A new toolbox to compare target localizations for non-invasive brain stimulation: An application of rTMS treatment for auditory hallucinations in schizophrenia.

BACKGROUND: Most repetitive transcranial magnetic stimulation (rTMS) studies aiming to reduce auditory verbal hallucinations (AVH) in schizophrenia target the left temporo-parietal junction (TPJ), but the efficacy of this approach remains controversial. The observed differences in efficacy could be attributed to inaccurate target localization. Here, to precisely quantify anatomical bias induced by localization method, we developed a free open-source software (GeodesicSlicer) that computes shortest curved path (i.e. geodesic) between rTMS targets. Here we compare a personalized target with accurate anatomical criteria with a standardized target based on the 10-20 EEG system (the middle between T3 and P3 electrodes: T3P3).

METHODS: We compare in 69 patients with schizophrenia the geodesic distances of two approaches for rTMS target localization within the left TPJ. In addition, we characterize the personalized target according to the 10-20 EEG system.

RESULTS: A differential of 3 cm in term of geodesic distance between rTMS localization approaches was observed. Moreover, this personalized target to treat AVH is located at 25% in the T3-P3 axis.

CONCLUSIONS: This software for rTMS localization comparison demonstrates the difference between standardized and personalized rTMS target. This difference has the potential to explain a part of the dissonant clinical results found in previous rTMS studies.