THORACIC SPINAL NERVE AND ROOT CONDUCTION - A MAGNETIC STIMULATION STUDY

We describe a technique of magnetic coil (MC) stimulation of the thora cic spinal nerves and roots in 12 normal subjects and a patient with d iabetes mellitus. We kept the MC flat against the vertebral column in the midline over T-7, T-8, and T-9 spinous processes and obtained comp ound muscle action potentials from the upper rectus abdominis, externa l oblique, and intercostal muscles. We obtained mean latencies to thes e muscles after stimulation in the posterior axillary line. We noted t hat the onset latencies remained fixed despite increasing the intensit y of stimulation from 30% to 100% and on moving the coil up to 3 cm la teral to the spinous processes suggesting that the stimulation of the fastest conducting fibers was occurring at a fixed site, most likely a t the intervertebral foramina. Prolonged latencies in the diabetic pat ient confirmed the diagnosis of radiculoneuropathy. (C) 1995 John Wile y and Sons, Inc.