Intensity dependent effects of transcranial direct current stimulation on corticospinal excitability in chronic spinal cord injury

Lynda M Murray; Dylan J Edwards; Giulio Ruffini; Douglas Labar; Argyrios Stampas; Alvaro Pascual-Leone; Mar Cortes

doi:10.1016/j.apmr.2014.11.004

Intensity dependent effects of transcranial direct current stimulation on corticospinal excitability in chronic spinal cord injury

Arch Phys Med Rehabil. 2015 Apr;96(4 Suppl):S114-21. doi: 10.1016/j.apmr.2014.11.004. Epub 2014 Nov 22.

Authors

Lynda M Murray¹, Dylan J Edwards², Giulio Ruffini³, Douglas Labar⁴, Argyrios Stampas⁵, Alvaro Pascual-Leone⁶, Mar Cortes⁷

Affiliations

¹ 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.
² Non-invasive Brain Stimulation and Human Motor Control Laboratory, Burke Medical Research Institute, White Plains, NY; Neurology Department, Weill Cornell Medical College, Cornell University, New York, NY; Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Nedlands, WA, Australia.
³ Starlab Barcelona SL, Barcelona, Spain.
⁴ Non-invasive Brain Stimulation and Human Motor Control Laboratory, Burke Medical Research Institute, White Plains, NY; Neurology Department, Weill Cornell Medical College, Cornell University, New York, NY.
⁵ Burke Rehabilitation Hospital, White Plains, NY.
⁶ Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA.
⁷ Non-invasive Brain Stimulation and Human Motor Control Laboratory, Burke Medical Research Institute, White Plains, NY; Neurology Department, Weill Cornell Medical College, Cornell University, New York, NY; Department of Neurology, University of Barcelona, Barcelona, Spain.

Abstract

Objective: To 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).

Design: Single-blind, randomized, sham-controlled, crossover study.

Setting: Medical research institute and rehabilitation hospital.

Participants: Volunteers (N = 9) with chronic SCI and motor dysfunction in wrist extensor muscles.

Interventions: Three 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 measures: Corticospinal 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.

Results: Mean 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.

Conclusions: The 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.

Keywords: Anodal stimulation transcranial direct current stimulation; Rehabilitation; Spinal cord injuries; Upper extremity.

Publication types

Randomized Controlled Trial
Research Support, N.I.H., Extramural

MeSH terms

Adult
Chronic Disease
Cross-Over Studies
Electromyography
Evoked Potentials, Motor / physiology*
Female
Humans
Male
Middle Aged
Muscle, Skeletal / physiopathology
Physical Therapy Modalities
Pyramidal Tracts / physiopathology*
Single-Blind Method
Spinal Cord Injuries / rehabilitation*
Transcranial Direct Current Stimulation / adverse effects
Transcranial Direct Current Stimulation / methods*
Transcranial Magnetic Stimulation / methods
Wrist / physiopathology

Abstract

Publication types

MeSH terms

Grants and funding