Steady-State Cortico-cortical Evoked Potential.

PURPOSE The present study evaluated the utility of the steady-state responses of cortico-cortical evoked potentials (SSCCEPs) and compared them with the responses of conventional CCEPs. METHODS Eleven patients with medically intractable focal epilepsy who underwent the implantation of subdural electrodes or stereoelectroencephalography were enrolled. Conventional CCEPs were obtained by averaging responses to alternating 1-Hz electrical stimuli, and 5-Hz stimuli were delivered for recording SSCCEPs. The distribution of SSCCEPs was assessed by a frequency analysis of fast Fourier transform and compared with conventional CCEPs. RESULTS Steady-state responses of cortico-cortical evoked potentials were successfully recorded in areas consistent with conventional CCEPs in all patients. However, SSCCEPs were more easily disturbed by the 5-Hz stimulation, and small responses had difficulty generating SSCCEPs. CONCLUSIONS Steady-state responses of cortico-cortical evoked potentials may be a useful alternative to conventional CCEPs.