Ординатура / Офтальмология / Английские материалы / Primary Care Ophthalmology_Palay, Krachmer_2005
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212 CHAPTER 12 • Neuro-ophthalmology
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FIGURE 12–6 Optic disc drusen in an adult. A, Drusen can be seen in this left eye as yellowish-white lumps (inset), giving the disc margin a bumpy, scalloped appearance. B, Visual acuity is 20/20, but peripheral visual field loss (nasal step) is present.
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FIGURE 12–7 Buried optic disc drusen in a 7-year-old girl. In young people, drusen may be buried deep in the substance of the disc. The resulting disc elevation is difficult to distinguish from papilledema. A, Right eye. B, Left eye.
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Optic Nerve Tumors
Symptoms
•Vision loss is slow and progressive.
•Proptosis (eye pushed forward) or double vision is possible.
Signs
•Gradual onset of optic disc pallor is typical, although the disc may appear normal early in the disease (Fig. 12–8C).
•Disc edema is possible in anterior lesions.
•Vascular shunt vessels may be noted on the optic disc.
•Optic nerve–related visual field defects demonstrate a slow, relentless progression (Fig. 12–8B).
•Nystagmus may be present in children.
Etiology
•In children, optic nerve glioma is most common; 90% of the tumors are diagnosed before the age of 20 years, and 25% are associated with neurofibromatosis. The clinical course with this tumor is slow in children. In adults, the tumor is very aggressive, resulting in blindness and death.
•Optic nerve meningiomas are more common in adults and originate from the optic nerve sheath or adjacent dural structures.
•Metastatic disease to the orbit may cause compression of the optic nerve.
Differential Diagnosis
Other disorders that may present in a similar fashion include the following:
•Optic neuritis (especially with vision loss and a normal fundus)
•Other optic neuropathies, including glaucoma
•Thyroid eye disease, which can cause optic nerve compression, proptosis, and diplopia
Workup
•Neuroimaging (computed tomography [CT] or MRI of both brain and orbits with contrast) is needed (see Fig. 12–8A).
Treatment
•Ophthalmology and neurosurgery consultations are required for definitive diagnosis and management.
Chiasmal Compression
As discussed at the beginning of this chapter, the visual field defect arising from a chiasmal lesion typically interrupts the crossing nasal retinal fibers to produce a
214 CHAPTER 12 • Neuro-ophthalmology
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FIGURE 12–8 Optic nerve compression. The patient was a 32-year-old woman who reported gradual loss of vision in her right eye. A, MRI study shows an enhancing mass (1) abutting the right optic nerve, consistent with a meningioma. B, Resultant visual field loss in the right eye. C, Optic disc pallor in the right eye. D, Normal left optic disc.
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bitemporal visual field defect (see Fig. 12–1). The most common cause is a mass lesion arising from the parasellar region.
Symptoms
•Slow, progressive vision loss may occur in one or both eyes.
•Headache sometimes occurs.
•Symptoms related to the pituitary dysfunction may be identified.
Signs
•Insidious optic disc pallor develops over time.
•Bilateral temporal visual field defects occur with chiasmal compression (Fig. 12–9B).
•The third through sixth cranial nerves may be affected by tumors that invade the cavernous sinus.
Etiology
•Chiasmal dysfunction usually is the result of compression by a mass lesion: pituitary macroadenoma (or apoplexy), meningioma, craniopharyngioma, or other suprasellar masses.
Differential Diagnosis
Other disorders that may produce bilateral temporal visual field defects include the following:
•Bilateral optic neuropathies, especially those affecting central vision and enlarging the (temporal) blind spot, such as Leber’s and other hereditary optic neuropathies and toxic or nutritional optic neuropathies
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216CHAPTER 12 • Neuro-ophthalmology
•Anomalous optic discs, in which abnormalities of the retina around the blind spot can produce temporal visual field defects
•Trauma to the chiasm
Workup
•Neuroimaging (MRI with contrast preferred) is performed, with attention to the sellar region (see Fig. 12–9A).
Treatment
•Neurosurgical consultation is necessary.
•Ophthalmic consultation is necessary for formal visual field testing to follow the progress of the disease, to monitor success of treatment, and to watch for recurrence.
Anisocoria
Anisocoria (unequal pupils) is caused by unequal pupillary motor inputs to the two eyes. Vision loss, even total blindness in one eye, does not cause anisocoria.
To evaluate anisocoria, the examiner first determines which pupil is abnormal by noting pupil size in darkness and in light. When the larger pupil is abnormal (does not constrict well), the degree of anisocoria is greatest in bright light (as the normal pupil becomes small). When the smaller pupil is abnormal (does not dilate well), the degree of anisocoria is greatest in darkness (as the normal pupil dilates). As a general rule, the pupil that reacts poorly to direct light is the abnormal pupil. Essential, or physiologic, anisocoria is common, with a small difference in pupillary size (generally less than 1 mm) remaining constant in light and dark. Previous trauma and eye surgery are common causes for different pupil sizes.
When the Larger Pupil Is the Abnormal One
Etiology, Associated Factors and Diseases, and
Differential Diagnosis
•In third nerve palsy, a dilated pupil with ptosis and/or a motility abnormality suggests compression of the third cranial nerve (i.e., an aneurysm). Pupillary dilation in isolation, without any other sign of oculomotor nerve dysfunction, is unlikely to result from compression of the third cranial nerve.
•Adie’s syndrome results from an often idiopathic insult to the ciliary ganglion in the orbit. The pupil responds to near focus (when the patient attempts to focus on a target inches from the nose), but the reaction to light is absent or very poor (Fig. 12–10).
•Pharmacologic causes of a dilated pupil include instillation of any anticholinergic or sympathomimetic compound into the eye (e.g., dilating drops, contamination from scopolamine patches, jimsonweed).
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FIGURE 12–10 Adie’s pupil. In room light, the anisocoria is evident (1). In bright light, the normal right pupil becomes small, but the affected left eye responds poorly (2). With a sustained near focus, however, the affected pupil does become smaller (3). This finding of a better response to a near stimulus than to a light stimulus is termed light-near dissociation and is characteristic of Adie’s pupil.
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•Because of possible non-neurologic causes such as eye trauma, iritis, angle-closure glaucoma, and eye surgery, patients with anisocoria should undergo an ophthalmologic evaluation.
Workup
•An ophthalmologist may use pharmacologic tests for cholinergic supersensitivity in Adie’s pupil, with pilocarpine 0.125% producing marked constriction of the affected pupil and little effect on the normal eye. Pharmacologic dilation with anticholinergic agents can be identified with the use of pilocarpine 1%; this agent does not constrict the affected eye but produces marked constriction in the normal eye.
Treatment
•If a third nerve palsy is suspected as the cause of a dilated pupil, immediate referral to an ophthalmologist (a neuro-ophthalmologist if available), neurologist, and/or neurosurgeon is necessary to evaluate the possibility of an expanding aneurysm.
218 CHAPTER 12 • Neuro-ophthalmology
FIGURE 12–11 Horner syndrome. The mild ptosis (1 to 2 mm) and smaller pupil can be seen on the affected right side.
•If no sign of third nerve dysfunction is present, the patient should be seen again within a week; pharmacologic dilation should have resolved (unless repeated) and the examiner can recheck for any developing signs of third nerve dysfunction.
When the Smaller Pupil Is the Abnormal One
Etiology, Associated Factors and Diseases, and
Differential Diagnosis
•In patients with Horner syndrome (oculosympathetic paresis), a 1- to 2-mm ptosis is virtually always present in addition to the miosis. Facial anhidrosis (unilateral lack of sweating) may be more difficult to identify (Fig. 12–11).
•Other causes of a small pupil such as eye trauma, iritis, angle-closure glaucoma, and eye surgery probably will be evident on ophthalmologic evaluation.
Workup
•An ophthalmologist may use pharmacologic tests to verify an oculosympathetic paresis in patients with suspected Horner syndrome. Cocaine 10% has a less potent mydriatic effect on the abnormal pupil than on the unaffected one. Hydroxyamphetamine does not dilate the affected pupil well in postganglionic lesions (from the superior cervical ganglion in the neck to the eye). Common etiologic processes for postganglionic lesions include cluster headache and carotid artery dissection, but postganglionic Horner syndrome often is idiopathic. Preganglionic lesions (affecting fibers from the hypothalamus, traveling through the brainstem, spinal cord, chest cavity, and neck to the superior cervical ganglion) frequently are serious (e.g., malignancy, stroke), requiring specialist evaluation and imaging of the brain, neck, and chest.
Treatment
• The underlying etiology determines treatment.
Disorders of the Visual Motor System
Third Nerve Palsy
The third cranial nerve (oculomotor nerve) is complex, innervating all of the extraocular muscles (including the levator palpebrae, which elevates the eyelids) except
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the lateral rectus and superior oblique muscles. It also innervates the pupillary sphincter.
Symptoms
•A ptosis typically is present and often is profound.
•Diplopia results if the drooping eyelid does not cover the pupil.
•Headache or periorbital pain often is present, depending on the etiology.
Signs
•The eye often is turned down and out.
•The ptosis may be mild or complete.
•Deficiencies in raising, lowering, or moving the eye toward the nose may be partial or complete (Fig. 12–12).
•A dilated pupil is an important sign, because it is more common with compression (aneurysm) than with ischemia.
Etiology
•An ischemic cranial mononeuropathy is a common cause in patients who are elderly or have conditions associated with increased risk for vascular problems, such as hypertension and diabetes.
•Vasculitis (giant cell arteritis) can cause ischemic cranial neuropathies.
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FIGURE 12–12 Third cranial nerve paresis with pupil involvement. Note the profound right ptosis (lid droop) and the down- and-out position of the right eye (1). Gaze positions demonstrate poor elevation (2), depression (3), and inability to turn the eye inward (adduction) (4). Note the dilated pupil in the affected right eye.
220CHAPTER 12 • Neuro-ophthalmology
•Compression by aneurysm, tumor, or even uncal herniation can cause third nerve dysfunction.
•Head trauma is a common cause.
Differential Diagnosis
Other diagnostic considerations include the following:
•Ocular myasthenia gravis
•Thyroid eye disease
•Brainstem lesions
Workup
•MRI of the brain with contrast (and often MR angiography) is required in patients without obvious vascular risk factors.
•Cerebral angiography may be necessary in patients suspected to have an aneurysm, especially younger patients (younger than 45 years of age) and those with pupil involvement.
•An ophthalmologist who is confident in the diagnosis of a pupil-sparing third nerve paresis in a patient with vascular disease (with presumed ischemic mononeuropathy) may elect to simply observe if there is no evidence of giant cell arteritis.
Treatment
• The underlying etiology determines treatment.
Follow-up
•Patients with presumed ischemic mononeuropathy should return for follow-up evaluation within a week, to ensure that progression to pupil involvement has not occurred.
•Patients with ischemic mononeuropathy should recover in 6 to 12 weeks; further investigation is required for those who do not.
Fourth Nerve Palsy
The fourth cranial (trochlear) nerve innervates only the superior oblique muscle, but this muscle has a complex action. It can tilt, depress, and move the eye away from the nose.
Symptoms
•Vertical or oblique diplopia occurs.
•Objects may appear tilted.
Signs
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FIGURE 12–13 Traumatic right fourth cranial nerve paresis. Note that the right eye does not look as far down when the gaze is directed to the left and down (1). It also “overacts,” or looks up too far, in upgaze (2). This often subtle finding is best appreciated on comparison with the normal responses of the opposite eye in adduction (3 and 4).
Etiology
•A fourth nerve palsy is common after head trauma.
•Congenital fourth nerve palsies are very common and may be discovered incidentally.
•Other than trauma, the most common acquired cause is an ischemic cranial mononeuropathy in patients with vascular disease.
Differential Diagnosis
Other diagnostic considerations include the following:
•Ocular myasthenia gravis
•Skew deviation (vertical misalignment after brainstem stroke)
•Thyroid eye disease
Workup
•Fourth nerve palsies are difficult to diagnose and monitor without careful measurement of the ocular alignment by an ophthalmologist.
•In patients at risk for ischemic events, only minimal workup (i.e., determination of erythrocyte sedimentation rate to look for giant cell arteritis) may be needed.