Increased Cortical Excitability with Prefrontal High-Frequency Repetitive Transcranial Magnetic Stimulation in Adolescents with Treatment-Resistant Major Depressive Disorder

Objective: To examine changes in motor cortical excitability in adolescent subjects receiving 30 sessions of high-frequency prefrontal repetitive transcranial magnetic stimulation (rTMS). Methods: Eight adolescents with treatment-resistant major depressive disorder (MDD) enrolled in an open augmentation trial of 10 Hz rTMS. Resting motor thresholds were obtained by the visualization of movement method with a maximum likelihood threshold hunting computer algorithm at baseline and after every five sessions of rTMS. Motor threshold was recorded as the percentage of total machine output at each measurement. Results: Motor threshold data from baseline, weeks 2, 4, and 5 were included in a mixed model repeated measure analysis to examine a change in least square mean effect over time. The omnibus effect did not reach statistical significance (F = 1.25, p = 0.32). However, multiple comparisons from the overall model demonstrated a decrease in the least square mean motor threshold. The mean contrast from baseline to week 5 approached significance (p = 0.07). Moreover, a post-hoc analysis with a Wilcoxon signed ranks test demonstrated a significant decrease at week 5 (p = 0.03). Conclusions: This suggests that high-frequency rTMS may increase cortical excitability in adolescents with treatment-resistant MDD.