Comparison of effectiveness of common targeting heuristics in repetitive transcranial magnetic stimulation treatment of depression

Background Repetitive transcranial magnetic stimulation (rTMS) of the left dorsolateral prefrontal cortex (DLPFC) is an effective non-pharmacological, non-invasive intervention for depression. However, the optimal strategy for localising the DLPFC treatment site on the patient's scalp is heavily disputed. Routine strategies were previously incrementally refined and compared in terms of anatomical accuracy, but little is known about their impact on clinical outcomes. Objective To assess the impact of three common scalp-based heuristics for magnetic coil positioning on the treatment outcome of rTMS. Methods This retrospective analysis of real-world clinical data involved patients suffering from a major depressive episode (n=94) who received a 4-week course of excitatory rTMS to the left DLPFC. The treatment target (ie, coil position) was either determined at an absolute distance anterior to the motor hotspot ('6 cm rule') or defined in reference to the EEG electrode position F3 using a traditional ('Beam F3') or optimised ('Beam F3 Adjusted') approach. Findings There was no statistically significant difference between the '6 cm rule' and the 'Beam F3' method nor between the 'Beam F3' and the 'Beam F3 Adjusted' method in head-to-head comparisons of averaged per cent change of scores on depression rating scales (all p>0.605) and response rate (all p>0.475). Conclusions Enhancing targeting precision via scalp-based heuristics does not affect treatment outcomes. Clinical implications There is no need for clinicians to switch from their familiar to an 'advanced' approach among these common targeting heuristics.