Simultaneous and cumulative effects of tDCS on cerebral metabolic rate of oxygen in multiple sclerosis

IntroductionTranscranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique with simultaneous (during stimulation) and cumulative effects (after repeated sessions) on blood flow and neuronal metabolism. These effects remain mostly unclear especially in multiple sclerosis (MS). This work aims to elucidate brain metabolic and hemodynamic underpinnings of tDCS and its potential therapeutic impact in MS patients using quantitative tDCS-MRI.MethodsMS participants (n = 20; age = 45.4 ± 12.3 years, 7 males) underwent 3 T MRI scans before and after 20 daily sessions of dorsolateral prefrontal cortex (DLFPC) tDCS (2.0 mA, left anodal) paired with adaptive cognitive training (aCT). During both visits, imaging measurements of cerebral blood flow (CBF), cerebral venous blood oxygenation (Yv) and calculated cerebral metabolic rate of oxygen (CMRO2) were obtained at pre-tDCS, during-tDCS and post-tDCS.ResultsAt baseline, significant increase from pre- to during-tDCS was observed in CMRO2 (7.6%; p = 0.002), CBF (11.0%; p