David Darrow, MD, MPH
Assistant Professor, Department of Neurosurgery, University of Minnesota; Rockswold-Kaplan Endowed Chair for Traumatic Brain Injury, Hennepin County Medical Center; Principal Investigator, Restorative Neurotrauma Lab at Hennepin County Medical Center; Principal Investigator, E-Stand trial
Spinal Cord Stimulation Restores Synergies after Spinal Cord Injury
Stimulation of the spinal cord and nerve roots from the epidural space (epidural spinal cord stimulation) has generated great interest for the treatment of chronic thoracic spinal cord injury. Surgical implantation of an epidural stimulation system is performed as an outpatient procedure and takes approximately 90 minutes. Funded by the state of Minnesota with devices supplied by Abbott (St. Jude Medical), the E-STAND trial is a phase I and II clinical trial designed to test and optimize the effect of surgically-implanted epidural spinal cord stimulation for the treatment of motor-complete (AIS A/B) chronic SCI to restore volitional movement and autonomic function. Multiple studies have corroborated restored volitional motor control after motor-complete spinal cord injury (SCI) through the use of spinal cord stimulation (SCS/eSCS), but rigorous quantitative descriptions have been lacking. Using a structured surface electromyogram based (sEMG) task with and without SCS during the Epidural Stimulation After Neurological Damage (ESTAND) study in participants with chronic, motor and sensory complete SCI, we investigated muscle activity complexity and muscle synergies to better characterize neuromuscular control. In addition, competition exists between the task and neural origin hypotheses underlying muscle synergies, and this analysis in humans with motor and sensory complete chronic injury provided an opportunity to test these hypotheses. Muscle activity complexity was computed with Higuchi Fractal Dimensional analysis (HFD), and muscle synergies were estimated using non-negative matrix factorization (NNMF) in six participants with AIS A chronic SCI. We found that the complexity of muscle activity is immediately reduced with SCS in the SCI participants. We also found that over the follow-up sessions, the muscle synergy structure of the SCI participants became more defined, and the number of synergies decreased over time, indicating improved coordination between the muscle groups. Lastly, we found that the muscle synergies were restored with SCS, supporting the neural hypothesis of muscle synergies. Interestingly, we have found that chronic spinal cord stimulation after spinal cord injury restores volitional movement but with muscle synergies or primitives that are distinct from able-bodied individuals. SCS may be an effective therapy that produces a new normal for volitional control after spinal cord injury.
Dr. David Darrow is an Assistant Professor in the Department of Neurosurgery at the University of Minnesota and the Rockswold-Kaplan Endowed Chair for Traumatic Brain Injury at Hennepin County Medical Center, specializing in functional and pain neurosurgery. Dr. Darrow treats diseases of the central nervous system with neuromodulation including epilepsy, movement disorders, trigeminal neuralgia/facial pain, chronic pain, and psychiatric diseases. Dr. Darrow is co-PI of the Herman-Darrow Human Neuroscience Lab with a mission of understanding and treating disorders of the nervous system with neuromodulation. The Herman-Darrow Lab links together circuit-level electrophysiology with behavior. Dr. Darrow is also the PI of the Restorative Neurotrauma Lab at HCMC where electrophysiology and neuromodulation and used to better understand and treat traumatic injuries of the central nervous system. He is the PI for the E-STAND trial, where neuromodulation is used to restore function after Spinal Cord Injury.