3.2 Transcranial magnetic stimulation in the treatment of major depressive disorder

What are depressive disorder ranked as?

The single largest contributor to non-fatal health loss.

What are treatment options for depressive disorder?

Drugs, psychotherapy and the largest is ECT.

Why is the development of TMS important?

A low number of treatments is effective, and the most effective form is very intensive.

How does TMS ‘treat’ depressive disorder?

It is all about the treatment for psychotic depressions. It does not cure depression, but it does help during depressive episodes, wherefore the depression is bearable. Hereby it is all about depressions that do not have a clear cause. It does not clearly align with the circumstances.

Explain Faraday’s law of electromagnetic induction.

With a high voltage it is possible to create a strong magnetic field. This is really short, but it does make it possible to create electric changes of neurons. Therefore, you can modulate the neurons from the outside in a relatively focused manner.

Why does TMS only have an effect in the (motor) cortex?

Because it cannot go deep in the brain. The effectiveness decreases with the distance in the brain.

How can you up- or down regulate the cortex?

Giving TMS in ‘trains’; the frequency plays a role here.

What is the amount of Hz needed for up- and down regulation?

• 1 Hz → down regulation

• 10 Hz → up regulation

What happens in patients with depression?

There is a disbalance that causes less regulation of emotions and stress. They have poor regulation of their negative stress, and experience less fun/pleasure. One good thing can be experienced as less positive and a bad thing can be experienced as extremely negative.

What is the function of the left and the right half of the brain?

• Left brain: control rewarding

• Right brain: avoiding

What kind of imbalance is their in the left and right half of the brain?

Low reward and high avoiding imbalance

How will the rewarding system be increased?

By stimulating the left frontal cortex with pulses of TMS.

What did a meta-analyses about TMS prove?

TMS can definitely be effective as a treatment.

What is another advantage of TMS (proven by the meta-analyses)?

TMS can be used to treat patients that are not treatable with standard treatment.

What makes TMS so effective?

It only looks at 2 parameters; the model is really simple, because there is a imbalance between the left frontal cortex and the striatum.

Is TMs considered safe or unsafe?

Safe

In which cases did TMS have negative effects?

In patients that had brain damage or switched medications.

How can you also know if TMS works?

Something should also be happening to the right side of the brain.

Do lower frequencies of TMS have an effect?

The effect size was 0.63, which suggests they do, but the confidence interval is very large, so it’s not sure if lower frequencies really have an effect on the brain.

Why is the number for effectiveness of TMS so low, even though it seems like a reliable treatment?

Only patients that are/were resistent to standard treatment, started using TMS. Thus, only a small amount of patients tested TMS, and these patients are difficult to treat.

Why is it a reachable technique?

Because it has little side effects, and it can increase cognitivity.

What are 5 points of discussion regarding TMS?

• Individual differences in efficiacy;

• Acute antidepressant effects, but uncertainty about duration;

• Built up of neurophysiological resistance;

• Core pathophysiology is not cerebral;

• Alternative working mechanisms (e.g., immune activation).

How can you predict the outcome of TMS and thus optimalise TMS?

Using imaging models.

Can medication free, treatment-resistant, depressed patients who initially respond to TMS be maintained off medications?

In some cases it seems reachable to keep treatment-resistant, depressed patients off their medications using periodic TMS.

What is SAINT?

An innovative form of TMS that combines MRI guided selection of the intended brain area with an accelerated stimulation regime with multiple short TMS sessions per day, during 5 days (faster than regular).

What is an advantage of SAINT?

It is cost effective, because it takes less time than TMS.

How does deep TMS work?

A helmet sends magnetic pulses that directly target deeper and broader brain structures, and can influence their neural activity with succes..

How does transcranial direct current stimulation work (tDCS)?

Just like TMS, tDCS can be used to either stimulate or inhibit different parts of the brain.

What is an advantage of tDCS?

It is cheaper and easier than TMS, because only 2 electrodes are attached to the head.

How does magnetic seizure therapy (MST) work?

Via an magnetic coil, magnetic field pulses with high intensity are sent off. Quick fluctuating strong magnetic field pulses are set free in a targeted area of the brain and cause a seizure.

What are the 3 differences between MST and ECT?

MST works by inducing seizures via magnetic fields, while ECT does this through fluctuating electric currents. Moreover, MST works in a more concentrated manner than ECT so it has the ability to create a seizure with less total electrical charge. Compared to another form of ECT, MST supplies energy to more superficial cortical areas, whereby stimulation of the cognitive-related subcortex, such as the hippocampus and the basal ganglia, is avoided.

Is TMS used in adults, children of both?

Adults (with depressive disorder).

When is TMS covered by the health insurance in the Netherlands?

When it comes to treatment-resistant depression. The client must have tried and failed two previous guideline‐ based treatments to be eligible. This can be:

• 2 x psychotherapy

• 1 x psychoptherapy & 1 x antidepressant

• 2 x antidepressant