Abstract
Repetitive transcranial magnetic stimulation (rTMS) is an effective treatment for Major Depressive Disorder (MDD). There are clinical data that support the efficacy of many different approaches to rTMS treatment, and it remains unclear what combination of stimulation parameters is optimal to relieve depressive symptoms. Because of the costs and complexity of studies that would be necessary to explore and compare the large number of combinations of rTMS treatment parameters, it would be useful to establish reliable surrogate biomarkers of treatment efficacy that could be used to compare different approaches to treatment. This study reviews the evidence that neurophysiologic measures of cortical excitability could be used as biomarkers for screening different rTMS treatment paradigms. It examines evidence that: (1) changes in excitability are related to the mechanism of action of rTMS; (2) rTMS has consistent effects on measures of excitability that could constitute reliable biomarkers; and (3) changes in excitability are related to the outcomes of rTMS treatment of MDD. An increasing body of evidence indicates that these neurophysiologic measures have the potential to serve as reliable biomarkers for screening different approaches to rTMS treatment of MDD.
Disclosure statement
Dr Leuchter discloses that within the past 12 months he has received research support from the National Institutes of Health, Neuronetics, Breast Cancer Foundation, Department of Defense, and Neurosigma. He has served as a consultant to NeoSync, Inc. He is Chief Scientific Officer of Brain Biomarker Analytics LLC (BBA). Dr Leuchter owns stock options in NeoSync, Inc. and has equity interest in BBA.
Dr. Cook has received research support for this work from the National Center for Complementary and Alternative Medicine, NIMH, Covidien (formerly Aspect Medical Systems), Pfizer (formerly Wyeth Pharmaceuticals), and Eli Lilly and Company. He discloses that within the past 3 years, he has received NIH grant support along with funding from Aspect Medical Systems/Covidien, NeoSync, and Neuronetics. He has been an advisor, consultant, or reviewer for Allergan, Neuronetics, NeuroSigma, NIH (ITVA), and the VA (DSMB). He has served on the Speaker?s Bureau or received honoraria from Neuronetics and NeuroSigma. His biomedical patents have been assigned to the Regents of the University of California. He is employed by UCLA and the Veterans Health Administration and in 2014 became Chief Medical Officer of NeuroSigma, Inc., a company that has issued stock options to him.
All other authors have nothing to disclose.