Abstract
Abstract This chapter considers technical and methodological aspects of performing central motor conduction studies in patients. Whilst the measurement of muscle responses to peripheral nerve stimulation is relatively straightforward, quantification of the responses to brain stimulation is more difficult. I have attempted to answer some of the frequently asked questions on the use of transcranial magnetic stimulation (TMS) in a clinical setting. To excite the motor cortex of arm muscles, a circular coil is usually placed with its centre at the vertex (Fig. 8.1). With a coil of diameter 10-12 cm, the edge of the coil in this position is over the hand area. The direction of coil current (provided this is effectively monophasic-see Chapter 2) will determine which hemisphere is preferentially excited. Using a circular coil with the coil current flowing clockwise when viewed from above, the right hemisphere will be preferentially excited. Turning the coil over so that current now flows anticlockwise, the left hemisphere will be preferentially excited. With a figure-eight coil; the central linear segment should be over the motor area (Fig. 8.1).
Published Version
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