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MEPs and their clinical application

The generation of motor evoked potentials (MEPs) in the brain provides valuable information regarding the functionality of the central motor and sensory pathways, of particular interest when studying diseases of the motor system (Chiappa). Pioneered by Merton and Morton in 1980, the electric stimulation technique has been superseded in recent years, thanks to the development of TMS. Via TMS it is possible to generate MEPs without the discomfort associated with electrical stimulation and it is superior in the stimulation of deep and less accessible nerves.

With central nervous system responses, via a technique referred to as facilitation, it is possible to reduce the stimulation threshold by approximately 25%, increase the response amplitude 2-5 times and reduce response latency by some 1-3 ms through pre-activation of the target muscle (Rothwell at el. 1991).

Magnetically evoked motor potentials can be obtained by stimulating the motor cortex, spinal nerve roots and peripheral nerves. Specific patterns allow preferential stimulation of specific muscle groups. Responses can be measured using electromyographic (EMG) or evoked potential equipment.

Practical applications of TMS-generated MEPs include diagnosing multiple sclerosis and monitoring treatment response, stroke recovery and motor neuron disease diagnosis, amongst others.

References

  • Chiappa KH, Evoked potentials in Clinical Medicine, 1982.
  • Merton & Morton, Nature, 1980.
  • Rothwell et al, Experimental Physiology, 1991.

Products

  • Magstim 200²
    A single pulse, monophasic stimulator used for cortical and peripheral stimulation.
  • Magstim BiStim² & Upgrade
    The BiStim² is an extension of the 200². Two of the single pulse systems are combined through a connecting module, so that paired pulses can be delivered through one coil.
  • Magstim Rapid², Super Rapid², & the Super Rapid² Plus¹
    The Magstim Rapid² is a single pulse and repetitive stimulator with high frequency capabilities. It is ideal for therapeutic applications as well as a wide variety of research fields.
  • Interface Module
    The Magstim Stimulator Interface Module provides additional interface functionality for all of the 2nd generation Magstim Stimulators (200², BiStim² and Rapid²).
  • Neuronavigation
    Magstim is working to develop applications that will further advance the field of Neuronavigation, and supports ANT's Visor System.
  • Air Film Coil
    The Magstim Air Film Coil is the first of a new generation of stimulating coils which allow users to stimulate for extended periods of time. This improvement has been achieved as a result of an advanced, registered method of coil design and manufacture
  • Double 70mm Cooled Coil System
    The cooled coil is available in the double 70mm configuration and can be run for extended periods of time without overheating thus removing the need to replace coils during protocols of stimulation.
  • Double Cone Coil
    The Double Cone Coil elicits responses from relaxed muscles of the lower pelvic floor and lower limbs.
  • Double Small 25mm Coil
    The Double Small 25mm Coil has been designed for enhanced positional accuracy in peripheral stimulation.
  • High Power 90mm Circular Coil
    The High Power 90mm Coil can be used for central motor conduction studies. The design of the coil allows between 120 and 160 stimuli at the maximum power level before requiring a few minutes to cool.
  • HDCkit
    A cost-effective modular system for Direct Current (DC) stimulation, designed specifically for both research and clinical use.

Literature

Video

Resources

More about us

About Us

Magstim provides the means for neuroscientists to work with the human brain in awake subjects by manufacturing and supplying state-of-the-art clinical and research instruments in the fields of:

    - Neurology
    - Neurophysiology
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    Magstim equipment is able to work in conjunction with many measuring technologies (fMRI/ EEG /PET/Positioning systems) so that questions about brain function can be addressed.

    Through our machines, users can assess, protect and improve the function of the nervous system in a variety of clinical and research situations.

    Our principal products are the Magstim range of magnetic nerve stimulators.

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