Ординатура / Офтальмология / Английские материалы / Neuro-Ophthalmology_Kidd, Newman, Biousse_2008
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nerve palsy might indicate uncal herniation or posterior communicating artery aneurysm.
If ocular motor function in the brainstem is intact, there may be roving eye movements, characterized by conjugate or dysconjugate, slow ocular deviations in random directions. Periodic alternating or “ping-pong” gaze, refers to slow, repetitive, back and forth, horizontal conjugate eye movements. Spontaneous nystagmus is unusual in coma except in dorsal midbrain lesions associated with convergence-retraction nystagmus. Patients with ocular bobbing, usually comatose because of severely destructive pontine lesions, have a fast conjugate downward deviation followed by a slow upward correction to midposition. Ocular dipping, with a quick upward deviation followed by a slow downward movement, has the same neuroanatomical localization.
Comatose patients exhibiting spontaneous, full, conjugate eye movements, as well as normal pupillary reactivity and eyelids, can be considered to have intact third, fourth, and sixth nerve function, as well as preserved internuclear connections. Individuals having absent or abnormal spontaneous eye movements should be tested using oculocephalic (head turning or doll’s head) or oculovestibular (ice-water caloric) maneuvers. In comatose patients with intact brainstem function but abnormal cortical influences, the oculocephalic response may be overly brisk (disinhibited), and ice-water stimulation in one ear may result in ipsiversive eye deviation without the contraversive corrective phase. These maneuvers may uncover a vertical gaze paresis, skew deviation, sixth nerve palsy, or internuclear ophthalmoplegia useful for brainstem localization. In early metabolic coma, the oculocephalic and oculovestibular reflexes are usually preserved. Absent oculocephalic and oculovestibular reflexes may indicate diffuse brainstem dysfunction and is seen in late transtentorial (rostral-caudal) herniation and brain death.32
ABNORMAL OCULAR FUNDI IN COMA
Papilledema
Papilledema refers to optic disc swelling resulting from increased intracranial pressure. Early papilledema occurs first in the superior-inferior axis and is associated with disc hyperemia. Opacification of the nerve fiber layer may cause obscuration of retinal vessels as they leave the disc. Hemorrhages, cotton wool spots, and exudates are common as papilledema progresses. Although an inconsistent finding, the presence of spontaneous pulsation of the retinal veins makes the presence of increased intracranial pressure less likely. Finally, the optic cup is preserved until papilledema is well developed. Papilledema is usually bilateral, although findings may occasionally be asymmetric.36
A history of other clinical features such as transient visual obscurations, morning headache, nausea, ataxia, or horizontal diplopia would also be compatible with increased intracranial pressure. Etiologies to consider would include mass lesions, hydrocephalus, venous thrombosis, and infectious meningitis.
TERSON’S SYNDROME
Terson’s syndrome is vitreous, subhyaloid, or retinal bleeding in association with subarachnoid hemorrhage. The exact mechanism by which this occurs is
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unclear, although it has been postulated that it may be because of subarachnoid blood tracking down the optic sheath or outflow obstruction resulting from the sudden rise in intracranial pressure causing venous engorgement and hemorrhage. Although Terson’s syndrome is most commonly seen in association with ruptured anterior communicating aneurysms, it may occur after subarachnoid hemorrhage from any etiology.36
REFERENCES
1.Liu GT: Disorders of the eyes and eyelids. In Samuels MA, Feske S (eds): Office Practice of Neurology. New York, Churchill Livingstone, 1996, p. 41.
2.Rizzo JF III: Embryology, anatomy and physiology of the retina. In Miller NR, Newman NJ (eds): Walsh and Hoyt’s Clinical Neuro-Ophthalmology, 6th ed. Philadelphia, Lippincott Williams & Wilkins, 2005, pp 3–24.
3.Patten J: Vision, the visual fields, and the olfactory nerve. Neurological Differential Diagnosis, 2nd ed. New York, Springer-Verlag, 1996, p 23.
4.Hoyt WF, Luis O: The primate chiasm. Arch Ophthalmol 1963;70:69–85.
5.Mason C, Kandel ER: Central visual pathways. In Kandel ER, Schwartz JH, Jessell T (eds): Principles of Neural Science, 3rd ed. Norwalk, CT, Appleton & Lange, 1991, p. 437.
6.Glaser JS, Sadun AA: Anatomy of the visual sensory system. In Glaser JS (ed): Neuro-Ophthalmology, 2nd ed. Philadelphia, Lippincott, 1990.
7.Horton JC: Wilbrand’s knee of the primate optic chiasm is an artifact of monocular enucleation. Trans Am Ophth Soc 1997;95:579–609.
8.Frisen L, Holmegaard L, Rosencrantz M: Sectoral atrophy and homonymous horizontal sectoranopia: A lateral choroidal artery syndrome. J Neurol Neurosurg Psychiatry 1978;41:374–380.
9.Horton JC, Hoyt WF: The representation of the visual field in human striate cortex. A revision of classic Holmes map. Arch Ophthalmol 1991;109:816–824.
10.Moore KL: Clinically Oriented Anatomy, 4th ed. Baltimore, Lippincott, Williams & Wilkins, 1999.
11.Galetta SL: Cavernous sinus syndromes. In Margo CE, Hamed LM, Mames RN (eds): Diagnostic Problems in Clinical Ophthalmology. Philadelphia, WB Saunders, 1994, p 610.
12.Balcer LJ, Galetta SL, Bagley LJ, et al: Localization of traumatic oculomotor nerve palsy to the midbrain exit site by magnetic resonance imaging. Am J Ophthalmol 1996;122:437–439.
13.Galetta SL, Liu GT, Volpe NJ: Diagnostic tests in neuro-ophthalmology. Neurol Clin 1996;14:201–222.
14.Trobe JD: Third nerve palsy and the pupil: Footnotes to the rule [editorial]. Arch Ophthalmol 1988;106:601–602.
15.Zee DS, Newman-Toker DE: Supranuclear and internuclear ocular motor disorders. In Miller NR, Newman NJ (eds): Walsh and Hoyt’s Clinical Neuro-Ophthalmology, 6th ed. Philadelphia, Williams & Wilkins, 2005, pp 907–967.
16.Silverman IE, Liu GT, Volpe NJ, Galetta SL: The crossed paralyses: The original brain-stem syn-
dromes of Millard-Gubler, Foville, Weber, and Raymond-Cestan. Arch Neurol 1995;52:635–638. 17. Galetta SL, Balcer LJ: Isolated fourth nerve palsy from midbrain hemorrhage: Case report.
J Neuro-Ophthalmol 1998;18:204–205.
18.Miller NR: Neural control of eye movements. In Miller NR (ed): Walsh and Hoyt’s Clinical Neuro-Ophthalmology, 4th ed. Baltimore, Williams & Wilkins, 1985, pp 608–633.
19.Pierrot-Deseilligny C: Saccade and smooth-pursuit impairment after cerebral hemispheric lesions. Eur Neurol 1994;34:121–134.
20.Zee DS: The organization of the brainstem ocular motor subnuclei. Ann Neurol 1978;4:384–385.
21.Kardon RH: Anatomy and physiology of the autonomic nervous system. In Miller NR, Newman NJ (eds): Walsh and Hoyt’s Clinical Neuro-Ophthalmology, 6th ed. Philadelphia, Lippincott, Williams & Wilkins, 2005, pp 649–714.
22.Slamovits TL, Glaser JS: The pupils and accommodation. In Glaser JS (ed): Neuro-Ophthalmology, 2nd ed. Philadelphia, JB Lippincott, 2005, p 464.
23.Frisen L: Visual acuity. In Clinical Tests of Vision. New York, Raven Press, 1990, pp 24–46.
24.Hart WM: Acquired dyschromatopsias. Surv Ophthalmol 1987;32:10–31.
25.Moseley MJ, Hill AR: Contrast sensitivity testing in clinical practice. Br J Ophthalmol 1994;78:795.
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26.Browning DJ, Tiedeman JS: The test light affects quantitation of the afferent pupillary defect. Ophthalmology 1987;94:53–55.
27.Johnson LN: The effect of light intensity on measurement of the relative afferent pupillary defect. Am J Ophthalmol 1990;109:481–482.
28.Pilley SF, Thompson HS: Pupillary “dilatation lag” in Horner’s syndrome. Br J Ophthalmol 1975;59:731–735.
29.Nunery WR, Cepela M: Levator function in the evaluation and measurement of blepharoptosis. Ophthalmol Clin 1991;4:1–16.
30.Sedwick LA: Ptosis. In Margo D, Hamed L, Mames R (eds): Diagnostic Problems in Clinical Ophthalmology, Philadelphia, WB Saunders, 1994, pp 38–42.
31.Plum F, Posner JB: The pathologic physiology of signs and symptoms of coma. In The Diagnosis of Stupor and Coma, 3rd ed. Philadelphia, FA Davis, 1980, pp 1–86.
32.Liu GT: Disorders of the eyes and eyelids: Disorders of the eye movements. In Samuels MA, Feske S (eds): The Office Practice of Neurology, New York, Churchill-Livingstone, 1996, p 50.
33.Bleck TP: Levels of consciousness and attention. In Goetz CG, Pappert EJ (eds): Textbook of Clinical Neurology. Philadelphia, WB Saunders, 1998, pp 2–16.
34.Quality Standards Subcommittee of the American Academy of Neurology: Practice parameters for determining brain death in adults (summary statement). Neurology 1995;45:1012.
35.Wijdicks EFM: Determining brain death in adults. Neurology 1995;45:1003.
36.Laskowitz D, Liu GT, Galetta SL: Acute visual loss and other disorders of the eyes. Neurol Clin North Am 1998;16:323–353.
2Is It a Neuro-Ophthalmic Problem? (If Not, What Else
Could It Be?)
NANCY J. NEWMAN
Clinical Evaluation: Recognizing
an Optic Neuropathy
Clinical Entities That are not Optic Neuropathies
Ocular Media Abnormalities Abnormalities of the Macula and
Outer Retina
Retinovascular Occlusion and
Retinal Detachment
Retinal Degenerations
Investigations
It is an Optic Neuropathy!
References
Key Points
The neurologist will see patients complaining of visual loss and should be able to evaluate the visual system and determine the location of the problem along the visual pathways from the eyes to the occipital lobes.
The neurologist must be able to differentiate between visual loss from an optic neuropathy and visual loss from retinal and ocular causes.
The classic features of an optic neuropathy are central visual loss, clear view through to the optic nerve, a relative afferent pupillary defect, and a swollen or pale optic nerve head.
Ancillary testing, especially retinal electrophysiology, is often helpful, especially when differentiating bilateral optic neuropathies from subtle maculopathies and retinal degenerations.
Essentially all categories of disease processes can cause an optic neuropathy.
The neurologist is not infrequently confronted with a patient complaining of visual loss. On some occasions, the patient has already been seen by an ophthalmologist or, more commonly, an optometrist. However, it is not unusual for the neurologist to be the first health care provider to examine the patient. As an expert on the central nervous system, of which the eye is a part, the neurologist is expected to be able to evaluate a patient’s complaint of visual loss and provide at least a cursory examination of the ocular apparatus and visual pathways.
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Traditionally, the only part of the “eye” considered the domain of the neurologist is the optic nerve and its connections into the brain. At the very least, therefore, the neurologist should be able to recognize when visual loss is caused by an optic nerve problem and when it is not. The neurologist must know the classic defining features of an optic neuropathy. When these defining characteristics are not met, other abnormalities involving the ocular media and the retina should be considered. To localize the lesion within the eye and to generate a diagnosis, the neurologist must at least be aware of the other clinical entities that can cause visual loss, especially sudden visual loss, in addition to optic nerve damage. No one realistically expects the neurologist to be an expert on the eye. However, there are certain “red flags” on clinical evaluation that should make the neurologist think about these other diagnoses and seek prompt ophthalmologic referral. In some situations, it is the neurologist, with his or her particular knowledge of the brain and its adnexa, who makes the correct diagnosis and initiates the appropriate management, even when the problem is ocular and should have been the domain of the ophthalmologist.
Clinical Evaluation: Recognizing an Optic Neuropathy
It has been estimated that the optic nerves contain 38% of all the axons entering or leaving the brain.1 Not surprisingly, therefore, neurologists often find themselves confronted by patients with complaints of visual impairment. The neuro-ophthalmic evaluation has been detailed in Chapter 1. In this chapter, we emphasize the historical and clinical features that help differentiate an optic neuropathy from the more common ocular causes of visual loss. Optic neuropathies account for most instances of neurogenic visual loss.
The classic features of an optic neuropathy are as follows:
1.Central visual loss
2.Clear view through to the optic nerve
3.Relative afferent pupillary defect
4.Swollen or pale appearing optic nerve (Fig. 2–1)
If all these features are met, there is little question as to localization of the lesion. Of course, it is not always so clear-cut. Some optic neuropathies may spare central visual acuity. Glaucoma is a prime example. Furthermore, in up to 50% of patients with nonarteritic anterior ischemic optic neuropathy, for example, visual acuity is good despite altitudinal visual field loss. In other acute optic neuropathies, such as the majority of cases of retrobulbar idiopathic optic neuritis, the optic nerve appears normal for at least 4 to 6 weeks before optic nerve head pallor ensues. However, in the last two examples, the presence of other features, especially a relative afferent pupillary defect, facilitates recognition of the optic nerve as the locus of pathology. A more difficult situation occurs when the optic neuropathy is bilateral and symmetrical, and, therefore, a relative afferent pupillary defect may not be present.
Clinical Entities That are not Optic Neuropathies
There are many causes of visual loss that are not optic neuropathies with which the neurologist should be familiar. In the remainder of this chapter, we consider those causes of visual loss that are not a result of primary optic nerve injury.
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Figure 2–1 Appearance of the optic nerve on funduscopic examination. A, Normal-appearing optic nerve head. B, Swollen optic nerve head. C, Pale optic nerve head.
These entities are categorized by how many of the criteria for the classic diagnosis of an optic neuropathy they meet.
OCULAR MEDIA ABNORMALITIES
Clinical entities that cause visual loss and do not allow a clear view back to the fundus are almost always problems with the ocular media: the cornea, the anterior chamber, the lens, or the vitreous.2,3 Many of these problems can be recognized with penlight observation or use of the direct ophthalmoscope focused on the more anterior eye (i.e., with more plus diopters dialed in). Corneal surface changes, scarring, edema, or structural abnormalities (such as keratoconus) will make the view in difficult. A hyphema (blood in the anterior chamber) may be visible to the naked eye. Cataracts will cause blurring, darkening, or an orangebrown discoloration of the fundus details, a glaring reflection of the ophthalmoscope’s light, or complete obscuration of view (Fig. 2–2). Vitreous hemorrhage, inflammation (uveitis), or debris may also completely obscure or blur the view of the optic nerve and retina.
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Figure 2–2 Nuclear sclerotic and cortical cataract as it would look when viewed through a direct ophthalmoscope focused anterior to the fundus (more plus diopters).
Angle closure glaucoma is a sudden rise in intraocular pressure usually occurring in patients anatomically predisposed for a narrow drainage angle.2 Normally, the aqueous fluid of the eye is produced at the ciliary body (located just behind the peripheral circumference of the iris), passes through the pupil into the anterior chamber, and then drains from the eye mostly through Schlemm’s canal, which is located in the sclera near the junction of the cornea and the base of the iris. Elevation of the iris periphery, as can occur with pupillary dilation in some patients, narrows the path to Schlemm’s canal and can cause sudden, significant blockage of outflow and rise in intraocular pressure. The patient typically has nausea as part of the vagal reflex, a painful eye from the elevated pressure, a red eye from increased vascular congestion, a large and nonreactive pupil from ischemia to the iris, and subnormal vision from corneal haze. Corneal haze can be recognized with the direct ophthalmoscope looking for a reduction in the normal luster of the corneal surface, especially as compared with the fellow eye, and the view in will be hazy. The presence of a fixed dilated pupil and pain may mislead the physician to conclude that there is aneurysmal compression of the third nerve. However, the other ocular findings and the absence of ptosis or motility disturbances should lead to appropriate diagnosis and management. On rare occasions, angle closure may be intermittent, thereby causing transient blurring of vision (usually with associated eye pain or headache), mimicking so-called amaurosis fugax. If left untreated, optic nerve damage may ensue, contributing to visual loss and resulting in a relative afferent pupillary defect, potentially leading to further confusion in diagnosis. However, by the time optic nerve injury has occurred, the ocular media findings should be quite apparent.
Vitreous hemorrhage (Fig. 2–3) most commonly occurs in the diabetic with diabetic retinopathy and neovascularization but also occurs after trauma and after subarachnoid hemorrhage (Terson’s syndrome). Smaller vitreal hemorrhages are usually described as large “floaters” that move when the eye is moved. Larger vitreal hemorrhages persistently disrupt central vision. Examination will reveal a diminished red reflex and the view of the fundus will be obscured on direct
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Figure 2–3 Vitreous hemorrhage. A, Vitreous hemorrhage (green haze within the eye) obscuring the normal red reflex in a post-subarachnoid hemorrhage patient with Terson’s syndrome, as seen with a direct ophthalmoscope focused anterior to the fundus (more plus diopters). B, Funduscopic appearance of a different patient with vitreous hemorrhage obscuring visualization of the details of the left retina inferiorly.
ophthalmoscopy. The inpatient from the neurosurgery service who has visual loss on awakening after a subarachnoid hemorrhage almost always has unilateral or bilateral vitreous hemorrhage.
ABNORMALITIES OF THE MACULA AND OUTER RETINA
The most common problem faced by the neurologist in the differential diagnosis
of visual loss is deciding whether the visual loss is the result of a lesion of the optic nerve or a lesion of the macula.1,2,4 Both optic nerve lesions and macular
lesions can reduce central acuity and both can cause central scotomas on visual fields. Both may also affect color vision, although the amount of color vision deficit for any given visual acuity deficit is usually much greater for an optic neuropathy than a maculopathy. Maculopathies are rarely painful, as opposed to some causes of optic neuropathy, especially idiopathic optic neuritis in which pain, particularly pain exacerbated by eye movement, is a common feature. Classically, maculopathies cause visual distortions and vision is slow to recover after bright light, features not usually found among optic neuropathies. The visual field defects of an optic neuropathy may respect the horizontal meridian, whereas macular lesions will not. If the macula definitely looks abnormal, the answer is clear, but some retinal lesions are quite subtle and difficult to detect.4,5
However, it is the absence of a relative afferent pupillary defect that should lead the examiner to suspect a problem removed from the optic nerve. Very often, the retinal findings may be so subtle that examination by an ophthalmologist with slit lamp fundus biomicroscopy is essential, and more sophisticated electrophysiologic testing is required for diagnosis.
Central serous retinopathy (CSR) (Fig. 2–4) is a relatively common cause of visual loss that occurs when serous fluid accumulates in the subretinal space underneath the macula causing a relative detachment of the layers of the retina. It makes the macula look like a blister. Presumably fluid has leaked from the choroid through a break in the retinal pigment epithelium. It occurs preferentially in males (male to female ratio of 10:1) in their fourth and fifth decades
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Figure 2–4 Central serous retinopathy of the right eye macular region. Note the blister-like elevation of the inner retina from accumulation of fluid in the subretinal space.
of life, especially so-called type A personalities under increased stress. The symptoms are fairly sudden in onset and consist of painless blurred and dim central vision and there is usually metamorphopsia. Most eyes improve spontaneously within 1 to 6 months. Fifty percent of patients experience recurrences. The clinical picture may be mistaken for optic neuritis, but the male gender, the metamorphopsia, the lack of pain, and the usual absence of a relative afferent pupillary defect should raise suspicion for CSR.
Macular degeneration is typically a progressive, bilateral acquired degeneration of the outer retina in the region of the macula. With age, some patients develop chronic degenerative changes, so-called age-related macular degeneration (Fig. 2–5). An early sign of the process is the appearance of yellow-white deposits with irregular borders known as drusen (a completely different entity
Figure 2–5 Macular degeneration in the left eye with macular drusen deposits.
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from the drusen found in optic nerves). These drusen result from thickening of Bruch’s membrane or from the retinal pigment epithelial cells’ inability to dispose of lipofuscin and other waste products. Hypopigmentation or hyperpigmentation of the retinal pigment epithelium may also be present.
There are many other causes of maculopathy, many hereditary, occasionally toxic, almost always bilateral. A specific diagnosis depends on the location of the deposits, the results of fluorescein angiography, the age of the patient, and the family history. Most patients with severe visual loss from macular degenerations develop choroidal neovascularization, which places them at increased risk for subretinal hemorrhage, subretinal exudate, and macular edema.
A macular hole is just that (Fig. 2–6). Idiopathic macular holes and cysts occur primarily in women in the sixth through eighth decades of life, probably as a result of progressive vitreoretinal traction. A fully formed hole is visible as a sharply delineated defect in the middle of the macula. The other eye may become similarly involved in up to 30% of patients.
Acquired enlargement of the physiologic blind spot, both symptomatic and asymptomatic, is usually the result of swelling of the optic nerve head. Occasionally, however, blind spot enlargement may occur with a normal-appearing optic nerve and signify peripapillary outer retinal dysfunction, the so-called acute idiopathic blind spot enlargement (AIBSE) syndrome (Fig. 2–7). AIBSE is a syndrome characterized by the sudden onset of a monocular temporal blind area centered on the physiologic blind spot, often with associated photopsias in the scotomatous field. Women are affected at least twice as frequently as men, and most patients are between the ages of 20 and 40 years. Visual acuity and color vision are typically spared and there may or may not be a relative afferent pupillary defect (present less than 50% of the time). Ophthalmoscopic and fluoroangiographic findings are often normal or consist of nonspecific pigmentary changes or subtle grayish discoloration of the peripapillary retina. The electroretinogram (ERG)
Figure 2–6 Macular hole in a patient’s right eye.