Concurrent Transcranial Magnetic Stimulation and Electroencephalography Measures are Associated with Antidepressant Response from rTMS Treatment for Depression

Abstract

Background Response rates to repetitive transcranial magnetic stimulation (rTMS) for depression are 25-45%. Biomarkers predicting response to rTMS may reduce treatment burden. TMS-evoked neural activity recorded via electroencephalography (EEG) has potential as a biomarker of 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. The control group showed more negative N100 amplitudes than the combined depression group. 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 late P60 and N100 amplitudes. Receiver Operator Characteristic (ROC) curve analysis indicated the difference between single and pp100 slopes provided excellent sensitivity (1.00), but poor specificity (0.455). Limitations Our study had a small sample size. Conclusion Left hemisphere TEPs, in particular N100 slope, may be useful in predicting non-responders to rTMS treatment for depression. Non-response prediction may be useful in saving clinical resources and patient time.

TMS-EEG shows mindfulness meditation is associated with an altered excitation/inhibition balance in the dorsolateral prefrontal cortex

“…Several clinical disorders, including anxiety and depression, are believed to be associated with E/I ratio uncoupling and the resulting disordered prefrontal oscillatory phase coherence (Lisman, 2012; Radhu et al, 2014; Voineskos et al, 2019; Yizhar et al, 2011). The altered E/I ratio following TMS applied to the DLPFC of meditators may suggest a potential target for therapeutic interventions, where therapies could aim to adjust the E/I ratio in a way that might relate to improvement of clinical symptoms following a mindfulness intervention (Piet & Hougaard, 2011; Strauss et al, 2014), Interestingly, recent research has suggested that a steeper N100 slope (driven by a larger P60 amplitude) is found in individuals who respond to TMS treatment for depression, a finding that may be analogous to our finding of a larger P60/N100 ratio in the current research, highlighting a potential clinical implication of the current study (Bailey et al, 2023d).…”