Magnetic stimulation of spinal nerve roots and cortical somatosensory evoked potentials

Abstract

Somatosensory evoked potentials (SEPs) elicited by the electrical stimulation at the peripheral nerves have many clinical applications since the work of Dawson (1947). This electrical stimulation, however, is painful and difficult to apply to the spinal roots at the thoracic and lumbar levels and proximal nerve trunks. Magnetic stimulation is a new method which was developed for non-invasive stimulation of the human motor cortex by Barker et al., in 1985. Since then, transcranial magnetic stimulation of the motor cortex has been used to evoke potentials (motor evoked potentials, MEPs) from the hand and foot muscles for the analysis of upper and lower motor neuron functions in patients with neurological diseases (Mills et al., 1987; Uozumi et ah, 1991). This method is non-invasive, and less painful than the electrical stimulation of the human motor cortex through the scalp (Merton et al., 1980). Recently, magnetic rather than electrical stimulation of the human motor cortex has been used in the analysis of neurological diseases.