Chapter 209 – Vascular Disorders
THOMAS R. HEDGES JR.
• Vascular lesions are congenital or acquired abnormalities of blood vessels that may affect all parts of the sensory and motor pathways of the eye and central nervous system.
• Aneurysms, carotid–cavernous fistulas and shunts, and arteriovenous malformations produce damage to the eye and brain and have discrete, often disparate, clinical features and management.
• Transient visual loss, both monocular and binocular, may or may not be associated with demonstrable vascular lesions.
• Transient ischemic attacks and stroke have characteristic symptoms and signs. Their diagnosis, investigation, and management depend on the locale of the insult to the central nervous system.
The visual pathways and oculomotor system can be affected by virtually all types of vascular disease. Aneurysms most commonly cause a third cranial nerve palsy, although visual loss also may occur. Carotid–cavernous (C–C) fistulas, especially shunts, can be mistaken for other more benign causes of an inflamed eye. Arteriovenous malformations (AVMs), especially cryptic AVMs, can cause highly variable cerebral neurological deficits. Transient visual loss (TVL) and cerebral ischemic attacks cause concern about impending stroke.
Epidemiology and Pathogenesis
Based on pathology studies, the incidence of diagnosed saccular aneurysms is estimated at 9%. Most saccular aneurysms occur as isolated, nonhereditary lesions. However, because intracranial aneurysms of 2?mm or smaller are found in 70% of routine autopsies, this incidence is underestimated markedly. Women are more susceptible, especially to internal carotid–posterior communicating (IC–PC) artery aneurysms. The peak incidence of aneurysms occurs during the fifth and sixth decades, and 85% of aneurysms originate from branches of the internal carotid artery, usually at the posterior communicating or the ophthalmic artery, or within the cavernous sinus. Aneurysms of 25?mm or greater almost always are symptomatic, often by mass effect, and account for 3–13% of unruptured and 3–25% of ruptured symptomatic aneurysms. Aneurysms may be multiple in about 20% of adults.
Aneurysms that affect the following portions of the circle of Willis have ophthalmologic manifestations:
• The IC–PC artery junction causing third nerve palsy
• The carotid–ophthalmic artery junction causing compression of the optic nerve or chiasm or both
• The intracavernous carotid artery causing extra oculomotor palsy, fifth cranial nerve facial sensory loss, and (rarely) optic nerve compression
IC–PC aneurysms most commonly affect young women; they can manifest as a sudden apoplectic event caused by subarachnoid hemorrhage or can enlarge slowly without rupture to produce third nerve palsy. This type of aneurysm is responsible for 13–30% of acquired oculomotor palsy  ; 90% of asymptomatic, unruptured IC–PC aneurysms cause signs of third nerve palsy.
Carotid–ophthalmic aneurysms are rarer than IC–PC aneurysms, affect the sensory visual pathways by compression of the optic nerve and chiasm, occur most commonly in women during the fourth to seventh decades of life, and often are associated with other intracranial aneurysms. Carotid–ophthalmic aneurysms may rupture and cause subarachnoid hemorrhage, but most often they produce symptoms by compression of the adjacent optic nerves and chiasm, which results in unilateral visual loss with an inferior visual field defect. These aneurysms arise from the ophthalmic artery beneath the optic nerve and compress the nerve superiorly against the superior dural shelf of the optic canal. Insidious, slowly progressive visual loss occurs in most cases. Rarely, an acute painful course with central scotoma and ipsilateral afferent pupillary deficit can mimic retrobulbar optic neuritis or ischemic optic neuropathy. When ophthalmic aneurysms expand posteriorly and superiorly, chiasmal or optic tract syndromes can be seen. Medial expansion may even compress the contralateral optic nerve.
The main difference between IC–PC aneurysms and internal carotid–ophthalmic aneurysms is that the former produce motor (third cranial nerve) signs and symptoms and the latter produce sensory (optic nerve and chiasm) symptoms and signs.
Aneurysms that arise from the internal carotid artery within the cavernous sinus behave differently. They can grow quite large before rupture; when they do rupture into the cavernous sinus they may produce a C–C sinus fistula.
Intracavernous carotid aneurysms enlarge gradually within the cavernous sinus. Anterior expansion may erode the optic foramen and superior orbital fissure, which results in compressive optic neuropathy, ocular motor nerve paresis, and proptosis. Erosion medially into the sella area may produce hypopituitarism.
Patients with unruptured intracavernous aneurysms have oculomotor palsies, with the sixth cranial nerve involved most commonly. The trigeminal nerve may be involved late, which results in facial pain. Apparent pupillary sparing of the third cranial nerve may occur because of involvement of both oculosympathetic and parasympathetic pupillary pathways.
Most patients who develop an acute oculomotor nerve paresis are left with a permanent disorder—often with secondary oculomotor nerve synkinesis or aberrant regeneration (including lid retraction on downgaze; Fig. 209-1 ) despite no previous acute third nerve dysfunction. Primary oculomotor nerve synkinesis most commonly occurs with meningiomas or, rarely, schwannomas.
Trigeminal nerve dysfunction commonly accompanies intracavernous aneurysms. The first division of the fifth nerve is affected most often. Pain usually is constant, lancinating, and severe,
Figure 209-1 A 36-year-old patient with aberrant regeneration—third cranial nerve synkinesis. A, Ptosis. B, Medial rectus paresis with lid retraction on adduction. C, Typical lid retraction on downgaze. D, Magnetic resonance angiogram showing internal carotid–posterior communicating artery aneurysm (arrow).
Figure 209-2 A 40-year-old patient with right internal carotid–posterior communicating artery aneurysm. A, Primary position ptosis. B, Paralysis of vertical gaze and dilated pupil. C–D, Arteriograms showing internal carotid–posterior communicating artery aneurysm directed down, out, and inferiorly on the third cranial nerve (arrows).
but it can be episodic. Trigeminal sensory loss is rare, and only occurs late in the disease.
Visual loss is not as characteristic of intracavernous aneurysm as it is with ophthalmic aneurysms, unless they arise from the most distal portion of the intracavernous artery.
Three clinical signs usually are apparent:
• Ipsilateral facial, orbital, or eye pain
• Extraocular muscle and levator involvement
• Pupillary paresis
Head pain can be caused by both ruptured and unruptured aneurysms. Ruptured aneurysm pain is severe, sudden in onset, throbbing, and radiates posteriorly. Neck pain and stiffness are signs of subarachnoid hemorrhage. Third cranial nerve palsy most commonly occurs concomitantly but may not develop for hours or days. Headache and eye pain from unruptured aneurysms may occur intermittently for weeks or months before third nerve palsy or aneurysm rupture occurs.
Ophthalmoplegia is variable but develops in virtually all patients eventually. It is the author’s experience that ptosis and extraoculomotor paresis occur at the same time, especially with ruptured aneurysms. An apoplectic onset with subarachnoid hemorrhage may overshadow the observation of diplopia or ptosis. Any muscle supplied by the third nerve can be affected; however, the superior rectus and levator muscles are damaged most commonly, because the aneurysm presses on the nerve from above the subarachnoid space ( Fig. 209-2 ).
Recently interventional neuroradiology has radically altered management of aneurysms. When arteriography reveals the aneurysm has a broad neck, then transcranial clipping is still necessary in many patients. However, if the aneurysm has a narrow neck then angiocatheter coils may be used to close off the aneurysm with greatly decreased risk.
Pupillary involvement can be the initial sign of an unruptured or “about to rupture” aneurysm but is rarely, if ever, an isolated sign in a ruptured aneurysm. Pupillary dilatation may occur shortly before, at the same time, or shortly after oculomotor paresis occurs. Pupil involvement mandates immediate efforts to rule out an aneurysm by magnetic resonance imaging (MRI) or magnetic resonance angiography. In an emergency, a computed tomography (CT) scan can be performed immediately to rule out subarachnoid hemorrhage. Complete pupil sparing, which may accompany extraocular muscle paresis with an IC–PC aneurysm, has been reported rarely.  
The appropriate ophthalmic management of possible aneurysms is to make the right diagnosis. Any patient with a possible third nerve palsy should be observed carefully for pupillary dysfunction. Complete third nerve paresis and a normal pupil are extremely unlikely in a patient with an aneurysm.
However, Miller states that any patient with an incomplete extraoculomotor palsy and a normal pupil should undergo neuroimaging. When aneurysms are greater than 4?mm in diameter, they can be seen on dynamic CT scans and by MRI, as well as by magnetic resonance angiography. The author feels, however, that an older hypertensive or diabetic patient, without head pain, need be observed only, because most likely there is a microvascular etiology for the third nerve palsy. A single tear in the intracavernous portion of the internal carotid artery usually is diagnosed from a history of severe head trauma. Symptoms and signs may occur directly after injury or several days to weeks later. Although relatively rare, direct fistulas may develop spontaneously. Such patients may suffer from diffuse arterial disease manifested by aortic, femoral, and popliteal aneurysms, as well as other signs of large-vessel disease, such as systemic hypertension, arteriosclerosis,  or an underlying connective tissue disorder.
Treatment, Course, and Outcomes
Recovery of extraocular muscle function occurs in most patients with IC–PC aneurysms, either spontaneously or after surgical treatment, whether or not the aneurysm has ruptured. Recovery is most likely in incomplete paresis, when no rupture has occurred and when successful clipping is performed within 1–2 weeks of onset. Incomplete recovery after several months leaves secondary oculomotor nerve synkinesis or aberrant regeneration of the oculomotor nerve (see Fig. 209-1 ).
CAROTID–CAVERNOUS SINUS FISTULAS AND DURAL SHUNTS
Epidemiology and Pathogenesis
Abnormal communications between the cavernous sinus and dural veins and the carotid arterial system can be classified according to cause (traumatic versus spontaneous), velocity of blood flow (high versus low flow), and anatomy (direct versus dural; internal carotid versus external carotid, versus both). C–C fistulas, characterized by direct flow into the cavernous sinus from the intracavernous carotid artery, are of the high-flow type; these usually are traumatic and most often diagnosed in young men. Nontraumatic, low-flow dural fistulas may develop spontaneously or with atherosclerosis, hypertension, collagen vascular disease, and during or after childbirth; these more often are seen in the elderly, especially women. After childbirth, however, low-flow dural shunts are seen most in post-menopausal women. Spontaneous shunts occur between the cavernous sinus and one or more meningeal branches of the internal carotid artery (usually the meningohypophyseal trunk), the external carotid artery, or both. These shunts have a low amount of arterial flow and almost always produce signs and symptoms spontaneously.
Dural shunts between the arterial and venous systems have lower flow, yet they may produce symptoms in younger patients spontaneously or in older patients due to hypertension, diabetes, atherosclerosis, or other vascular disorders. Anatomically, these shunts arise between the meningeal arterial branches and the dural veins. The meningohypophyseal trunk and the artery of the inferior cavernous sinus provide the arterial supply to most dural shunts.
Such shunts may be due to an expansion of congenital arteriovenous malformation or due to spontaneous rupture of one of the thin-walled dural arteries that traverse the sinus.
Ocular signs of C–C fistulas are related to venous congestion and reduced arterial blood flow to the orbit. Diminished arterial flow to cranial nerves within the cavernous sinus may cause diplopia. Stasis of venous and arterial circulation within the eye and orbit may cause ocular ischemia, and increased episcleral venous pressure may cause glaucoma. These abnormalities usually are unilateral, but they can be bilateral or even contralateral to the fistula. 
Exophthalmus is a common sign that occurs in almost all patients who have C–C fistulas; rapid-flow fistulas may cause exophthalmus within hours or several days. The orbit can become “frozen,” with no ocular motor function. Usually, this is accompanied by conjunctival chemosis and hemorrhage. Vision may be reduced markedly because of optic nerve ischemia.
“Pulsating exophthalmus” is uncommon in C–C fistula. Usually, the orbit is too rigid from hemorrhage and edema for “pulsation.”
Chemosis of the conjunctiva and arterialization of the episcleral vessels occurs in most patients. Arterialization of episcleral veins is the hallmark of all C–C fistulas or dural shunts ( Fig. 209-3 ).
Bruits associated with fistulas and dural shunts can be appreciated both subjectively and objectively. A bruit can be heard best when the examiner uses a bell stethoscope over the closed eye, over the superior orbital vein, or over the temple. A bruit is not pathognomonic of C–C fistula. It also can be heard in normal infants, in young children, and in patients with severe anemia.
In cases of C–C fistula, the abducens nerve is affected most often, because it lies in the cavernous sinus, itself. Because the third and fourth cranial nerves are encased in the superior internal dural wall of the sinus, they may be protected from changes caused by the fistula. Mechanical restriction from venous congestion and orbital edema also may contribute to limitation of eye movements.
Immediate or delayed visual loss occurs frequently in direct C–C fistulas, due to optic nerve ischemia from apical orbital
Figure 209-3 Exophthalmus. A, A 60-year-old female patient, who has left chronic “red eye.” B, Corkscrew (arterialized) vessels caused by low-flow (carotid–cavernous sinus) fistula. C, Color Doppler image that shows impedance and reversal of flow in superior orbital vein (arrow). (B, Courtesy of Dr. Christopher Kelley, Wills Eye Hospital.)
compression. Longstanding fistulas can lead to loss of vision from distension of the cavernous sinus or of retrobulbar ischemia.
Ophthalmoscopic findings due to venous stasis and impaired retinal blood flow include retinal venous engorgement and dot-and-blot retinal hemorrhages. Central retinal vein occlusion may be observed in high-velocity C–C fistulas with arterialized venous channels.
Despite high episcleral and intraocular pressures, the elevated pressure, in the author’s experience, rarely results in damage to the optic nerve. In the unusual cases of central vein occlusion, neovascular glaucoma can occur.
Misdiagnosis is more common with dural shunts than with C–C fistulas. Dural shunts may be mistaken for chronic conjunctivitis, orbital cellulitis, orbital pseudotumor, or thyroid disease. However, in dural shunts the palpebral conjunctiva is not involved, and the bulbar vessels are not affected as diffusely as in inflammatory processes. Signs of dural shunt usually are unilateral, but they can be bilateral or even contralateral to the shunt.
Exophthalmus generally occurs to a varying degree (see Figs. 209-3 , A and B), and ocular motor (usually abducens) palsies may be seen. A subjective bruit (heard by the patient) almost always can be obtained from the history; however, an objective bruit heard over the orbit or temple by auscultation is relatively uncommon. Wide pulsation of Schiötz or applanation intraocular pressure amplitude is an important clue to the diagnosis.
A direct C–C fistula should be suspected in any patient who suddenly develops a red eye with chemosis and exophthalmus, especially after head trauma. Investigation by MRI or standard angiography reveals a ruptured intracavernous aneurysm. Orbital ultrasonography, CT, and MRI often show a “hockey stick” sign of an engorged superior ophthalmic vein, which also may be demonstrated by computer Doppler imaging. The ultimate test, however, is selective arteriography of both internal and external carotid arteries.
Treatment, Course, and Outcomes
As with a C–C fistula, the diagnosis of a dural shunt can be made using CT scans, MRI, and computer Doppler imaging, because each reveals superior ophthalmic vein enlargement (see Fig. 209-3 , C). However, selective intra-arterial angiography may be necessary to define the dural shunt. Carotid color Doppler imaging may show reversal of flow in the ophthalmic artery, which may help to establish the diagnosis (see Fig. 209-3 , C).
Many patients with dural shunts improve spontaneously or after angiography. Thus, proper diagnosis, reassurance, and conservative follow-up usually suffice.  Emolization or coil placement by interventional radiology (as in aneurysms) may be necessary in patients who have unacceptable or progressive signs or symptoms such as vision loss, diplopia, pain, or intolerable bruit. Although significant risk must be considered, the present status of interventional radiology is such that these risks are minimal. Only in the rare case is embolization necessary, as for a patient who has unacceptable symptoms and signs of visual loss (e.g., central vein occlusion), diplopia, severe exophthalmus, or intolerable bruit. Although significant risks of neurological or visual sequelae from treatment must be considered, treatment of the dural fistula should precede surgery in cases of high intraocular pressure.
The prognosis of direct C–C fistula varies, but severe visual loss is often immediate and permanent, especially when a “frozen orbit” is encountered. Some patients may not be aware of the visual loss because of an overriding concern for the chemosis proptosis and lid swelling. In many cases, conservative management is propitious. However, closing the fistula with an angiocatheter balloon may be effective.
Compared with the dural shunt syndrome, the prognosis for C–C fistula is much more serious, because direct fistulas do not resolve spontaneously and are less amenable to occlusive techniques. The optimal treatment of C–C fistula is closure of the fistula along with preservation of carotid artery patency. Older procedures that required occlusion of the carotid artery to trap the fistula resulted in orbital hypoxia, which often made matters worse.
Detachable, flow-guided balloons are used to close these fistulas. Insertion of one or more balloons into the cavernous sinus can occlude the fistula successfully along with preservation of carotid flow. Complications may occur, such as worsening of orbital congestion and ocular motor nerve paresis. Fortunately, these complications are usually transient. Successful occlusion usually results in gradual resolution of orbital signs within days, weeks, or sometimes months. Visual loss is often permanent.
AVMs are the most common form of intracranial vascular hamartoma. The occasional relationship between cerebral (mesencephalic) and retinal AVMs was recognized first by Wyburn-Mason in 1943. Most intracranial AVMs involve only pial vessels, but
TABLE 209-1 — TERMINOLOGY OF TRANSIENT VISUAL LOSS
TRANSIENT MONOCULAR VISUAL LOSS
Seconds to minutes
Optic disk swelling and anomalies
Seconds to minutes
Often altitudinal; carotid, cardiac source (embolic) or vasospastic
Prolonged transient visual loss
Hypertension; hematopoietic and other systemic (vascular) problems; “retinal” migraine
TRANSIENT BINOCULAR VISUAL LOSS
No other symptoms
Isolated visual migraine (Hedges)
Acephalic migraine (O’Conner)
All similar episodic attacks (see text)
Migraine accompaniments (Fisher)
some involve both pial and dural vessels. Most AVMs are of congenital origin, but those that involve the meningeal arteries or vertebral arteries that drain into the dural sinuses may be acquired.
AVMs that are only a few millimeters in size cannot be identified by neuroimaging and are referred to as cryptic or occult. Conversely, AVMs may be so large as to occupy an entire cerebral hemisphere. Although AVMs usually are congenital, they may become symptomatic at any age. However, 70% of AVMs produce symptoms during the second and third decades of life, and most are reviewed supratentorial.
Most cerebral AVMs produce signs of intracerebral or subarachnoid hemorrhage, which include seizures or isolated neurological symptoms and signs. Headache is a frequent symptom and may mimic migraine, although the headaches always are on the same side, in contrast to typical migraines.
Improvements in microguidewire and microcatheter technology have made it possible to treat previously unreachable and untreatable AVMs. The specific endovascular techniques vary according to the anatomy of the lesion, the same as intracranial aneurysms and C–C fistulae and dural shunts.
TRANSIENT VISUAL LOSS
Epidemiology and Pathogenesis
TVL is a common symptom that may be benign or a harbinger of serious disease. Because clinical findings often are absent in patients with TVL, it is imperative to take a meticulous history.
The terminology of TVL ( Table 209-1 ) is important, because it designates not only the anatomical location of the problem, but also its pathogenesis. Specific types of transient, monocular visual loss include transient visual obscurations (which are very brief [1–5 seconds] episodes of visual loss typically seen in patients with papilledema due to increased intracranial pressure), amaurosis fugax (1–5 minutes, caused by embolic or hemodynamic retinal arterial insufficiency), and prolonged monocular TVL (which occurs in patients with hypertension, blood dyscrasias, and “retinal migraine”). Binocular TVL may be seen with classic migraine, with or in the absence of headache, and other rare binocular or homonymous disturbances due to occipital ischemia or seizures.
Physical clues which help in the diagnosis of patients with TVL include abnormalities of vision, pupillary abnormalities, color vision loss, Amsler chart defects, and abnormalities of the optic nerve
Figure 209-4 Cholesterol emboli impacted in superior and inferior retinal arterioles with branch occlusion (arrows).
or retina. The most important ocular finding in monocular TVL is an impacted embolus in the arteries within the optic nerve or in the retina. The appearance of different types of emboli can provide clues to the source. Localized, hard, white material suggests calcium, which may come from a damaged aortic or mitral valve. Thromboplatelet emboli usually conform to a segment of a retinal branch arteriole and may have a white or gray appearance. Hollenhorst or cholesterol plaques are yellow or golden and tend to gleam ( Fig. 209-4 ). Both thromboplatelet emboli and cholesterol emboli can be missed easily, especially if they are small. Gentle pressure on the eye often makes the embolic material “light up,” which allows better visualization of an embolus ( Fig. 209-5 ).
Retinal emboli are the major cause of amaurosis fugax; the carotid artery is the likely source, although such emboli also can come from the aorta or heart. Auscultation of a bruit in the neck at the angle of the jaw further indicates the need for carotid magnetic resonance arteriography or, at least, carotid Doppler imaging.
An often-neglected anterior sign in any of the ocular ischemic syndromes is sludging of the conjunctival microcirculation. Slit-lamp magnification with red-free light shows micropools and a varying degree of sludging in the conjunctival blood vessels when a vascular impedance or hyperviscosity is present. In patients with ocular ischemia from severe carotid artery stenosis or occlusion, TVL may occur when the eye on the affected side is exposed to bright light.
The age of the patient with TVL is very important—older, arteriopathic patients have different causes than do younger individuals. The character of the episode must be ascertained in detail.
NATURE OF THE EPISODES.
The following need to be established:
• Where, when, and how did the episode occur?
• Did it appear and disappear suddenly or gradually?
• Did field loss occur and, if so, what type?
The typical curtain effect of altitudinal, monocular visual field loss is most significant, because this implies carotid occlusive disease or a cardiac source.
TYPE OF VISUAL LOSS.
Monocularity is not always easy to determine. Although most patients with monocular TVL often are clear about monocularity, patients with binocular TVL or isolated visual migraine commonly state that the right or left eye was involved when, in reality, loss of vision only in the larger temporal homonymous visual field occurred.
Figure 209-5 Combined thromboplatelet retinal emboli digital pressure maneuver (arrows). A, Before pressure. B–D, During digital pressure on the eye to elicit previously only suspected embolus.
LENGTH OF EPISODES.
The duration of transient monocular loss of vision due to carotid artery disease typically lasts 1–5 minutes. Often, the patient initially does not calculate the duration accurately, but with recurrent attacks both monocularity and duration are better appreciated.
FREQUENCY OF EPISODES.
The frequency of attacks also provides a clue by which to differentiate monocular from binocular TVL. An isolated monocular attack may be sufficient to warrant investigation, at least with carotid Doppler studies. Recurrent attacks over a short interval are a strong indication for a full workup. Binocular episodes almost invariably are widely separated, often four to five in a lifetime, and rarely more often than once to twice per year.
Accompanying symptoms usually are absent in TVL. It is the isolation that makes TVL episodes unique. It is rare for a patient with an isolated visual migraine to proffer any other neurological symptoms. Contralateral numbness or weakness that occurs with transient monocular loss of vision implies severe carotid stenosis. Cerebral transient ischemic attacks imply either emboli to the brain or a hemodynamic cause, such as hypertension. Transient binocular blindness due to posterior circulation ischemia from atherosclerosis often occurs with other symptoms of vertebrobasilar insufficiency, such as dizziness, lightheadedness, or syncope.
UNDERLYING RISK FACTORS.
Contributory causes can be determined from a thorough history and appropriate investigation. Hypertension, diabetes, or hematopoietic disorders in all age groups are important. In young people, contraceptive pill use and congenital or acquired heart disease must be excluded. In older patients, any history of myocardial, femoral, or aortic disease is an important indication of a diffuse arteriopathic state.
Young patients with TVL should be screened carefully for hyperviscosity or hypercoagulable disorders. Elevated antiphospholipid-cardiolipin antibody levels in a young woman with a strong history of migraine may be important. Cardiac workup may identify mitral and aortic valvular disease, mural thrombi, and arrhythmia, especially intermittent atrial fibrillation.
Treatment, Course, and Outcomes
The goal in the management of patients with TVL is to prevent further episodes that could lead to permanent visual loss or cerebral stroke. However, a single attack of monocular TVL does not necessitate invasive studies. Noninvasive carotid and orbital color Doppler imaging, when properly performed, may be sensitive enough to provide the required information; thus, many patients who have TVL may not require more invasive studies. Older patients with risk factors for large-vessel disease probably should be assessed using magnetic resonance angiography. Any patient with a history of cardiac signs or symptoms should be assessed using an echocardiogram.
In summary, symptomatic patients with or without retinal emboli or a bruit should be assessed using carotid and orbital color Doppler imaging or magnetic resonance angiography. Invasive angiography may not be necessary.
Transient Bilateral Loss of Vision: Isolated Visual Migraine
Transient binocular loss of vision is one of the most common complaints addressed in ophthalmic practice. It has been called acephalgic migraine and migraine accompaniments. The term isolated visual migraine, however, identifies clearly an isolated transient binocular attack, similar to that described as the visual aura or prodrome of migraine.
Symptoms may last from 15 seconds to 3 hours; however, the classic description of kaleidoscopic, heat-wave, or scintillating bright lights that last 10–20 minutes makes the diagnosis, which usually is a great relief to the patient.
Miller feels that a diagnosis of migraine should not be made unless embolic and thrombotic cerebrovascular disease or seizures have been excluded. Although typical migraine can occur concomitantly with other problems, including AVM, tumor, and arteritis, the migraine is very common and the others are rare. It would be nonproductive if all such patients were studied, as proved by Fisher’s study, and the costs would be prohibitive. One must be certain to make proper diagnosis, however, before exclusion of further studies, because all patients who have monocular TVL do need a workup. Fisher concludes, as does the author, that “migraine accompaniment” justifiably can be regarded as benign.
One group isolated visual, ocular (acephalgic), retinal, and ophthalmoplegic migraine within the category of complicated migraine. The author feels that the term complicated migraine should be reserved for those who develop a prolonged neurological deficit, which lasts for hours or days after a migrainous episode. Indeed, isolated visual migraine might be considered the most benign form of migraine.
Visual field testing sometimes should be performed. It is still the best way to be sure that stroke, AVM, or tumor is not the problem.
Monocular loss almost always needs investigation. Management of binocular episodes usually is conservative. The typical 10–20 minute attack of transient bilateral homonymous loss of vision with a kaleidoscopic or heat-wave visual disturbance is so characteristic of isolated visual migraine that a diagnosis can be made with confidence, the patient reassured, and no further investigation made. These patients primarily need reassurance and do not need further investigation unless extenuating circumstances are present. The author recommends aspirin to such patients.
PEDIATRIC, OPHTHALMOPLEGIC, AND BASILOVERTEBRAL MIGRAINE.
These three entities are grouped together, because they occur predominantly in children or young adults.
Pediatric migraine commonly is seen but often is overlooked or misdiagnosed by the ophthalmologist, because the child often does not complain of typical migraine, but instead presents a “fragmented” clinical syndrome characterized by:
• Periodicity of episodes
• Mild headache
• Atypical visual disturbance with migraine characteristics
• The most important, a family history of migraine
Prensky and Sommer emphasize that these children do not need medication. As in migraine or isolated visual migraine, a proper diagnosis precludes unnecessary tests.
Epidemiology and Pathogenesis
TRANSIENT ISCHEMIC ATTACKS AND STROKE.
The most reliable indicator of impending stroke is a transient ischemic attack (TIA). Vascular sites of disease that produce TIAs and stroke are:
Figure 209-6 Ocular ischemic syndrome. Typical diffuse dot and blot hemorrhages and venous dilatation in inferior fundus.
• Carotid–ophthalmic artery
• Middle cerebral artery (MCA)
• Posterior cerebral (terminal basilar) artery
• Basilar artery
CAROTID–OPHTHALMIC ISCHEMIC ATTACKS AND STROKE.
Carotid–ophthalmic artery TIAs most commonly manifest as amaurosis fugax caused by hypoperfusion of the retina. The patient is at risk of permanent visual loss, usually from occlusion of the central retinal artery. This constitutes an ocular “stroke,” and requires investigation of carotid, cardiac, and hemodynamic diseases (see Chapter 114 ).
Severe chronic common or bilateral internal carotid artery diseases may lead to hypoperfusion of the optic nerve and retina, and also cause the ocular ischemic syndrome (see Chapter 118 ) ( Fig. 209-6 ).  Impacted cholesterol or fibrin platelet emboli in the retina are an indication of carotid artery atheroma as the source; they are seen in 60–70% of patients with branch retinal artery occlusion. Nonarteritic ischemic optic neuropathy, both anterior and posterior, rarely may be the initial manifestation of internal carotid artery occlusion.
Monocular blindness with contralateral hemispheric symptoms and signs (e.g., hemiparesis) is a well-recognized, although rare, entity in patients with carotid artery disease. Blindness is caused by retinal ischemia. However, these patients may have the simultaneous occurrence of cerebral infarction and ipsilateral ischemic optic neuropathy.
The ocular ischemic syndrome causes insidious, slowly progressive loss of vision, in contrast to the acute loss due to retinal or optic nerve infarction. The affected eye is often injected and vision is poorer than expected. Neovascular glaucoma and vitreous hemorrhage often follow. Atherosclerotic occlusion or severe stenosis of the common, external, and internal carotid arteries is found in most patients who have a risk of stroke due to poor cerebral perfusion  (see Chapter 118 ).
The second major ocular sign of carotid occlusive disease is partial or complete contralateral homonymous hemianopia, often the result of hypoperfusion in the MCA, although posterior cerebral occlusion is by far the most common cause of homonymous hemianopia. Cerebral TIAs tend to be longer in duration than ocular TIAs. Ischemic reversible neurological deficit occurs when symptoms such as numbness or weakness last days and then disappear. When the defect persists, the term stroke should be used. As the term stroke can be very upsetting to the patient, it should be emphasized that a TIA is not a completed stroke.
Ischemia of the cortical and deep cerebral branches of the left MCA produces isolated motor aphasia and, often, contralateral hemiparesis and sensory loss. When TIAs of the MCA are on the right (nondominant) side, transient motor or sensory loss is produced on the left, without aphasia.
The frequency of TIAs of MCAs is much less than that of internal carotid arteries (64% vs. 20%); also, the internal carotid artery has more TIAs per patient (103 vs. 3). Binocular TVL is not usually considered a manifestation of MCA TIAs, even though homonymous hemianopia is common in a completed MCA stroke. Caplan et al. found MCA TIAs to be more common in the young, in blacks, and in females.
The MCA stroke often fluctuates and progresses gradually. Anterior MCA branch occlusion produces hemiparesis in the leg and loss of sensation without hemianopia. Posterior MCA branch occlusion produces incomplete incongruous homonymous hemianopia, without macular sparing. Optokinetic responses may be reduced when stripes or checks are moved in the direction of the affected parietal lobe. Left MCA stroke produces aphasia, in contrast to right-sided lesions that produce contralateral hemispatial neglect and supranuclear horizontal gaze paresis toward the side of the lesion.
Homonymous hemianopia is the major neuro-ophthalmic sign of MCA stroke; it may be the only sign. It is the result of damage to the optic radiation. The prognosis in MCA stroke is poor and, until recently, no known treatment existed. Stroke centers now have a urokinase anticoagulation protocol—if treatment can be instituted within a few hours, the prognosis is much better.
Transient visual symptoms due to posterior cerebral artery (PCA) hypoperfusion are encountered less commonly and are less dramatic to the patient than amaurosis fugax of carotid origin. Isolated visual migraine must be differentiated from that of an impending stroke. Fisher states that visual migraine that occurs as a spectral march (buildup) or progression of the visual phenomenon often differentiates isolated visual migraine from occipital TIA and stroke. Clinically, visual migraine is very common, in contrast to occipital TIA, although each can mimic the aura of classic migraine. True vascular TIAs that involve the occipital lobes usually are sudden in onset, with a complete or incomplete homonymous hemianopia. They may be accompanied by basilar vertebral symptoms, such as unsteadiness, dysarthria, facial numbness, or weakness.
Isolated homonymous hemianopias usually are caused by vascular occlusion of the PCA and, therefore, are the hallmarks of occipital stroke. Infarction of the PCA is the result of embolism; rarely is it caused by atherosclerosis. Usually, PCA strokes occur without warning.
Calcarine cortex infarction results in complete or incomplete hemianopia and usually spares the macular field. Invariably it is congruous. A complete homonymous hemianopia spares the macula as a rule and usually visual acuity is normal, although patients often complain of blurred vision. Many patients are unaware of the defect until it is pointed out.
Hemianopia with splitting of the macula often causes difficulty with reading. The Amsler chart is a valuable test by which to prove macular involvement; it also is a great asset when explaining the problem to the patient.
Clinically, homonymous hemianopia due to stroke in the temporoparietal and occipital areas can be differentiated by diminished optokinetic nystagmus. When stripes or other stimuli are moved in the direction of a lesion that involves the deep parietal lobe, the responses are dampened, whereas in isolated occipital (calcarine) lesions the responses are equal.
Improvement of the field defect within weeks or months is the rule, particularly when the defect has sloping margins or it is not absolute to variously sized test objects. Neurological symptoms and signs of temporoparietal origin separate those cases caused by optic radiation damage from isolated homonymous hemianopia of occipital origin.
Hemianopia always should lead to inquiry as to other neurological deficits. Ophthalmologists should recognize alexia without agraphia, wherein the patient usually can name individual letters or numbers but cannot recognize simple words, although able to write words. Right PCA occlusion can result in prosopagnosia, or the inability to recognize familiar faces. Cerebral dyschromatopsia (color blindness) also can occur in occipital stroke.
Rehabilitation is very difficult in permanent homonymous hemianopia. The author has found that in some selected patients a 20–25D Fresnel prism, base-out, on the temporal half of one spectacle lens on the side of the hemianopia can help.
Reduction in vertebral-basilar blood flow produces neurological and visual disturbances, from damage to the midbrain, pons, medulla, cerebellum, and occipital lobes. These disturbances may be transient, persistent, inconsequential, or catastrophic. Both oculomotor and visual symptoms play a role in diagnosis.
Figure 209-7 Common areas of atherosclerotic lesions in the anterior carotid and posterior vertebrobasilar cerebral arterial systems. (Adapted from Hoyt WF. Some neuro-ophthalmological considerations in cerebral vascular insufficiency: carotid and vertebral insufficiency. Arch Ophthalmol. 1959;62:260–72.)
In the vertebrobasilar territory, TIAs are much more varied than they are in the carotid system. Vertigo is the most common neurological symptom, along with dysarthria, transient weakness, drop attacks, and occipital headaches.  The most common visual symptom is a characteristic, brief binocular “gray-out” of vision, which lasts a few seconds (rarely, up to 5 minutes). Transient diplopia is a rare symptom from ischemia of the ocular motor nerves or nuclei, or supranuclear and internuclear pathways. Typically, this symptom lasts 5–10 minutes. Episodic oscillopsia or “jumping vision” may occur during attacks of vertigo or dizziness.
The cause of vertebrobasilar TIA is speculative. Congenital vascular anomalies, hypertension, and hematological disorders are possible causes; however, atheromatous disease is the major problem in most patients ( Fig. 209-7 ).
Stroke usually occurs without previous TIAs in vertebrobasilar disease. Hypertension and atherosclerosis are the most common causes, in addition to emboli from the heart or distal large arteries. Combined brainstem symptoms and signs include vestibular nystagmus, miotic pupils, and sixth cranial nerve, conjugate gaze, internuclear, and facial palsies. Terminal PCA ischemia may occur alone or with a homonymous hemianopia. Lesions here can produce bilateral deficits, whereas carotid lesions produce unilateral deficits.
Brainstem signs most often arise from the lesions in the dorsal midbrain, primarily characterized by abnormal vertical gaze, upgaze or downgaze paresis with lid retraction, or as isolated upgaze paresis. Pupillary signs, internuclear ophthalmoplegia, and skew deviation also may be present.
See-saw and convergence retraction nystagmus accompany periaqueductal midbrain infarction. The more ventral medial midbrain syndrome of oculomotor nerve dysfunction and contralateral hemiplegia (Weber’s syndrome) and Benedikt’s syndrome with contralateral cerebellar signs also may result from infarction of midbrain. Strokes that involve these structures can be identified using MRI.
Pontine stroke produces primarily horizontal disorders of eye movement. Such strokes usually are associated with dizziness, facial nerve palsy, contralateral hemiparesis, hemisensory symptoms, and cerebellar signs. Isolated sixth cranial nerve palsy without neurological signs also has been shown, using MRI, to be caused by a fascicular lesion. Unilateral internuclear ophthalmoplegia may be due to infarction of the medial–longitudinal fasciculus in the pons.
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