Findings on brain MRI from research studies of occupational exposure to known neurotoxicants

OBJECTIVE. The expanding use of MRI in large-scale epidemiologic studies of CNS outcomes has led to increasing concern for the consistent handling of incidental findings. Our purpose is to identify the prevalence of incidental neuroradiologic abnormalities in an adult population with past occupational exposure to lead who underwent brain MRI as part of a large, longitudinal cohort study. MATERIALS AND METHODS. Structural MR images obtained for the research study were reviewed by a neuroradiologist on an ongoing basis for findings of clinical concern. The subjects were recruited as part of a longitudinal research study designed to examine the effects of past lead exposure on CNS structures. The cohort examined consisted of 589 men who previously worked at an organolead manufacturing facility and had a wide range of lead exposure durations and intensities. MR images were also reviewed from 67 population-based control subjects from the same study who had no history of occupational lead exposure. RESULTS. Incidental findings were detected in 84% (548/656) of research subjects. Of the 548 subjects with abnormalities, 30% (167) required no referral, 51% (280) required routine referral, 17% (93) required urgent referral, and 1.5% (8) required immediate referral. Incidental findings of all categories were observed in a larger percentage of older subjects, aged 60 years and above. Using multivariable logistic regression analysis, we found that age (p < 0.0001), but not lead history, was associated with an increased risk of incidental neuroradiologic abnormalities. CONCLUSION. In the population examined, there was a high prevalence of incidental brain and head and neck abnormality. Of particular concern were the serious health problems observed requiring urgent or immediate referral in 18.5% of the subjects. These findings underscore the need for radiologists to evaluate the anatomic images generated by research studies, particularly those with an older population base.