Transcranial magnetic stimulation ( TMS ) is a method in which a changing magnetic field is used to cause an electric current to flow in a small region of the brain through electromagnetic induction. During the TMS procedure, magnetic field generator, or "coil", is placed near the head of the person receiving the treatment. The coil is connected to a pulse generator, or stimulator, which gives an electric current change to the coil.
TMS is used diagnostically to measure the relationship between the central nervous system and skeletal muscle to evaluate damage in various disease states, including stroke, multiple sclerosis, amyotrophic lateral sclerosis, impaired movement, and motor neuron disease.
Evidence suggests it is useful for neuropathic pain and major drug-resistant depressive disorders. The 2015 Cochrane Review found that there was not enough evidence to determine its effectiveness in treating schizophrenia. For the negative symptoms, other reviews find the possibility of efficacy. By 2014, all other recurring TMS uses that have been investigated have little or no clinical efficacy.
Matching TMS's discomfort to distinguish the true effects of placebo is an important and challenging issue that affects clinical trial results. The harmful effects of TMS are rare, and include fainting and infrequent seizures. Other adverse effects of TMS include discomfort or pain, hypomania, cognitive changes, impaired hearing, and current induction by accident in embedded devices such as pacemakers or defibrillators.
Video Transcranial magnetic stimulation
Medical use
The use of TMS can be divided into diagnostic and therapeutic uses.
Diagnosis
TMS can be used clinically to measure the activity and function of certain brain circuits in humans. The most powerful and widely accepted use is in measuring the relationship between the main motor cortex and muscle to evaluate the damage caused by stroke, multiple sclerosis, amyotrophic lateral sclerosis, movement disorders, motor neurone disease and injuries and other disorders affecting the face and other skulls. nerves and spinal cord. TMS has been suggested as a means to assess short-term intracortical inhibition (SICI) that measures the internal pathway of the motor cortex but this use has not been validated.
Treatment
For neuropathic pain, for which there is little effective treatment, repeated high frequency (RTM) TMS (RTM) appears effective. For major treatment-resistant depressive disorders, HF-RTM from the left dorsolateral prefrontal cortex (DLPFC) appears to be effective and low frequency (LF) RTM from the right DLPFC has a potency of efficacy. The Royal Australia and New Zealand College of Psychiatrists have endorsed RTM for treatment-resistant MDD treatment. In October 2008, the US Food and Drug Administration endorsed the use of rTMS as an effective treatment for clinical depression.
Maps Transcranial magnetic stimulation
Adverse effects
Although TMS is generally considered safe, the risk is increased for therapeutic RTM compared with a single TMS or pair for diagnostic purposes. In the field of therapeutic TMS, the risk increases with a higher frequency.
The biggest direct risk is the rarity of syncope (fainting) and induced seizures.
Other short-term adverse effects of TMS include discomfort or pain, temporary hypomania induction, temporary cognitive changes, temporary hearing loss, temporary interruption of working memory, and induced currents in electrical circuits on the device being grown.
Devices and procedures
During the transcranial magnetic stimulation procedure (TMS), magnetic field generator, or "coil" is placed near the head of the person receiving the treatment. The coil produces a small electric current in the brain region just below the coil via electromagnetic induction. The coil is positioned by finding anatomical signs on the skull including, but not limited to, inion or nasion. The coil is connected to the pulse generator, or the stimulator, which gives an electric current to the coil.
Most devices provide a shallow magnetic field that affects most neurons on the surface of the brain, delivered with a coil shaped like an eight figure. Some devices can provide deeper penetrating magnetic fields, used for "inner TMS", and have various types of coils including H-core C-core coils, and circular coiled crowns; in 2013, coil H used in devices made by Brainsway is the most developed.
Theta-burst stimulation
Theta-burst stimulation (TBS) is a protocol used in transcranial magnetic stimulation. Originally described by Huang in 2005. This protocol has been used in major depressive disorders with both right and left dorsolateral prefrontal cortex (DLPFC) stimulation. The left stimulated (TBS) while the right is inhibited (cTBS). In theta-burst stimulation pattern, 3 pulses are given at 50 Hz, every 200 ms. In the intermittent theta burst stimulation pattern (iTBS), a 2-second train of TBS is repeated every 10 seconds for a total of 190 (600 pulses). In the continuous theta continuous stimulation paradigm (cTBS), a disturbed 40s TBS carriage is supplied (600 pulses).
In the March 2015 publication Bakker demonstrated with 185 patients equally divided between standard 10 Hz protocol (30 min) and theta-burst stimulation, that the results (reduction of Ham-D and BDI scores) were the same.
Society and culture
Approval settings
Neurosurgical planning
Nexstim obtained 510 (k) FDA clearances for major motor cortex assessment for pre-procedural planning in December 2009 and for neurosurgical planning in June 2011.
Depression
A number of in-depth TMS have received the FDA 510K permission to be marketed for use in adults with major depression-resistant medication disorders.
Migraine
Use of a single pulse TMS approved by the FDA for migraine treatment by December 2013. It is approved as a Class II medical device under " de novo pathway".
More
In the European Economic Area, various versions of Deep TMS H-coils have CE marks for Alzheimer's disease, autism, bipolar disorder, chronic pain epilepsy major depressive disorder Parkinson's disease, post-traumatic stress disorder (PTSD), schizophrenia (negative symptoms) and to help quit smoke. One review found temporary benefit for cognitive improvement in healthy people.
Health insurance
United States
Commercial health insurance
In 2013, several commercial health insurance plans in the United States, including Anthem, Health Net, and Blue Cross Blue Shield of Nebraska and Rhode Island, discussed TMS for the treatment of depression for the first time. In contrast, UnitedHealthcare issued a medical policy for TMS in 2013 stating that there is insufficient evidence that this procedure is beneficial for health outcomes in patients with depression. UnitedHealthcare noted that methodological concerns raised about the scientific evidence that the TMS studied for depression included small sample sizes, lack of false ratios validated in randomized controlled studies, and variables using outcome measures. Other commercial insurance plans for 2013 medical coverage policy state that the role of TMS in the treatment of depression and other disorders is unclear or remains under investigation including Aetna, Cigna and Regence.
Medicare
Policies for Medicare coverage vary among local jurisdictions within the Medicare system, and Medicare coverage for TMS varies between jurisdictions and with time. As an example:
- In early 2012 in New England, Medicare discussed TMS for the first time in the United States. However, the jurisdiction then decided to end the coverage after October 2013. In August 2012, jurisdictions covering Arkansas, Louisiana, Mississippi, Colorado, Texas, Oklahoma, and New Mexico determined that there was not enough evidence to close care, but the same jurisdiction then determined that Medicare would bear TMS for the treatment of depression after December 2013.
United Kingdom National Health Service
The National Institute for Health and Nursing Excellence UK (NICE) publishes guidelines for the National Health Service (NHS) in England, Wales, Scotland and Northern Ireland. GREAT guidance does not cover whether the NHS should fund the procedure. The local NHS agency (primary care trust and hospital confidence) makes decisions about funding after considering the clinical effectiveness of the procedure and whether the procedure represents the money value for the NHS.
NICE evaluated TMS for severe depression (IPG 242) in 2007, and then considered the TMS for reassessment in January 2011 but did not alter its evaluation. The Institute found that TMS was safe, but there was insufficient evidence for its efficacy.
In January 2014, NICE reported the TMS evaluation results to treat and prevent migraines (IPG 477). NICE found that short-term TMS is safe but there is not enough evidence to evaluate safety for long-term and frequent use. It was found that evidence on the efficacy of TMS for migraine treatment is limited in number, that evidence for migraine prevention is limited in both quality and quantity.
Technical information
TMS uses electromagnetic induction to generate electrical current in the scalp and skull without physical contact. A plastic covered wire roll is held next to the skull and when activated, generates an orthogonally oriented magnetic field to the coil plane. The magnetic field passes unhindered through the skin and skull, inducing a directly directed current in the brain that activates nearby nerve cells in the same way as currents applied directly to the cortical surface.
This current path is difficult to model because the brain is irregularly shaped and electricity and magnetism are not evenly distributed across the network. The magnetic field has almost the same strength as the MRI, and the pulse generally reaches no more than 5 cm to the brain except using a deep transcranial magnetic stimulation variant of the TMS. Deep TMS can reach up to 6 cm to the brain to stimulate a deeper layer of the motor cortex, such as those that control leg movement.
Action mechanism
Dari hukum Biot-Savart
it has been shown that the current through the wire produces a magnetic field around the wire. Transcranial magnetic stimulation is achieved by rapidly removing the current from large capacitors into the coil to produce a pulsed magnetic field between 2 and 3 T. By directing the magnetic field pulses in the targeted area of ​​the brain, one can depolarize or hyperpolarize neurons in the brain. The magnetic flux pulse density generated by the current pulse through the coil causes the electric field as described by the Maxwell-Faraday equation,
This electric field causes a change in the transmembrane currents of the neuron, leading to depolarization or hyperpolarization of the neurons and the firing of action potentials.
Detailed details of how TMS functions are still explored. The effects of TMS can be divided into two types depending on the stimulation mode:
- TMS single or paired pulses cause neurons in the neocortex below the stimulation site to depolarize and excrete action potentials. When used in the primary motor cortex, it produces a muscle activity called a potential generating motor (MEP) that can be recorded on electromyography. If used in the occipital cortex, 'phosphenes' (flashes of light) may be felt by the subject. In most other areas of the cortex, participants do not consciously experience any effects, but their behavior may be slightly altered (eg, slower reaction times in cognitive tasks), or changes in brain activity can be detected using sensing devices.
- Repetitive TMS produces long-term effects that persist after the initial period of stimulation. rTMS may increase or decrease the stimulation of the corticospinal tract depending on the intensity of the stimulation, the orientation of the coil, and the frequency. This effect mechanism is unclear, although it is widely believed to reflect a change in synaptic efficacy similar to long-term potentiation (LTP) and long-term depression (LTD).
The MRI images, which were recorded during the TMS of the brain's motor cortex, have been found to match very closely with PET generated by the voluntary movement of hand muscles innervated by TMS, to 5-22 mm accuracy. Localization of motor areas with TMS has also been seen to correlate closely with MEG and fMRI as well.
Coil Type
The design of transcranial magnetic stimulation coils used in either treatment or diagnostic/experimental studies may differ in various ways. These differences should be considered in the interpretation of the research results, and the type of coil used should be determined in the study method for each published report.
The most important considerations include:
- the type of material used to build the coil core
- coil configuration geometry
- the biophysical characteristics of the pulse generated by the coil.
With respect to the coil composition, the core material may be an inert substrate of magnet (ie, so-called 'air-core' coil design), or has a solid ferromagnetic active material (ie, called 'core-design). The solid core coil design results in a more efficient transfer of electrical energy into the magnetic field, with a substantially reduced amount of energy being spent as heat, so it can operate under a more aggressive duty cycle that is often mandated in therapeutic protocols, heat accumulation, or the use of coil cooling accessory method during operation. Varying the geometric shapes of the coils themselves can also produce variations in the focality, shape, and depth of cortical penetration of the magnetic field. The difference in the coil substance as well as the electronic operation of the power supply to the coil may also result in variations in the biophysical characteristics of the generated magnetic pulses (eg, the width or duration of the magnetic field pulses). All these features should be considered when comparing results obtained from different studies, with respect to safety and efficacy.
A number of different types of coils exist, each producing a different magnetic field pattern. Some examples:
- round coil: original type of TMS coil
- the number eight coil (ie the butterfly coil): produces a more focused activation pattern
- double-cone coil: in accordance with the shape of the head, useful for deeper stimulation
- four-leaf coil: for focal stimulation of peripheral nerves
- H-coil: for deep transcranial magnetic stimulation
Variety of designs in the form of TMS coil allows deeper penetration of the brain than the standard depth of 1.5-2.5 cm. The circular coil of the crown, Hesed (or H-core) coil, double conical coil, and other experimental variations can lead to deeper excitation or inhibition of neurons in the brain including activation of motor neurons for the cerebellum, legs, and pelvic floor. Although able to penetrate deeper in the brain, they are less able to produce a focused and localized and relatively non-focal response.
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History
Luigi Galvani undertook pioneering research on the electrical effects on the body in the late 1700s, and laid the foundations for the field of electrophysiology. In the 1800s Michael Faraday discovered that an electric current has a corresponding magnetic field, and that changing one, can change the other. Working to directly stimulate the human brain with electricity began in the late 1800s, and by the 1930s electroconvulsive therapy had been developed by Italian physicians Cerletti and Bini. ECT became widely used to treat mental illness and became overused because it began to be seen as a "psychiatric elixir", and a counterattack against it grew in the 1970s. Around that time Anthony T. Barker began exploring the use of magnetic fields to convert electrical signals in the brain, and the first stable TMS device was developed around 1985. They were originally intended as a diagnostic and research tool, and only then therapeutic use was explored. The first TMS device was approved by the FDA in October 2008.
Research
The TMS research on animal studies is limited due to preliminary FDA approval of TMS treatment of drug-resistant depression. Because of this, there is no specific coil for the animal model. Therefore, there are a number of TMS coils that can be used for animal research. There have been several attempts in the literature that show new coil designs for mice with enhanced stimulation profiles.
Areas of research include:
- aphasia rehabilitation and motor defects after a stroke,
- tinnitus,
- anxiety disorder, including panic disorder and obsessive-compulsive disorder. The most promising areas to target for OCD are the orbitofrontal cortex and additional motor areas. Older protocols targeting the dorsal prefrontal cortex were less successful in treating OCD.
- amyotrophic lateral sclerosis,
- multiple sclerosis,
- epilepsy,
- Alzheimer's disease,
- Parkinson's disease,
- schizophrenia,
- substance abuse, addiction, and post-traumatic stress disorder (PTSD).
- autism
- brain death, coma, and other persistent vegetative state.
- Functional connectivity between the cerebellum and other areas of the brain
- Traumatic brain injury
- Stroke
Study blind
It is difficult to establish a convincing form of a false TOR to test a placebo effect during a controlled trial in a conscious individual, due to neck pain, headache and twitch on the scalp or upper face associated with the intervention. Manipulation of TAM manipulation can affect cerebral glucose metabolism and MEP, which can disrupt the results. This problem is exacerbated when using measures of subjective improvement. The placebo response in rTMS trials in severe depression was negatively related to refractoriness to treatment, varying between studies and may affect outcomes.
A 2011 review found that only 13.5% of 96 randomized controlled studies from RTM to the dorsolateral prefrontal cortex have reported dazzling success and that, in the study, people in the RTM group were significantly significantly more likely to think they had received TMS is real, compared to those in the fake rTMS group. Depending on the research question posed and the experimental design, matching the discomfort of rTMS to distinguish the true effects of placebo can be an important and challenging issue.
See also
- Cortical stimulation mapping
- Stimulation of skull electrotherapy
- Electrical brain stimulation
- Electroconvulsive Therapy
- Low magnetic field stimulation
- Transcranial direct-flow stimulation
- Transcranial backflow stimulation
- Stimulation of transkranial noise
References
Further reading
- Wassermann, EM; Epstein, CM; Ziemann, U; Walsh, V; Pope, T; Lisanby, SH (2008). Oxford Handbook from Transcranial Stimulation (Oxford Handbooks) . Oxford University Press, USA. ISBN: 0-19-856892-4.
- Freeston, I; Barker, A (2007). "Transcranial magnetic stimulation". Scholarpedia . 2 (10): 2936. doi: 10.4249/scholarpedia.2936.
- George, Mark S.; Belmaker, Robert H. (2000). Transcranial magnetic stimulation in Neuropsychiatry . American Psychiatric Press. ISBN: 9780880489485.
- Cohen, D.; Cuffin, B. N. (1991). "Developing More Focal Magnetic Stimulator Part I: Some Basic Principles". Journal of Clinical Neurophysiology . 8 : 102-111. doi: 10.1097/00004691-199101000-00013.
External links
- Stutter Triggered by Transkranial Magnetic Stimulation (video)
Source of the article : Wikipedia
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