What is the role of electrical stimulation in motor evoked potentials (MEPs)?

Updated: Aug 20, 2019
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Answer

Electrical stimulators have a simpler design than magnetic stimulators. The stimulation is transmitted through cutaneous electrodes. The main advantage is a better depth of penetration, allowing direct spinal cord stimulation. The main limitation is the local discomfort that is created by the stimulation.

Electrical stimulators contain a capacitor that produces constant current, high-voltage pulses of brief duration for percutaneous stimulation. The output current range is 0-1000 milliamperes, from a source voltage as high as 400V. The pulse-width range can be varied from 50 milliseconds to 2 milliseconds. The voltage is kept constant during the stimulation, but the intensity of stimulation depends on the skin impedance.

Some electrical stimulators can deliver repetitive (2-9) pulses, which have been shown to facilitate induction of motor responses. These stimulators can be particularly useful for monitoring the spinal cord during surgical procedures.


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