Somatosensory potentials evoked by magnetic stimulation of lumbar roots, cauda equina, and leg nerves

Cortical somatosensory evoked potentials (Septembers) were studied by noninvasive magnetic stimulation at T‐10, T‐12, and L‐5 vertebral levels and in mid‐gluteus muscle and ankle in 27 normal subjects and 7 patients with neurological diseases. Cortical components P2 and N2 were recorded in all normal subjects. The mean peak latencies of P2 were 20.3 ± 0.9 (standard deviation), 21.1 ± 1.2, 23.5 ± 1.4, 27.9 ± 2.0, and 38.1 ± 1.8 msec at the T‐10, T‐12, L‐5, mid‐gluteal and ankle sites of stimulation, respectively. No substantial difference in morphology of P2 and N2 was seen between magnetic and electrical stimulation at T‐12. Amplitudes of P2 and N2 were maximal after magnetic stimulation at motor threshold. P2 and N2 may originate from the sensory cortex. P2 and N2 evoked by T‐10 and T‐12 stimulation were normal in peak latency and morphology in patients with polyneuropathy or polyradiculoneuropathy. Peak latencies of P2 and N2 evoked by T‐10 and T‐12 stimulation were significantly delayed in patients with myelopathy. The patients with radiculopathy showed a delayed peak latency and conduction time of P2 evoked by L‐5 stimulation. Magnetic stimulation of spinal root is able to detect lesions of spinal cord noninvasively.

[1]  A. Eisen,et al.  Paraspinal stimulation to elicit somatosensory evoked potentials: an approach to physiological localization of spinal lesions. , 1987, Electroencephalography and clinical neurophysiology.

[2]  K. Mills,et al.  Magnetic and electrical transcranial brain stimulation: physiological mechanisms and clinical applications. , 1987, Neurosurgery.

[3]  B L Day,et al.  Some experiences of techniques for stimulation of the human cerebral motor cortex through the scalp. , 1987, Neurosurgery.

[4]  A. Barker,et al.  NON-INVASIVE MAGNETIC STIMULATION OF HUMAN MOTOR CORTEX , 1985, The Lancet.

[5]  G. Klem,et al.  k tibial nerve stimulation: Normative values , 1984 .

[6]  G. Klem,et al.  Effect of stimulus intensity on subcortical and cortical somatosensory evoked potentials by posterior tibial nerve stimulation. , 1984, Electroencephalography and clinical neurophysiology.

[7]  R P Lesser,et al.  Origin of far-field subcortical evoked potentials to posterior tibial and median nerve stimulation. A comparative study. , 1983, Archives of neurology.

[8]  K. Shimoji,et al.  Human spinal cord potentials evoked by different sources of stimulation and conduction velocities along the cord. , 1982, Journal of neurophysiology.

[9]  G. Klem,et al.  Surgical monitoring of spinal cord function: cauda equina stimulation technique. , 1982, Neurosurgery.

[10]  M A Edgar,et al.  Sensory nerve conduction in the human spinal cord: epidural recordings made during scoliosis surgery. , 1982, Journal of neurology, neurosurgery, and psychiatry.

[11]  G. Klem,et al.  Origin of far-field subcortical potentials evoked by stimulation of the posterior tibial nerve. , 1981, Electroencephalography and clinical neurophysiology.

[12]  H. Morton,et al.  Stimulation of the cerebral cortex in the intact human subject , 1980, Nature.

[13]  Mahendra Somasundaram,et al.  New Developments in Electromyography and Clinical Neurophysiology. , 1974 .

[14]  K. Shimoji,et al.  Epidural recording of spinal electrogram in man. , 1971, Electroencephalography and clinical neurophysiology.