Epidemiology and clinical presentation of a seasonal ataxia in western Nigeria.

The epidemiological and clinical presentation in 37 patients (males/females 1.5:1, median age 37 years, range 12-85 yrs) with a seasonal ataxic syndrome of unknown etiology peculiar to parts of Western Nigeria is reported. All patients belonged to the low socio-economic strata, and all subsisted on a monotonous diet of high-carbohydrate meals with minimal protein supplementation. All patients consumed a stew containing the roasted larvae of Anaphe venata, a seasonal protein supplement peculiar to the area of endemicity in their last meals prior to the onset of disease. The clinical features seen in the patients studied were mainly those of acute cerebellar ataxia in all, with ophthalmoplegias and encephalopathy in the more severe cases. These features are remarkably similar to those of acute thiamine deficiency and the results in concert provide clinical and epidemiological support for an etiological hypothesis of acute thiamine deficiency in this seasonal ataxic syndrome.