Neurogenic mixed evoked potentials elicited by anterior spinal cord stimulation through thoracoscopy

Background. Anterior thoracic discectomy procedures with endplate ablations followed by posterior spinal fusions are advocated far patients with severe scoliosis or kyphosis. Anterior arthrodesis is usually accomplished through extensive thoracotomy or lumbotomy. Video-assisted thoracic surgery (VATS) has been recently introduced in the field of spinal diseases, and has been used to release the anterior spines of patients with severe spinal deformities. In this case, posterior approach is usually delayed for 1 or 2 days. Methods. In this article we report neurogenic motor evoked potential recording after spinal cord stimulation by electrodes seated into the intervertebral disc through thoracoscopy in five patients undergoing VATS. Results. Well-defined potentials were obtained after a short averaging (20-30 sweeps). NMEP (neurogenic mixed evoked potential) recording consisted of a mainly biphasic wave, which in each case was very similar to the one obtained after posterior spinal stimulation during the posterior approach. NMEPs remained unchanged during the whole surgical procedure (range 2-6 h). There was no case of pre- or postoperative neurological complications. Conclusion. This method could be of interest for spinal cord monitoring when posterior access is impossible and when reliable information regarding spinal motor pathways is necessary.