[Motor and cortical sensory evoked potentials by magnetic stimulation]

Motor evoked potentials (MEP) by magnetic stimulation on the scalp and the spinous processes of the 7th cervical (C 7) and 5th lumbar (L 5) vertebrae were studied in 20 normal subjects and 10 patients with the pyramidal tract lesions. The magnetic stimulator composed of two flat helical coils with mean inner diameters of 12.0 and 2.2 cm. The evoked muscle action potentials were recorded from the thenar muscle in the hand and abductor hallucis muscle in the leg. The mean peak latencies of MEP recorded from the thenar muscle were 22.1 +/- 1.7 and 12.8 +/- 0.9 msec at the stimulations on the scalp and C 7, respectively. The central motor conduction time (CMCT) between the cortex and C 7 was 9.1 +/- 1.1 msec. On the other hand, the peak latencies of MEP were 41.0 +/- 3.2 and 21.6 +/- 2.3 msec at the stimulations on the scalp and L 5, respectively. CMCT between the cortex and L 5 was 19.3 +/- 2.3 msec. The patients with pyramidal tract involvements showed delayed peak latencies or absent MEP. The cortical somatosensory evoked potentials (SEP) by the noninvasive magnetic stimulation on the levels of Th 10, Th 12 and L 5 spines, gluteus and ankle were studied in 20 normal subjects and 7 patients with neurological diseases. Cortical components P 2 and N 2 were recorded clearly in all normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)