Transcranial magnetic stimulation (TMS) is a non-invasive method of treating depression that uses repetitively pulsed magnetic fields to generate an electrical current in a targeted region of the brain.   

The magnet energy extends only 2 to 3 cm into the brain in an area of about size of 50 cent piece. It penetrates farther, 4-6cm with dTMS (deep TMS), using a Brainsway machine.

Unlike medication, this is a non-systemic treatment that has virtually no side effects, yet often has long term benefit.

Transcranial magnetic stimulationRunning electricity through a copper coil creates a magnet.  A static magnet placed on the brain does nothing.   However, if a powerful magnet goes off and on rapidly, electrical changes occur in the neurons within the magnetic field.   The neurons are either excited or inhibited, depending on the position of the coil, the position of the neurons and the type of pulses administered.  Each pulse is 280 microseconds long in a Magpro Machine by Magventure, and pulse width is similar in other brands.

Where and how to treat was basically discovered empirically.  There is one reasonable theory of why TMS works, though it is probably more complicated.   The left brain is hypoactive during depression.   Excitatory TMS treatment of the left DLPFC (dorsolateral prefrontal cortex) causes an increase in blood flow, metabolism and activity for about 45 minutes. Then activity returns to normal and there is no detectable difference in the body.    After many treatments, usually 5 to 15, the depression begins to lift.  Perhaps we are inducing he left brain to come to normal activity.  .

It is harder to explain why inhibitory treatment on the right works for depression as well.  Maybe it inhibits that area until both sides of the brain are matched in activity?  Also, there are individuals who respond best to left inhibitory treatment and others who respond to right excitatory.

WHAT DOES TMS INVOLVE? 

  • I usually do at least a 1 hour evaluation—including history, blood pressure and weight. If the patient is eager to start, and/or they have come a long ways for the appointment,   I often combine evaluation, obtaining the MT (motor threshold) and first treatment all in one visit.  But I don’t charge for all that.

The first treatment visit involves:

  • Transcranial Magnetic Stimulation - focal field pattern

    By MistyHora at the English language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=5152920

    Finding the MT (motor threshold), which takes about ½ hour. This is done only on the first visit, and is repeated periodically.  The MT is the amount of stimulus (magnetic energy, technically Teslas) applied to the hand area of the motor strip sufficient to cause motor movement in the thumb or fingers of the hand contralateral to the stimulus.  We use the MT to determine how much stimulus to use for the treatment (anywhere from 80% to 120% of MT, depending on protocol).

  • Each patient has his own cap, which is positioned the same on each visit. After MT is determined and other measurements are made, the place of treatment is determined and marked on the capsule.   Thereafter we can easily repeat the treatment in the same place each time.
    • The place of treatment is the DLPFC (dorsolateral prefrontal cortex), usually determined by going 6cm anterior in the sagittal plane to the “hotspot”—the area of the motor cortex where we elicited movement in the hand. We also determine it by finding F3 and F4 by the Beam method.   F3 and F4 are roughly equivalent to the left and right DLPFC. They are positions of placement for an EEG on the 10-20 system.   If these two positions are very far apart we may elect to treat between them.  Research indicates that the Beam method is probably more accurate than the “6cm rule.”
  • The treatment itself lasts about 30 minutes. If the patient is unipolar (or only mildly polar), the treatment is usually HF-L