Occupational exposure to methyl isobutyl ketone causes lasting impairment in working memory.

The authors describe serial evaluations of a 44-year-old man who became cognitively impaired during a 6-year period of repeated exposure to high levels of methyl isobutyl ketone (MIBK). Neuropsychological tests administered six times over 10 years demonstrated a stable pattern of cognitive impairment. Dynamic imaging studies suggested persistent CNS dysfunction. The authors conclude that chronic, high-level, occupational MIBK exposure can cause a persistent cognitive syndrome best explained by impaired working memory.