MR findings in the brains of compressed-air tunnel workers: relationship to psychometric results

Cranial MR imaging was performed in 30 subjects who had been involved in compressed-air tunnel projects in and around Milwaukee, WI. Nineteen of these subjects had been exposed to various degrees of hyperbaric air as calculated by an exposure index (average PSI pressure gauge multiplied by the number of years exposed), while 11 of the subjects were age-matched controls who belonged to the same labor union but had not been exposed to hyperbaric air. All MR scanning was done on a 1.5-T unit, and axial, sagittal, and coronal T1, proton density, and T2-weighted images were obtained. Ventricular size was measured objectively. Foci of increased T2 intensity within deep white matter tracts were evaluated as to number and location, and psychometric testing was performed on both groups to exclude preexisting organic brain disease. The 19 subjects in the experimental group had a statistically higher number (p = .05) of white matter lesions (more than 152) than the control group (22 lesions), and 37% of the experimental group had more than 20 white matter lesions each (seven of 19 subjects) while only 18% of the control group had 10 or 11 lesions each. The experimental group had a five times higher risk than the control group of having high-grade lesions, and a high statistical correlation (p = .02) was found between the number and severity of lesions in the experimental group as compared with the control group when linear trend analysis was performed. No correlation was found between exposure index, MR grade or number, or aseptic necrosis. Ventricular size was normal in all subjects.(ABSTRACT TRUNCATED AT 250 WORDS)