Cauda equina lesion due to thorotrast.

Thorotrast (Thorium dioxide) has been used in the past as a radiological contrast medium. Its use resulted in serious side-effects, often after a delay of many years. There was an increased incidence of tumours and blood dyscrasias. Meningeal fibrosis, hydrocephalus and progressive lesions of the cauda equina have followed its injection into the sub-arachnoid spaces. A patient with such a cauda equina lesion is reported.