Chapter

Evoked Motor Responses of the Brain, Spinal Cord, and Roots

Jay A. Liveson and Dong M. Ma

in Laboratory Reference for Clinical Neurophysiology

Published in print May 1999 | ISBN: 9780195129243
Published online March 2012 | e-ISBN: 9780199847792 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780195129243.003.0017
Evoked Motor Responses of the Brain, Spinal Cord, and Roots

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Since 1980, techniques have been developed to stimulate the motor cortex using surface stimulation. P. A. Merton and H. B. Morton utilized brief, high-voltage stimuli. Subsequently, A. T. Barker and associates developed magnetic stimulation. These methods have been used to stimulate cortical structures and also the spinal cord and root regions. The safety, side effects, reliability, and clinical applicability of these procedures are still being evaluated. Potentially, they present a measure of descending motor pathways, from the cortex, through the cord, to the periphery. Special stimulators are required. High-voltage methodology necessitates an output of 750 volts and a low-output impedance. Magnetic stimulation is via a flat helical coil. A large current (maximally 5,000 amperes) produces a magnetic field of two tesla. The former procedure is better localized. The latter is painless and can be delivered without skin contact, but it is difficult to localize the point of stimulation precisely.

Keywords: motor cortex; surface stimulation; high-voltage stimuli; magnetic stimulation; spinal cord; motor pathways; magnetic field

Chapter.  1016 words.  Illustrated.

Subjects: Neuroscience

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