Transcranial Magnetic Stimulation
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Introduction[edit | edit source]
Transcranial Magnetic Stimulation (TMS) is a focal, noninvasive form of brain stimulation based on principles of electromagnetic induction. The device is placed on the scalp and either single (sTMS) or repeated (rTMS) magnetic pulses are delivered. The frequency, intensity, duration and interval times of pulses can be varied[1].
There is a sufficient body of evidence to accept:
- Level A (definite efficacy) for the analgesic effect of highfrequency (HF) rTMS of the primary motor cortex (M1) contralateral to the pain and the antidepressant effect of HF-rTMS of the left dorsolateral prefrontal cortex (DLPFC)[2]
- Level B recommendation (probable efficacy) is proposed for the antidepressant effect of low-frequency(LF) rTMS of the right DLPFC, HF-rTMS of the left DLPFC for the negative symptoms of schizophrenia, and LF-rTMS of contralesional M1 in chronic motor stroke[2].
- Level C (possible efficacy) for the effect of LF rTMS of the left temporoparietal cortex in tinnitus and auditory hallucinations[2]
Historical Background[edit | edit source]
Throughout history, brain stimulation techniques such as TMS have proved to be powerful tools for investigating neurophysiology as well as for mapping and modulating neural circuitry[1].
First emerging as a potential tool for noninvasive neuronal stimulation in the early 20th century[3], repetitive transcranial magnetic stimulation (rTMS) has undergone multiple stages of development. Anthony Barker invented the first modern-day rTMS device in 1985 as a way to study electrophysiology[4]. In 1995, George et al. (1995) used rTMS to target specific prefrontal brain regions thought to be involved in the etiology or pathophysiology of major depression in an open-label study. Although most of the research has supported the antidepressant properties of rTMS, the degree of clinical benefit has been variable and, in some cases, marginal. However, a clear trend toward more robust effects has been seen as both stimulation technique (e.g., dose, coil placement, and course duration) and research quality (e.g., better sham stimulation and larger sample sizes) improve. rTMS has become a recognized, accepted, and clinically available therapeutic intervention.
Functioning[edit | edit source]
The equipment consists of a high current pulse generator able to produce a discharge current of several thousand amperes that flows through a stimulating coil, generating a brief magnetic pulse with field strengths up to several Teslas. This magnetic pulse, by the principles of electromagnetism, produces secondary electric fields in the opposite direction to the field generated by the coil[5][6][7][8]. If the coil is placed on the head of a subject, the magnetic field thus created undergoes little attenuation by extracerebral tissues (scalp, cranial bone, meninges, and cerebrospinal fluid layer) and is able to induce an electrical field sufficient to depolarize superficial axons and to activate neural networks in the cortex.
Resources[edit | edit source]
- ↑ 1.0 1.1 Holtzheimer, P., & McDonald, W. (Eds.), A Clinical Guide to Transcranial Magnetic Stimulation. Oxford, UK: Oxford University Press. Retrieved 16 Jan. 2022,
- ↑ 2.0 2.1 2.2 Lefaucheur JP, André-Obadia N, Antal A, Ayache SS, Baeken C, Benninger DH, et al. "Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS)". Clinical Neurophysiology. 2014; 125 (11): 2150–2206.
- ↑ Thompson, S. P. . A physiological effect of an alternating magnetic field. Proceedings of the Royal Society B: Biological Sciences, 1910; 82(557): 396–398.
- ↑ Barker, A. T., Freeston, I. L., Jalinous, R., Merton, P. A., & Morton, H. B.. Magnetic stimulation of the human brain. Journal Physiology, 1985; 369: 1–3.
- ↑ Barker AT, Jalinous R, Freeston IL. NON-INVASIVE MAGNETIC STIMULATION OF HUMAN MOTOR CORTEX. The Lancet. 1985;325:1106-1107.
- ↑ Hallett M. Transcranial magnetic stimulation and the human brain. Nature. 2000;406:147-150.
- ↑ Hallett M. Transcranial Magnetic Stimulation: A Primer. Neuron. 2007;55:187-199.
- ↑ Siebner H, Rothwell J. Transcranial magnetic stimulation: new insights into representational cortical plasticity. Experimental Brain Research. 2003;148:1-16.
