Power spectrum analysis of EEG at diagnosis and follow up of patients with solvent induced chronic toxic encephalopathy.

Electroencephalographic changes have been studied in a group of 32 men aged 30-65 (mean 49) with diagnosed chronic toxic encephalopathy. The group had been carefully scrutinised for other possible causes of brain dysfunction and the diagnosis was based on neuraesthenic symptoms and pathological psychometric performance. The EEGs were recorded from four areas of the brain and the power spectrum analysed. Comparisons have been made with a group of 50 healthy male workers with no occupational exposure to solvents. For 24 of the 32 patients a follow up EEG recording was made after 17-75 months (mean 33). The results showed a doubling of the EEG power in the patients for all four recording channels with a significant reduction at follow up but not to the level of the control group. No exposure effect relation could be established. Acute exposure at the time of the first recording, exposure free, or follow up time did not influence the results. The frequency of the dominant EEG activity and the relative frequency distribution were equal in the two groups and did not change during the follow up period. Five of the 32 subjects took benzodiazepine drugs regularly and they had greater total power in all four recording channels compared with the other 27 patients; the difference was not statistically significant. The relative frequency distribution showed less alpha- and more theta- and beta-power in these five subjects. A reduction in total power during follow up was also found in the subgroup that took benzodiazepines.(ABSTRACT TRUNCATED AT 250 WORDS)