Ординатура / Офтальмология / Английские материалы / Neuro-Ophthalmology_Kidd, Newman, Biousse_2008
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Figure 3–31 Lacrimal gland carcinoma, showing flecks of calcification, molding around the right globe, and extending back along the lateral orbital wall and through the superior orbital fissure.
recurrence, in some cases malignant. Definitive treatment for lacrimal gland carcinoma remains controversial, as recurrence of adenoid cystic carcinoma may occur after a long latency; current advice is tumor debulking (which may even be complete) and external beam irradiation of both the orbit and ipsilateral cavernous sinus. Implantation brachytherapy has been advocated as delivering a globe-sparing, high-radiation dosage to the lacrimal gland fossa, but this approach fails to treat the cavernous sinus or pterygopalatine fossa, which is commonly affected by perineural invasion. Although intracarotid chemotherapy may have a role as an adjunct to radiotherapy in advanced disease, there is no reliable evidence to suggest that the disfigurement of either exenteration or “superexenteration” (with removal of the neighboring orbital bones) leads to a reduced tumor recurrence or improved survival. Sadly, most patients with adenoid cystic carcinoma will eventually suffer a painful and relentlessly progressive recurrence of the disease, either locally or with pulmonary metastasis.
Adult Orbital Malignancy
Orbital malignancy presenting in adulthood tends to be secondary to systemic disease or arises by direct spread from the neighboring paranasal sinuses or intraocular tumors.
Lymphoproliferative lesions show a spectrum of disease, from benign histology with well-organized follicular pattern (reactive lymphoid hyperplasia) to frank malignant lymphoma, and diagnosis of these lesions has improved greatly with immunohistochemical stains for lymphocytes and their precursors. Orbital lymphomas—effectively all B-cell non-Hodgkin’s lymphomas—account for about 10% of all orbital masses and generally present in patients aged older than 50 years as a slow-growing orbital mass causing eyelid swelling, proptosis, or diplopia; a pink subconjunctival mass will often be evident, providing an ideal site for biopsy (Fig. 3–10). Younger patients tend to develop more aggressive lymphomas; these often arise in the paranasal sinuses and secondarily invade
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Figure 3–32 Proptosis and patchy infiltration of fat caused by bilateral orbital lymphoma; the tumor does not cause marked displacement of orbital structures or disruption of orbit functions.
the orbit. CT identifies a moderately well-defined soft tissue mass, pervading multiple tissues, molding to the globe, but usually without any widespread disruption of intraorbital structure or invasion of bone (Fig. 3–32); calcification is extraordinarily rare in lymphomas. All pervasive orbital masses should be biopsied and, if shown to be lymphoma, the patient should undergo investigation for systemic disease. If purely orbital disease exists, this tends to respond well to fractionated radiotherapy (24 to 35 cGy, dependent on the variant), whereas systemic involvement generally requires chemotherapy and, in some cases, adjunctive orbital radiotherapy. Although the visual prognosis is very good, the overall morbidity and mortality is variable, with systemic lymphoma becoming evident several years after the presentation of isolated orbital disease.
In contrast to childhood, metastasis from systemic malignancy favors the uveal tract in adults, and metastatic disease represents only 2% to 3% of all orbital tumors in adulthood. Nevertheless, orbital signs are occasionally the first manifestation of an occult primary tumor; the commonest sites of origin are breast, prostate, lung, kidney, and gastrointestinal tract. Orbital metastases may present with painful proptosis and diplopia; these signs potentially mimic orbital inflammation or abscess (Fig. 3–33). Fractionated local radiotherapy is the mainstay of treatment, although, in certain cases, there may be a role for surgical debulking.
Secondary orbital infiltration may occur from any of the neighboring structures, such as the eyelids or paranasal sinuses, or from the globe. Meibomian gland (sebaceous cell) carcinomas of the eyelid—or neglected basal cell and squamous carcinomas—tend to invade the orbit and cause diplopia because of mechanical restriction of eye movements. Perineural invasion, commonest with squamous carcinoma of the forehead, generally occurs along branches of the frontal nerve and is often associated with pain. Sebaceous carcinoma of the lid has a propensity for intraepithelial (Pagetoid) spread and, by this means, an apparently localized eyelid mass may involve the whole ocular surface and necessitate orbital exenteration. Squamous carcinoma is the commonest sinus malignancy to invade
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Figure 3–33 Orbital cellulitis because of necrosis within a carcinomatous metastasis; the patient had undergone sinus exploration prior to referral.
the orbit, generally by direct destruction of the intervening bone and periorbita, and, as this represents advanced disease, the prognosis tends to be poor. Management often involves diagnostic biopsy and later wide surgical clearance (including exenteration if there is direct orbital involvement) with radiotherapy. Other rare paranasal tumors that invade the orbit include adenocarcinoma, adenoid cystic carcinoma, esthesioneuroblastoma, and melanoma. Primary uveal melanoma is the commonest intraocular tumor of adulthood and may spread directly to the orbit through scleral emissary veins or, very rarely with more aggressive tumors, by direct invasion of the sclera or optic nerve. Uveal melanoma with orbital extension is treated with fractionated radiotherapy but carries a poor prognosis because there is often concurrent systemic disease.
Other adulthood orbital malignancies are exceptionally rare: Malignant neurilemmoma may arise de novo or be associated with neurofibromatosis and management (after confirmatory biopsy) involves wide surgical clearance and possibly adjunctive radiotherapy or chemotherapy. Orbital hemangiopericytoma has a spectrum of invasiveness; the more benign lesions are cured by intact excision and the more malignant and pervasive tumors require wide clearance with orbital exenteration, although local or remote recurrence is common with malignant hemangiopericytoma.
4Transient Monocular Visual Loss
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VALERIE BIOUSSE
Mechanisms of TMVL
TMVL Caused by Ocular Conditions (Other Than Arterial Diseases)
TMVL Caused by Vascular Arterial Ischemia
Natural History of TMVL
Retinal Stroke
Cerebral Hemispheric Stroke
Death
Diagnosis
History
Ophthalmic Examination
Ancillary Studies
Treatment
Carotid Endarterectomy
Other Measures
References
Key Points
TMVL has numerous causes but most often results from transient retinal ischemia.
TMVL may herald permanent visual loss or devastating stroke and patients with TMVL should be evaluated urgently.
A practical approach to the evaluation of the patient with TMVL must be based on the patient’s age and the suspected underlying etiology.
In the older patient, tests should be performed to investigate giant cell arteritis, atherosclerotic large vessel disease, and cardiac abnormalities.
In the younger patient, TMVL is usually benign and the evaluation should be tailored to the particular clinical setting.
Transient monocular visual loss (TMVL) describes acute and temporary visual loss in one eye.1–3 As indicated in Table 4–1, there are numerous nonischemic causes of TMVL,1–4 which must be ruled out by a careful ocular examination before considering a vascular mechanism. This is why we prefer avoiding the term “amaurosis fugax,” usually referring exclusively to transient ischemia of the retina.3
The most important step in evaluating a patient with visual loss is to establish whether the visual loss is monocular or binocular.2,3 Monocular visual loss always results from lesions anterior to the chiasm (the eye or the optic nerve), whereas binocular visual loss results from lesions of both eyes or optic nerves, or, more likely, of the chiasm or retrochiasmal visual pathway. Deciding whether an episode of acute visual loss occurred in one eye or both is not always easy; very few patients realize that binocular hemifield (homonymous) visual field loss affects the fields of both eyes. They will usually localize it to the eye that lost
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TABLE 4–1 Differential Diagnosis of Transient Monocular Visual
Loss (TMVL)
Vascular
Orbital ischemia (ophthalmic artery)
Retinal ischemia (central retinal artery and its branches, central retinal vein) Optic nerve ischemia (short posterior ciliary arteries/ophthalmic artery) Choroidal ischemia (posterior ciliary arteries)
Vasospastic TMVL (central retinal artery)
Ocular Diseases
Anterior segment:
Dry eyes
Keratoconus
Hyphema
Angle closure glaucoma
Retinal detachment
Optic Nerve Disorders
Papilledema (transient visual obscurations)
Optic disc drusen (transient visual obscurations)
Congenitally anomalous optic disc (transient visual obscurations)
Optic nerve compression (gaze-evoked TMVL)
Uhthoff’s phenomenon (demyelination)
its temporal field. The best clues to the fact that visual loss was actually binocular are reading impairment (monocular visual loss does not impair reading unless the unaffected eye had prior vision impairment) and visual loss confined to a hemifield (monocular visual loss does not usually cause visual loss respecting the vertical meridian).2
Mechanisms of TMVL
In most cases of TMVL, the underlying mechanism is arterial ischemia of the retina or optic nerve (Table 4–1). However, numerous other ocular disorders may produce episodes of reversible monocular visual loss and can be easily ruled out by a careful ophthalmologic examination.
TMVL CAUSED BY OCULAR CONDITIONS (OTHER THAN
ARTERIAL DISEASES)
Ocular disorders changing the patient’s refractive error (such as elevated blood sugar) and alterations in corneal properties (such as dry eyes or keratoconus) or in transparency of the anterior chamber (such as hyphema) often produce episodes of blurry vision that may last from a few seconds to a few hours. Sudden elevations in intraocular pressure (such as in episodic angle closure glaucoma) may also produce acute monocular visual loss, with or without ocular pain, often preceded or associated with halos around lights.2–4
Another important cause of TMVL is a swollen or congenitally anomalous optic disc (with or without optic disc drusen), which may pinch off its own
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ciliary blood supply or the central retinal artery (Figs. 4–1, 4–2, and 4–3).2,3,5 In such cases, the episodes of TMVL last only seconds, occur frequently during the day, and are often provoked by changing gaze position or, more commonly, by assuming the upright posture (orthostatic TMVL). These brief episodes of visual loss are called “transient visual obscurations.”2,3,5 Orbital tumors may intermittently compress the ophthalmic or central retinal artery, thereby producing brief gaze-evoked TMVL (Fig. 4–4).3,4
Rarely, TMVL may arise from impending occlusion of the central retinal vein (Fig. 4–5).6
Figure 4–1 Congenitally crowded optic nerve (without true disc edema) responsible for brief episodes of transient visual obscurations.
Figure 4–2 Optic nerve head drusen in a patient with transient visual obscurations.
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Figure 4–3 Disc edema in the setting of raised intracranial pressure (i.e., papilledema) presenting with episodes of transient visual obscurations.
Figure 4–4 Right orbital mass revealed by episodes of acute complete visual loss in the right eye triggered by eye movements. The patient lost the vision in her right eye each time she looked to the right. Her visual function was normal in primary position.
Figure 4–5 Impending central retinal vein occlusion in the left eye of a young man with hyperhomocysteinemia who presented with recurrent episodes of diffusely blurry vision in his left eye. He described seeing rain showers with increased brightness lasting approximately 30 minutes. Note the dilated and tortuous retinal veins associated with flame and dot-blot retinal hemorrhages consistent with central retinal vein occlusion.
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TMVL CAUSED BY VASCULAR ARTERIAL ISCHEMIA
TMVL most often results from impaired perfusion in the ophthalmic, retinal (central or branch retinal arteries), choroidal (posterior ciliary arteries), or optic nerve (posterior ciliary arteries) circulation (Figs. 4–6 and 4–7).
There are three main mechanisms responsible for episodes of vascular arterial TMVL. They comprise (1) arterial emboli that originate in proximal arteries or the heart (usually to the ophthalmic artery, central retinal artery or its branches),
(2) ocular hypoperfusion secondary to hemodynamic impairment (stenosis or occlusion of the aortic arch, carotid or ophthalmic arteries, reduced cardiac output or systemic hypotension), and (3) arterial vasospasm (usually involving the central retinal artery). Each of these mechanisms may occur separately or in association with each other. The characteristics of the episode of TMVL and the
fundus appearance help characterize the mechanism (Figs. 4–8, 4–9, 4–10, 4–11, 4–12, and 4–13).1–3,7–9
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Figure 4–6 Blood supply to the orbit and potential collateral circulation following occlusion of the ipsilateral internal carotid artery. The ophthalmic artery, a branch of the internal carotid artery, provides most of the blood supply to the eye and orbit. It gives the central retinal artery and the posterior ciliary arteries. In case of occlusion of the internal carotid artery and a poorly functional circle of Willis, the flow within the ophthalmic artery may be reversed to protect the ipsilateral anterior cerebral hemisphere from ischemia. In this setting, the blood flow comes from branches of the external carotid artery (mostly the maxillary, facial, and middle meningeal arteries). This phenomenon is responsible for the rare observation of dilated episcleral arteries in patients with chronic internal carotid artery occlusion and for a relative ocular “steal phenomenon” that produces episodes of hemodynamic transient monocular visual loss (TMVL). (From Netter FH: Nervous system. The CIBA Collection of Medical Illustrations, vol 1, part II. CIBA Pharmaceutical Company, New York, NY, USA, 1986, Section III , Plate 7, p 57.)
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Figure 4–7 Diagram demonstrating the ophthalmic artery and its branches (central retinal artery and posterior ciliary arteries). The central retinal artery penetrates the optic nerve and divides into superior and inferior branches at the level of the optic nerve head. It vascularizes the inner portion of the retina. The ciliary arteries are very small caliber arteries and provide the blood supply to the outer retina, the choroid, and the optic nerve head. Various degrees of ocular (or orbital) ischemia may result from lesions occurring at the level of the internal carotid artery, ophthalmic artery, central retinal artery or ciliary arteries. (From Zide BM, Jelks GW: Surgical Anatomy of the Orbit. New York, Raven Press, 1985.)
Figure 4–8 Funduscopy showing two yellow refractile retinal emboli characteristic of cholesterol emboli. This patient had recurrent episodes of transient monocular visual loss (TMVL) in his left eye secondary to a tight atheromatous stenosis of his left internal carotid artery.
Retinal Emboli
TMVL was first linked to retinal arterial emboli 50 years ago when white frag-
ments were observed by ophthalmoscopy to travel through the retinal arterial vessels during episodes of TMVL.3,7,8 These emboli originate most often from
an atherosclerotic plaque at the carotid bifurcation (Fig. 4–14) and less com-
monly from the aortic arch or ophthalmic artery (Fig. 4–15). Patients with this symptom typically complain of TMVL that lasts a few minutes at most.3,10,11
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Figure 4–9 Platelet-fibrin emboli in a branch of the inferior branch of the central retinal artery in a patient with ulcerated plaques of the aortic arch.
Figure 4–10 Multiple cholesterol and platelet-fibrin emboli responsible for recurrent episodes of right transient monocular visual loss (TMVL) and a small retinal infarction in a patient with diffuse atherosclerotic disease.
Anterior Circulation Stenosis
Severe stenosis of the carotid or ophthalmic arteries or stenosis of the aortic arch (in severe aortic arch atherosclerosis or Takayasu arteritis) may cause TMVL by hypoperfusion rather than embolism.1–3,12
Hypotension
Reduced cardiac output or systemic hypotension may also produce TMVL.3 Although TMVL is not typically an isolated symptom of systemic hypotension,