Effects of transcranial direct current stimulation on multiple sclerosis and neuromyelitis optica spectrum disorder: A double-blind, randomized, crossover trial

Objectives: There are no effective therapies for nonmotor symptoms of multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD), including cognitive impairment, fatigue, depression, and pain. Transcranial direct current stimulation (tDCS), a neuromodulatory technique, enhances rehabilitation effects, and has been applied to multiple neurological diseases. We attempted to clarify the effectiveness of tDCS on the nonmotor symptoms of MS/NMOSD. Methods: A double-blind, randomized cros-over trial was conducted with five MS/NMOSD patients randomly assigned to active (real) or sham tDCS groups. Patients received 10 sessions of tDCS combined with rehabilitation, with assessments at baseline and poststimulation, A second session under the alternate condition followed. The anodal electrode was placed over M1 (C3 in the 10–20 system), and the cathode over Fp2, delivering 1.0 mA for 900 s. Functional magnetic resonance imaging was conducted before and after stimulation to assess functional connectivity (FC) using region of interest (ROI)-to-ROI analysis across six ROIs. Results: No adverse events related to tDCS were observed. A significant improvement was observed in working memory and information-processing ability, as assessed by using the Paced Auditory Serial Addition 2-s version after active stimulation compared to sham stimulation. In the anterior cingulate cortex-precuneus FC, significant changes were observed following active stimulation. Conclusion: Anodal tDCS over M1 may be a useful means of improving cognitive function in patients with MS/NMOSD and altered FCs beyond M1.