Case report: arachnoiditis following intracranial 'Thorotrast'.

A patient is reported with a painless, progressive cauda equina lesion due to arachnoiditis, the result of the contrast medium 'Thorotrast' (thorium dioxide) introduced into the brain over 30 years previously. Contrast medium introduced into the lumbar spine can give rise to aseptic adhesive inflammation (arachnoiditis). It rarely gives rise to clinical problems but, when it does so, is usually associated with back pain and only very rarely with progressive neurological deficit.