Clinical Pathways in Neuro-ophthalmology : An ... - E-Lib FK UWKS

14 Clinical Pathways in Neuro-Ophthalmology, second edition
Table 1–8. Evaluation of an Atypical or Unexplained Optic Neuropathy
First-line testing
Magnetic resonance imaging of optic nerve(s)
Erythrocyte sedimentation rate
Complete blood count with differential
Syphilis serology
Antinuclear antibody (ANA)
Chest radiograph
Angiotensin-converting enzyme (antineutrophil cytoplasmic antibody, ANCA)
Lumbar puncture
Second-line testing
Gallium scan if sarcoidosis suspected
Purified protein derivative (PPD) skin testing if tuberculosis suspected
Anti–double-stranded DNA, complement levels, etc., if systemic lupus erythematosus or other
collagen vascular disease suspected
Leber’s hereditary optic neuropathy mutation blood test
Heavy metal screen
Serum vitamin B 12 and folate levels
Lyme titer if endemic area or exposure history
Paraneoplastic antibody profile (e.g., autoantibodies for collapsin response mediated protein
(CRMP)-5 may be associated with optic neuropathy in patients with lung cancer, especially
small-cell type, or thymoma) (Cross, 2002; Thambisetty, 2001; Yu, 2001)
Consider more specific serologic studies if infectious process suspect (e.g., Bartonella titers for
cat-scratch disease, toxoplasmosis titers, toxocara titers, etc.)
scotomas), but their clinical presentations may be variable. Unfortunately, CON may
mimic the clinical presentation of toxic optic neuropathy, and neuroimaging is recommended.
The determination of presumed toxic or nutritional optic neuropathy should
include a complete evaluation to exclude other etiologies of bilateral, painless, and
progressive optic neuropathies (e.g., hereditary optic neuropathy, bilateral compressive
optic neuropathy, etc.). The evaluation of presumed toxic optic neuropathy is outlined
in Table 1–11 (class IV, level C).
Is There a History of Radiation Exposure to
the Optic Nerves?
Radiation optic neuropathy (RON) is thought to be an ischemic disorder of the optic
nerve that usually results in irreversible severe visual loss months to years after
radiation therapy to the brain or orbit (Arnold, 1995; Borruat, 1993, 1996; Ebner, 1995;
Girkin, 1997; Glantz, 1994; Goldsmith, 1992; Guy, 1991, 1995; Hudgins, 1992; Jiang, 1994;
Landau, 1996; Leber, 1998; Liu, 1992; McClellan, 1995; Parsons, 1994; Polak, 1995;
Roden, 1990; Tachibana, 1990; Young, 1992; Zimmerman, 1990). It is most often a
retrobulbar optic neuropathy, and thus the optic nerve may appear normal on initial
examination. Approximately three fourths of patients have bilateral involvement. The
visual loss is characteristically rapid and progressive, with the disc becoming pale over
a period of 4 to 6 weeks. Final vision is NLP in 45% and worse than 20=200 in an