Tobacco-alcohol amblyopia: a proposed biochemical basis for pathogenesis

Nutritional optic neuropathies

Nutritional deficiency may be the cause of a genuine optic neuropathy, sometimes associated with involvement of the peripheral nervous system. Nutritional optic neuropathies are usually bilateral, painless, chronic, insidious and slowly progressive. Most often, they present as a non-specific retrobulbar optic neuropathy. The differential diagnosis with other causes of optic nerve involvement, in particular of toxic origin, may be particularly difficult. Nutritional deficits are often associated with toxic effects from alcohol and tobacco; therefore, the separation of the nutritional and toxic components is often illusory and artificial. The pathophysiological mechanisms involved in nutritional -- and toxic -- optic neuropathies affect biochemical pathways involved in cell energetic production, correction of oxidative stress and quenching of free radicals. The recognition of these mechanisms could provide future therapeutic alternatives. Currently, the treatment is limited to the intensive use of vitamins with variable results in individual cases, and to the implementation of preventive measures, when feasible.

Tropical myeloneuropathies revisited

An interesting neurological syndrome, characterized by recurrent optic neuritis, cervical myelopathy from syringomyelia, paraparesis, amenorrhea-galactorrhea, and other endocrine problems, has been described among young black women in the French West Indies. The etiology remains unknown, but possible links with Devic's disease, acute disseminated encephalomyelitis, and neurotoxicity from quinolines in Annona muricata teas have been postulated. The largest epidemic of neuropathy in this century occurred in Cuba in 1991-1994. Clinical features and etiologic studies are reviewed. Its primary cause was nutritional. A similar epidemic was recently described in Tanzania. A number of infectious neuropathies and myopathies are reviewed, including leprosy, tuberculosis, hemorrhagic fevers (Ebola and Marburg filoviruses, Lassa, Argentinean and Bolivian arenaviruses), the human retrovirus human T-cell lymphotropic virus type I, Lyme disease and postimmunization neuropathies. The tropics continue to contribute interesting and important clinical conditions that may illuminate the etiopathiogenesis of other common disorders.

Prevalence and factors associated to the epidemic neuropathy in a population assisted by a family doctor in Cuba

With the outbreak of an epidemic neuropathy (EN) of unknown ethiology, a study of the prevalence and factors associated to the disease was carried out in the Zamora community, municipality of Marianao, Havana City. There were 11 patients identified with EN for a prevalence rate of 1.7/100. The major risk group was the one between 45 and 64 years of age, female sex, black skin. In the univaried analysis, a high prevalence ratio (PR) was found linked to beverage intake (PR = 5.32 95%; confidence intervals (CI) = 1.2-24.4), frequent drugs intake (PR = 6.59; CI = 1.8-24.6), consumption of edible of non certified fats (PR = 4.48; CI = 1.2-16.7) and the smoking habit (PR = 3.6; CI = 1.1-12.2). More than 73/100 (CI = 68.7-78.3) of the people under serologic study were infected with Coxsakie virus A-9 (strain 47) isolated from a patient still under research. It seems there are many factors like linder intake, antecedents of hemorrhagic conjunctivitis, nutritional aspects and others that, with the virus isolated were associated with this epidemiologic situation.

Epidemic optic neuropathy in Cuba--clinical characterization and risk factors

BACKGROUND

From 1991 to 1993, epidemic optic and peripheral neuropathy affected more than 50,000 people in Cuba. The number of new cases decreased after the initiation of vitamin supplementation in the population. In September 1993, Cuban and U.S. investigators conducted a study to characterize and identify risk factors for the optic form of the syndrome.

METHODS

We conducted ophthalmologic and neurologic examinations, assessed exposure to potential toxins, administered a semiquantitative food-frequency questionnaire, and assessed serum measures of nutritional status in 123 patients with severe optic neuropathy, matched for sex and age to randomly chosen normal subjects.

RESULTS

In the case patients, prominent clinical features were subacute loss of visual acuity with field defects, diminished color vision, optic-nerve pallor, and decreased sensitivity to vibration and temperature in the legs. Tobacco use, particularly cigar smoking, was associated with an increased risk of optic neuropathy. The risk was reduced among subjects with higher dietary intakes of methionine, vitamin B12, riboflavin, and niacin and higher serum concentrations of antioxidant carotenoids. The risk was also reduced among subjects who raised chickens at home or had relatives living overseas--factors that may be indirect measures of increased food availability.

CONCLUSIONS

The epidemic of optic and peripheral neuropathy in Cuba between 1991 and 1993 appears to be linked to reduced nutrient intake caused by the country's deteriorating economic situation and the high prevalence of tobacco use.

Nutrition and optic nerve disease

The syndrome characterized by papillomacular bundle damage, central or cecocentral scotoma, and reduction of color vision can be produced by toxic, nutritional, or hereditary causes. Patients who present with such a picture should be evaluated for toxic sources such as tobacco or alcohol use. Nutritional deficiencies must be considered and a good family history should be obtained to explore hereditary factors. DNA mutation analysis is available to detect genetic abnormalities. A trial of nutritional replacement may be advisable even in the face of normal laboratory values. Previous reports have shown dramatic visual improvement with intramuscular hydroxocobalamin and other oral vitamin B complexes, even when specific deficiencies are not found.

Epidemic neuropathy in Cuba not associated with mitochondrial DNA mutations found in Leber's hereditary optic neuropathy patients. Cuba Neuropathy Field Investigation Team

An epidemic neuropathy in Cuba has caused bilateral optic neuropathies in more than 26,000 people during the past three years. Various pathogenetic factors have been proposed, including toxins, nutritional deficiencies, and an underlying genetic predisposition involving mitochondrial DNA. As part of a case-control collaborative investigation, 135 Cuban blood samples were analyzed for the most common mitochondrial DNA mutations associated with Leber's hereditary optic neuropathy. None of the participants tested were found to have the mitochondrial DNA mutations at nucleotide positions 11778, 3460, 14484, 7444, or 9804. Of 57 definite case subjects and 69 normal control subjects, three case and three control subjects had the mutation at nucleotide position 9438, three different case and three different control subjects had the mutation at position 13708, and one case and one control subject had the mutation at position 15257 in association with the mutation at position 13708. The most common mitochondrial DNA mutations associated with Leber's hereditary optic neuropathy do not appear to be contributing factors in the epidemic neuropathy in Cuba. We also identified a large Cuban family with maternally related members who experienced visual loss consistent with the diagnosis of Leber's hereditary optic neuropathy. Maternal family members harbored the highly pathogenetic mutation at nucleotide position 11778.

Tobacco-alcohol amblyopia neuro-ophthalmological findings and clinical course

The clinical picture of 40 patients with tobacco-alcohol amblyopia (TAA) is described. In 15 patients the course of the disease was studied longitudinally over a period of 31 months. In addition in six patients the acute development of the disease was studied during a period of four weeks in-patient treatment. TAA is characterised by distinct bilateral visual disturbances, symmetric scotomas, acquired disturbances of colour vision and mostly normal fundi. Visual acuity is usually grossly diminished. Central scotomas were present in 80% of the cases while the centrocecal from prevailed in the rest. The acquired disturbances of colour vision usually concerned the red-green sense (84%). The amplitudes of the visual evoked potentials were always reduced and deformed. In 33% we could not detect a P-100. In 5% the latency of the P-100 was prolonged. Full field stimulation was the best method of defining the P-100. By foveal stimulation the deformations of the amplitudes were more evident. The prognosis of the visual disturbances was unpredictable. The abnormalities improved in one half of the patients, but complete recovery was never reached despite substitution with vitamins.