From the Guidelines
TMS does not cause significant brain damage, and its benefits in treating major depressive disorder outweigh the minimal and manageable adverse events. The most recent and highest quality study, published in 2022 in the Annals of Internal Medicine 1, suggests that the benefits of rTMS for treatment-resistant depression (TRD) in improving symptoms and facilitating remission outweigh the harms. The study found that rTMS had a significantly higher response and remission rate compared to sham treatment, with a number needed to treat of 3.4 to 9 patients for response and 5 to 7 patients for remission.
Risks and Side Effects
The most common side effects of TMS are mild to moderate and include:
- Headache
- Scalp discomfort
- Lightheadedness
- Tingling sensations These side effects usually resolve shortly after treatment. More serious risks, though rare, include:
- Seizures (risk less than 1 in 30,000 sessions)
- Hearing problems if ear protection isn't used
- Potential worsening of bipolar symptoms in undiagnosed patients
Contraindications
TMS is contraindicated for patients with:
- Metal implants in or near the head (except dental fillings)
- History of seizures
- Certain neurological conditions
Treatment Protocol
The standard protocol for TMS typically involves 20-30 sessions over 4-6 weeks, with each session lasting about 20-40 minutes. TMS works by delivering magnetic pulses to stimulate nerve cells in the dorsolateral prefrontal cortex of the brain, which is involved in mood regulation. While TMS doesn't require anesthesia and allows patients to resume normal activities immediately after sessions, it requires a significant time commitment for the full course of treatment. Insurance coverage varies, so patients should verify coverage before beginning treatment. TMS is not typically recommended as a first-line treatment but can be particularly valuable for patients who cannot tolerate medication side effects or have not achieved remission with pharmacotherapy, as noted in the 2022 guideline 1.
From the Research
Risks of TMS
- The risk of seizure is a significant concern with TMS, although it is considered low, even in patients taking drugs acting on the central nervous system, at least with the use of traditional stimulation parameters and focal coils for which large data sets are available 2.
- TMS is contraindicated for many patients due to the risk of seizure, particularly those with a history of seizures or epilepsy 3.
- Minor side effects of TMS include headache, scalp discomfort, and facial twitching 4, 2.
Recommendations for TMS Use
- TMS is well tolerated with very few side effects and is now approved for major depression disorder and obsessive-compulsive disorder 4.
- The use of TMS in diverse neurological conditions, including stroke and spasticity, migraine, and dementia, has shown promising results with objective clinical and basic science data 4.
- TMS has been used as a diagnostic tool to explore changes in cortical excitability and as a tool for therapeutic neuromodulation, particularly in the treatment of stroke, traumatic and anoxic brain injury 3.
- Repetitive TMS (rTMS) has been shown to restore interhemispheric interactions following stroke by inhibiting the healthy cortex with frequencies ≤1Hz, or by exciting the lesioned cortex with frequencies between 3 and 50Hz 3.
Safety Guidelines for TMS Use
- The International Federation of Clinical Neurophysiology (IFCN) has updated safety guidelines for the application of TMS in research and clinical settings, including recommendations for screening subjects/patients, neurophysiological monitoring, and managing seizures 2.
- New issues discussed in detail include safety issues of recently developed stimulation devices and pulse configurations, duties and responsibility of device makers, and novel scenarios of TMS applications such as in the neuroimaging context or imaging-guided and robot-guided TMS 2.
- Operational guidelines are provided for safety in planning future trials based on traditional and patterned TMS protocols, as well as a summary of the minimal training requirements for operators 2.
Brain Damage and TMS
- There is no evidence to suggest that TMS causes brain damage, and it is considered a safe and noninvasive means of electrically stimulating the brain by electromagnetic induction 5.
- TMS is capable of probing intracortical circuits and modulating cortical activity in humans, and has been instrumental in studying the neurophysiology and functional neuroanatomy of the frontal lobes 5.