I’d like to introduce a series of blog posts I’ll be doing about transcranial magnetic stimulation, or TMS. You’ll hear us talk a lot about it here at Breakwater Neuro, because it’s one of the most exciting and interesting things we do.
First, some background: sometimes you’ll see us talk about “TMS” around here, and sometimes about “rTMS”. “TMS” stands for “transcranial magnetic stimulation”, which signifies that we’re using magnetic energy to stimulate the brain across or through ( from the Latin, trans-) the skull (-cranial). The additional “r” in “rTMS” stands for “repetitive”.
Okay, I can’t resist a little historical digression. TMS was originally invented in the 1980s by English medical physicist Anthony Barker. He designed it as a research tool whose purpose was to enable neuroscientists to study the effects of stimulating the brain, focally and non-invasively, from outside the scalp.
Before TMS was invented, the only really effective way to stimulate the brain involved removing its overlying skull and poking it with an electrical probe. I kid you not. Here’s a fun “Heritage Minute” video about the famous Canadian neurosurgeon Dr. Wilder Penfield, who pioneered doing exactly that:
So, yeah. Not exactly non-invasive. But after the 80s Dr. Barker’s ingenious new tool allowed researchers to accomplish something very similar simply by holding an electromagnetic coil over a particular spot on the brain’s surface and creating brief, powerful pulses of magnetic energy underneath the coil by firing electrical current through it at high speed.
One of the cool things about magnetism as a form of energy is that it can be swapped back and forth easily for electrical energy. For example, if you pass a magnet through a loop of copper wire, you’ll create a momentary electrical current in the wire. Conversely, if you hook the same loop of wire up to a battery and pass a electrical current through it, you create a magnetic field around it, essentially turning it into a temporary magnet that can be switched on and off.
Dr. Barker’s TMS device leveraged this principle by creating a powerful magnetic field that would pass easily and painlessly across the scalp and skull, and induce a momentary electrical current where it contacted the surface of the brain. Presto: instant electrical brain stimulation, without any need for pesky wires, or holes in the skull, or that sort of thing.
Now, Dr. Barker’s device was really only designed to deliver one very brief pulse at a time, or at most a few in a row, because its intended purpose was to “poke” the brain only momentarily. However, scientists being scientists, one of them decided along the way to try using a TMS machine to stimulate the brain with long trains of repeated pulses. This practice came to be tagged with an extra “r” and called repetitive TMS, or rTMS, to distinguish it from more conventional uses of TMS.
Incidentally, repetitive TMS created some technical issues that the field is still working to overcome. Because TMS machines were never really designed to create hundreds of magnetic pulses in a row for long stretches of time, they tend to overheat when asked to do so. To this day, TMS machines used in this way have to have clever cooling systems, to prevent them from getting too hot and shutting themselves down. You’ll see just this sort of cooling system operating in our Breakwater Neuro TMS facility.
All of the clinical applications of TMS technology to things like depression, anxiety, and neurological disorders employ these long, repeated trains of magnetic pulses. Originally, then, they all used the term “rTMS”. But as these applications became more plentiful and widely known, people started dropping the “r” and referring to rTMS simply as “TMS”. And no one really seemed to complain, so they went with it. We tend to use “TMS” at Breakwater Neuro, as well.
So how do we use TMS to alleviate symptoms? More on that to come!