TMS coil

Brain stimulation theraphy

When clicking on my website you will notice that I have used a variety brain stimulation methods. Before going into further detail it is good to point out that I mostly refer to non-invasive brain stimulation methods. Non-invasive methods do not damage any tissue, meaning that they are not painful. Side effects are limited to some annoyance and maybe a small headache. Those techniques are the one that I have used.

An invasive method of brain stimulation is deep brain stimulation. For this a brain surgery is necessary, and a stimulator is placed insight the brain. Deep brain stimulation can be very effective in the treatment of depression, Parkinson's disease and more. However, since surgery is required, this option is typically limited to only severe cases.

Non-invasive brain stimulation methods include TMS, tDCS and tACS (read more in the Neuroscience Methods section). Since stimulation is applied on the outside of the head they are less precise and less effective than deep brain stimulation. However, given the limited side effects they can be applied in a much wider range of disorder severity. Below I will give a few lines of research where non-invasive brain stimulation is used as a therapeutic method.

TMS treatment for depression

When TMS is applied repeatedly, rTMS, brain activity can be altered for some time after stimulation. When rTMS is applied for multiple days over several weeks these changes can lasting. Such rTMS interventions have received FDA approval for treatment of both unipolar and bipolar depression in the US. Similar approval is received in Canada, Australia and Brazil. In some European countries, such as Germany and Finland, rTMS treatment for depression is partially or fully covered by health care providers.

Research has shown that depression is frequenty associated with an imbalance in frontal cortex activity. The goal of rTMS is to restore this balance in frontal regions. Various research studies have investigated the efficacy of rTMS on depression. With clinical response rates between 40% and 65%, this treatment is effective in many people, but significant improvements can be made. Currently, a custom intensity is set per participant. Besides this a one-size-fits-all approach is often used. Currently, research, by us and other labs in the world, focuses on personalizing rTMS to increase response rates.

TMS therapy

tDCS treatment for depression

Recent research has focused on using tDCS for treatment depression. Since tDCS is cheaper and easier to apply than TMS, it may be a good alternative. Also, physical properties of TMS and tDCS differ. TMS targets a specific region, whereas tDCS targets an entire network. Therefore, it could be that patients who not respond to TMS, may respond to tDCS and vice versa. Thus rather than a replacement tDCS offers yet another method for treatment of depression using non-invasive brain stimulation.

In a recent meta-analysis of 23 studies, performed by Razza and colleagues (2020), tDCS effectiveness on depressive symptoms was comparable to TMS. However, this study did not analyze follow up effects. So, currently it is not established of tDCS effects on depression are long-lasting. Consequently, more research is needed before FDA approval can be received.


TMS treatment for Obsessive-compulsive disorder

In 2018 TMS over the mid-frontal part of the brain has received FDA approval for treatment of obsessive-compulsive disorder in the United States. The treatment involves a TMS treatment with very fast pulse trains, which is repeated for 6 weeks. This protocol was based on an extensive international study on 99 participants divided over 11 clinical centers, published by Carmi and colleagues (2018). Clinical response rates of 38% to 45% were found, with effects lasting for at least one month. Whether the effect lasts longer is unknown, as this was not assessed by this study.

As with TMS therapy for depression, ongoing investigations aim to improve response rates, by taking individual differences into account. 

TMS therapy

TMS treatment for migraine

Another protocol that has received FDA approval in the US, is TMS therapy for migraine with auras. Approval was based on a study from Lipton and colleagues (2013). Interestingly, the protocol used here is quite different from the protocols used for depression and obsessive-compulsive disorder. Rather than a fixed multi-week treatment, patients in this study applied TMS themselves in the case of a migraine attack. To do this, they were given a TMS machine for home use, for a period of three months. Whenever they had a migraine attack they could apply TMS over the occipital cortex at the back of the head. Of the 201 participants 38% reported to be fully pain-free within 2 hours of TMS application. 

Although the response rate is not overwhelming, the observation that symptoms completely disappeared means that this method can be very promising. At least for those who respond to it. Given the costs and limited mobility of TMS machines, pratical use is currently limited, but these findings are certainly encouraging.


tDCS treatment for attention-deficit hyperactivity disorder

Together with a number of colleagues, we performed a meta-analysis on the effect of tDCS in treatment of attention-deficit hyperactivity disorder. We found beneficial effects of tDCS of the frontal part of the brain in relation to restraining oneself, which relates to reducing hyperactivity. Some potential benefits on working memory was observed as well, which relates to attention symptoms. However, the observed effect size was small. Also, it is currently unclear what the clinical response rate is. Thus, initial research is promising, but more evidence is needed.

Given the small amount of side effects related to tDCS, it could be an alternative to chronic medication use. Ethical issues have been raised about the application of "electricity" to a childrens brain. However, in a systematic review on the safety an tollerability of tDCS, colleagues and I have established that there are no concerns regarding the use of tDCS in children.

tDCS therapy

TMS therapy for stroke recovery

After a stroke, patients are left with a lesion in their brain. Sometimes large parts of the brain are lost that unfortunately never recover. Often lesions happen in the motor cortex, which is why individuals who have suffered a stroke display impaired movement of arms and/or legs. The damaged brain tissue may not come back, but other parts of the brain can take over some of the lost movement functions. Therefore, it is crucial to start training to recover mobility as soon as possible after the stroke. A large amount of studies has applied TMS during training to recover mobility. Results are promising and training results are often improved by TMS, with increased recovered mobility. Given the number of studies it is somewhat surprising that no FDA approval has yet been granted. However, this may be due to variability in exact methods. A number of TMS parameter settings has been shown to have beneficial effects. Currently, there is no consensus on which set parameters is the "best". 

MRI stroke

tACS treatment for schizophrenia

TACS is the youngest brain stimulation technique. Clinical studies using tACS are very limited, thus investigation of its therapeutic effects is still in its infancy. Nevertheless, some initial promising findings have been reported. Since tACS specifically targets brain oscillations, it is expected to be effective in disorders that are characterized by abnormal brain oscillations. One example is schizophrenia. Abnormal high-frequency gamma oscillations are observed in patients suffering from schizophrenia. These relate to both positive symptoms, such as delusions and psychosis, as well as negative symptoms, such as flattening and withdrawal. Initial case studies and small sample clinical trials have found positive effects of tACS on these symptoms. However, high sample size, multi-center, and meta-analytic studies are warranted to make further conclusions.

Transcranial alternating current stimulation

Other avenues of TMS and tDCS

The effects of TMS and tDCS are explored in a variety of other psychiatric and neurological disorders. These include post-traumatic stress disorder, autism, anxiety, Alzheimer's disease, Parkinson's disease, chronic pain, and fibromyalgia. Currently, no conclusions can be drawn from the evidence that has been provided. Positive findings are reported, but there is a lot of variability between methods used by different labs. Nevertheless, the future of non-invasive brain stimulation is exciting. I will keep you posted!