Vestibulospinal evoked potential versus motor evoked potential monitoring in experimental spinal cord injuries of cats.

Changes in vestibulospinal evoked potentials (VsEP) and motor evoked potentials (MEP) were examined in 10 cats before and after two different weight-dropping spinal cord injuries. In six animals somatosensory evoked potentials (SEP) were also monitored. The recordings were done from epidural spinal cord electrodes. Before and after severe and light weight-dropping spinal cord injuries all 3 modalities were recorded at the same time intervals till the end of 4th hour postinjury. According to a scoring system, evoked potential changes below and above the level of injury were monitored, and compared with each other. This study showed that the different motor stimulation methods use different descending spinal tracts, and both can be useful as a monitoring tool. Both descending tracts carrying VsEP and MEP had similarly remarkable changes after severe spinal cord injury. These consisted of major deformation, development of an evoked injury potential and complete potential loss. During the 4 hour monitoring period, no case showed EP recovery in the severe injury group. Light spinal cord injury caused somewhat more deterioration in MEPs than VsEP. The higher numbers of severe potential alterations in the lightly injured animals suggest that MEP is a more sensitive method for spinal cord monitoring compared to VsEP and also to SEP. On the other hand, this sensitivity might be a disadvantage during intraoperative monitoring, if MEP alone were used.