The patients first undergo the basic preparation phase, which involves removing any magnetic-sensitive objects such as jewelry or credit cards. This is because TMS uses magnetic pulses. The patients are then supplied with earplugs to wear during treatment for their comfort and hearing protection, as TMS produces a loud clicking sound with each pulse, much like an MRI machine. Patients are then seated to receive their TMS treatment session.
The first TMS session starts with the brain mapping procedure, to first locate the motor strip and then the target location. The target location for depression is the lateral pre-frontal cortex. Different target locations may be used to treat other conditions. The physician systematically measures the patient’s motor threshold, by administering a series of brief pulses of escalating intensity. The motor threshold, which will vary from individual to individual, is calculated as the minimum amount of power necessary to make the patient’s thumb twitch. The physician must measure the motor threshold to determine the individualized treatment settings and calculate the specific amount of energy required to provide the desired degree of stimulation to the brain neurons. The motor threshold may be re-checked during subsequent treatments if there is suspicion it may have changed for some reason, such as because of a medication change.
Once the motor strip has been located and the motor threshold has been determined, the coil is moved a specific number of centimeters in a specific direction to the target location. In the treatment of depression, the coil is moved forward on the head to the prefrontal cortex. The physician will take several measurements to ensure that the TMS coil is properly positioned over the desired target location on the patient’s scalp. These individualized measurements are recorded on a patient specific cap, so that the same exact location is treated in subsequent sessions. Once this is all done and the TMS coil has been placed over the desired location, the treatment session can begin. During a session patients hear a series of clicking sounds and experience a tapping sensation under the treatment coil. After 20 minutes the session is complete.