Epileptic phenomena in bismuth toxic encephalopathy.

Seventy patients admitted to hospital with bismuth encephalopathy had repeated clinical and EEG examinations. All the patients exhibited myoclonic jerks, but no paroxysmal features ever appeared on EEG. Computed tomography showed cortical hyperdensities. Seizures were observed in 22 patients, but epileptic EEG patterns appeared only when the bismuth blood level was below 1500 microgram/1. It is suggested that a high cortical intracellular bismuth concentration induces a "cortical inhibition" which causes suppression of physiological electrical brain activity, the absence of EEG paroxysmal phenomena during myoclonic jerks, and explains the rarity of epileptic seizures.