Miscellaneous Optic Neuropathies and Neurologic Disturbances

  • 1.

    A young woman complains of headaches. Her vision is 20/20 in each eye with no evidence of afferent pupillary defect. She has a bitemporal visual-field cut. What do you suspect?

    Suspect a chiasmal lesion. Schedule a magnetic resonance imaging (MRI) scan to make an evaluation.

  • 2.

    What may simulate a bitemporal field defect?

    A bitemporal field defect may be simulated by sector retinitis pigmentosa, coloboma, or a tilted disc.

  • 3.

    A patient has 20/20 vision in her right eye and 20/400 in her left eye. Her left eye has an afferent pupillary defect and decreased color plates. What should you evaluate in her right eye?

    Check visual fields in both eyes. A central scotoma in one eye may be accompanied by a superior temporal field loss in the other. This condition, called a junctional scotoma, is also found in chiasmal lesions. See the chapter on visual fields ( Chapter 6 ).

Key Points: Differential Diagnosis of Chiasmal Visual Defects

  • 1.

    Pituitary lesion—tumor or apoplexy

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  • 4.

    Is there a difference in the treatment of secreting and nonsecreting symptomatic pituitary tumors?

    Yes. A prolactinoma secretes prolactin and may be treated successfully with bromocriptine. A nonsecreting tumor probably requires surgery. Of course, an endocrinologist should fully evaluate the patient for other hormonal imbalances.

  • 5.

    What visual field is often seen in a toxic or metabolic optic neuropathy?

    Bilateral central or centrocecal scotomas. Optic nerves show temporal pallor ( Fig. 32-1 ). Alcohol, tobacco, and vitamin B 12 deficiency, as well as drugs such as chloramphenicol, ethambutol, digitalis, chloroquine, and isoniazid, have been implicated. Check for heavy metals and order a complete blood count as well as serum levels of vitamins B 11 , B 12 , and folate. Consider Leber’s hereditary optic neuropathy as a diagnosis.

    Figure 32-1

    Fundus views reveal mild temporal optic disc pallor in right optic disc A, and left optic disc B . More interesting in B, however, is the loss of the nerve fiber layer in the papillomacular bundle. This patient, who had tobacco–alcohol amblyopia (mixed toxic and nutritional deficiency optic neuropathy), also had a visual acuity of 20/400 in each eye, which recovered to only 20/100 after changes in habit and diet and vitamin therapy. In this class of optic neuropathies, relatively severely compromised visual acuity and dyschromatopsia often are found with minimal optic disc atrophy. (From Sadun AA, Gurkan S: Hereditary, nutritional, and toxic optic atrophies. In Yanoff M, Duker JS [eds]: Ophthalmology, ed 2, St. Louis, Mosby, 2004, 1275–1278.) C, Visual field exam reveals centrocecal scotoma. A lesion of the papillomacular bundle (nerve fiber layer or optic nerve) is the usual cause of this defect.

    (From Burde RM, Savino PJ, Trobe JD: Unexplained visual loss. In Burde RM, Savino PJ, Trobe JD [eds]: Clinical Decisions in Neuro-Ophthalmology, ed 3, St. Louis, Mosby, 2002, pp 1–26.)

  • 6.

    A 60-year-old man presents with gradual vision loss to 20/400 in his right eye. On examination, the right optic nerve is pale and dot-and-blot retinal hemorrhages are seen. The left eye is normal. What history may be helpful?

    A history of radiation treatment. The patient reports radiation to his right frontal sinus 3 years earlier. There is no treatment for radiation optic neuropathy. Panretinal photocoagulation for neovascular disease and anti-vascular endothelial growth factor treatment is used for radiation retinopathy.

  • 7.

    What may cause a constricted visual field?

    • Retinitis pigmentosa

    • End-stage glaucoma

    • Thyroid ophthalmopathy

    • Optic nerve drusen

    • Vitamin A deficiency

    • Occipital strokes

    • Panretinal photocoagulation

    • Hysteria

    • Malingering

  • 8.

    How do you differentiate hysteria and malingering from real disease?

    Have the patient do a tangent screen at two different distances. The closer the patient stands, the smaller the field should be. In a patient with nonphysiologic visual loss, the fields are often of equal size. Patients also may demonstrate spiraling with kinetic visual-field testing (see Chapter 6 ).

  • 9.

    A 55-year-old man notices that the vision in his left eye has worsened suddenly. He has 20/30 vision in his right eye and 20/100 in his left eye. The left eye also shows an afferent pupillary defect and decreased color plates. Visual-field examination reveals an inferior altitudinal defect on the left with a normal full field on the right. On fundus examination, the left optic nerve appears pale and swollen superiorly. What is your concern?

    An altitudinal defect is a classic finding with ischemic optic neuropathy (ION). The two types are arteritic and nonarteritic (see Table 32-1 ). Because they are treated differently, you must differentiate the two. First, it is important to ask about symptoms of giant cell arteritis, such as weight loss, anorexia, fever, jaw claudication, headache, scalp tenderness, and proximal joint and muscle pain. Check for a palpable, tender, nonpulsatile temporal artery. Immediately order an erythrocyte sedimentation rate (ESR), a C-reactive protein (CRP), and a platelet count if you believe that giant cell arteritis is a consideration. The upper limits of normal for an ESR is age divided by 2 for men and age +10 divided by 2 for women. The CRP is not affected by age and may be more sensitive than ESR. However, both are nonspecific tests; any inflammatory process can elevate them. Temporal arteritis patients have elevated platelet counts.

    Table 32-1

    Nonarteritic and Arteritic Ischemic Optic Neuropathy

    Age of onset 40-60 years Usually older than 50 years
    Gender Either equally More often female
    Presenting visual acuity May be better than 20/100 Often count fingers or worse
    Visual-field defect Altitudinal or involving central visual field Altitudinal or involving central visual field
    Ophthalmic exam Hyperemic disc swelling, may be segmental with flame-shaped hemorrhages; later atrophy without cupping Pale, swollen disc with few flame hemorrhages; later, optic atrophy and cupping
    Symptoms None Jaw pain, scalp tenderness, night sweats, fever, weight loss
    Systemic associations Diabetes, hypertension, hyperlipidemia, sleep apnea; potential increase in use of erectile dysfunction drugs if a crowded disc initially Polymyalgia rheumatica
    Lab evaluation Lab tests normal Elevated ESR, C-reactive protein, and platelet counts
    Disruption of internal elastic lamina on temporal artery biopsy

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Jul 8, 2019 | Posted by in OPHTHALMOLOGY | Comments Off on Miscellaneous Optic Neuropathies and Neurologic Disturbances

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