Evoked potentials in the assessment of neurotoxicity in humans

The present paper reviews strengths and weaknesses of evoked potentials (EPs) as an index of toxic insult to the nervous system. EPs are obtained by averaging successive samples of EEG time-locked to the presentation of stimuli. Components of the resulting waveform can be measured for amplitude, latency, and distribution. Normal ranges of these parameters have been characterized for auditory, visual and somatosensory stimuli. Auditory EPs have been studied in humans exposed to lead, trichloroethylene, and carbon monoxide. Changes in timing of short latency components and in amplitude of later cortical components have been reported. Methyl mercury, n-hexane and carbon monoxide cause complex changes in the waveshape of flash and patterned visual EPs. Similarly, specific components of somatosensory EPs are altered following exposure to carbon monoxide, lead and acrylamide. The current lack of standardized recording and analysis techniques has sometimes generated contradictory results, but the evidence thus far supports the ultimate usefulness of EPs as a neurotoxicological screening tool.