The use of MR‑less MNI based neuronavigation for 10 Hz rTMS depression therapy: electrophysiological and clinical implications.

Repetitive transcranial magnetic stimulation (rTMS) is a popular and effective treatment for drug resistant depression. However, there is considerable variability in clinical outcomes, in previous studies and between patients. Because of high requirements for the use of fMRI based neuronavigation, many practitioners of rTMS still choose to use a standard 5 cm rule for rTMS coil placement which leads to large variations in which brain regions are being stimulated. We decided to test the possibilities of a MNI based MR‑less neuronavigation system in rTMS depression treatment, by comparing the physiological effects and clinical outcomes of 3 distinct stimulation targets. Forty‑six patients (thirty‑three female, thirteen male) from the Republican Vilnius psychiatric hospital, all with drug resistant depressive disorder, participated in the study. All patients received high frequency (10 Hz) stimulation for 10 to 15 daily rTMS sessions. However, before the treatment they were randomly sorted into 3 groups according to stimulation target in MNI map: Group 1 received rTMS at point ‑40; 48; 35; Group 2 received rTMS at point ‑46; 45; 38; Group 3 received rTMS at point ‑38; 44; 26. Electroencephalography (EEG) recordings and clinical tests were obtained the day before the rTMS course and after the last session. There were some notable differences in physiological changes between the groups, with the largest EEG band spectral power increases found in Group 1 patients and the lowest in Group 2 patients. There was a significantly larger decrease of the Hamilton Depression Rating Scale (HAM-D) scores in the Group 3 (66.94%) compared to Group 1 (57.52%) and Group 2 (56.02%). This suggests it is possible to achieve higher clinical efficacy and less physiological impact on the brain when using different targets in a neuronavigated MNI based MR‑less rTMS system.