The relationship between individual alpha peak frequency and clinical outcome with repetitive Transcranial Magnetic Stimulation (rTMS) treatment of Major Depressive Disorder (MDD)

Abstract

BackgroundThe individual α frequency (IAF) has been associated with the outcome of repetitive Transcranial Magnetic Stimulation (rTMS) treatment of Major Depressive Disorder (MDD), but the association has been inconsistent. HypothesisProximity of IAF to the stimulation frequency, rather than the value of IAF per se, is associated with outcome for patients receiving 10 Hz rTMS. MethodsWe examined the relationships between IAF, rTMS stimulation frequency, and treatment outcome in 147 patients. All patients initially received 10 Hz rTMS unilateral treatment delivered to left dorsolateral prefrontal cortex (DLPFC) (10UL), with subsets of patients changed to unilateral 5 Hz to left DLPFC (5UL) or sequential bilateral (SB) stimulation (10 Hz/1Hz) to left and right DLPFC based upon worsening symptoms with or intolerance of 10UL. Outcome was percent change in total score on the Inventory of Depressive Symptomatology – Self Report (IDS-SR) scale from pre-treatment baseline to the 30th treatment. IAF values and absolute difference between IAF and 10 Hz (|IAF-10Hz|) were examined in relation to outcome for the overall sample and for each stimulation group separately. ResultsThere was no correlation between IAF value, or |IAF-10Hz| and outcome in the overall sample. ANCOVA showed a significant interaction between IAF measures and treatment type. Post-hoc analyses revealed that IAF and |IAF-10Hz| were both significantly associated with degree of improvement (IDS-SR % change) for patients who received 10UL (P < 0.01) but not 5UL or SB stimulation. There was a trend-level difference in IAF between responders and non-responders only within the 10 Hz group, but not within the other treatment groups (n.s.). For the 10UL group, membership in the highest IAF quartile was associated with significantly greater clinical improvement than membership in the lowest IAF quartile (p = 0.0034). ConclusionsIAF measures were associated with clinical outcome of patients treated with 10UL but not 5UL or SB rTMS treatment. This suggests that interactions between endogenous frequencies and treatment outcome may be related to the selected stimulation parameters and/or physiologic and clinical characteristics of patients who benefit from those parameters.