Plasma thiocyanate and free radicals in Jamaican neuropathy (tropical paraparesis

ABSTRACT

Tropical spastic paraparesis (TSP) in West African countries is caused by a combination of excess cyanide from the ingestion of cassava and a deficiency of the sulphur-containing amino-acids required to detoxify the cyanide. Free radical damage to long axons has also been reported to result in damage similar to that seen in Jamaican TSP. To investigate the possibility that these mechanisms may be responsible for Jamaican TSP, venous blood from non-smoking blood donors and 22 patients with TSP were analysed for thiocyanate, superoxide dismutase and glutathione. Serum thiocyanate is an index of cyanide exposure. Superoxide damage is an important sulphur-containing peptiae. Levels of thiocyanate in the patients with TSP were similar to those in control patients. Glutathione was elevated in all the patients, and a superoxide dismutase activity was normal. The low levels of thiocyanate suggest that cyanide toxicity is not the primary cause of Jamaican TSP and, in any event, sufficient amounts of sulphur-containing amino-acids are present to detoxify cyanide. Free radical mechanisms are also unlikely to be responsible for damage to the neurons in these patients (AU)