Is Jamaican neuropathy (TSP) caused by cyanide intoxication? - abstract

ABSTRACT

Jamaican neuropathy, one of the earliest forms of tropical Spastic Paraparesis (TSP) to be described, is a major cause of neurological disability in Jamaica. Its cause has not been satisfactorily established, but chronic treponemal and, more recently, retroviral infections (HTLV-I) have been considered likely aetiological agents. Cyanide toxicity is regarded as the cause of TSP in certain West African countries. Free radicals have also been reported to cause damage to long axons. Although cassava and other cyanogenic items are used as staple items of diet in Jamaica, levels of this toxin have not been measured in Jamaican patients with TSP. The present study was therefore undertaken to determine whether (a) cyanide toxicity was associated with Jamaican TSP and (b) the levels of substances which protect against free radical damage were altered in these patients. Venous blood, obtained from twenty-two (22) patients with TSP, was analysed for thiocyanate (SCN). The levels of Cu/Zn superoxide dismutase, glutathione peroxidase and total glutathione, agents which protect against free radical damage, were also measured. Control samples were obtained from non-smoking blood donors matched for age. All patients and controls were questioned about their dietary habits. The levels of thiocyanate found in patients with the Jamaican form of TSP were similar to those found in control patients. Glutathione levels were elevated in all the patients. Superoxide dismutase activity was normal in all patients. The results obtained suggest that (a) cyanide toxicity is not the primary cause of Jamaican TSP; (b) sufficient amounts of sulphur containing amino-acids are present to detoxify cyanide, even when present in high concentrations, and (c) free radical mechanisms are unlikely to be responsible for damage to the neurones in these TSP subjects (AU)