Ординатура / Офтальмология / Английские материалы / Neuro-Ophthalmology_Kidd, Newman, Biousse_2008
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TABLE 3–2 Systemic Investigations to Be Considered for Various Orbital Conditions
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Orbital Condition |
Tests for Associated Systemic Disease |
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Thyroid orbitopathy |
Ultra-sensitive TSH |
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Free T3, Free T4 |
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TSH receptor antibodies |
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Anti-peroxidase antibodies |
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Anti-thyroglobulin antibodies |
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Orbital cellulitis |
Full blood count |
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Blood cultures (if systemically toxic) (cultures of |
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abscess contents) |
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Orbital inflammatory |
Full blood count |
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disease |
Erythrocyte sedimentation rate |
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C-reactive protein |
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Angiotensin-converting enzyme |
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cANCA, pANCA |
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Anti-nuclear antibody and extractable nuclear antigens |
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Anti-double-stranded DNA |
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Rheumatoid factor |
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Ro and La antibodies (Sjo¨gren’s) |
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Syphilis serology |
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Sputum acid fast bacilli, Mantoux test |
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Viral serology (EBV, Coxsackie) |
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Bartonella henselae (cat scratch disease) |
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Antiproteinase-3 |
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Vascular endothelial growth factor |
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Recurrent orbital |
Full blood count (film) |
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hemorrhages |
Bleeding time |
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Activated partial thromboplastin time |
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Prothrombin time |
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Thrombin time |
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Fibrinogen |
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Factor VIII |
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Ristocetin |
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Platelet desegregation time |
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Orbital metastatic |
Carcinoembryonic antigen |
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disease |
Prostate-specific antigen |
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Vanillylmandelic acid |
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Homovanillic acid |
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EBV, Epstein-Barr virus; TSH, thyroid-stimulating hormone.
free-T3 (with concomitant suppression of thyroid-stimulating hormone [TSH]), but a minority with typical signs of this condition will be euthyroid or even hypothyroid at presentation.
Ultrasonography has a higher resolution than CT or MRI and is particularly suited to the detection of intraocular lesions, scleritis, and periocular inflammation (manifest as fluid in the sub-Tenon’s space). Color-coded Doppler B-mode imaging is useful for sizing and assessing flow characteristics of vascular anomalies, such as arteriovenous malformations, low-flow dural shunts, and infantile
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capillary hemangiomas. A low-flow dural arteriovenous shunt often causes an enlargement of the superior ophthalmic vein, with reversal of flow and the appearance of a detectable arterial wave-form; in contrast, dilation of the vein because of pressure at the orbital apex or superior orbital fissure causes reduced flow in the normal (anteroposterior) direction, without an arterial wave-form.
As the orbital and periorbital structures have naturally high radiographic contrast, thin-slice CT is the most effective and economical method for orbital imaging. A single run of axial scans with intravenous contrast (unless contraindicated), with coronal reformatting, is usually adequate both to give a probable diagnosis and to plan subsequent management; contrast is not generally required for orbital fractures and thyroid orbitopathy. Parasagittal reformats along the plane of the vertical recti and optic nerve may provide greater detail of the relationship between orbital pathology and the course of the optic nerve.
MRI should be used when detail of the optic nerve or intracerebral tissues is required (especially in areas of high bone content), or when a nonferromagnetic, nonradio-opaque foreign body is present. T1-weighted images identifying anatomical detail and T2-weighted images reflecting water content are useful in assessing inflammation or tumors with high internal vasculature. STIR (short tau inversion recovery) sequences have been used to monitor inflammatory edema in muscles in thyroid orbitopathy, although clinical examination is thought to be as sensitive. Because of the high T1 signal returned from orbital fat, administration of gadolinium-DTPA contrast without the use of fat suppression protocols tends to reduce the clarity of orbital lesions. Although various orbital structures give typical imaging, the signal characteristics are not specific enough to be able to differentiate inflammatory processes from tumors.
Magnetic resonance angiography (MRA) demonstrates vascular flow in most orbital masses, although selective internal and external carotid contrast arteriography remains important in the exclusion of small aneurysms and low-flow dural arteriovenous fistulae and in the investigation of pulsatile proptosis not explained by other imaging modalities. MRA is also useful in the planning for surgery or preoperative embolization of high-flow tumors, such as hemangiopericytoma.
Positron emission tomography (PET) and single photon emission CT (SPECT) do not yet play a significant role in orbital imaging but are currently used for staging some patients with non-small cell carcinoma of the lung, malignant melanoma, Hodgkin’s or non-Hodgkin’s lymphoma, colorectal carcinoma, or malignancies of the head and neck. PET scanning using fluorine-labeled deoxyglucose radiotracer has proved as reliable as conventional scanning for identifying primary or metastatic tumors and is superior to clinical examination (or other imaging) for detecting nodal metastases; unfortunately, the imaging technique presently lacks anatomic detail. A major current role, particularly in patients with lymphoma, is in the differentiation of tumor from fibrous tissue after radiotherapy.
Following the discovery of somatostatin receptors on the activated lymphocytes associated with thyroid orbitopathy, radiolabeled octreotide (a somatostatin analogue) has been used as a semiobjective tool in the evaluation of the disease activity in this condition. The test is, however, extremely expensive and its use limited to a few research centers.
Tissue biopsy is the gold standard for investigating most orbital infiltrative disease. With the exception of typical scleritis, myositis, or orbital apex syndrome,
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the practice of initiating oral steroid treatment before orbital biopsy is likely to mislead the clinician and possibly jeopardize the patient’s health or life. As histologic diagnosis depends largely on structure—rather than just cell type—open biopsy provides the greatest diagnostic accuracy; in collaboration with an experienced cytologist, however, fine needle aspiration biopsy of anterior orbital lesions may have a role in the confirmation of a metastasis when there is known systemic malignancy. Postequatorial lesions are more safely and accurately accessed by open biopsy and enable a greater amount of biopsy material to be obtained for histologic analysis.
Common Orbital Diseases
The incidence of orbital disease is rare, the majority accounted for by thyroid eye disease. Knowledge of common orbital disease is, however, valuable because some will present to the neurologist with subtle orbital signs associated with periorbital pain or headache.
BENIGN ORBITAL DISEASES
There is a wide spectrum of benign disease, from discrete developmental lesions—such as dermoid and epidermoid cysts (6% to 37% of benign lesions) or capillary hemangiomas (8% to 13%)—to inflammatory processes (especially thyroid eye disease or infections) or trauma (about 7% in some series). Tumors of the optic nerve within the orbit, either glioma or meningioma, are related to the management of their intracranial components and are not discussed here.
Structural Lesions of the Orbit and Paranasal Sinuses
Epithelial cysts arise from squamous, conjunctival, or respiratory epithelia sequestered in the orbit along lines of fusion during embryologic development, by implantation after trauma, or from intraorbital expansion of the epitheliallined paranasal sinuses.
Superficial dermoid or epidermoid cysts commonly present in infancy, usually lie in the superotemporal quadrant (associated with the zygomatico-frontal suture; Fig. 3–11) but are sometimes located superonasally. Accumulation of desquamated epithelium, sebum, and hairs causes a slow enlargement of the cyst, and leakage of the contents may cause inflammation of the surrounding tissues—evident histologically in many cases; deep orbital cysts may be asymptomatic until inflammatory episodes occur in adulthood. Occasionally, a dermoid cyst communicates with the skin surface and presents as a chronically inflamed and discharging sinus (Fig. 3–12). Implantation cysts may behave in a similar fashion to congenital lesions but tend to occur at sites of previous periocular trauma. Dermoid cysts generally have a thin radio-opaque wall, which has ill-defined thickening when inflamed and a radiolucent center—the latter markedly so when filled with sebaceous oil rather than keratin. Bone scalloping, with intact cortex, resulting from pressure is commonly seen on CT and the dermoid cyst will, in many cases, extend up to or through clefts in the bone. Characteristic lesions presenting in childhood do not require radiologic
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Figure 3–11 Right superotemporal dermoid attached to the zygomatico-frontal suture.
Figure 3–12 Small cutaneous sinus, containing hair follicles, in the upper lid—this sinus communicates with an anterior orbital dermoid.
investigation. All dermoid cysts should be excised intact, before inflammatory adhesions impair the function of surrounding orbital structures and complicate their surgical excision.
Dermolipomas, although not cystic, also arise from dermis (epithelium and subdermal fat) sequestered on the surface of the globe—typically overlying temporal sclera (Fig. 3–13)—and occasionally are associated with Goldenhar’s syndrome. The abnormal epithelium may bear hairs and sebaceous glands that cause chronic conjunctivitis. Prolapsed subconjunctival fat, in which the conjunctiva is normal, usually occurs in obese adults and is the main differential diagnosis. If unsightly, or causing significant ocular irritation, the abnormal epithelium and associated fat should be excised by an experienced surgeon; injudicious excision of lesions
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Figure 3–13 Hairy dermolipoma overlying the lateral sclera of the right eye; the hairs and squamous epithelium of the lesion tend to cause ocular irritation and discharge.
in the superotemporal conjunctival fornix can be associated with major morbidity, such as dry eye or diplopia.
Retention mucoceles most commonly arise from the ethmoidal and frontal paranasal sinuses and may expand into the orbit, causing slowly progressive proptosis or episodes of eyelid and orbital inflammation (Fig. 3–14). Maxillary sinus mucoceles may lead to collapse of the orbital floor and secondary enophthalmos, and retention mucoceles of the sphenoidal sinus may present with chronic headaches and visual failure, the latter because of the proximity with the optic canals. On CT, sinus mucoceles appear as a cystic cavity smoothly expanding and thinning the bones of the affected sinus and filled with moderately radio-opaque, often homogeneous, material; MRI appearances vary considerably because of changes in the mucus and water content of the mucocele. Management depends on the presentation: a severe acute sinusitis or orbital cellulitis requires intravenous antibiotics and surgical drainage if there is a threat to vision. Definitive ear-nose-throat (ENT) management is required once the acute phase has passed and may involve enhancing sinus drainage or removal of the mucosal lining of the affected sinuses. An infected mucocele may be complicated by orbital abscess formation, irreversible visual loss because of raised intraorbital pressure, or transcutaneous fistula.
Microphthalmos with cyst arises from incomplete closure of the fissure in the optic vesicle, with the cyst sited below, or as part of, a microphthalmic globe (Fig. 3–15). Cysts show considerable variation between infants and typically grow slowly, with secondary expansion of the orbital bones; such cysts should be removed, often with the globe itself, before excessive orbital expansion occurs. Cephaloceles, which may be associated with neurofibromatosis, comprise a congenital herniation of intracranial contents through a skull defect and may contain meninges (meningoceles), cerebral tissue (encephaloceles), or both (meningoencephaloceles); anterior cephaloceles tend to lie in the paranasal region (Fig. 3–16) and impair lacrimal drainage, whereas posterior ones tend to occupy the midline.
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Figure 3–14 Lateral displacement of the left globe caused by a large ethmoidal mucocele, a well-defined lesion associated with smooth expansion of the ethmoidal skeleton.
CT delineates the bone defects associated with these anomalies, the treatment of which is neurosurgical and ophthalmic.
Vascular Anomalies of the Orbit
Orbital capillary hemangioma, affecting 1% to 2% of infants, is the commonest vascular anomaly in childhood and is more prevalent in girls or in children of low birth weight. They may arise from tissue of placental origin and usually present as variable eyelid swelling within a few months of birth, the lesion shows growth for about 6 to 12 months before typically undergoing spontaneous decay, often with superimposed growth cycles that may occur over several years before eventual regression. Predominantly intradermal lesions are bright red and dimpled (so-called strawberry nevus), whereas the deeper orbital lesions have a blue coloration and spongy texture; both may increase slightly in size with crying or straining; larger hemangiomas may cause amblyopia because of mechanical ptosis or astigmatism. Doppler ultrasonography reveals numerous vessels with very high blood velocity (up to 1 m/sec) of arterial wave-form; this characteristic is useful in
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Figure 3–15 Large cyst associated with a microphthalmic eye.
Figure 3–16 Infant with bilateral lacrimal drainage obstruction because of paranasal anterior encephaloceles.
differentiating them from malignant rhabdomyosarcoma, which have a similarly rapid growth pattern in infancy. Management involves ophthalmic monitoring for amblyopia, refraction when old enough to wear spectacles, and intervention when there is a significant threat to visual development; intralesional or systemic steroids slow the growth of capillary hemangiomas and large lesions not involving the skin may occasionally be considered for surgical excision.
Low-flow vascular lesions, such as varices or lymphangiomas, are probably developmental anomalies that only become evident in early adulthood. They are usually unilateral, may involve the orbit, face, and brain, and are typically composed of an admixture of venous channels, with (varices) or without (lymphangioma) intravascular blood. The variceal component may have a variable degree of communication with the systemic circulation—leading, in some cases,
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to saccular anomalies that are distensible on Valsalva maneuver (Fig. 3–2)— whereas lymphangiomas tend to show a greater cellular inflammatory infiltrate. Varices present with spontaneous painful hemorrhage in childhood that may be associated with marked vomiting or, in young adults, as an orbital ache with increasing tendency to painful proptosis on bending or straining. CT may show an enlarged orbit containing a serpiginous lesion (with calcified phleboliths in some) among otherwise normal orbital structures (Fig. 3–17). Lymphangiomas often manifest in the first decade with cystic lesions of the lid margin and conjunctiva, with globe displacement because of retrobulbar masses or with spontaneous hemorrhage (so-called chocolate cysts); the increase in size during respiratory tract infections may be due to lymphoid hypertrophy or vascular congestion. Imaging (CT or ultrasonography) may show an ill-defined mass with cystic spaces, sometimes with fluid levels (when hemorrhage has occurred) among the structures of an expanded orbit. Blood flow through these lesions is minimal. Drainage of a hemorrhage may be required when it causes optic neuropathy, and resection of large lymphangiomas may be indicated for aesthetic reasons, although amblyopia is common with large lymphangiomas, despite all efforts to maintain normal visual development.
The commonest benign orbital mass in adults is cavernous hemangioma. Usually lying in the retrobulbar space, they generally present in middle age with slowly progressive, painless axial proptosis, reduced extremes of eye movement, induced presbyopia, and choroidal folds or optic disc swelling. Cavernous hemangiomas may rarely be associated with persistent retrobulbar headaches, and small cavernous hemangiomas, wedged in the orbital apex, typically cause early and severe compressive optic neuropathy. They appear as a well-defined, ovoid intraconal lesion on imaging—often with optic nerve displacement—and show patchy contrast enhancement because of a very slow blood flow (Fig. 3–18); on MRI, the mass is hypointense to fat on T1-weighted images and isointense to vitreous and hyperintense to fat on T2 sequences. Although asymptomatic lesions may be
Figure 3–17 Abnormal ipsilateral ethmoidal and maxillary sinuses in association with an expanded orbit because of extensive intraorbital varices.
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Figure 3–18 Intraconal cavernous hemangioma showing patchy contrast enhancement on computed tomography (CT).
stable for many years, surgical removal should be undertaken when optic neuropathy, increasing proptosis, or diplopia is present (Fig. 3–19).
High-pressure arteriovenous communications, either in the orbit or the anterior part of the intracranial circulation, may lead to pulsatile proptosis and orbital congestion because of raised venous pressure, the latter causes restriction of eye movements, optic disc congestion, conjunctival edema (“chemosis”), and raised intraocular pressure. Characteristic imaging includes mild proptosis with slightly enlarged extraocular muscles, widespread engorgement of orbital vessels, and, in some cases, slight enlargement of the ipsilateral cavernous sinus; orbital ultrasonography may demonstrate arterial waveforms within veins, with a reversal of flow (normally posteriorly directed) within the superior ophthalmic vein. Intraorbital arteriovenous malformations are very rare, occur spontaneously or as a result of injury, and are commonly supplied by branches of both the internal or external carotid arteries. Management options include superselective embolization of supplying branches from the internal and external carotid arterial territories or placement of thrombogenic coils within the orbital venous circulation (via the dilated superior ophthalmic vein). Dural shunts commonly present with persistence of a “red eye” of sudden onset (Fig. 3–8) and are due to a spontaneous fistula between a minor dural vessel and the cavernous venous sinus; most resolve spontaneously over a year, but ophthalmic care may be required for raised intraocular pressures. Arteriography (with occlusion of the shunt) is indicated in the presence of significant optic neuropathy or severe proptosis. Carotico-cavernous fistulae are high-pressure, high-flow communications that present with acute proptosis, lid swelling, and engorged episcleral vessels with chemosis and raised intraocular pressure; retinal hemorrhages, ocular ischemia, and third, fourth and sixth cranial nerve palsies may also occur. Such high-flow fistulae may occur spontaneously in atheromatous individuals, with intracavernous rupture of the internal carotid
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Figure 3–19 Cavernous hemangioma during surgical removal from the intraconal orbital space, and a typical lesion after intact excision.
siphon, or may arise after severe head injury (Fig. 3–20). Imaging shows a more extreme version of the changes seen with low-flow dural shunts, and radiologically guided balloon occlusion of the fistula is effective in most cases, with low morbidity.
Inflammatory Diseases of the Orbit
Acute or chronic inflammation may affect almost any orbital tissue and may be associated with systemic diseases, such as sarcoidosis, Sjo¨gren’s syndrome, Wegener’s granulomatosis, or rheumatoid arthritis. The commonest orbital condition—thyroid eye disease—is characterized by chronic inflammation of orbital fat and muscles with autoimmune thyroid gland disease (generally thyrotoxicosis).