A short history of rTMS and the brain, starting at 1985 and ending at 2005 was published by The Regence Group. The following is a citation from the web-site of the Regence Group.
“Transcranial magnetic stimulation” was first introduced in 1985 as a new method of noninvasive stimulation of the brain. The technique involves placement of a small coil over the scalp; a rapidly alternating current is passed through the coil wire, producing a magnetic field that passes unimpeded through the brain. Transcranial magnetic stimulation was initially used to investigate nerve conduction; for example, transcranial magnetic stimulation over the motor cortex will produce a contralateral muscular-evoked potential. Interest in the use of transcranial magnetic stimulation as a treatment for depression was prompted by the development of a device that could deliver rapid, repetitive stimulation. In contrast to electroconvulsive therapy, transcranial magnetic stimulation does not require anesthesia, and does not induce a convulsion. Specifically, early studies suggested that transcranial magnetic stimulation of the left prefrontal cortex was associated with antidepressant properties.
While devices for transcranial stimulation have received approval by the U.S. Food and Drug Administration (FDA) for diagnostic uses, at the present time, no device has received FDA approval for transcranial magnetic stimulation of the brain as a therapeutic procedure. One device, NeoPulse (Neuronetic, Atlanta, GA) has received approval in Canada and Israel as a therapy for depression.
Transcranial magnetic stimulation of the brain is considered investigational as a treatment of all psychiatric disorders, including, but not limited to depression.
The published literature regarding transcranial magnetic stimulation (TMS) as a treatment of depression or other mood disorders is comprised of several small controlled trials of limited follow-up, consisting of differing patient populations, location of stimulus, and stimulation parameters.
A representative sample of the sham, controlled trials is reviewed below.
Pascual-Leone and colleagues performed a sham controlled study that included a crossover design, enrolling 17 patients with medication-resistant depression of psychotic subtype. (2) Nine of the patients had previously responded to electroconvulsive therapy (ECT). An attempt was made to withdraw medication before the TMS therapy but that was not possible in all patients, and some patients required reintroduction of medications during the trial. To create sham stimulation, the magnetic coil was held obliquely to the scalp surface, which mimicked the sensation of „real” TMS, but did not induce an intracerebral current. Each course of TMS consisted of 5 sessions over 5 consecutive days. The patients received 5 different courses of TMS, both real and sham; each applied at different scalp positions. The authors concluded that stimulation of the dorsal left prefrontal cortex had marked antidepressant effect, with 11 of 17 patients showing a decline in Hamilton Depression Rating Scale scores of 50%.
George and colleagues reported the results of a placebo-crossover trial in 12 medication resistant depressed patients who sequentially underwent TMS of the left prefrontal cortex or sham treatment. (3) Each treatment course consisted of 10 sessions over a 2-week period followed by crossover to the other study arm. There was a modest decline in Hamilton Depression Rating Scale scores when the subjects received active treatment.
Klein and colleagues conducted a randomized placebo controlled trial in 70 patients with depression who were assigned to receive active or sham TMS. (4) The stimulation parameters used in this study, described as „slow” (<1 Hz) were different than the above studies, which used „fast” (>1 Hz) stimulation. In addition, sham TMS consisted of stimulation over the right (as opposed to left) prefrontal cortex using a differently designed coil. Treatment consisted of 10 daily sessions over a 2-week period. At the end of the study, 41% of those in the treatment group reported at least a 50% reduction in Hamilton Depression Rating Scale scores compared to 17% of those in the sham-treated group.
Loo and colleagues reported conflicting results from a double-blind study of 18 depressed adults who were randomly assigned to a 2-week course of real or sham TMS, using the same stimulation parameters as Pascual-Leone, reviewed above. (5) Both groups improved significantly during the 2-week study period.
While these studies suggest the potential of TMS as a treatment of depression, larger placebo-controlled trials of a homogeneous group of patients are needed to further define the optimal stimulation parameters and validate a treatment effect. All of the above studies only examined the treatment effect immediately after the study ended, so durability of results is also unknown. The role of TMS in the overall treatment of depression requires further study. For example, it is not known whether TMS would be used as an alternative to electroconvulsive therapy or as an adjunct to partially effective pharmacologic therapy. Finally, at the present time, there are no TMS devices that have received FDA approval as a treatment of any neuropsychiatric disorder, including depression.
An updated search of the MEDLINE database through February 9, 2005 identified several additional published studies and review articles; however, none alter the conclusions reached above. In a meta analysis of 16 published trials, a Cochrane Review concluded that there is no strong evidence of benefit from TMS when used in the treatment of depression, finding no difference between TMS and sham TMS based on results of the Beck Depression Inventory or Hamilton Depression Rating Scale. In addition, the Cochrane Review found electroconvulsive therapy was more effective than TMS. Other studies and reviews of studies found no or modest clinically significant differences between TMS and sham TMS treatment. Studies comparing ECT to TMS found that response rates and relapse rates for depression were comparable or that ECT was more effective. Several studies found no or minimal effect of TMS on other neuropsychiatric disorders such as other mood disorders, post-traumatic stress disorders, Tourette’s Syndrome, and schizophrenia”.
An excellent paper on TMS in cognitive neuroscience was written by Vincent Walsh and Alan Cowey (2000), from the Department of Experimental Psychology, University of Oxford and is cited below.
“Transcranial magnetic stimulation and cognitive neuroscience”
Transcranial magnetic stimulation has been used to investigate almost all areas of cognitive neuroscience. This article discusses the most important (and least understood considerations regarding the use of transcranial magnetic stimulation for cognitive neuroscience and outlines advances in the use of this technique for the replication and extension of findings from neuropsychology. We also take a more speculative look forward to the emerging development of strategies for combining transcranial magnetic stimulation with other brain imaging technologies and methods in the cognitive neurosciences.
Transcranial magnetic stimulation (TMS) is now an established investigative tool in the cognitive neurosciences, and several groups have begun to exploit its potential in the study of perception, attention, learning, plasticity, language and awareness.
It is also finding applications in the study and treatment of movement disorders, epilepsy, depression, anxiety disorders, stuttering and schizophrenia. Despite the breadth and depth of the published research, the considerations behind the use of TMS and its value in addressing neuropsychological questions remain poorly understood. In this article we confront some of the most common confusions about TMS and show how it can be used to complement and extend existing techniques.
The use of TMS in clinical neurophysiological studies is highly advanced and has been reviewed elsewhere. Likewise, parameters for the safe use of TMS have been established and have been documented extensively in other sources that are required reading for those contemplating the use of TMS. Our aim is not to provide a technical introduction. Here we focus on the role of TMS in the cognitive neurosciences and propose a conceptual framework for the future application of TMS to this area.