Spinal cord potentials after transcranial magnetic stimulation during muscle contraction

✍ Scribed by Kazuo Kaneko; Shinya Kawai; Yasunori Fuchigami; Gen Shiraishi; Takashi Ito

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 278 KB
• Volume: 19
• Category: Article
• ISSN: 0148-639X
• DOI: 10.1002/(sici)1097-4598(199605)19:5<659::aid-mus17>3.0.co;2-i

✦ Synopsis

Magnetic stimulation of the human brain can elicit muscle action potentials and a single magnetic cortical stimulation can produce multiple descending potentials in the pyramidal t r a ~t s . ~-~, ~, ' ~

In clinical study, motor evoked responses are usually recorded during muscle contraction of target muscles, which shortens the latency and enhances the amplitudes of these response^.^^^*'^ The prolonged latency responses recorded during muscle relaxation may be explained by the temporal summation of multiple corticospinal descending potentials. It is important to define the voluntary facilitation mechanism involved in transcranial magnetic stimulation, which is currently unexplained. No data are available which adequately explain the differences between corticospinal potentials in the relaxed and the contracted states. In our study, we attempted to clarify the mechanism of this facilitation by direct measurement of evoked spinal cord potentials after magnetic brain stimulation.

Methods

Six patients, 19 and 61 years of age (5 women and 1 man) were studied. Two patients had midthoracic spinal cord tumors, and 4 patients had unilateral brachial plexus injuries. Informed consent for the procedure was obtained in all cases. Epidural electrodes (Unique Medical Co., Japan, UKG100-5PM) were inserted percutaneously in the midline of the