Objectives: The term tropical ataxic neuropathy (TAN) is currently used to describe several neurological syndromes attributed to toxiconutritional causes. However, TAN was initially proposed to describe a specific neurological syndrome seen predominantly among the Ijebu speaking Yorubas in south western Nigeria. In this study, the prevalence of TAN was determined in Ososa, a semiurban community in south western Nigeria described as endemic for TAN in 1969, and its neurological features were compared with Strachan's syndrome, prisoners of war neuropathy, the epidemic neuropathy in Cuba, and konzo.

Methods: A census of Ososa was followed by door to door screening of all subjects aged 10 years and above with a newly designed screening instrument. Subjects who screened positive had a neurological examination, and the diagnosis of TAN was made if any two or more of bilateral optic atrophy, bilateral neurosensory deafness, sensory gait ataxia, or distal symmetric sensory polyneuropathy were present.

Results: A total of 4583 inhabitants were registered in the census. Of these, 3428 subjects aged 10 years and above were screened. The diagnosis of TAN was made in 206 of 323 subjects who screened positive for TAN. The prevalence of TAN was 6. 0%, 3.9% in males and 7.7% in females. The highest age specific prevalence was 24% in the 60-69 years age group in women.

Conclusion: The occurrence of TAN in Ososa continues at a higher prevalence than was reported 30 years ago. Its neurological features and natural history do not resemble those described for Strachan syndrome, epidemic neuropathy in Cuba, or konzo. The increasing consumption of cassava foods linked to its causation makes TAN of public health importance in Nigeria, the most populous African country.