• Lynda M Murray, Dylan J Edwards, Giulio Ruffini, Douglas Labar, Argyrios Stampas, Alvaro Pascual-Leone, and Mar Cortes.
• Non-invasive Brain Stimulation and Human Motor Control Laboratory, Burke Medical Research Institute, White Plains, NY; Physical Medicine and Rehabilitation Department, Rumailah Hospital, Hamad Medical Corporation, Doha, Qatar; School of Exercise and Health Sciences, Edith Cowan University, Joondalup, WA, Australia. Electronic address: LMurray@hmc.org.qa.
• Arch Phys Med Rehabil. 2015 Apr 1;96(4 Suppl):S114-21.

ObjectiveTo investigate the effects of anodal transcranial direct current stimulation (a-tDCS) intensity on corticospinal excitability and affected muscle activation in individuals with chronic spinal cord injury (SCI).DesignSingle-blind, randomized, sham-controlled, crossover study.SettingMedical research institute and rehabilitation hospital.ParticipantsVolunteers (N = 9) with chronic SCI and motor dysfunction in wrist extensor muscles.InterventionsThree single session exposures to 20 minutes of a-tDCS (anode over the extensor carpi radialis [ECR] muscle representation on the left primary motor cortex, cathode over the right supraorbital area) using 1 mA, 2 mA, or sham stimulation, delivered at rest, with at least 1 week between sessions.Main Outcome MeasuresCorticospinal excitability was assessed with motor-evoked potentials (MEPs) from the ECR muscle using surface electromyography after transcranial magnetic stimulation. Changes in spinal excitability, sensory threshold, and muscle strength were also investigated.ResultsMean MEP amplitude significantly increased by approximately 40% immediately after 2mA a-tDCS (pre: 0.36 ± 0.1 mV; post: 0.47 ± 0.11 mV; P = .001), but not with 1 mA or sham. Maximal voluntary contraction measures remained unaltered across all conditions. Sensory threshold significantly decreased over time after 1mA (P = .002) and 2mA (P = .039) a-tDCS and did not change with sham. F-wave persistence showed a nonsignificant trend for increase (pre: 32% ± 12%; post: 41% ± 10%; follow-up: 46% ± 12%) after 2 mA stimulation. No adverse effects were reported with any of the experimental conditions.ConclusionsThe a-tDCS can transiently raise corticospinal excitability to affected muscles in patients with chronic SCI after 2 mA stimulation. Sensory perception can improve with both 1 and 2 mA stimulation. This study gives support to the safe and effective use of a-tDCS using small electrodes in patients with SCI and highlights the importance of stimulation intensity.Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

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