On the use of evoked potentials for quantification of pain

Pain is a subjective and individual sensation causing major discomfort. So, it is necessary to put into practice methods to objectively quantify it. Several studies indicate that evoked potentials (EP) generate responses which may reflect painful processes. This study reports the results of the application of two different protocols by using biopotentials to objectively measure pain. The first (protocol 1) evaluates the relation between pain, induced by electrical stimulation, and subjective perception and also with nociceptive flexion reflex (NFR) represented by muscle activity (electromyography) detected on the femoral biceps after sural nerve stimulation. The second protocol (protocol 2) verifies whether there is some correlation between M-wave parameters and subjective pain sensation. The results obtained from protocol 1 suggest that the area of the EMG envelope and entropy estimated from the EMG activity are correlated with subjective sensation of pain. The analysis of data obtained from protocol 2 shows a correlation between the global minimum of the M-wave and pain increase. These results contribute to studies which seek to objective measures for pain quantification based on the analysis of biopotentials.