How Does TMS Work

Written By: Butler Hospital on April 22, 2021

TMS is non-invasive and does not involve surgery or insertion of intravenous lines or anything else put into your body. It also does not require any anesthesia or sedation. TMS uses a small electromagnetic coil controlled by a computer program to deliver short, powerful bursts of magnetic energy-focused precisely on the left side of the brain’s frontal cortex. The TMS magnetic fields are the same type and strength as those produced by a magnetic resonance imaging (MRI) machine.

A treatment coil is applied to the head above the targeted area of the brain, called the prefrontal cortex. This part of the brain is involved with mood regulation. TMS magnetic fields do not directly affect the whole brain; they only reach about 2-3 centimeters into the brain directly beneath the treatment coil. As TMS magnetic fields move into the brain, they produce very small electrical currents. The electrical currents activate cells within the brain, which are thought to release neurotransmitters.

The typical initial treatment course consists of five treatments per week over a four to six-week period, for an average of 20-30 total treatments. Additional treatments may be used to maintain optimal antidepressant benefits, but a frequency schedule for “maintenance” TMS treatments has not yet been established. Each treatment session lasts about one hour. 

More About TMS

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 to determine its safety and efficacy for the treatment of major depression. Early results from other trials have encouraged researchers to further investigate TMS therapy as a treatment for major depression.

The short pulses of magnetic energy produced by the TMS therapy system are aimed at the treating clinician at the structures in the brain thought to control mood. The left pre-frontal 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.

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.

Results of Transcranial Magnetic Stimulation

The type of TMS machine used at Butler Hospital was determined by the FDA to provide safe and well-tolerated treatment for depression. The data collected in these clinical trials resulted in FDA clearance “for the treatment of major depressive disorder in adult patients who have failed to achieve satisfactory improvement from one prior antidepressant medication at or above the minimal effective dose and duration in the current episode."

In an open-label trial, approximately one out of two patients treated with the TMS therapy device used at Butler Hospital experienced significant improvement in depression symptoms. TMS treated patients who also experienced significant improvement in anxiety, appetite changes, aches and pains, and lack of energy associated with depression.


Approximately one out of three patients treated with TMS therapy experienced complete symptom relief at the end of six weeks.

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