Evaluation of blink reflex results obtained from workers previously diagnosed with solvent-induced toxic encephalopathy

We reviewed blink reflexes recorded from 51 railroad workers with long-term occupational exposure to solvents who were diagnosed by others with solven t-induced toxic encephalopathy. No worker fulfilled conventional clinical c riteria for dementia or trigeminal mononeuropathy. All workers had normal R 1 and R2 blink reflex latencies. R1 latencies correlated significantly with several nerve conduction measures, including F wave latencies, suggesting that some intersubject variability reflected intrinsic conduction propertie s not isolated brain-step function, Although normal, the workers' R1 latenc ies were significantly prolonged compared with historical control groups, i ncluding gender-matched control subjects of similar mean age (11.2 ms vs 9. 9 ms; P < 0.0001). Stepwise multiple regression models demonstrated signifi cant associations of R1 latency with age and use of CNS-active prescription medications (P = 0.003), but duration of occupational solvent exposure did not enter into the models. Paradoxically, workers using CNS-active medicat ions had significantly shorter R1 latencies compared with workers not using such medications (10.9 vs 11.7 ms; P = 0.01). job title, another potential surrogate measure of exposure, was not significantly related to reflex lat encies. The geographical site of predominant solvent exposure did influence R1 latency, and workers from one site had longer exposure duration and lon ger R1 latencies than remaining workers. However, an interaction between ag e and, exposure duration (r = 0.39; P = 0.003) confounded interpretation of this observation. Disability or work status, mental status findings, or cl assification of encephalopathy did not influence blink reflex latencies. Th e overall results do not support, but dot not entirely exclude, a possible relationship between subclinical blink reflex abnormalities and occupationa l exposure to solvents. Nevertheless, it is clear from these results that t he small group differences in R1 latency between exposed workers and contro l subjects are of no diagnostic importance and of uncertain physiologic imp ortance, and they may reflect unrecognized confounders and technical factor s.