Transcutaneous spinal cord stimulation for restoration of upper extremity function after spinal cord injury

Abstract

Spinal cord injury is currently incurable. Standard of care after spinal cord injury focuses on prevention of the secondary complications and maximizing residual function. The most common site of injury is the cervical level that results in tetraplegia. Incomplete cervical injury is the most frequent neurological category. Loss of motor control and sensory function in the upper extremity is a particularly devastating aspect of cervical injuries that impairs the ability to perform activities of daily living. Restoration of hand and arm function is consistently rated as the highest treatment priority among people with tetraplegia due to cervical spinal cord injury, 5-fold higher than any other function included in the surveys. Nevertheless, current approaches to improve hand and arm function are largely ineffective. Electrical spinal cord stimulation, however, is one of the emerging neuromodulation strategies to restore motor function. The aims of this dissertation are to (1) review the applications of therapeutic electrical spinal cord stimulation after spinal cord injury, (2) determine improvements in hand and arm function resulting from non-invasive electrical cervical spinal cord stimulation, and (3) quantify long-term benefits that may persist beyond the stimulation. Therapeutic potential of transcutaneous spinal cord stimulation is evaluated in a prospective, open-label, two arm cross-over study. Intervention arms consist of intensive upper limb functional task training alone and transcutaneous electrical cervical spinal cord stimulation combined with training. The Graded Redefined Assessment of Strength, Sensation and Prehension is used as the primary outcome measure. Improvements achieved by training alone are compared to those obtained when transcutaneous spinal cord stimulation is paired with training. The findings demonstrate that transcutaneous cervical spinal cord stimulation has augmentative effect on restoration of hand and arm function. Additionally, gains are maintained up to six months without stimulation or training, suggesting that electrical stimulation can promote neuroplasticity. This dissertation provides evidence that transcutaneous spinal cord stimulation is a highly promising intervention for recovery of upper extremity function after cervical spinal cord injury, with the significant advantage of not requiring surgery.