Concurrent transcranial magnetic stimulation and electroencephalography measures are associated with antidepressant response from rTMS treatment for depression

Background: Response rates to repetitive transcranial magnetic stimulation (rTMS) for depression are 25-45%. Participant features obtained prior to treatment that are associated with response to rTMS may be clinically useful. TMS-evoked neural activity recorded via electroencephalography (EEG) prior to treatment may be associated with treatment response. We examined whether these measures could differentiate responders and non-responders to rTMS for depression. Methods: Thirty-nine patients with treatment-resistant major depressive disorder (MDD) and 21 healthy controls received TMS during EEG recordings (TMS-EEG). MDD participants then completed 5-8 weeks of rTMS treatment. Repeated measures ANOVAs compared N100 amplitude, N100 slope, and theta power across 3 groups (responders, non-responders and controls), 2 hemispheres (left, F3, and right, F4), and 2 stimulation types (single pulse and paired pulses with a 100ms inter-pulse interval [pp100]). Results: Neither N100 amplitude nor theta power differed between responders and non-responders. Responders showed a steeper negative N100 slope for single pulses and steeper positive slope for pp100 pulses at F3 than non-responders. Exploratory analyses suggested this may have been due to the responder group showing larger P60 and N100 amplitudes. Limitations: Our study had a small sample size. Conclusion: Left hemisphere TEPs, in particular N100 slope, may be related to response rTMS treatment for depression. If our future research with larger sample sizes verifies this result, the finding may provide clinical utility in recommendations for rTMS treatment for depression.