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TMS Therapy involves the use of very short pulses of magnetic energy to stimulate nerve cells in the brain. First used in 1985, TMS Therapy has been used by researchers around the world to help understand the function of different parts of the brain. Special sequences of repetitive TMS Therapy have been tested by Neuronetics to determine its safety and efficacy for the treatment of major depression. Neuronetics' pivotal trial is not the first to investigate the potential anti depressant effects of TMS Therapy. Early results from other trials have encouraged researchers to further investigate TMS Therapy as a treatment for major depression. However it is not an FDA approved procedure for depression.
The short pulses of magnetic energy produced by NeuroStar TMS Therapy SystemTM are aimed by the treating clinician at the structures in the brain thought to control mood (the brain’s limbic system structures, many of which are thought to be involved in mood regulation). The left prefrontal cortex is used to access these structures non-invasively from outside the brain with TMS Therapy. The unique nature of magnetic fields allows them to pass through the skull and into the cortex without being distorted in any way. This facilitates a very focal type of stimulation, minimizing stimulation of brain tissue not involved in mood.
Source: Neuronetics
Once inside the brain, the dynamic (rapidly changing) nature of the magnetic pulses induces electrical charges to flow. The amount of electricity created in the brain is very small, and can not be felt by the patient. When in the correct orientation relative to brain cells (neurons), these very small electric charges can cause the neurons to fire or become active. The objective of TMS Therapy is to stimulate (or activate) brain cells. Patients remain awake and alert during a TMS Therapy procedure.
TMS Therapy differs from techniques where direct electrical energy is applied to the brain, such as ECT, because the electric field is magnetically derived and is more directly focused to the target site. TMS Therapy also differs from the use of low-level static magnetic fields because they do not induce electrical currents in the cortex.
It is generally assumed that TMS Therapy produces its behavioral effects through the production of electrical current in the cortex of the brain and an induced stimulation of the mood circuits (limbic system). The magnetic field induced by TMS Therapy declines rapidly with distance away from the coil. Thus, TMS Therapy coils directly stimulate only a small region in the cortex, and do not produce direct electrical stimulation deep in the brain. Deeper brain structures can be influenced by cortical TMS Therapy, however, due to the cortex's massive interconnections and redundant cortical-subcortical loops.
TMS is still being studied by scientists and researchers. There are several clinical trials currently being conducted around the country. There is no estimate or timetable as to when the study results will be presented to an FDA panel for review and recommendation for approval.
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