Transcranial Magnetic Stimulation: A Look Under the Hood


It’s an FDA approved technology, but what exactly is TMS and why should you be aware of it?

with David Carreon, MD and Jessica A. Gold, MD, MS

This is Part 1 of a 3-part interview. Part 2 can be found here. Part 3: TMS: A Top-Down Process. Transcranial magnetic stimulation: an exciting FDA approved technology in psychiatry. But exactly what is TMS, and why should psychiatrists-and perhaps even the general-public be aware of it?

That's the key question the hosts of this short podcast (the first in a series of three on the topic) put to Richard Bermudes, MD, founder and medical director of TMS Health Solutions and founding member of the clinical TMS society, Inc. Here, Dr. Bermudes talks about some basics: what these devices look like, how they work, and about the patient experience.


David Carreon: Welcome to Psyched, a podcast about psychiatry that covers everything from the foundational to the cutting edge, from the popular to the weird. Thanks for tuning in. This is David Carreon.

Jessi Gold: This is Jessi Gold.

David Carreon: This is Psyched. We have with us today, Dr. Richard Bermudes, the founder and medical director of TMS Health Solutions. He earned his medical degree from the University of California San Diego in 1997. He served as chief resident for the family medicine and psychiatry combined program at the University of Cincinnati, then completed a fellowship at the Beck Institute for Cognitive Therapy and Research in Philadelphia. He's the founding member of a clinical TMS society, and he chaired the first annual meeting in 2013. Now was elected president of the society in 2015. Dr. Bermudes, thank you for joining us.

Bermudes: Thank you.

David Carreon: I wanted to talk to you a little bit about TMS. This is something that is a new and exciting technology in psychiatry, and just wanted to give you the chance to talk about ... What is TMS, and why should psychiatrists and maybe even the general public be aware of it?

Bermudes: That's a great question, and actually, it's a question I think about a lot. Probably too much. In its simplest form, TMS is transcranial magnetic stimulation. It's an FDA approved treatment for adult patients who have not responded to one or more anti-depressants, medications. In its basic form, we're using high powered magnetic coil to generate energy across the cortex. We're using that to modulate populations of neurons, so to speak.

David Carreon: You're taking this device, and walk us through, what does the device look like? If you're a patient walking into the office, what happens to you?

Bermudes: Well, the devices are pretty ... Each device essentially has a few components, but there's generally a stimulator with a bank of capacitors. This basically is a way for energy to store up and be discharged quite quickly, in milliseconds. This current then goes through a coil. There are various shapes of coils, the most common being, there's kind of two shapes that are pretty common. I won't digress yet, but basically, this current gets discharged into a coil, and then perpendicular to that coil, a fairly high powered magnetic field abruptly is on and then off.

This happens, it's a fluctuating current, which produces a fluctuating field. It's because it's not static, because it's fluctuating in milliseconds that it actually affects [inaudible] channels essentially. The discovery of this in the 80's  by Mark George and others, that really kind of took our initial offering of, basically we've been waving magnets around the brain for quite a bit of time trying to change it. It's sort of this notion that it's a fluctuating current with a fluctuating magnetic field that makes it pretty powerful for the brain.

Patients would see, generally there's sort of a cart, or some sort of bank, or stimulator. Then there's some sort of arm that holds these coils. There's usually a user interface for the technician or physician to sort of navigate that coil around the person's head. There's generally some sort of medical looking chair to these systems as well.

Jessi Gold: I'd imagine patients don't get exposed to magnets in their brains very often. Probably the only thing they know from magnets would either be like, the little kid toys or maybe an MRI or something like that. Does that come up? Are people nervous about the idea of a magnet on their brain?

Bermudes: We get a lot of responses when we talk to patients about this procedure. I think it really depends on the patient, how they're conceptualizing their depression, or how they've been taught to think about their depression. Certainly, the experience of treatments and then, what treatments they're also being offered. For example, if I'm talking to a patient who's been on five, six, ten antidepressants and has suffered a lot of side effects, maybe have had an MRI in their life. The fact that it's a magnetic field, you know, they've had the MRI before, they know that's tolerable. Had side effects from the antidepressants, it's generally not a big deal to think about. Particularly for patients with moderate or moderately high or severe depression. They've been suffering for years.

It's not a first line of treatment. It's generally third, fourth, fifth line treatment. For the right patient population, it's actually pretty acceptable. Sometimes we have to clarify that it's not ECT. Patients will ask, "Are you going to shock my brain?" We're not generating a seizure. This is sub-seizure threshold. TMS actually introduced the idea that we could do neuro-modulation without generating a seizure and improve mood.

Jessi Gold: Since you brought up ECT, is there a reason why TMS doesn't get the reaction that ECT has? You know, right outside there were protestors. People tend to be pretty scared of ECT. The press has kind of destroyed it at one point and it's come back into fruition. They don't necessarily know it's better. Is there a reason TMS hasn't had that same reaction?

Bermudes:  I'm a big believer in ECT. I used to do ECT. It's a very powerful treatment, very effective treatment. We don't have to overcome the kind of stigma that I used to have with patients who were getting consultated for ECT. I think some of the reasons, you know, not having to go under general anesthesia. It's a treatment that is accessible for patients who aren't as severely ill as those who are getting ECT. It's an outpatient setting. There's been no cognitive side effects associated with this procedure. All the modern day stimulation protocols for ECT, the cognitive side effects are pretty mild to non-existent.
You know, you started battling that legacy with ECT. I think people have been able to differentiate the two treatments.

David Carreon: You say it's not shocking the brain, but come on, it's a pretty powerful magnet you're putting out. 1.5 Teslas for a lot of these guys. That's a pretty hefty stimulation, isn't it?

Bermudes: Yeah, so it's kind of an interesting dynamic when we're demonstrating this with patients, because on the one hand, I'm saying, "Yeah, it's a fairly benign procedure. The seizure is rare. It's a benign procedure. The seizure is rare. It's not what we're trying to induce. Here I'm going to place this over your meta-cortex, and I'm going to get your thumb to move." That's a pretty powerful demonstration of how we can do non-invasive neuro-modulation at this point in time. It is powerful, but it doesn't have that stigma.

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