Transcutaneous magnetic stimulation of descending tracts in the cervical spinal cord in humans

Percutaneous magnetic stimulation in humans allows non-invasive stimulation of deeply situated nervous structures with little, if any, discomfort and has proven its utility for brain stimulation. At the level of the vertebral canal, magnetic stimulation readily elicits muscle responses through activation of the motor spinal roots, but there has been no evidence for direct stimulation of the spinal cord itself. The present results document the feasibility of directly stimulating descending systems of the cervical spinal cord which synaptically activate motoneurones. A working hypothesis is that the structure thus stimulated may be cortico-motoneuronal pyramidal axons or the propriospinal system.