Transcranial magnetic stimulation for spinal cord monitoring

Intraoperative monitoring with somatosensory evoked potentials (SEPs) is a well established methodology. Despite well preserved SEPs severe postoperative motor disability may occur1. Therefore, monitoring of the motor pathways is of great importance. Initial experience with intraoperative MEP monitoring was gained using high-voltage electric stimulation during orthopaedic2 and neurosurgical procedures3. Edmonds et al.4 were the first to apply magnetic transcranial stimulation for intraoperative MEP monitoring during scoliosis surgery. Whereas good results were obtained during scoliosis surgery in neurologically intact patients, the same group reported inability to record MEPs following magnetic stimulation in neurologically impaired patients with spinal cord tumours during nitrous oxidebased anaesthesia5.