Catastrophic Neurologic Disorders in the Emergency Department , 2nd Edition

Chapter 3. See Nothing, See Double, See Shapes and Images

Much like acute focal signs, sudden loss of visual acuity, clarity, or newly formed images may herald the rapid development of a major neurologic condition. A certain appearance (e.g., third nerve palsy) may indicate that immediate magnetic resonance imaging (MRI) or cerebral angiography is required. Some patients may need urgent neuro-surgical intervention or a consultation by an ophthalmologist, particularly when a glaring contradiction between findings on examination and neuroimaging exists. Skill, knowledge, and additional investigations are required to diagnose acute neuro-ophthalmologic conditions. Many enigmatic presentations of monocular blindness are due to acute retinal or optic nerve disorders. Monocular visual loss may suggest a lesion involving the anterior cerebral circulation. Acute transient binocular visual loss may point to occlusion in the territory of the posterior cerebral circulation.

The emergency department may not be the place to commit oneself to definitively resolving the differential diagnosis of any of these conditions, and these patients may need admission. This chapter is included for the purpose of describing common urgent neuro-ophthalmologic disorders associated with decreased vision and positive visual phenomena.

Clinical Assessment

The testing methods in the emergency department are limited, but certain tests should be performed on every patient presenting with major symptoms of a defective visual system. Blindness is usually referred to as “vision of less than 20/200 with correction or a field not subtending an angle greater than 20 degrees” (legal blindness). It is simpler to describe it by a diagram (Box 3.1). Poor vision due to a refractive error is easily discovered by having the patient look through a pinhole punched in a piece of paper. (Vision will improve if decreased from a refractive cause.) The first test in a patient with marked reduction in vision is to assess “blink to threat.” This is preferably performed in patients with reduced level of consciousness or those who claim no vision. The best technique is to approach both eyes from the lateral visual field with a closed fist and then open up the fist to a hand with spread-out fingers several inches before the eyes. (Blinking to bright light is not a reliable test.) Absence of blinking to threat often is noticed in hemianopic fields. Confrontation field testing is useful to delineate hemianopic and altitudinal defects, but it requires quiet cooperation of the patient and is not very sensitive. The best technique is to present two fingers in each visual field quadrant of both eyes, typically midway between the patient and the examiner. Movement or finger counting can be used to indicate vision. Testing is followed by examination of the pupillary size and pupillary reaction to light. Pupillary abnormalities are important telltale signs, but the interpretation is much more difficult than appreciated. A common mnemonic, PERRLA, reminds the investigator of the different components of pupil assessment (pupil equal, round, reactive, light response, accommodation response); to further localize the anisocoria requires neuro-ophthalmologic examination with 10% cocaine or diluted pilocarpine. Anisocoria without any change in dim or bright light is physiologic and greater in dim light, possibly due to Horner's syndrome or structural pupillary abnormalities such as prior synechia or uveitis. In Horner's syndrome, interruption of the oculosym-pathetic pathway also produces ptosis or reduced upper lid folding. The face is warm, the skin is dry, and conjunctival vessels may be dilated. Enophthalmos is an optical illusion due to a narrowed interpalpebral fissure. In carotid dissection, distention of the injured arterial wall damages the sympathetic fibers. Anhidrosis is typically absent in Horner's syndrome in lesions above the bifurcation (the fibers supplying the face accompany the external carotid below the carotid bifurcation). Anisocoria increasing in bright light is virtually always caused by mydriasis due to pharmacologic effects but could be due to a third nerve palsy if the reaction to diluted pilocarpine (0.1%) is negative and constriction occurs with 1.0% pilocarpine.

Box 3.1. Degree of Visual Loss


Legal blindness


Finger counting

2/1000 Arm movements

20/∞ Light perception


No light perception

Dilating the pupils with phenylephrine, which stimulates the iris dilator, generally should be discouraged in acutely progressive neuro-ophthalmologic disorders because it may take several hours for the pupil to regain its response to light. Pupillary abnormalities are shown in Chapter 8 for further reference.

Funduscopy is necessarily limited to the optic disk and retinal vasculature, and specific note should be made of die caliber of the arteries, flame-like hemorrhages, edema, or change in color of the retinal pigment. Examination is followed by testing of ocular eye movements in the horizontal and vertical directions with the intent of detecting misalignment. Voluntary gaze in all fields includes up, down, left, and right, but it is useful to use figure-of-eight tracking (Fig. 3.1).

Figure 3.1 Baseline examination of eye movements and responsible muscles using standard figure-of-eight tracking. RSR, right superior rectus; LIO, left inferior oblique; RIO, right inferior oblique; LSR, left superior rectus; RLR, right lateral rectus; LLR, left lateral rectus; LMR, left medial rectus; RMR, right medial rectus; RIR, right lateral rectus; LIR, left inferior rectus; LSO, left superior oblique; RSO, right superior oblique.


Monocular blindness is more common than acute loss of entire vision. In addition, transient Monocular blindness is more commonly encountered in the emergency department than persistent monocular defect. Transient monocular visual loss often includes embolization due to lesions of the aortic arch, heart valves, or carotid artery but may also include abnormalities associated with increased viscosity or hypercoagulability. It is not further considered here because many patients would need admission for further evaluation of its mechanism. Visual loss (uni- or bilateral) may result from lesions of the cornea and at any topographic location of the afferent visual system ending in the occipital poles. Monocular visual loss often indicates an ophthalmologic disorder, and these are shown in Table 3.1. A neurologic cause for monocular visual loss is most likely optic neuropathy. It typically manifests with markedly reduced visual acuity (20/200), inability to recognize color or its brightness (particularly red), and often no obvious findings on neurologic examination except an afferent pupil defect. The optic disk may take time to become abnormal but may show pallor or elevation. An afferent pupillary defect (Marcus Gunn) is traditionally examined, using the swinging flashlight test. The patient is asked to fixate on a distant target to eliminate the miotic effect of accommodation. A bright light is moved from one eye to the other. The response may vary from minimal asymmetry to pupils failing to constrict or dilate when the penlight moves to the affected eye. In its most pronounced form, pupils dilate immediately when the light shines into the diseased eye. Afferent pupillary defect is linked to optic neuropathy, but a retinal lesion or massive intravitreous hemorrhage (Terson's syndrome) may produce similar findings (see Chapter 13).

Table 3.1. Ophthalmologic Disorders



Central retinal artery occlusion

·  Afferent pupil defect

·  Retinal edema

·  Optic disk pallor and cherry-red spots

Retinal vein occlusion

·  “Blood and thunder” fundus (extensive intraretinal hemorrhage)

Retinal detachment

·  Translucent gray wrinkled retina

Ischemic optic neuropathy

·  Pale optic nerve

·  Milky, edematous

·  Scalp tenderness and absent temporal artery pulsation (giant cell arteritis)

Optic neuritis

·  Normal findings (“patient sees nothing, doctor sees nothing”)

·  Early pallor

Vitreous hemorrhage

·  Diabetes, hypertension, or subarachnoid hemorrhage

Optic neuritis is associated with periocular pain and pain on eye movement in 90% of cases.1 The causes of optic neuritis are manyfold and can typically be divided into inflammatory causes and the first manifestations of multiple sclerosis (5-year probability of 30%).2,3 Inflammatory causes an include common bacterial infections, such as streptococcus and staphylococcus, but also more exotic infections, such as toxoplasmosis, cryptococcosis, aspergillosis, and mucormycosis in susceptible immunosuppressed patients. In other patients, optic neuritis may occur after a vaccination or viral illness or in the setting of connective tissue disease or sarcoidosis. Hereditary optic neuropathy may also present with acute monocular visual loss; and in approximately 50% of patients, family history can be elicited. Certain toxic optic neuropathies have been described; they include methanol, ethambutol, isoniazid, thiamine (B1) and folate deficiency.4

Acute blindness may involve both eyes and, excluding ophthalmologic disorders, points to bilateral involvement of the occipital lobes. Differential diagnosis involves acute basilar artery occlusive disease, sagittal sinus thrombosis, posterior reversible encephalopathy syndrome, and many drug-induced encephalopathies that include vincristine, methotrexate, cyclosporine, and tacrolimus (see Chapter 18).


Acute diplopia is complex to analyze, and the underlying deficit may remain ambiguous. Monocular diplopia, almost always due to abnormalities in the refractive media, precludes further neurologic work-up. Binocular diplopia is difficult to assess because in some patients multiple cranial nerve involvement is present. Questions that could clarify the chief complaint in acute diplopia should include mode of onset, diplopia disappearing after one eye is closed, whether vertically or horizontally oriented, whether always present or fluctuating, and whether more pronounced in a certain gaze.

Figure 3.2 Nine gaze positions in (a) III nerve palsy, (b) IV nerve palsy, and (c) VI nerve palsy.

Figure 3.2 shows nine cardinal positions of gaze in oculomotor palsies, each providing fairly characteristic deviations of the globe. In addition, Table 3.2 provides an oversimplification of, but is useful in sorting out, the different cranial nerve palsies associated with diplopia. Table 3.3 lists disorders that indicate the need for urgent evaluation. Skew deviation may be associated with diplopia and indicates an internuclear lesion. It is a result of abnormalities in fibers ascending vertically from vestibular nuclei with the medial longitudinal fasciculus. Not infrequently, it is due to a pontine stroke in elderly patients and multiple sclerosis in younger patients (Fig. 3.3).

The cause of acute diplopia, however, may also include other factors, such as difficulty with movement of the globe due to mass effect in the orbit (thyrotoxicosis), diplopia caused by an acute manifestation of myasthenia gravis, and chronic progressive external ophthalmoplegia, particularly if ptosis is bilateral. A cavernous sinus lesion should be considered when an abducens lesion is associated with Homer's syndrome.

Acute oculomotor palsy with preceding retroorbital pain may be a sign of unruptured posterior communicating aneurysm, and two-thirds may be smaller than 6 mm (Fig. 3.4). It may herald rupture and indicate rapid aneurysm growth.5 Development of pupil involvement, albeit uncommon, may be particularly worrisome for pending rupture.6 A very urgent condition is carotid cavernous fistula. Trauma to the orbit may be remote (e.g., hit windshield) or comparatively early, such as after transsphenoidal pituitary surgery, carotid end-arterectomy, or ethmoidal surgery.7,8,9 Associations with Ehlers-Danlos syndrome and pregnancy have been noted. It may occur spontaneously. Lid swelling and orbital pain with characteristic pulsating exophthalmos and tortuous conjunctival vessels point to its diagnosis (see Color Fig. 3.5 in separate color insert). Funduscopy may demonstrate pulsating venous dilation and, in more extreme forms, disk edema and ophthalmoplegia. Ophthalmoplegia may be due to restricted excursions or cranial nerve injury in the segments traversing the cavernous or petrosal sinus. Visual loss is a consequence of increased intraocular pressure and reversal of flow or thrombus in the superior ophthalmic vein. There is a need for full angiographic documentation. Immediate opacification of the cavernous sinus is seen after carotid injection.

Table 3.2. Diplopia Due to Cranial Nerve Palsy

Cranial Nerve

Position of Eye


Additional Features


Down and out


Ptosis, dilated fixed pupil




Head tilted away from affected side, chin down




Head turned to affected side

Table 3.3. Urgent Disorders in Acute Diplopia

Acute III nerve palsy

·  Basilar artery aneurysm, posterior communicating artery aneurysm*

·  Pituitary apoplexy

·  Acute midbrain infarct or hemorrhage

·  Mucormycosis*

·  Carotid cavernous fistula

·  Granulomatous inflammation (Tolosa-Hunt)

·  Diabetic microvascular disease†

Acute VI nerve palsy

·  Carotid aneurysm

·  Cavernous sinus thrombosis*

·  Nasopharyngeal carcinoma

·  Increased intracranial pressure

Acute IV nerve palsy

·  Trauma

·  Meningitis, infectious or neoplastic*

·  Herpes zoster ophthalmicus*

* Also known as the painful ophthalmoplegias.
† More often pupil-sparing.

Complete Ptosis

A curious phenomenon is apraxia of eyelid opening when the patient is unable to open the eyes.10,11 The orbicularis oculi does not contract, and the frontalis muscles are used to try to perform this act, though the eyes may remain completely closed. This disorder has been linked to acute nondominant hemispheric lesions (e.g., putaminal hemorrhage and large hemispheric infarcts).12,13,14 The pathways are unknown but involve supranuclear connections in the nondominant hemisphere (Fig. 3.6). It maybe at brain-stem level and is more common when herniation occurs.14

Figure 3.3 Internuclear ophthalmoplegia.

Visual Illusions

Positive visual phenomena may need careful attention and evaluation. Images perceived as false may indicate an acute hemispheric lesion or significant neurotoxicity. Visual hallucinations may take many forms, from dots, geometric shapes, and lines to dream-like descriptions of figures, animals (often frightening), and detailed movie-like scenes (midbrain peduncular hallucinations). First, neurotoxicity should be excluded by history. Drugs to treat Parkinson's disease (e.g., levodopa, lisuride, mesulergine, pergolide) or depression (e.g., amitriptyline, imipramine, lithium carbonate), stimulants (amphetamine, cocaine), and immunosuppressive agents (cyclosporine, tacrolimus) should be considered. Hallucinations with migrainous components, such as fortifications (zigzag lines in parallel) that are constantly in the same visual field, could point to an arteriovenous malformation.15 Visual hallucinations could be due to seizures—albeit rare—certainly when isolated, not accompanied by head or eye deviation or rapid blinking, or associated with a transient hemianopic field defect. However, it is not always appreciated that colored comma shapes or white streaks flashing in a vertical direction may be due to vitreous detachment.

Palinopsia involves an image that persists after looking at a subject, rapidly fades or returns hours later, and is superimposed on certain objects. It has been noted with encephalitis, fulminant multiple sclerosis, and brain tumors; but illicit drugs (lysergic acid diethylamide) and major psychiatric pathology are equally common.16,17,18,19

Micropsia (objects appear smaller) is rarely caused by cerebral lesions and is more typically seen with retinal lesions. Unilateral metamorphopsia (illusion that objects are distorted) (also common in macular degeneration) may indicate a parietal lobe lesion and may be limited to facial images. It probably only occurs as an ictal phenomenon.20

Line of Action

There are many conditions associated with diplopia or visual loss. Some acute neuro-ophthalmologic conditions may point to an acute neurologic condition that needs immediate evaluation. The critical steps in gathering key features of the patient with the most urgent concerns are shown in Figure 3.7. This most likely involves immediate MRI or cerebral angiography. A neuro-surgical consult is mandated in any patient with a painful ophthalmoplegia, due to its correlation with lesions that may require skull base surgery or endovascular procedures. A compressive or infiltrative lesion that affects the optic nerve should be excluded by an MRI scan. An MR angiogram to exclude an intracranial aneurysm should be considered when appropriate because an anterior cerebral aneurysm can leak into the optic sheath and be responsible for acute monocular blindness.21 Balloon or coil occlusion in carotid-cavernous fistula has been successful but not without worsening of symptoms. However, reversibility of blindness has been reported.22

Figure 3.4 III nerve palsy due to posterior communicating artery aneurysm.

Figure 3.6 Complete ptosis in hemispheric stroke in non-dominant hemisphere. Note gaze preference.

Unexpected loss of vision may have many causes and can be further delineated by an emergent ophthalmology examination. A particularly worrisome condition is anterior ischemic optic neuropathy. When considered, and when the erythrocyte sedimentation rate is elevated (normal age plus 12 in males and normal age plus 10 to 12 in females), immediate administration of methyl-prednisolone 250 mg IV qid for 3 days should be done to prevent involvement of the opposite eye.

Figure 3.7 Critical steps in acute neurophthalmology. MRI/A, magnetic resonance imaging/angiography; CSF, cerebrospinal fluid.


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