Transcranial magnetic stimulation (TMS) over left dorsolateral prefrontal cortex (L-DLPFC) is an FDA approved treatment for treatment-refractory depression (TRD), but only partially effective, with response and remission rates of 41.2% and 35.3%, respectively1,2.
The FDA approved protocol for TRD identifies the left DLPFC stimulation site by moving the coil 5cm anterior to the “hand motor hotspot” (motor cortex) along the curvature of the scalp (one-size-fits-all). This approach provides only approximate targeting of left DLPF (misses frequently the DLPFC), with no consistent differentiation among potentially relevant DLPFC subregions.
One reason why some people respond well and others do not may have to do with individual variations in brain organization, which would require stimulation to be applied to slightly different locations in different individuals.
An important goal of TMS therapy is to guide TMS targeting on a personalized basis, in order to improve consistency of targeting across individuals.
Alternative methods to DLPFC target identification can be used to personalize treatments using intrinsic (resting state) functional connectivity MRI, a powerful imaging technique that applies correlations in spontaneous fluctuations in the blood oxygen level-dependent signal to assess functional relationships between brain regions.
The differences in brain organization can be detected using individualized functional MRI scans, which then allow the coil placement to be determined separately for each individual.
1. Horvath JC, Mathews J, Demitrack MA, Pascual-Leone A. The NeuroStar TMS device: conducting the FDA approved protocol for treatment of depression. J Vis Exp. 2010 Nov 12;(45):2345.
2. Connolly KR, Helmer A, Cristancho MA, Cristancho P, O’Reardon JP. Effectiveness of transcranial magnetic stimulation in clinical practice post-FDA approval in the United States: results observed with the first 100 consecutive cases of depression at an academic medical center. J Clin Psychiatry. 2012 Apr;73(4):e567-73.