Neuropsychiatric manifestations of methyl iodide toxicity

Methyl iodide is an industrial chemical used in methylation for pharmaceutical intermediates. Its toxicity is a rare industrial hazard. Its toxicity is reported with both acute sudden exposure and gradual exposure. The authors report a case of methyl iodide toxicity occurring in a 47 year-old male with sudden exposure to this chemical. He presented with neuropsychiatric symptoms primarily slurring of speech, ataxia followed by delusion and hallucinations which resolved within 2 weeks with parenteral thiamine and an antipsychotic. Symptoms reappeared after a re-exposure, this time with more prominent psychiatric symptoms which were late to resolve (4 weeks) with similar treatment. Neuroimaging revealed hyperintensities in posterior regions of the brain which resolved after 4 weeks. The patient had prominent neurocognitive deficits which were persistent. The case highlights the rare chemical toxicity with neuropsychiatric manifestations with persistent neurocognitive symptoms.