Transcranial magnetic stimulation

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Depiction of how the magnetic field from the coil creates the electric current in the brain.

Transcranial magnetic stimulation, or TMS, is a non-invasive method of brain stimulation. During the procedure, a magnetic coil is placed over the scalp of the person receiving the treatment. The magnetic field penetrates the skull and the electric stimulus activates the neurons in the target area. This can be used to explore how the brain works, by disrupting its normal behaviour with the stimulation, or, in the case of repetitive stimulation, to modulate the brain activity for therapeutic purposes.[1][2]

Two TMS devices, NeuroStar TMS Therapy system from Neuronetics,[3] Inc., and Brainsway Deep TMS system[4] have been approved by the U.S. Food and Drug Administration for the treatment of depression[1] One session usually lasts 30 to 60 minutes.[5] for which TMS is a cost-effective alternative as opposed to antidepressants.[6][7]

Main characteristics

A simplified circuit diagram of a single-pulse magnetic stimulator.

The magnetic field created by the the coil produces electrical current in the brain of the subject due to the electromagnetic induction effect. This produces secondary ionic current which activates the near-surface neuronal axons in the target area. However, TMS, especially in higher intensities, may activate any neuron along the way.[2] The magnetic field can reach up to 2 T and usually lasts for about 100 µm.[7]

TMS system is composed of two parts. A high-voltage charge-discharge component that produces the required current waveform. This is a RLC circuit modified so it produces the waveform with the lowest amount of heat generated. The second components is the current carrying coil that servers as the emitter of the magnetic field. Although the design of the coils vary, the most used are two circular coil in parallel so as they resemble the number eight, or butterfly, shape. The coils are made of copper wiring and enclosed in a plastic chassis, with the diameter ranging from 4 to 9 centimetres.[8][9]

Purpose

Company & People

Important Dates

Enhancement/Therapy/Treatment

Ethical & Health Issues

Public & Media Impact and Presentation

Public Policy

Related Technologies, Projects or Scientific Research

References

  1. 1.0 1.1 ELDAIEF, Mark C., PRESS, Daniel Z. and PASCUAL-LEONE, Alvaro, 2013, Transcranial magnetic stimulation in neurology A review of established and prospective applications. Neurology: Clinical Practice. 2013. Vol. 3, no. 6, p. 519–526. DOI 10.1212/01.CPJ.0000436213.11132.8e.
  2. 2.0 2.1 RIDDING, Michael C and ROTHWELL, John C, 2007, Is there a future for therapeutic use of transcranial magnetic stimulation? Nature reviews. Neuroscience. 2007. Vol. 8, no. 7, p. 559–567. DOI 10.1038/nrn2169.
  3. https://neurostar.com/
  4. http://www.brainsway.com/about-brainsway
  5. http://www.nimh.nih.gov/health/topics/brain-stimulation-therapies/brain-stimulation-therapies.shtml
  6. NGUYEN, Kim-Huong and GORDON, Louisa G, 2015, Cost-Effectiveness of Repetitive Transcranial Magnetic Stimulation versus Antidepressant Therapy for Treatment-Resistant Depression. Value in health : the journal of the International Society for Pharmacoeconomics and Outcomes Research [online]. 2015. Vol. 18, no. 5, p. 597–604. DOI 10.1016/j.jval.2015.04.004. Available from: http://www.sciencedirect.com/science/article/pii/S1098301515019270
  7. 7.0 7.1 HALLETT, Mark, 2007, Transcranial Magnetic Stimulation: A Primer. Neuron. 2007. Vol. 55, no. 2, p. 187–199. DOI 10.1016/j.neuron.2007.06.026.
  8. WAGNER, Timothy, VALERO-CABRE, Antoni and PASCUAL-LEONE, Alvaro, 2007, Noninvasive human brain stimulation. Annual Review of Biomedical Engineering [online]. 2007. Vol. 9, no. 1, p. 527–565. DOI 10.1146/annurev.bioeng.9.061206.133100. Available from: http://dx.doi.org/10.1146/annurev.bioeng.9.061206.133100\nfiles/392/Wagner et al. - 2007 - Noninvasive Human Brain Stimulation.pdf
  9. KOBAYASHI, Masahito and PASCUAL-LEONE, Alvaro, 2003, Basic principles of magnetic stimulation. The Lancet. 2003. Vol. 2, p. 145–156. DOI 10.1016/S1474-4422(03)00321-1.