Lead neuropathy and electrophysiological studies in low level lead exposure: a critical review

The literature on nerve conduction velocity (NCV) studies and electromyography in lead exposed populations was reviewed. All studies revealed some degree of defect in their experimental design. Disregarding these limitations, a consensus of the studies indicates that a mild slowing (7%) of motor and sensory NCV may be present in the median and posterior tibial nerves, but that ulnar and peroneal NCVs are not slowed in subjects with blood lead levels of less than 60 micrograms/dl. No clinical correlations to this mild slowing were reported in studies where concurrent motor and sensory examinations were performed. A majority of the studies did not find a correlation between blood lead level and NCV at blood lead levels below 70 ug/dl or length of exposure and NCV. Most studies of electromyographic activity in lead exposed population found abnormalities only in patients with blood lead levels above 60-70 ug/dl or in patients with lead colic or other systemic symptoms of lead intoxication. This review does not find evidence that the slowing of NCV in low level lead exposure is clinically significant or evidence that would suggest that it is a subclinical manifestation of clinical lead neuropathy in man.