310 NEUROLOGIC

OPTOCILIARY SHUNT VESSELS Meningioma, glioma, CRVO, ON drusen, fibrous dysplasia, glaucoma (leading cause), arachnoid cyst, idiopathic

PAINFUL HORNER’S SYNDROME Carotid artery dissection

PARADOXICAL PUPILS Congenital stationary night blindness (CSNB), achromatopsia, ON hypoplasia, Leber’s congenital amaurosis, Best’s disease, albinism, RP. Defined as immediate constriction within 20 seconds after room lights are turned off followed by slow dilation after 1 minute.

PULSATILE TINNITUS Arteriovenous malformation (AVM), aneurysm, pseudotumor cerebri (PTC).

SENSORY NYSTAGMUS WITH ‘‘NORMAL EXAM’’ CSNB, Leber’s congenital amaurosis, achromatopsia

TEMPORALIZATION OF DISK VESSELS Situs inversus, albinism

VISION LOSS FROM ON DISEASE Pain is suggestive of inflammatory (intense pain) or compressive (dull pain) etiologies.

Lasting only a few seconds: transient visual obscurations (TVO)

Few minutes: amarousis fugax

Fifteen to 45 minutes: migraine

Sudden onset (seconds to minutes): occlusive vascular disease (embolic, thrombotic, or arteritic), vascular spastic (migraine)

Insidious onset (hours to days): inflammatory (multiple sclerosis [MS])

Gradual onset (weeks to years): compressive (neoplastic, aneurysm, structural)

Exam and Imaging

CALORIC VESTIBULAR TESTING Cold water causes nystagmus beating to the opposite side, and warm water causes ipsilateral beating nystagmus. Indicates the direction of the fast phase of nystagmus in an awake patient with an intact vestibular system. If abnormal, indicates a supranuclear lesion or that a comatose patient with tonic deviation usually has no nystagmus. Bilateral cold water gives fast-phase upward nystagmus.

COLOR VISION TESTING In general, patients with ON disease tend to have decreased red-green color vision (similar to protans and deutans), whereas patients with retinal disease (including the ganglion-cell dysfunction seen with glaucoma) tend to have blue-yellow color deficits (resembles tritans).

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Pseudoisochromatic plates (PIPs): different tests by various manufacturers; frequently used for quick color vision screening, but were designed for diagnosis of congenital defects (patients with acquired defects may not correctly identify the figures).

Farnsworth-Munsell tests: use color chips mounted in caps. Patients with mildly defective color vision (anomalous trichromats) can pass.

D-15: patients asked to order the color hue caps beginning at the fixed blue reference cap.

Trichromats: patients arrange caps appropriately from 1 to 15.

Deutans: patients arrange colors as follows: 1, 15, 2, 3, 14, 13, 4, 12, 5, 11, 6, 7, 10, 9, and 8. Plotted on the score sheet, the axis of confusion for the deutan is shown to run parallel to the color wheel axis that runs through green and redpurple.

Protans: patients arrange hues in order as follows: 15, 1, 14, 2, 13, 12, 3, 4, 11, 10, 5, 9, 6, 8, and 7. On the score sheet, the protan’s axis of confusion runs parallel to the red and blue-green axis.

FM-100: actually only 85 color chips in four boxes that if arranged in a circle would make a color wheel. Can classify patients with normal color vision as having superior (total error score 0–16, 16% of the population), average (error score 20–100, 68% incidence), or low (score >100, 16% of the population) color discrimination. In addition, it is probably the best test to measure the zones of color confusion for patients with either acquired or congenital color vision deficits.

NEUROLOGIC EXAM Full eye exam, with particular attention to:

Visual function: BCVA distance and near, color plates, and VF (confrontation, perimetry)

May also test stereo vision, brightness, Amsler’s grid (tests the central 20 degrees of the visual field), and Pulfrich’s phenomen.

Photostress test: determine how long it takes the patient to read his or her best line of VA after 30 seconds of bright light exposure. Normal is <60 seconds even with ON disease. However, often >2 minutes is needed to recover with macular disease.

Pupils

Motility

CN V and VII function

Exophthalmometry

External, anterior segment, and fundus

NEUROLOGIC HISTORY AND ASSESSMENT Neuro-ophthalmic disease evaluation can often be confusing and daunting; thus, be precise in your

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312 NEUROLOGIC

thinking, but be flexible. Try to identify one unifying diagnosis if there are several symptoms or signs. Look for patterns. If disease is nonorganic, attempt to prove that the patient has normal vision.

Elicit chief complaint: a brief sentence summarizing the main problem, such as loss of vision or double vision (monocular or binocular).

Determine past medical, surgical, ophthalmic, and neurologic histories (headache, migraines, stroke, etc.).

Take social, family, medication, and allergy histories.

Review tests: MRI, CT (with or without contrast), lumbar puncture, VEP, EEG.

Review of systems (especially neurologic symptoms).

Review the chief complaint, and elicit the history of the present illness, with a chronological history of the chief complaint and a history of any interventions.

Localization: determine where the lesion is (afferent vs. efferent system) and its etiology.

Afferent system: retina, optic disk, optic nerve, chiasm, optic tracts, LGN, optic radiations, occipital lobe, visual association areas, and other supranuclear pathways

Efferent system: EOM (intrinsic or extrinsic), neuromuscular junction, cranial nerve, nerve fasicle, cranial nerve nucleus, and supranuclear pathways

Pathophysiology: organize by diagnosis, then by therapeutics.

OPTIC NERVE EVALUATION Look at the color, contour, capillarity, complement of NFL and the size of the disk. On direct ophthalmoscopy, the smallest aperture in sharp focus is approximately the size of the normal adult ON.

OPTOKINETIC NYSTAGMUS (OKN) Requires at least 20/200 VA and tests pursuits and saccades. Abnormal if asymmetric response, usually from parietal lesions, nonorganic blindness, or homonymous hemianopsia. Reversal of OKN seen with congenital motor nystagmus.

Cecocentral scotomas, nasal > temporal defects, and altitudinal defects: localize to the optic nerve.

Temporal field defect attached to the blind spot: often ON hypoplasia, tilted disk (often superotemporal), or retinal vascular event.

Monocular VF defects: prechiasmal lesions only, with the exception of an anterior occipital lobe infarct causing a monocular temporal crescent defect.

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Figure 8–7 Schema, superior view, localizing visual field defects from lesions in the left anterior and right posterior visual pathways. 1, optic disk (e.g., AION); 2, optic nerve; 3, anterior chiasm (junctional scotoma); 4, chiasm; 5, optic tract; 6, temporal lobe optic radiations; 7, parietal lobe optic radiations; 8, occipital lobe; 9, superior posterior occipital lobe.

Junctional scotoma (a central scotoma in one eye and a contralateral superotemporal VF defect): lesion in the anterior chiasm or optic nerve lesion just anterior to the chiasm involves one entire nerve plus the infranasal fibers (known as Wilbrand’s ‘‘knee’’) from the opposite ON that briefly enter that nerve (many experts believe this is no longer anatomically accurate).

Binasal defects: bilateral retinal or optic nerve lesions, or rarely from lateral compression of the chiasm.

Bitemporal hemianopia: localizes to the optic chiasm (affects the crossing nasal fibers), usually from pituitary adenoma, meningioma, craniopharyngioma, aneurysm, trauma, or empty sella syndrome.

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