Hemodynamic characteristics at baseline and following repeated transcranial magnetic stimulation treatment

The mechanism underlying the efficacy of repetitive transcranial magnetic stimulation (rTMS) remains unclear, particularly regarding its impact on different severities of depression. From a personalized treatment perspective, evaluating functional improvements by illness severity is crucial. This study investigated changes in cerebral hemodynamics before and after six weeks of rTMS treatment in 45 patients with depression, using functional near-infrared spectroscopy (fNIRS). The aim was to assess changes in hemodynamics according to the severity of depressive symptoms, as classified by the 17-item Hamilton Depression Rating Scale (HAM-D 17). Prior to treatment, patients with higher severity (HAM-D 17 score ≥ 24) exhibited significantly reduced blood flow in brain regions such as the frontopolar area, and dorsolateral and inferior prefrontal areas compared to patients with lower severity. After six weeks of rTMS treatment, a significant increase in hemodynamic response was observed in the frontopolar cortex and left lateral frontal regions. Moreover, a significant increase in hemodynamic response was noted in the frontopolar cortex in both the mild and severe groups, compared to the moderate group. Notably, patients exhibiting increased hemodynamics parameters also demonstrated significant improvements in depressive symptoms, as reflected by reductions in HAM-D scores. These findings suggest a potential correlation between rTMS-induced hemodynamic changes in the frontal region and improved treatment outcomes. Furthermore, the results imply that rTMS may promote neuroplasticity in specific brain regions, thereby contributing to the alleviation of depressive symptoms.