NEUROLOGICAL AND ELECTROPHYSIOLOGICAL EXAMINATION ON WORKERS EXPOSED TO MERCURY VAPORS

The authors carried out neurological examination, visual evoked potent ials (VEP) examination, and electromyography (EMG) on 77 workers, aged 21 - 61 yrs, who were exposed occupationally to Hg degrees vapors for 1 - 20 yrs (mean 9 yrs). The mean air-borne concentration of Hg degre es was 0.25 mg/m(3) (range 0.02 - 1.00 mg m3) and the mean Hg urinary concentration was 0.21 mg/l (range 0.02 - 0.77 mg/l). Symptoms of eret hism (generally accepted as a typical sign of micromercurialism) were reported in about 80% of the workers. The static tremor of fingers (in 25%), and the absence of ankle jerk (in 20%) were the most frequently observed signs. VEP was abnormal in 39 workers (51%), but in 25 of th ose, an explanation for this finding could be found in their history a nd/or neurological status. In the 14 remaining cases, the connection w ith exposure to Hg degrees has been considered. A polyneuropathic patt ern of EMG abnormality was found in 5 workers, an isolated EMG abnorma lity of the sural nerve in 13 workers. In 9 workers no other obvious c ause for EMG abnormality was found but exposure to mercury. The associ ation of EMG abnormality (especially decreased conduction velocity of the sural nerve) with VEP abnormality (especially shortening of latenc y) seems to be a relatively characteristic electrophysiological patter n in persons exposed to mercury vapors, suggesting an incipient, or su bclinical damage to the nervous system. (C) 1996 Intox Press, Inc.