Somatosensory evoked potential (SEP) waveforms were recorded over the scalp in response to tibial nerve stimulation at the ankle of 47 normal subjects. The SEP data was analyzed with the correlation coefficient and delay time, by using the program in a Cadwell Quantum 84 EMG system, to determine the reproducibility of the waveforms, and to identify side-to-side symmetry.
The purpose of this study was to find out the mean and standard deviation (SD) of the correlation coefficient and its differences between the sides of extremities, and between the raw and windowed data in normal subjects.
The results were as follows:
1) There were no significant differences between right and left sides in correlation coefficient and delay time, that were taken from raw and windowed data.
2) In raw and windowed data, the correlation coefficient compared with the ipsilateral side showed higher values than the contralateral side.
3) There was a significantly higher correlation coefficient from windowed data than raw data.
4) In the comparison between ipsilateral and contralateral sides of correlation coefficient and delay time, the more correlation coefficients were increased, the more delay times were decreased significantly.
Therefore, we conclude that the correlation coefficient analyzed by the computerized program can provide objective and quantitative waveform data that complements latency and amplitude measurement in the clinical interpretation of somatosensory evoked potential waveforms.
