Prevention of spinal cord injury with time-frequency analysis of evoked potentials: an experimental study

Objectives-To verify the applicability and validity of time-frequency analy sis (TFA) of evoked potential (EP) signals in detecting the integrity of sp inal cord function and preventing spinal cord injury. Methods-The spinal cord was simulated during surgery in 20 mature rats by m echanically damaging the spinal cord. Cortical somatosensory evoked potenti al (CSEP), spinal somatosensory evoked potential (SSEP), cortical motor evo ked potential (CMEP), and spinal cord evoked potential (SCEP) were used to monitor spinal cord function. Short time Fourier transform (STFT) was appli ed to the CSEP signal, and cone shaped distribution (CSD) was used as the T FA algorithm. for SSEP, CMEP, and SCEP signals. The changes in the latency and amplitude of EP signals were measured in the time domain, and peak time , peak frequency, and peak power were measured in the time-frequency distri bution (TFD). Results-The TFDs of EPs were found to concentrate in a certain location und er normal conditions. When injury occurred, the energy decreased in peak po wer, and there was a greater dispersion of energy across the time-frequency range. Strong relations were found between latency and peak time, and ampl itude and peak power. However, the change in peak power after injury was si gnificantly larger than the corresponding change in amplitude (p <0.001 by ANOVA). Conclusions-It was found that TFA of EPs provided an earlier and more sensi tive indication of injury than time domain monitoring alone. It is suggeste d that TFA of EP signals should therefore be useful in preventing spinal co rd injury during surgery.