title: Augmentation of Voluntary Locomotor Activity by Transcutaneous Spinal Cord Stimulation in Motor-Incomplete Spinal Cord-Injured Individuals.
abstract: The level of sustainable excitability within lumbar spinal cord circuitries is one of the factors determining the functional outcome of locomotor therapy after motor-incomplete spinal cord injury. Here, we present initial data using noninvasive transcutaneous lumbar spinal cord stimulation (tSCS) to modulate this central state of excitability during voluntary treadmill stepping in three motor-incomplete spinal cord-injured individuals. Stimulation was applied at 30 Hz with an intensity that generated tingling sensations in the lower limb dermatomes, yet without producing muscle reflex activity. This stimulation changed muscle activation, gait kinematics, and the amount of manual assistance required from the therapists to maintain stepping with some interindividual differences. The effect on motor outputs during treadmill-stepping was essentially augmentative and step-phase dependent despite the invariant tonic stimulation. The most consistent modification was found in the gait kinematics, with the hip flexion during swing increased by 11.3° ± 5.6° across all subjects. This preliminary work suggests that tSCS provides for a background increase in activation of the lumbar spinal locomotor circuitry that has partially lost its descending drive. Voluntary inputs and step-related feedback build upon the stimulation-induced increased state of excitability in the generation of locomotor activity. Thus, tSCS essentially works as an electrical neuroprosthesis augmenting remaining motor control.
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Ursula S
authors.initials: US
authors.lastname: Hofstoetter
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Krenn
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.|Institute of Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria.|Department of Neurobiology and Anatomy, Drexel University of Medicine, Philadelphia, PA.
authors.forename: Simon M
authors.initials: SM
authors.lastname: Danner
authors.affiliation: Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Vienna, Austria.|Otto Bock Healthcare Products GmbH, Vienna, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Hofer
authors.affiliation: Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Vienna, Austria.|Department of Physical Medicine and Rehabilitation, Wilhelminenspital Wien, Vienna, Austria.
authors.forename: Helmut
authors.initials: H
authors.lastname: Kern
authors.affiliation: Hulse Spinal Cord Injury Lab, Crawford Research Institute, Shepherd Center, Atlanta, GA, USA.
authors.forename: William B
authors.initials: WB
authors.lastname: McKay
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Winfried
authors.initials: W
authors.lastname: Mayr
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Karen
authors.initials: K
authors.lastname: Minassian
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D008161:Lumbosacral Region; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology; D013116:Spinal Cord / Q000503:physiopathology; D013119:Spinal Cord Injuries / Q000628:therapy*; D062187:Spinal Cord Stimulation; D016138:Walking / Q000502:physiology*
keywords: Human; Locomotor training; Neuromodulation; Spinal cord injury; Transcutaneous spinal cord stimulation