostosis (Figure 11). The tumor enhances on contrast.
Figures 10A and B: (A) Clinical photograph of patient with sphenoid ridge meningioma, with proptosis and fullness of the right temporal region.
(B) Axial CT scan of the same patient, showing large tri-radiate soft tissue lesion extending intracranially, into the temporal fossa and the orbit. The lesion is centered on the area of the sphenoid ridge, which shows bone destruction