Identifying brain imaging correlates of clinical response to repetitive transcranial magnetic stimulation (rTMS) in major depression

Background Partial response and non-response to treatments are common problems in major depression. The identification of biological markers of clinical response may be of special interest for some adjunctive treatments, such as repetitive transcranial magnetic stimulation (rTMS), as it may ultimately improve their cost-effectiveness. Objective To identify pre-treatment functional imaging correlates of clinical response to rTMS in major depression. Methods We evaluated 21 depressed patients. They were randomized to receive 15 sessions of active or sham rTMS on the left dorsolateral prefrontal cortex. Functional magnetic resonance imaging (fMRI) was used to assess pre-treatment regional brain activity evoked by a word generation task. These regional activations were correlated (voxel-wise) with the Hamilton Rating Scale for Depression (HAM-D) reduction between baseline and end of treatment. A group of 13 healthy controls was also assessed using the same fMRI protocol to obtain reference imaging measurements. Results At the end of treatment, the percentage of patients with a HAM-D reduction greater than 50% was larger in the active than in the sham rTMS group (70% vs. 27.3%). In the active rTMS group, larger HAM-D reductions were significantly correlated with smaller deactivations during pre-treatment fMRI assessment in the anterior cingulate, the left medial orbitofrontal and the right middle frontal cortices, in addition to larger activations in the left ventral-caudal putamen. Conclusions These results suggest that brain activity in regions arguably relevant for major depression may predict clinical response to rTMS. This approach may help in identifying the most suitable candidates to undergo rTMS treatment.