What is Transcranial Magnetic Stimulation?
Transcranial magnetic stimulation is an investigational procedure used to treat major depression. The technique involves use of an electromagnetic coil to create electromagnetic pulses in the brain which have an antidepressant effect. Both the treatment and the machine used to deliver the treatment are experimental. The fact that they are experimental means that the Food and Drug Administration (FDA) has not yet approved TMS as a treatment for major depression. TMS is, however, approved for other medical uses. Studies involving TMS are being done to evaluate its safety and effectiveness as a treatment for depression. How is TMS administered? TMS is offered in the United States both in private practice and through research studies. While most studies are free or of low cost, treatment in private practice can be more expensive and will not be covered by insurance. The treatment is typically administered five times per week at the same time of day for up to six weeks. The patient is awake
Transcranial magnetic stimulation (TMS) is a relatively recent technique for both the treatment of cognitive disorders such as depression or auditory hallucinations, and for brain research. It works by using an inductive magnetic field, similar to a metal detector but significantly more powerful, to excite neurons electrically. The first successful TMS study was carried out in 1985, making the field relatively recent within medical science. TMS looks promising as an alternative to the much more invasive electroconvulsive therapy. TMS is capable of being targeted with a precision of several millimeters, and is designed only to research the very surface of the brain – the cortex. Because many cognitive functions are located in the cortex, however, this is not a serious limitation. Research is ongoing and the scientific community has high hopes for TMS, with preliminary experiments even suggesting that it could be used one day to build a machine that quickly induces REM sleep, giving the
We asked Juliet Goldman, M.D., Ziad Nahas, M.D., and Mark S. George, M.D., of the Brain Stimulation Laboratory, Department of Psychiatry, Medical University of South Carolina, Charleston. In the last 20 years scientists have developed many ways to observe the workings of the living human brain, but until very recently they have been able to achieve direct stimulation of precise brain regions only by placing electrodes on exposed tissue during surgery. Transcranial magnetic stimulation (TMS) is an exciting new technique that permits direct brain stimulation without surgery. It works this way: a brief but powerful electric current is passed through a coil of wire placed near the head, creating a strong magnetic field, which in turn induces electrical currents in brain cells. Unlike electrical fields, magnetic fields pass through the scalp and skull without becoming diffused and absorbed. Thus current is delivered to the brain with great efficiency. The strength of a magnetic field falls
TMS has been available for the last 15 years (introduced by Anthony Barker) and has been used primarily as a research tool. Its based on Faradays principles of electromagnetic inductions. A pulse of current flowing through a coil of wire generates a magnetic field. If the magnitude of this magnetic field changes in time, it induces a current in a nearby conductor, like neurons. So the stimulating coil is held over a subjects head and as a brief pulse of current is passed, a magnetic field is generated that passes through the subjects scalp and skull. This stimulates the neural tissue, causing neuronal depolarization. In many experiments, single pulses of stimulation are applied, which is similar to conventional electric stimulation of peripheral nerves. To date, single-pulse techniques appear completely safe when applied to healthy individuals. In addition, repetitive pulses (repetitive TMS, or rTMS) can also be applied. With repetitive pulses, one must be careful of potential harmful
The TMS lab is a leader in research on this potential, new treatment for psychiatric disorders. TMS is a non-invasive means of stimulating the brain using magnetic fields. TMS is administered by holding a magnetic coil on the head. The coil is about the size of a ping-pong paddle. This coil generates a strong but brief magnetic field. The field enters the brain, where it stimulates the brain cells, or neurons. If the coil is held over the area of the brain that causes movement, the TMS will cause a twitch in the muscle whose brain representation we are focusing on. TMS has proven to be a useful tool in studying brain function. Combined with functional neuroimaging (PET, or fMRI), TMS can map brain circuits underlying complex functions like language, memory, vision, the control of movement, and even emotional processes. Our clinical interest in TMS focuses on its potential utility as a focal treatment for depression, obsessive-compulsive disorder, schizophrenia and other disorders. Func
