Transcranial  Magnetic Stimulation 

Transcranial Magnetic Stimulation (TMS) makes use of a magnetic field to stimulate the brain for the treatment of depression, anxiety, OCD, and smoke cessation.

The clinical use of TMS started with FDA approval of the Neuronetics TMS device in 2008. In 2013 Brainsway came out with a different coil (the H coil embedded in a helmet) that penetrated more deeply than the Neuronetics coil, and thus was called deep TMS (dTMS). TMS has been approved for the treatment of OCD using the Brainsway dTMS device (in 2018) as well as the Magventure deep butterfly coil. OCD is treated using a different coil placement and different stimulation parameters than used to treat depression. Other approved uses of TMS are for anxious features associated with a severe major depressive episode (FDA approved in 2021 for Brainsway dTMS), and smoking cessation (2020). It should be said that no form of TMS has been shown to be superior to another. However, a deeply penetrating coil is needed to treat OCD as the brain structures we are targeting lie deeper inside the brain. The deeper penetrating coils are the Magventure butterfly coil and the Brainsway dTMS device.

TMS in any of its forms is delivered 5 days a week for 4 to 6 weeks. For the treatment of depression, the coil is placed on the left side over an area called the dorsolateral prefrontal cortex (DLPFC). The area of stimulation is important and specific to each disease state TMS IS being used to treat. We use neuronavigation so before we begin treatment, we will need a 3D MRI of the brain. One of the biggest variables that come up with treatment is where precisely the treatment coil is placed. There is a lot of room for inconsistencies of coil placement. It turns out that the left front part of the skull is big by TMS standards, and it is possible to stimulate very different structures with small changes in placement of the magnet. The use of neuronavigation to be ensures that the coil is placed precisely and consistently for every treatment every day. We also use neuronavigation to be able to decide precisely where we place the magnet. This description of what TMS is like is specific to the way we treat depression. Treating OCD or other indications is similar, but the coil may be different, and the coil placed in a different area.

TMS stimulation causes neurons to be stimulated which then stimulate the other neurons its connected to. Neurons are connected in a circuit or what is called a neurocircuit. Different neurocircuits underly different functions of the brain, such as motor control or higher cognitive processes. The stimulation over the DLPFC stimulates neurocircuits whose dysfunction is implicated in mood regulation and anxiety. With every pulse of the magnetic coil a ripple of neurons responding to the stimulation underneath the coil will move through these neurocircuits. It appears left sided high frequency or iTBS affects the areas important in mood regulation differently than with right sided treatment. There is much more to learn that will help us devise the best treatment approaches for our patients and ultimately to improve treatment outcomes.

There has been a lot of excitement recently for the use of an accelerated treatment approach using iTBS for depression (aiTBS). The idea was basically to squeeze as many treatments in a week as possible. aiTBS is delivered for 9 minutes (1800 pulses), then the patient waits for 50 minutes of rest, then it’s repeated for a total of 10 times. This is done daily for 5 days. Although the number of people formally studied is relatively small, we have used aiTBS for the most depressed. The research studies indicate a large proportion of patients respond to treatment and we have also seen good results. It is an important treatment option to consider given the brief period of treatment and the good likelihood of a treatment response.

Some people notice improvement in the first week, but this is a minority of patients receiving TMS. For most it is between 4 and 6 weeks. Our experience with patients who have been severely ill, and disabled is it more often 6 weeks. The early response to TMS is different than we normally see for antidepressant treatment of depression. At the beginning of the week the patient may be disappointed that there is no change, but on Thursday they note a clear improvement. The message is that the experience of improvement isn’t linear or predictable by how one has felt over the prior 4 weeks. This makes it a challenge receiving TMS; you can’t anticipate whether you will feel better tomorrow, and yet you must be patient getting treated daily for over a month before you do feel better. For our part, we provide encouragement and the perspective of using TMS to treat patients with severe depression over 20 years. We can help. The aiTBS treatment is designed as a 5-day treatment. There is a significant minority that either has a partial response or no response after 5 days. For those patients it appears that 50% or better will respond to a second week of aiTBS. There is not yet good data, but this is the impression at this time. Insurance approves 36 treatments: 6 weeks of 5 days a week, then 6 ‘taper’ treatments. It is done this way because the original study that resulted in FDA approval of TMS for treatment resistant depression was designed this way. The study wasn’t designed to show how much TMS would maximally reduce symptoms for all the patients. Our experience is that, like with medication, sometimes more than the approved number of treatments is required to get a treatment response. While an outlier, there was a patient who required over 70 treatments to have a treatment response. That patient was completely well and stopped TMS after 92 treatments. This case illustrates that there are no hard and fast rules with the number of treatments required or how long treatment is before a treatment response is apparent.

TMS is always prescribed, and motor threshold done at the start of treatment by a TMS physician. After that, the treatment is delivered by an experienced TMS technician under supervision by the TMS physician. The technician or physician will always be present during the treatment. The patient can ask to stop treatment at any time due to discomfort or their concerns.

TMS does not require anesthesia nor hospitalization. There is no need for a recovery time after TMS before you leave to go home or to work. There is no perceptible effect on cognition or memory and so can return to usual activities immediately after TMS treatment is completed.

TMS is well tolerated with few side-effects noted in research trials and in clinical use. Most side effects, like discomfort under the magnet at the site of stimulation, will resolve over the first 5-7 treatments. About 1/3 of patients will have painful sensations under the magnet or facial twitching. The stimulation intensity or small adjustments in coil position can immediately be made to reduce the discomfort. Those patients with the most discomfort at the beginning of treatment will eventually become comfortable with it. By the second or third week many patients watch TV or meditate. Among those with site pain, a minority will have a headache after. Over-the-counter medications can be used post-TMS for headache. Patients who have a history of migraines may have a migraine post treatment. The patient’s usual medication for migraine will work in that case. TMS induces a loud click with each pulse. It is recommended that patients wear earplugs. In the initial studies using the Neuronetics device and 10Hz 3000 pulses over 37-minute treatment there was a transient high frequency hearing loss. It’s not clear that there is the same risk with 9-minute iTBS but it’s a precaution we recommend. There is a risk of iTBS or high frequency TMS induced seizure. This is the most serious side effect of TMS but it is an exceedingly low risk. It was reported in one exhaustive review of the safety of TMS that there was a risk of 1/100,000 treatments for iTBS in particular.

Existing evidence to date suggests that patients who have failed to respond to fewer antidepressant medications respond better to TMS compared to those who are more highly treatment resistant. There is a lot of research currently being done to answer this question.

Patients with any type of non-removable metal in their heads (except for braces or dental fillings), should not receive TMS. Failure to follow this rule could cause the object to heat up, move, or malfunction, and result in serious injury or death. The following is a list of metal implants that can prevent a patient from receiving TMS: Aneurysm clips or coils Stents in the neck or brain Deep brain stimulators Electrodes to monitor brain activity Metallic implants in your ears and eyes Shrapnel or bullet fragments in or near the head Facial tattoos with metallic or magnetic-sensitive ink Other metal devices or object implanted in or near the head