Transcranial Magnetic Stimulation
What is transcranial magnetic stimulation?
Transcranial magnetic stimulation or TMS is a neurophysiological technique that allows the induction of a current in the brain using a magnetic field to pass the scalp and the skull safely and painlessly. In TMS, a current passes through a coil of copper wire that is encased in plastic and held over the subject's head. This coil resembles a paddle or a large spoon and is held in place either by the investigator or by a mechanical fixation device similar to a microphone pole. As the current passes through the coil it generates a magnetic field that can penetrate the subject's scalp and skull, and in turn induce a current in the subject's brain.
TMS has been studied for more than twenty years and a certain type of TMS has been FDA approved to treat depression. It continues to be used in clinical neurophysiology to study the nerve fibers that carry the information about movements from the brain cortex to the spinal cord and the muscles. It is important that before agreeing to participate in a TMS study, all the questions of potential subjects or patients be answered.
What is repetitive TMS?
Technical developments in the devices used for TMS made it possible in the late 1980s to apply TMS in trains of multiple stimuli per second. This form of TMS is called repetitive TMS or rTMS. Repetitive TMS can be used to study how the brain organizes different functions such as language, memory, vision, or attention. In addition, rTMS seems capable of changing the activity in a brain area, even beyond the duration of the rTMS application itself. In other words, it seems possible to make a given brain area work more or less for a period of minutes, or even weeks when rTMS is applied repeatedly several days in a row. This has opened up the possibility of using rTMS for therapy of some illnesses in neurology, rehabilitation, and psychiatry (see FDA approval for Depression).
Are there any adverse effects?
TMS, particularly rTMS, can have adverse effects. The most worrisome of which is its potential to induce a seizure or epileptic convulsion, even in subjects without any predisposing illness. The risk of adverse effects is low, but appropriate safety guidelines and precautions need to be followed, and the person performing rTMS needs to be properly trained. Subjects considering their participation in a TMS study, and patients planning to undergo rTMS for treatment of any disease should know that there are relative and absolute contraindications to TMS. It is important to discuss these with the investigators and physicians and undergo proper screening.
Articles About TMS
To learn more about TMS consult the following articles:
- TMS: Studying Brain-behavior Relationship by Induction of “Virtual Lesions”. Trans Royal Philosophical Society 354(1387): 1229-38(1999), Pascual-Leone A, Bartres-Faz D, Keenan JP.
- TMS in Cognitive Neuroscience: Virtual Lesion and Neurochronometry. Current Opinion in Neurobiology 10: 232-237 (2000), Pascual-Leone A, Walsh V, Rothwell J.
- Studies in Cognition: The Problems Solved and Created by Transcranial Magnetic Stimulation. J Cog Neurosci 15: 948-960 (2003), Robertson EM, Theoret H, Pascual-Leone.
- Transcranial Magnetic Stimulation in Neurology. Lancet Neurology 2: 145-156 (2003), Kobayashi M, Pascual-Leone.
- Fregni F, Pascual-Leone A. Transcranial Magnetic Stimulation for the Treatment of Depression in Neurological Disorders. Curr Psychiatry Reports 7: 381-390 (2005).
- Pascual-Leone A. Disrupting the brain to guide plasticity and improve behavior. Prog Brain Res. 2006;157:315-329.
- Wagner T, Valero-Cabre A, Pascual-Leone A. Noninvasive human brain stimulation. Annu Rev Biomed Eng. 2007;9:527-65.
- Fregni F, Freedman S, Pascual-Leone A. Recent advances in the treatment of chronic pain with non-invasive brain stimulation techniques. Lancet Neurol. 2007;6(2):188-91.
- Fregni F, Pascual-Leone A. Technology insight: noninvasive brain stimulation in neurology-perspectives on the therapeutic potential of rTMS and tDCS. Nat Clin Pract Neurol. 2007;3(7):383-93.
- Frye RE, Rotenberg A, Ousley M, Pascual-Leone A. Transcranial magnetic stimulation in child neurology: current and future directions. J Child Neurol. 2008;23(1):79-96.
- Wu AD, Fregni F, Simon DK, Deblieck C, Pascual-Leone A. Noninvasive brain stimulation for Parkinson's disease and dystonia. Neurotherapeutics. 2008;5(2):345-61.
- Rossi S, Hallett M, Rossini PM, Pascual-Leone A; Safety of TMS Consensus Group. Safety, ethical considerations, and application guidelines for the use of transcranial magnetic stimulation in clinical practice and research. Clin Neurophysiol. 2009 Dec;120(12):2008-39. Epub 2009 Oct 14.
