Usefulness of time-frequency patterns of somatosensory evoked potentials in identification of the location of spinal cord injury.

Somatosensory evoked potentials (SEPs) have been widely used to monitor the neurological integrity of the spinal cord during spinal surgery. However, the location of neurologic impairment cannot be determined from SEPs. Previous studies imply that the time-frequency characteristics of SEPs may reflect the location of the spinal cord injury. To validate the hypothesis that time-frequency patterns of SEPs are associated with the location of neurologic deficits in the spinal cord, we studied the time-frequency distributions of SEPs at different injury levels. Twenty-four rats were equally divided into one normal group and three injury groups, in which weight-drop contusions were delivered to the spinal cord of the rats at C4, C5, or C6 level, respectively. By comparing the time-frequency patterns of SEPs across groups, we found significant differences in several time-frequency regions of interest in the time-frequency distributions of the normal group and the injury groups. Importantly, the regions of interest were different across injury groups, suggesting that these regions of interest could be specific to injury locations. The results imply that changes of the time-frequency patterns of SEPs may be related to the location of the spinal cord injury.