Left prefrontal activation predicts therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) in major depression

There is evidence that repetitive transcranial magnetic stimulation (rTMS) applied to the prefrontal cortex has antidepressive properties. In the present study we evaluated the clinical status and the hemodynamic responses during mental work in the prefrontal cortex before therapeutic rTMS. Twelve patients diagnosed with major depression (DSM-IV) were randomized in a sham-controlled cross-over treatment protocol of 4 weeks' duration consisting of two periods of 5 days with rTMS separated by 9 days of no stimulation. rTMS (10 Hz) was applied to the left dorsolateral prefrontal cortex. Hemodynamic changes in the prefrontal cortex during mental work were evaluated by multi-site near-infrared spectroscopy (NIRS). Scores on the Hamilton Depression Rating Scale (HAMD) decreased significantly by -5.4 points after 5 days of active stimulation, whereas it did not change (+1.6 points) after sham stimulation. Absence of a task-related increase of total hemoglobin concentrations at the stimulation site (P<0.005), but not at other locations, before the first active rTMS significantly predicted the clinical response to active rTMS. Clinical benefits of rTMS are predicted by low local hemodynamic responses and support the idea of activation-dependent targeting of rTMS location.