Reproducibility and durtion of the antidepressant effect of rRMS in treatment-refractory depression

Background: Repetitive transcranial magnetic stimulation (rTMS) applied to the left dorsolateral prefrontal cortex (LDLPFC) has antidepressant effect, but their clinical significance and duration is uncertain. Specifically, the reproducibility and efficacy of repeated sessions of rTMS as maintenance treatment for Major Depressive Disorder (MDD) has not been reported. Methods: Sixteen medication-free patients with medication-refractory MDD were studied. All of the patients accepted into the study had an initial anti-depressant response to a two-week course of 10 Hz rTMS (1600 pulses at 90% of motor threshold) applied to LDLPFC. These stimulation parameters were utilized during subsequent treatments in the maintenance study. Severity of depression was evaluated with the Hamilton Depression Rating Scale-28 item (HDRS) and the Beck Depression Inventory (BDI). These evaluations were collected before and after completion of each two-week rTMS treatment session. Subjects were eligible for repeat treatment if they remained medication-free and the HDRS score went back above 18. Results: Subjects who remained in the study continued to show a 50% reduction in HDRS scores after each rTMS treatment cycle. The HDRS and BDI scores were both significantly reduced (p,0.0001) by each two-week follow-up assessment. The mean interval between treatment cycles for this group was approximately five months. Conclusions: Maintenance rTMS for medication-refractory patients has demonstrated a prolonged and reproducible antidepressant effect. While the duration of effect varies between subjects, the reproducibility of the antidepressant effect has remained consistent across patients over time. Further follow-up will be useful in determining the long-term effectiveness of maintenance therapy.