Retrobulbar neuritis

The answer is e. (Katzung, p 807.) Retrobulbar neuritis can occur with the use of ethambutol. It is dose related and typically occurs with prolonged therapy. The drug is not recommended for young children whose symptoms may not be easily assessed. 

Much of the toxicological interest in cyanide relating to mammals has focused on its rapid lethal action. However, its most widely distributed toxicologic problems are due to its toxicity from dietary, industrial, and environmental factors (Way 1981, 1984 Gee 1987 Marrs and Ballantyne 1987 Eisler 1991). Chronic exposure to cyanide is correlated with specific human diseases Nigerian nutritional neuropathy, Leber s optical atrophy, retrobulbar neuritis, pernicious anemia, tobacco amblyopia, cretinism, and ataxic tropical neuropathy (Towill etal. 1978 Way 1981 Sprine etal. 1982 Beminger et al. 1989 Ukhun and Dibie 1989). The effects of chronic cyanide intoxication are confounded by various nutritional factors, such as dietary deficiencies of sulfur-containing amino acids, proteins, and water-soluble vitamins (Way 1981). 

Retrobulbar neuritis is the major adverse effect noted in patients treated with ethambutol. Patients usually complain of a change in visual acuity and/or inability to see the color green. Vision testing should be performed on all patients who must receive ethambutol for more than 2 months. 

Adverse reactions may include acneiform eruptions allergic dermatitis arthropathy multiple cases of cholestatic and fulminant hepatitis drowsiness fatigue headache hepatotoxicity resembling viral or alcoholic hepatitis impotence metallic or garlic-like aftertaste peripheral neuropathy polyneuritis optic or retrobulbar neuritis restlessness occasional skin eruptions. 

Its most important adverse effects are visual disturbances. This ocular toxicity is dose dependent and has an incidence of lower than 1 % at low doses but can reach 5% at high dose regimens. Ocular toxicity manifests itself as retrobulbar neuritis usually after the second month of use. If therapy is discontinued immediately it is mostly reversible but not always. During the treatment visual function should periodically be tested. Age under 8 years is a relative contraindication as visual symptoms are difficult to monitor. 

The major toxicity associated with ethambutol use is retrobulbar neuritis impairing visual acuity and red-green color discrimination this side effect is dose related and reverses slowly once the drug is discontinued. Mild GI intolerance, allergic reaction, fever, dizziness, and mental confusion are also possible. Hyperuricemia is associated with ethambutol use due to a decreased renal excretion of urates gouty arthritis may result. 

A. Ethambutol is associated with retrobulbar neuritis, resulting in loss of central vision and impaired red-green discrimination. Ethionamide (B) is an analogue of isonicotinic acid and is associated with GI intolerance and peripheral neuropathy, but not the optic neuritis or color vision discrimination problems. Aminosalicylic acid (C) can cause GI irritation and bleeding problems, so caution is required in peptic ulcer patients. It has no neurological side effects. Rifampin (D) is associated with red-orange discoloration of saliva, tears, and urine but not the color vision problems. Isoniazid (E) is associated with peripheral neuritis in chronic alcoholics and malnourished individuals and requires pyridoxine supplements. It is not associated with optic neuritis. 

These drugs are contraindicated in patients with thrombophlebitis, thromboembolic phenomena, and cardiovascular and cerebrovascular disorders or a past history of these conditions. They should not be used to treat vaginal bleeding when the cause is unknown. They should be avoided in patients with known or suspected tumors of the breast or other estrogen-dependent neoplasms. Since these preparations have caused aggravation of preexisting disorders, they should be avoided or used with caution in patients with liver disease, asthma, eczema, migraine, diabetes, hypertension, optic neuritis, retrobulbar neuritis, or convulsive disorders. 

Hypersensitivity to ethambutol is rare. The most common serious adverse event is retrobulbar neuritis, resulting in loss of visual acuity and red-green color blindness. This dose-related adverse effect is more likely to occur at dosages of 25 mg/kg/d continued for several months. At 15 mg/kg/d or less, visual disturbances are very rare. Periodic visual acuity testing is desirable if the 25 mg/kg/d dosage is used. Ethambutol is relatively contraindicated in children too young to permit assessment of visual acuity and red-green color discrimination. 

Ethambutol Inhibits mycobacterial arabinosyl transferases, which are involved in the polymerization reaction of arabinoglycan an essential component of the mycobacterial cell wall Bacteriostatic activity against susceptible mycobacteria Given as four-drug initial combination therapy for tuberculosis until drug sensitivities are known also used for atypical mycobacterial infections Oral t mixed clearance (half-life 4 h) dose must be reduced in renal failure Toxicity Retrobulbar neuritis... 

Retrobulbar neuritis has been reported in a patient taking thiamazole (12). 

Chronic fatigue syndrome (CFS), encephalopathy, weakness, malaise, neurofibrillary tangles, neuritis, retrobulbar neuritis, neuropathy, pulmonary fibrosis, pneumonia, laryngitis, pharyngitis, bronchitis, dementia, presenile and senile dementia, decreased locomotor activity, and speech disorders... 

Retrobulbar neuritis is the major adverse effect noted in patients treated with ethambutol, Patients usually complain of a change in visual acuity and/or inability to see the color green. Vision testing should be performed on all patients who must receive ethambutol for more than 2 months. Impairment of eighth cranial nerve function is the most important adverse effect of streptomycin, Vestibular function is most frequently affected, but hearing may also be impaired. Audiometric testing should be performed in patients who must receive streptomycin for more than 2 months. Streptomycin occasionally causes nephrotoxicity. 

The optic nerve is of interest here because some drugs are toxic to this tissue.The antibiotics chloramphenicol, ethambutol, streptomycin, and sulfonamides can cause optic neuritis. Vitamin A, especially in large doses, can result in papilledema. Digitalis can cause retrobulbar neuritis (see Chapter 35). 

MS), which is a demyelinating disorder. When optic neuritis occurs without disc swelling, the condition is called retrobulbar neuritis. When disc swelling is associated with optic neuritis, the condition is called papillitis. Papilledema is bilateral disc edema associated with increased intracranial pressure OCP). Optic atrophy, the end stage of many optic neuropathies, is characterized by a pale disc and associated with a relative afferent pupillary defect (RAPD) and possible loss of visual acuity, color vision, and visual field. One example of disc atrophy occurs in cases of Leber s hereditary optic neuropathy... 

The incidence of optic neuropathy in thyroid eye disease is 5% to 10%. The class 6 patient usually has mild to moderate proptosis and relatively shallow orbits. Thyroid optic neuropathy may be evidenced by papilledema, papillitis, or retrobulbar neuritis and usually is characterized by a painless and gradual loss of visual acuity. Common visual field defects include central scotomas, arcuate or altitudinal defects, paracentral scotomas, or generalized depressions. Thus visual field and optic disc examinations are the best diagnostic tools for early optic neuropathy. Occasionally, vision loss can occur precipitously over 1 or 2 weeks. Other features of optic nerve dysfunction frequently associated with the decreased visual acuity are color vision disturbances, afferent pupillary defects in the less proptotic eye in patients with asymmetric involvement, and prolongation of the pupil cycle time. 

Venous occlusion Retrobulbar neuritis Orbital inflammation... 

Possible retrobulbar neuritis, yellow vision, diplopia, cranial nerve palsy, ptosis, visual hallucinations. 

Retrobulbar neuritis can be part of a disulfiram-induced polyneuritis, with dramatic reduction in visual acuity and impaired colour perception (SEDA-10, 349) (12). This complication is rare but serious. It occurs at dosages of 500 mg/day, and there is a latent period of 2-36 months. Tobacco abuse is thought to be a predisposing factor. Disulfiram can cause optic neuropathy (13,14). 

The onset of visual loss can be sudden and dramatic, with color vision defects in the red-green or blue-yellow spectra, as well as variable field defects. In acute cases, disc edema is accompanied by sphnter hemorrhages. Retrobulbar neuritis with ethambutol can be predominantly axial, presenting with reduced visual acuity and central scotoma, or periaxial, with peripheral field defects. In non-acute tjrpes the fundi and discs appear normal (13). Visual defects can be unilateral or bilateral. 

Eye disorders, such as blurred vision, ocular discomfort, irritation, and more severe problems, such as optic or retrobulbar neuritis and papilledema, have been described (SEDA-19, 96). 

Ocular effects, including optic neuritis, papilledema, and retrobulbar neuritis, are uncommon adverse effects of cisplatin-containing cancer chemotherapy. The risk of retinal toxicity is restricted to high-dose cisplatin therapy (for example 200 mg/m over 5 days) and can result in blurred vision and altered color perception, which can persist for several months. In contrast to cisplatin, carbo-platin is seldom involved in drug-induced visual disturbances. In two cases there was a relation between the administration of carboplatin (800-1200 mg/m ) and the occurrence of chnical cortical blindness (122). However, both patients had impaired renal function before the start of therapy with carboplatin. 

Regardless of the entry route, the major symptoms of thallium poisoning are gastrointestinal stress, neurological problems, and hair loss. Pain develops, fingers become numb, motor weakness is noted, and lower limbs may become paralyzed. The eyes become inflamed and retrobulbar neuritis with some loss of central vision follows. Intraocular hemorrhage, formation of cataracts, and optic nerve atrophy can occur. 

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