[Distribution of conduction velocity in the ulnar nerve among lead exposed workers]

Neuropathy can be one of the symptoms of the toxic effect of lead on the nervous system. The aim of this work was to perform clinical and neurophysiological assessment of the peripheral nervous system in workers exposed to lead.

The study included 34 exposed workers and 20 healthy controls. Motor (ulnar, peroneal) and sensory (ulnar, sural) conduction velocity as well as conduction velocity distribution in ulnar n. and EMG from the I. interosseus muscle were assayed. The whole blood value of Pb 400 microg/l was adopted as a borderline between workers with low and increased blood lead concentrations. The FEP value of 70 microg/100 ml erythrocytes was the borderline between those without or with biochemical signs of Pb loading. The workers' age and duration of occupational exposure did not differ significantly between the study and control groups.

None of the workers showed clinical signs of neuropathy or abnormalities in routine neurographic examination. As compared with controls, a significantly lowered conduction in slow-conducting motor fibers and neurogenic changes in EMG were observed in workers with the whole blood Pb concentration over 400 microg/l and in workers with FEP level over 70 tig/100 ml erythrocytes.

Neurotoxic effect of Pb on peripheral nerves is manifested by the damage of slow-conducting motor nerves fibers when overt neuropathy is not yet visible.