Ординатура / Офтальмология / Английские материалы / Oculoplasty and Reconstructive Surgery Made Easy_Garg,Touky, Nasralla_2009
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Imaging of the Orbit 269
Figure 11: Axial CT scan of sphenoid ridge meningioma, showing hyperostosis of the sphenoid bone and soft tissue lesion adjoining the lateral wall of the orbit
Differential diagnosis: Rarely, other tumors with both orbital and intra-cranial components, and showing lysis of the sphenoid bone, may mimic sphenoid ridge meningiomas.
Investigations: Neuroimaging may pick up other intracranial meningiomata. The definite diagnosis is by histopathological examination if a biopsy specimen.
Treatment: if the tumor is well-defined, it may be excised completely. Otherwise debulking of the tumor can provide relief from the symptoms. Residual or recurrent tumor after surgery can be treated by external beam radiotherapy.
Lymphoproliferative Disease of the Orbit
Signs: Lymphoproliferative disease of the orbit presents as a gradual onset of mass effect in the orbit. The eye may or may not show significant proptosis.
Computed tomography: There will be presence of orbital lesion bilaterally in 30% of the patients. The lesion is often extraconal, and superotemporal orbit is a common location. The lymphoproliferative lesions have smooth, regular outlines. The lesion extends into tissue spaces, conforming to the existing orbital structures. This ‘molding’ around structures is a very characteristic feature of lymphoproliferative disease, whether reactive lymphoid hyperplasia, atypical lymphoid hyperplasia or lymphoma (Figures 12A and B).
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Figures 12A and B: Axial and coronal CT scans of non-Hodgkin lymphoma in superolateral orbit, moulding around the globe without indentation
Differential diagnosis: Specific or non-specific orbital inflammatory disease must be differentiated from lymphoproliferative disorders.
Investigations: Biopsy of the suspicious lesion is the investigation of choice. Further systemic evaluation and choice of tests depends on the histopathological features of the biopsied specimen.
Treatment: Isolated orbital disease is treated by locoregional radiotherapy. Systemic involvement with lymphoma requires chemotherapy.
Lacrimal Fossa Tumors: Pleomorphic Adenoma
Signs and symptoms: The patient presents with eccentric proptosis and inferomedial displacement of the globe. Often there is a palpable mass in the superotemporal orbit.
Computed tomography: On a CT scan, a benign lacrimal tumor like pleomorphic adenoma will appear as a globular enlargement of the lacrimal gland, with smooth borders and homogeneous internal consistency. The large lacrimal gland may displace the globe inferomedially. A long-standing tumor would cause fossa formation in the adjacent bone (Figure 13).
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Figure 13: Coronal CT scan of pleomorphic adenoma shows well-defined lesion in the superolateral orbit, with smooth outline, heterogeneous internal density, separat from extraocular muscles, with fossa formation in the frontal bone
Differential diagnosis: Inflammations and lymphoproliferative disease of the lacrimal gland would have a more diffuse outline, and tend to conform to the contours of surrounding structures.
Malignant lacrimal gland tumors may have irregular borders. They may extend posteriorly in the orbit, as well as extend beyond the midline in the coronal plane. There can be erosion of the adjacent bone. Any malignant tumor may infiltrate the orbital structures such as the extraocular muscles; hence the muscle may not be distinguishable from the mass on a CT scan (Figure 14A and B).
Investigation: Any suspicion of malignancy should be followed up with biopsy and histopathological examination of the lesion.
Management: A pleomorphic adenoma of a lacrimal gland may be removed in toto through a suitable orbitototmy incision.
Orbital Invasion of Paranasal Sinus Disease
Signs and symptoms: A secondary tumor or fungal granuloma commonly extends to the orbit from an adjoining paranasal sinus. The patient presents with pain, progressive non-axial proptosis, dystopia of the globe, and limitation of ocular motility.
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Figures 14A and B: (A) Clinical photograph of patient with adenoid cystic carcinoma of the right lacrimal gland, showing proptosis with inferior and medial displacement of the globe, superior sulcus fullness, and visible enlargement of the right lacrimal gland. (B) Coronal CT scan of the same patient, showing soft tissue lesion in right superolateral orbit, with irregular outline, infiltrating right superior and lateral recti, with erosion of the orbital roof
Computed tomography: A homogeneous irregular mass would be seen extending from the paranasal sinus, most commonly the maxillary sinus. The mass enhances only slightly with contrast. The bony orbital wall between the sinus and the orbit is seen eroded. The mass lesion is seen displacing the globe in the opposite direction. The mass may be infiltrating the corresponding rectus muscle, which can no longer be identified separately on the image (Figures 15A and B).
Differential diagnosis: A lesion eroding the bony wall of the orbit and entering from the sinus may also be a mucocele. A sinus mucocele is however, smooth in outline.
Investigation: A biopsy specimen obtained by endoscopic sinus surgery or through an orbitotomy is essential for the histopathological diagnosis.
Management: The treatment of the condition varies according to the diagnosis obtained on histopathologic examination, and the extent of the disease.
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Figures 15A and B: (A) Clinical photograph of patient with fungal granuloma of the right paranasal sinus and orbit, showing right proptosis with lateral displacement of the globe. (B) Axial CT scan of the same patient showing the soft tissue shadow of the fungal granuloma in the ethmoid sinuses, eroding the medial wall of the orbit and extending into the orbit
COMBINED INTRACONAL AND
EXTRACONAL PATHOLOGY
Orbital Hemorrhage
Signs and symptoms: The patient usually presents with a history of trauma. There is rapid and progressive proptosis, pain, periorbital edema, ecchymoses, and limitation of ocular motility. The mass effect on the optic nerve may cause diminished vision.
Computed tomography: An orbital hemorrhage is seen as a diffuse or well-defined shadow of soft-tissue density on computed tomography. There may be associated fracture of orbital bones (Figure 16).
Figure 16: Axial CT scan showing soft tissue density shadows in orbital hematoma. The extreme proptosis of the globe has stretched the optic nerve and caused tenting of the globe at the posterior pole
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Magnetic resonance imaging: A diffuse or well-defined soft tissue shadow may be present in the orbit. The hematoma may be intraconal, extraconal, or combined. A sub-periosteal hematoma is seen as a well-demarcated lesion adjacent to the bony orbital wall, and delimited by the extent of the bony sutures. The intensity of the hematoma depends on the age of the hemorrhage: an acute hemorrhage is iso-intense on T1weighted sequences, and hypo-intense on T2-weighted sequences. A sub-acute presentation, within 2 days of the hemorrhage, shows hyper-intensity in both T1and T2weighted images. A chronic hemorrhage is hyper-intense in T1 sequences, and hypo-intense in T2 images (Figures 17A and B).
Differential diagnosis: An orbital hemorrhage is to be differentiated from tissue edema due to trauma. The trauma may also be accompanied by an orbital fracture.
Treatment: An orbital hematoma causing significant mass effect and compromising the visual function should be drained surgically.
Lymphangioma
Signs and symptoms: The deep lymphangiomas present with spontaneous, rapidly progressing proptosis; this is due to
Figures 17A and B: (A) Sagittal view of T1-weighted sequence or subperiosteal hematoma orbit. The hematoma is delimited, adjacent to the orbital roof, is hyper-intense to vitreous but hypo-intense to the orbital fat, and stretching the optic nerve. (B) Sagittal view of the same in T2weighted sequence, where the hematoma is hypo-intense to the vitreous
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hemorrhage into a previously undetected lesion. There may be restriction of ocular motility and strabismus. There may be features of optic nerve compression such as disc edema or relative afferent pupillary defect. The combined lymphangiomasareextensive,withbothsuperficialanddeepcomponents. There may be prolonged history of proptosis, and episodes of hemorrhage. The superficial lesions in the periocular skin or conjunctiva may show clear fluid or blood.
Computed tomography: A long-standing lesion will cause enlargement of the bony orbit. The lymphangioma is a diffuse non-encapsulated soft tissue shadow, which may extend in both the intraconal and extraconal compartments, as well as in the preseptal area. The internal consistency is nonhomogeneous, with some areas of low-density cyst-like appearance. Blood levels may be seen in some views. Circumscribed lymphangiomas resemble cavernous hemangiomas, and may even show phleboliths. On contrast injections, there may be irregular areas of enhancement, or rim enhancement (Figure 18).
MRI scan: MRI scan will depict a diffuse lesion, with multiple cystic spaces. The spaces may show fluid-fluid levels, which have different intensities due to difference in paramagnetic properties of blood of various ages. After contrast injection, there may be enhancement of some of the solid parts of the tumor (Figures 19A and B).
Figure 18: Coronal CT scan of orbital lymphangioma, showing diffuse lesion with heterogeneous density in the superior orbit, and fossa formation in the adjacent bone
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Figures 19A and B: Coronal and sagittal views of T2-weighted MR imaging in orbital lymphangioma, shows diffuse multi-loculated lesion, with variable intensity in different areas
Differential diagnosis: The lymphangioma should be distinguished from other vascular lesions of the orbit. A circumscribed lymphangioma may closely mimic a cavernous hemangioma.
Treatment: A lymphangioma with bleeding, or one causing a mass effect, is surgically debulked. Due to diffuse involvement of orbital tissues, complete excision may not be possible.
Orbital Varix
Orbital varices are distensible venous malformations of the orbit.
Signs and symptoms: A deep orbital varix causes intermittent proptosis enophthalmos due to fat atrophy, occasional bruising, and expansion on bending or Valsalva maneuver. There may be an accompanying superficial component with dark, tortuous Epibulbar or lid vessels. There may extensive involvement of peri-orbital or intracranial regions.
Imaging: An orbital varix has a smooth fusiform or globular appearance, and enhances strongly with contrast, increases in size during Valsalva maneuver during dynamic CT scanning.
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Other investigation: IncreasedsizeofthelesionisseenonA-and B-scan ultrasonography. Venography can demonstrate abnormal saccular vessels flowing out through venous channelsintheface,pterygopalatinefossaandcavernoussinus.
Differential diagnosis: The orbital varix is to be distinguished from other vascular lesions of the orbit.
Treatment: Most orbital varices can be safely observed. Surgical excision is technically difficult. Intraoperative venography and glue embolisation may be helpful, followed by excision.
INTRACONAL LESIONS OF THE ORBIT
Vascular Lesions of the Orbit
Orbital Hemangioma
Signs and symptoms: cavernous hemangiomas present in adults with gradually progressing proptosis. There may be associated globe indentation, choroidal folds and optic nerve displacement.
Computed tomography: Cavernous hemangiomas are wellcircumscribed smooth ovoid intraconal masses that enhance with contrast. Long-standing extraconal masses may cause bony fossa formation (Figure 20A). The globe is proptosed, and may show indentation (Figure 20B). The optic nerve is displaced in a large intraconal lesion. Small areas of high density representing calcification are seen in the presence of phleboliths.
Magnetic resonance imaging: The MRI scan shows a wellcircumscribed intraconal mass, which is round or ovoid. In T1 weighted sequences, it is hypointense relative to orbital fat, and isointense to muscle. In T2 weighted sequences, it is hyper-intense to fat and muscle. The tumor shows marked
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Figures 20A and B: (A) Coronal CT scan of orbital cavernous hemangioma showing ovoid lesion with smooth outline, with fossa formation in adjacent bone. (B) Coronal CT scan of the same patient, showing indentation of the globe by the tumor
enhancement after contrast injection in T1 weighted images
(Figures 21A and B).
Differential diagnosis: Cavernous hemangioma should be differentiated from hemangiopericytoma and circumscribed lymphangioma. The latter may have phleboliths, but will have heterogeneous internal density. Diffuse lymphangiomas are heterogeneous with irregular margins.
Treatment: Cavernous hemangiomas can easily be excised in toto by a suitable orbitotomy approach.
Figures 21A and B: (A) T1-weighted MRI of intraconal cavernous hemangioma, hypo-intense tumor with smooth outline. (B) T2-weighted MR image of the same tumor: the tumor appears hyper-intense in T2 sequences