Transcranial magnetic stimulation is a treatment method for depression developed to help patients who do not respond to first line treatment. Rough estimates suggest that up to a third of people with depressive symptoms remain symptomatic despite the use of pharmacological treatment and therapy.
This is a serious problem. As the leading cause of disability in the US for adults aged 18 to 44, and the most common kind of mental disorder, finding ways to treat depression and further research its impact is crucial.
While antidepressants are still widely effective and present a very low risk in most cases, it’s important to note that alternatives like TMS can provide patients with the relief they require. In recent years, that fact has been recognized by insurance companies throughout the country.
While still difficult to find in the early 2010s, TMS technology has since spread throughout the USA, and is more readily available for most patients due to support from major insurance providers, both private and public.
First developed in the 1980s to affect the brain through non-invasive and low-risk magnetic waves, TMS has since become a psychiatric tool with several different iterations and uses in the treatment of a list of disorders and conditions. While its off-label credentials are impressive, TMS’s approval list is short – so far, TMS has been approved by the FDA for the treatment of depression and obsessive-compulsive disorder. FDA approval is often helpful (if not critical) in securing coverage from insurance providers. Yet not all forms of TMS are equal.
How Transcranial Magnetic Stimulation Works
Transcranial magnetic stimulation functions because of Faraday’s law of induction, describing the basic interaction between magnetic fields and electric currents. The human body communicates through the central nervous system, which utilizes electrical currents running through neurons in the body to trigger muscle contractions and other activity.
Magnetic fields can, if properly directed and with appropriate force, affect neural activity in the brain by inducing an inverted electric current, much like running an actual current on the surface of the brain. The result is a change in the polarization of neurons in the affected area of the brain, causing nerve cells to either become more excitable, or less excitable.
Utilizing the same strength as an MRI (magnetic resonance imaging) machine, a magnetic coil is held over the scalp, running a field of magnetic energy over the scalp and into the brain. By targeting specific portions of the prefrontal cortex, TMS aims to reduce and even eliminate depressive symptoms.
However, some TMS technology is limited in its reach and efficacy. That is where more different forms of TMS come into play, such as repetitive transcranial magnetic stimulation (rTMS), and deep transcranial magnetic stimulation (dTMS).
dTMS vs. rTMS
dTMS and rTMS are based on the same technology, with a relatively simple difference – the coil used. Both technologies are developed by different companies and come with different pros and cons, yet one is definitively more effective according to the latest research.
TMS technology relies on the shape and size of the magnetic coil used in the machine to effectively deliver the magnetic fields past the bone of the skull. Repetitive transcranial magnetic stimulation reaches about half an inch (1.5 cm), limiting how deep it can affect the cells in the brain related to depression. On the other hand, deep transcranial magnetic stimulation reaches over an inch into the brain (approximately 4 cm), greatly improving its effectiveness.
dTMS – The Newer Solution
Deep transcranial magnetic stimulation is uniquely equipped to treat not only depression but also obsessive-compulsive disorder, because the added depth provided by its modified and improved coil allows it to access different portions of the brain.
One complaint is that the tolerability for dTMS is lower than that of rTMS, due to the increased depth of the treatment. This essentially means that dTMS is less comfortable, due to increased pressure and scalp discomfort. However, research also shows that dTMS is more effective, especially in a shorter period of time. Some studies suggest more research to investigate the efficacy of cutting treatment time down to two weeks (rather than the normal four to six weeks).
Currently, only Brainsway is developing and deploying dTMS technology, although there are several clinics and providers of Brainsway’s dTMS machines throughout the country.
How Is dTMS Provided?
The treatment takes place over the course of several weeks, with five sessions per week. Each session takes up to half an hour, although treatment protocols are being tested to reduce that time. Over the course of the treatment, the patient is encouraged to stay awake, and relax. They can read, watch television, listen to music, have a conversation with their TMS provider, or play a game.
The coil used to send magnetic energy into the brain is build into a helmet, worn on the head for the duration of each treatment session. Patients sit comfortably in a reclining chair while the treatment takes effect. Some patients report feeling better after a single treatment, while others don’t feel an effect until later on during the protocol.
The effectiveness of dTMS treatment for depression varies from patient to patient. In treatment-resistant drugfree patients, dTMS has a success rate of approximately two thirds of patients, with nearly half reporting total remission of depressive symptoms. The effects of dTMS are long-lasting.
Side effects are uncommon. The most commonly reported side effects are headaches and scalp discomfort, both of which seem to decrease in severity as the treatment continues.
When Is dTMS Useful?
dTMS and other forms of TMS are typically studied as part of a treatment regimen for patients with treatment-resistant depression, which describes when a patient does not respond to first line depression treatment (antidepressants and talk therapy), or augmentative strategies (alternate antidepressants and different forms of psychotherapy).
While not a last resort by any means, TMS therapy has shown particularly effective in helping patients who find no relief in antidepressant medication or therapies like CBT. More research may in the future show that TMS could be a drug-free alternative for patients with MDD without requiring first line treatment.