Transcranial Magnetic Stimulation (TMS) Efficacy and Guidelines

Introduction to TMS Efficacy

The American College of Physicians recommends TMS for patients with major depression who have not responded to two or more adequate pharmacological treatment attempts, with a number needed to treat of 3.4-9 for response and 5-7 for remission 2
TMS shows moderate efficacy in treatment-resistant depression with response rates of 29-48%, requiring at least 4-6 weeks of daily treatment, and has limited evidence for other indications 1, 2

The primary target for TMS in depression is the left dorsolateral prefrontal cortex (DLPFC) as a first-line approach 1
High-frequency protocols (10-25 Hz) are used to excite cortical neurons, while low-frequency stimulation (1 Hz) on the right DLPFC shows similar efficacy 1
A minimum of 4-6 weeks of daily sessions (up to 30 sessions) is required for significant clinical improvement 1, 2
Doubling the pulse number enhances clinical effects in depressive patients 1

DLPFC stimulation can reduce craving in substance-related disorders, with both left and right-sided stimulation showing positive effects on cognition and craving 3, 4, 5
High-frequency rTMS protocols (5-25 Hz) have been used to reduce spontaneous and cue-induced craving 3
77 out of 84 published TMS/tDCS studies (up to June 2018) targeted the DLPFC as the stimulation site 6

The FDA has approved deep rTMS for the treatment of OCD 7
Target regions include the supplementary motor cortex and dorsolateral prefrontal cortex 7
rTMS shows growing evidence for efficacy in OCD, with the pivotal study targeting the medial prefrontal cortex and anterior cingulate cortex 7

TMS delivers short, focal electromagnetic pulses through the skull to stimulate target regions, inducing neuronal discharges under the coil 1
Modulation of cortical excitability occurs through long-term potentiation (LTP)- and long-term depression (LTD)-like changes in synaptic coupling of neurons 1
High-frequency stimulation (10 Hz) induces LTP-like effects, while low-frequency (1 Hz) stimulation produces LTD-like effects 1

Common side effects include clicking sounds, scalp sensations, and mild muscle contractions during stimulation 1
Significantly fewer systemic side effects compared to antidepressants 1
Excessive stimulation can paradoxically reduce efficacy through homeostatic plasticity principles 1

For responders, transition to maintenance TMS over 6 months is recommended 1
Response rates can be maintained for 3-6 months in substance-related applications after a standard acute treatment course 2
Critical limitation: 71% of studies did not include follow-up beyond the day of intervention 2

Access can be challenging due to required frequent on-site visits (typically 5 sessions per week for 4-6 weeks) 2
Only highly motivated patients should be recruited for intensive treatment protocols 2
Systematic studies comparing different repetition intervals, frequencies, and intensities are lacking 1
The relationship between stimulation parameters and outcomes remains incompletely understood 1

TMS can be more effective when combined with behavioral interventions like cognitive behavioral therapy (CBT) 2
Promising results when combined with pharmacotherapy: nearly 50% of patients became abstinent from cigarettes when TMS was used with nicotine replacement therapy 2
Current medication should be continued as adjunctive therapy 1

Stimulation parameters such as duration, number of sessions, frequency, intensity, target region, and interval between treatments should be investigated to define the dose-response relationship 3, 4
Few of these parameters have been systematically studied for substance use treatment 3
82% of TMS studies used 2000 or fewer pulses per session 8
For tDCS, 2 mA is the most common intensity (21 studies), followed by 1 mA (10 studies) 8
88% of tES studies had 20 minutes of stimulation or less 8