Myoclonic seizure prior to diagnosis of chronic toxic encephalopathy: a case report

BACKGROUND "Thinner" is a widely used industrial mixture of organic solvents. Exposure to organic solvents is usually not considered to be a possible cause of epilepsy, despite descriptions of toxic effects on the central nervous system. There are only a few reports about a possible epileptogenic effect of organic solvents exposure. We report a case of myoclonic seizure at the workplace that shows a remarkable coincidence between exposure to a thinner mixture and the occurrence of an epileptic seizure. CASE PRESENTATION We present the case of a 50-year-old Belgian woman exposed to organic solvents for more than 20 years in a paintbrush manufactory. In 2009, her biological monitoring of hippuric acid (primary urinary metabolite of toluene) exceeded the threshold limit value of the American Conference of Governmental Industrial Hygienists. In 2012, after a period of high organic solvents exposure without the use of proper collective or personal airway protection, she had a seizure with myoclonic movements of her four limbs and loss of consciousness at her workplace. An electroencephalogram, computed tomography and magnetic resonance imaging of her head were within limits. Non-toxicological and toxicological causes were investigated. Her seizures did not reappear after workplace removal. Two years after her epileptic insult she was diagnosed with chronic toxic encephalopathy type 2b. In 2015, volatile organic compounds were measured at her workplace. Multiple (3/18) air samples exceeded the Belgian time-weighted average over 8 hours (77 mg/m3) for toluene. CONCLUSIONS Knowledge about the impact of solvent exposure on the occurrence of epileptic insults is lacking. Long-term exposure to organic solvents is usually not considered to be a possible cause of epileptic seizure. But epileptic discharges have been described on electroencephalogram recordings for patients with chronic toxic encephalopathy. Myoclonic encephalopathy has been reported in toxic conditions. This case emphasizes a possible unusual neurological presentation of occupational exposure to organic solvents. It may be explained by lowering of the threshold for seizures due to high solvents exposure, most probably by toluene. This case suggests a chronological connection between a high occupational exposure to solvents and an epileptic insult. We found no other plausible cause.