Early on in my psychiatry career, I would often lament about the lack of innovative treatments in psychiatry. While it was true new medications were always coming out, it seemed to me most of the time that they very similar to the ones that were already being used. However, in the last decade, that has been changing with the introduction of brain stimulation. Brain stimulation in psychiatric practice uses electrical currents or magnetic fields to alter neuronal firing in a targeted region of the brain. Electroconvulsive therapy (ECT) which also involves electrical stimulation to the brain to induce a seizure has been around for close to 90 years but more recent techniques include transcranial magnetic stimulation (TMS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS). These newer tools were initially used in neurology to treat epilepsy, tremors, dystonia, headaches and Parkinson’s Disease but quickly caught the attention of psychiatry eager to explore other alternatives to ECT in treating psychiatric conditions. In this article, I will primarily focus on the details of TMS and how it is starting to change the landscape of psychiatric treatment.
Description of TMS (Transcranial Magnetic Stimulation---also called rTMS for Repetitive Transcranial Magnetic Stimulation):
TMS is based on Faraday’s Law in which a changing magnetic field generates an electrical field. TMS is a non-invasive method of treatment that uses repetitively pulsed magnetic fields to generate an electrical current in a targeted area of the brain--the magnet energy extends only 2-3 cm in to the brain in an area about the size of a 50 cent piece. However, it can also penetrate farther, 4-6 cm with deep TMS, using a different machine for treating Obsessive Compulsive Disorder (OCD).
TMS was first FDA approved for the treatment of Major Depression in 2008 and OCD in 2018 but it has become a more realistic treatment option in recent years as insurance coverage has improved including Medicare. Most patients who choose TMS are treatment resistant who have failed many medication trials but according to the FDA a person only needs to fail one medication before a trial of TMS due to lack of response or severe side effects. With TMS, one third achieve complete remission, one third have partial benefit and one third have zero benefit. Some practitioners maintain a response rate of 50-80%. Most of the people I have referred have seen partial benefit—and that usually requires they continue on antidepressants during and after TMS. It is possible to reduce or come off antidepressants after TMS but one may need “maintenance” TMS on a regular basis over time.
What does TMS involve?
Unlike ECT, TMS does not involve a hospitalization, anesthesia, inducing a seizure or interfering with daily life. A typical treatment course involves 30 treatments that can be done once a day or several days a week. At the initial evaluation, the place of treatment is made on a cap that the patient will wear for each treatment. The place of treatment in the brain is called the dorsolateral prefrontal cortex which is located above the eye (usually performed on the left side). The treatment itself lasts about 30 minutes and a person can drive themselves to treatment and back and even return to work or school the same day. It seems that the total number of treatments is what is necessary, not the frequency. For 30 treatments, that could mean 3 treatments a week for 10 weeks or 5 treatments a week for 6 weeks.
Common and rare side effects
Side effects are usually mild and transitory—the most common being a headache the first 2-3 treatments as the copper coil is pressed upon the scalp muscles which then tense up but the muscles accommodate in subsequent treatments; patients often describe it like a woodpecker pecking on your forehead. The most serious and rare side effect is a seizure which occurs in 1 out of every 10,000. However, if someone has a pre-existing seizure disorder, a course of TMS will precipitate a seizure in 1-2%. The only contraindication to TMS is an iron magnetic plate in the brain as a result of prior brain surgery.
When do you expect a response?
Usually one sees a response in the 2nd week. If there is no response in the 3rd week (after 10-15 treatments) then the response rate goes down to 20% after 30 treatments—it would have to be reassessed whether it’s worth continuing TMS at that point.
How long does the benefit last?
Since depression is a chronic illness there are likely to be relapses. Some people relapse more regularly and will need maintenance treatment (e.g. 1-3 treatments once a month) but others may not relapse for several years. Compared to ECT, the benefits of TMS tend to last longer before relapse and relapse does not require another 30 treatments—more like 5-6 instead.
Why does it work?
The short answer is we do not know, but we can speculate. One expert in ECT and TMS at Columbia-Presbyterian for over 20 years, Harold Sackeim, PhD, believes the brain is curing itself of depression, and TMS is somehow enabling it—the electrical current stimulates areas of the brain referred to as depression circuits that that may not have been active to become active by stimulating them on a daily basis to alter brain function.
A few words about DBS (Deep Brain Stimulation) AND VNS (Vagus Nerve Stimulation)
DBS and VNS are two more additions to brain stimulation methods that were introduced about a decade following the first trials of TMS. They both involve surgery in which a device is surgically implanted under the skin of the chest. DBS is FDA approved for Obsessive Compulsive Disorder (not depression!) and acts as a pacemaker for the brain to reset abnormal brain rhythms via electrodes placed deep in the brain and connected to the stimulator device. VNS is FDA approved for epilepsy and Major Depression by stimulating the vagus nerve (there’s one vagus nerve on each side of the body but the left side is used) running from the chest and abdomen to the brain stem, which then sends signals to certain areas of the brain. In addition, it often takes up to a year for there to be a significant benefit in treating chronic depression. Clearly, the less invasive TMS would be preferred before considering these other treatment options but these options are also less laborious—rather than have to go a TMS center the implanted device does what is TMS is doing and able to better target the underactive circuits in the brain.
You may get the impression from this article that brain stimulation in psychiatric practice only addresses Major Depression and Obsessive Compulsive Disorder since they both have FDA approval for that purpose. However, TMS is being used off label to also address Bipolar depression, Mania, Post Traumatic Stress Disorder, chronic pain, Tourette’s tics, Parkinson’s Disease, substance abuse and autism. There’s also some exciting research being done with Deep Brain Stimulation to treat Schizophrenia by targeting an area in the brain called the basal ganglia that is misprocessing information as hallucinations and delusions. As time goes on, I predict these some of these other psychiatric disorders will also receive FDA approval and the next generation of stimulation devices will be even more effective in treating these conditions.