| Paper authors: | Daniel M. Blumberger, Jerome J. Maller, Lauren Thomson, Benoit H. Mulsant, Tarek K. Rajji, Missy Maher, Patrick E. Brown, Jonathan Downar, Fidel Vila-Rodriguez, Paul B. Fitzgerald, Zafiris J. Daskalakis |
| Year of paper publication: | 2016 |
| Post authors: | Caleb Pozdnikoff, Sarah Kesler, Fidel Vila-Rodriguez |
| Download the research article: | Blumberger et al. (2016) Unilateral and bilateral MRI-targeted repetitive transcranial magnetic stimulation for treatment-resistant depression: a randomized controlled study) |
Introduction
Unfortunately, depression is a common illness that can significantly impact quality of life. Many people with depression do not achieve remission (significant improvement in depressive symptoms) by taking standard antidepressants. When antidepressants do not work, the illness becomes classified as treatment-resistant depression.
Repetitive transcranial magnetic stimulation (rTMS) offers an alternative treatment for people with treatment-resistant depression. High-frequency left and low-frequency right rTMS treatments have shown to be effective when compared to sham (non-active, placebo treatment) stimulation.
High frequency left rTMS treatment involves a magnetic coil being placed on the left side of the head to activate brain cells during stimulation. However, high frequency left-rTMS has modest effects. So, the researchers examined the effectiveness of stimulating both sides of the brain in one session. This is known as sequential bilateral rTMS (stimulating the right side of the brain then the left).
Prior rTMS research faced limitations including one-sided (unilateral) stimulation, and non-individualized stimulation intensity and treatment site targeting. This is important because a greater distance between the rTMS device and an individual’s brain cortex could lead to understimulation. Understimulation could mean reduced treatment efficacy because intensity was not adjusted for this variability. Additionally, many studies had relatively short treatment durations, often just four weeks.
The study used magnetic resonance imaging (MRI) to address individualization challenges. The treatment was also extended up to six weeks. It was thought that these individualized methods would optimize treatment to lead to higher remission rates. The researchers anticipated higher remission for people in the bilateral rTMS group.
Methods
Researchers recruited 121 patients with treatment-resistant depression who had not responded to at least two prior antidepressants. The researchers used MRI to locate the site of stimulation for each rTMS treatment. Also, stimulation intensity was adjusted to individualize the treatment. Treatments occurred five days per week for three weeks, with the option to extend for another three weeks if depressive symptoms did not improve enough.
Participants were randomly assigned to one of three groups:
- Two-sided (sequential bilateral) rTMS
- One-sided rTMS (high-frequency left-rTMS)
- Placebo (sham) treatment
Results
- Two-sided rTMS improved remission rates
- One-sided rTMS showed a modest remission rate but was not statistically better to sham or bilateral treatment
- Surprisingly, the individualized MRI targeted location and stimulation intensity did not lead to higher efficacy rates compared to those in previous studies using simpler, non-individualized methods
Conclusion
This study found that two-sided rTMS significantly improved remission rates for people with treatment-resistant depression compared to placebo (sham). One-sided rTMS did not show a statistically superior effect over the other two treatment groups. Individualized techniques like MRI-targeted stimulation and intensity adjustments did not lead to higher efficacy rates than those reported in previous studies. This confirms that commonly used, non-MRI guided techniques are just as effective. More research is required to help us better understand the brain to make rTMS treatment more effective.