Conventional TMS is performed with what is called a “Figure-8” coil that delivers a focused magnetic pulse that reaches 0.7cm beneath the skull surface. TMS machines using this coil are manufactured by Neuronetics, Magstim and Magventure. A TMS session using a traditional “Figure-8” coil takes approximately 40 minutes.
Deep TMS is performed using a Brainsway dTMS machine using the H-1 coil. The magnetic pulse produced by the H-1 coil is focused but covers a broader area that a “Figure-8” coil. The H-1 pulse also reaches 1.7cm below the surface of the skull. A dTMS session using the H-1 coil takes approximately 20 minutes.
rTMS is the acronym for Repetitive Transcranial Magnetic Stimulation. This term refers to the repetitive series of magnetic pulses typically used to produce a more substantial and longer lasting antidepressant effect. A typical rTMS treatment will have 2,500 or more magnetic pulses delivered within a relatively short period of time. The term rTMS is used interchangeably with TMS.
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.
A TMS physician will always conduct the measurement of the motor threshold and the brain mapping procedure. The TMS treatment itself can be conducted by a physician-supervised TMS technician or by the TMS physician. The TMS technician or physician will always be present during the entire treatment to monitor the patient. A patient can ask to stop a treatment at any time if necessary.
TMS therapy involves a series of 36 treatment sessions. Treatment sessions vary in length depending on the TMS coil used and the number of pulses delivered during a session. Deep TMS using the advanced H-coil can deliver a depression protocol treatment session in 20 minutes. Advanced protocols that involve treating more than one location of the brain may take an additional 10 to 15 minutes. A very effective and frequently used treatment course protocol is comprised of Deep TMS treatments administered 5 days a week for the first 4 weeks and then twice a week for 8 weeks.
TMS does not involve any sedation or anesthesia. Patients are fully awake and alert during the TMS treatment. Because there is no recovery time necessary, patients can drive to and from TMS treatment on their own and afterwards immediately return to their usual daily activities.
TMS is generally well-tolerated and associated with few side-effects, especially when compared to medications. Only a small percentage of patients discontinue treatment because of side-effects. The most common side-effects of TMS are headaches and scalp discomfort. The headaches are mild and usually diminish over the course of the treatment. Over-the-counter pain medications are effective in treating the headaches. The scalp discomfort may be accompanied by facial twitching from the TMS pulses. These symptoms typically diminish over the course of treatment. Adjustments in coil positioning and stimulation settings can be made to reduce discomfort if necessary.
The TMS machine produces a loud noise as it delivers pulses during the treatment, which is the reason why earplugs are given to the patient to use during each session. A few patients may still complain of hearing problems immediately following treatment. This infrequent side effect is not permanent if earplugs are worn during the treatment.
The only potentially serious risk of TMS is seizures. This risk is extremely low and less than many commonly used medications. The most current safety guidelines are always followed to further minimize this risk. Overall, and especially in comparison to other procedures and medical treatments, TMS is considered extremely safe. TMS is not associated with any of the common side-effects caused by antidepressant medications, such as sexual dysfunction, weight gain, insomnia, gastrointestinal discomfort, dry mouth, or daytime sleepiness.
Due to safety reasons involving the use of a magnet, patients with any type of non-removable metal in their heads (with the exception of braces or dental fillings), cannot receive TMS. Exposure of one of these metal objects to repetitive magnetic impulses could cause the object to heat up, move, or malfunction, possibly resulting in serious injury or death. The following is a list of common metal implants that are not compatible with a patient receiving TMS:
• Electrodes to monitor brain activity
• Aneurysm clips or coils
• Metallic implants in your ears and eyes
• Stents in the neck or brain
• Deep brain stimulators
• Facial tattoos with metallic or magnetic-sensitive ink
• Shrapnel or bullet fragments in or near the head
Other metal devices or object implanted in or near the head
Patients who have not responded to numerous medication trials and are considered “treatment resistant” have responded very well to TMS. Existing evidence to date suggests that patients who are less treatment-resistant respond even better to TMS than those who are highly treatment-resistant. Studies are ongoing to further reveal what other variables would help predict a response to TMS.