Immediate cerebral metabolic changes induced by discontinuation of deep brain stimulation of subcallosal cingulate gyrus in treatment-resistant depression.

Positron emission tomography (PET) studies have shown that the antidepressant effect of chronic deep brain stimulation (DBS) of the subcallosal cingulate gyrus (SCG) may be consequence of modifications of brain metabolism at key structures involved in depression. Like clinical benefits, these metabolic changes may reverse when the stimulation is discontinued, even preceding clinical worsening. However no data on immediate effects of DBS discontinuation are available. The aim of this study was to determine immediate cerebral metabolism changes during a short switch-off of electrical stimulation in implanted patients with treatment-resistant depression (TRD) who had achieved clinical improvement after a period of chronic DBS.Seven patients with TRD who had been previously implanted for DBS in SCG were included. After a period of clinical stabilization two consecutive FDG-PET were acquired, the first with active stimulation and the second after 48 h of inactive stimulation. A HAMD-17 to assess depressive symptoms was performed before both scans. Analyses were performed with SnPM8.Inactive stimulation was characterized by metabolism decreases in dorsal anterior cingulate (Broadmann Area, BA24), premotor region (BA6) and putamen with respect to active stimulation. No clinical changes according to HAMD-17 were detected.The main limitation of this study is the small sample size.Our results point to immediate effects of DBS discontinuation on metabolism of brain depressive network which precede clinical changes, helping to disentangle the rationale behind DBS efficacy in TRD.